TRI-TOWN SEPTAGE TREATMENT FACILITY EVALUATION. August 2005

Transcription

1 TRI-TOWN SEPTAGE TREATMENT FACILITY EVALUATION August 2005

2 TRI-TOWN SEPTAGE TREATMENT FACILITY EVALUATION AUGUST 2005 Prepared For: Wastewater Management Steering Committee Town of Orleans, Massachusetts

3 TRI-TOWN SEPTAGE TREATMENT FACILITY EVALUATION TABLE OF CONTENTS SECTION DESCRIPTION PAGE 1 BACKGROUND AND PURPOSE 1.1 Background Purpose Report Overview DESCRIPTION AND APPRAISAL OF EXISTING FACILITIES 2.1 Plant Description Appraisal of Condition of Existing Facilities Plant Performance in Nitrogen Removal ESTIMATES OF SEPTAGE AND LIQUID SLUDGE QUANTITIES 3.1 Definition of Terms Methodology Current Quantities of Septage and Liquid Sludge Per-Capita Quantities of Septage Per-Capita Quantities of Liquid Sludge Population Projections Regional Sewering Scenarios Future Quantities of Septage and Liquid Sludge Sensitivity Analysis Capacity of Existing Septage and Wastewater Facilities Possibility of Tri-Town Expansion SITE CAPABILITY FOR WASTEWATER TREATMENT AND DISPOSAL 4.1 Overview USGS Modeling of Regional Groundwater Flow Mounding Analysis Siting of a Wastewater Treatment Facility Site Development Scenarios Orleans Sewering Scenarios Coordination with Long-Term USGS Marsh Monitoring ALTERNATIVE USES OF COMPOST SHED A ii Wright-Pierce

4 SECTION DESCRIPTION PAGE 6 UPGRADING RECOMMENDATIONS AND COSTS 6.1 Broad Options Specific Recommendations for Improvements Cost Estimates Conclusions CONTROL OF ODOR AND NOISE 7.1 Odor Control Noise Control REGULATORY AND PERMITTING ISSUES 8.1 Permits and Approvals Schedule IMPLEMENTATION STEPS SUMMARY OF FINDINGS AND RECOMMENDATIONS 10.1 Findings Recommendations APPENDICES A EVALUATION OF EXISTING FACILITIES... A-1 B GZA REPORT ON GROUNDWATER MOUNDING... B-1 C UPGRADING NEEDS... C-1 D DEP GROUNDWATER DISCHARGE PERMIT... D A iii Wright-Pierce

5 LIST OF TABLES TABLE DESCRIPTION PAGE 2-1 EVALUATION OF CURRENT PLANT CONDITIONS CURRENT SEPTAGE QUANTITIES POPULATION PROJECTIONS OVERVIEW OF REGIONAL SEWERING SCENARIOS FUTURE QUANTITIES OF SEPTAGE AND LIQUID SLUDGE SUMMARY OF PRELIMINARY USGS MODELING SUMMARY OF SITE DEVELOPMENT SCENARIOS SUMMARY OF UPGRADING NEEDS SUMMARY OF UPGRADING COSTS LIST OF FIGURES FIGURE DESCRIPTION PAGE 1-1 SITE LOCATION SITE PLAN PROCESS FLOW DIAGRAM EFFLUENT NITROGEN LOADS BASIS FOR ESTIMATING SEPTAGE/SLUDGE QUANTITIES ESTIMATES OF SEPTAGE AND SLUDGE QUANTITIES EFFLUENT DISPOSAL AREAS FOR USGS MODELING USGS MODELING SCENARIO USGS MODELING SCENARIO USGS MODELING SCENARIO USGS MODELING SCENARIO UPGRADING OPTIONS 2 AND SELECTED OPTIONS FOR SITE DEVELOPMENT WATERSHEDS ASSOCIATED WITH SEWERING SCENARIOS A iv Wright-Pierce

6 SECTION 1 BACKGROUND AND PURPOSE BACKGROUND The Tri-Town Septage Treatment Facility is located on a 26-acre parcel in Orleans, just to the northwest of the intersection of Route 6 and Route 6A. It is located in the Namskaket Creek watershed, one of three watersheds in the westerly portion of Orleans that discharge to Cape Cod Bay. The treatment facilities occupy the central portion of the site which is bordered by residential and light industrial development to the south, Route 6 to the east, residential development to the north and the Cape Cod Bike Trail and Namskaket Marsh to the west. An aerial photograph of the site is shown in Figure 1-1. The facility is designed to treat septage, grease and related trucked wastes. It was built to serve the Towns of Orleans, Eastham and Brewster, but it also receives trucked wastes from the three Lower Cape towns of Provincetown, Truro and Wellfleet, as well as small quantities from other nearby towns. While the Tri-Town site is owned by the Town of Orleans, the septage treatment and disposal facilities are owned and operated by the Orleans Brewster Eastham Groundwater Protection District (The District). The District was formed by a special act of the legislature (Chapter 327 of the Acts of 1988). The three District towns share capital costs on an equal basis, and operation and maintenance costs are recovered through tipping fees paid by all users on a pergallon basis. The three District towns have executed and amended inter-municipal agreements that govern their participation A 1-1 Wright-Pierce

7 FIGURE 1-1 Site Location 10461A 1-2 Wright-Pierce

8 PURPOSE The Tri-Town facility is nearing 20 years of age, and the original tanks and equipment are showing signs of wear. The District's Board of Managers and the Town of Orleans have agreed that it is time to formulate a plan to upgrade the facility. At the same time, the Town of Orleans is embarking on comprehensive wastewater management planning, and the Towns of Eastham and Brewster may follow suit. Given that setting, this report is intended to accomplish two goals: Identify the upgrading needs of the existing septage treatment facilities, and establish a capital budget, and Determine if the Tri-Town site may be suitable to satisfy some or all of the needs of the Town of Orleans for wastewater treatment, wastewater disposal, or both. REPORT OVERVIEW This report contains 10 sections and 4 appendices. Following this Section 1, Section 2 presents a summary of an appraisal of the condition of the Tri-Town facility, the details of which are presented in Appendix A. In Section 3, estimates are presented of future septage and liquid sludge quantities that may be received at Tri-Town. The capabilities of the Tri-Town site to serve as a location for wastewater treatment and/or disposal are discussed in Section 4, supported by a groundwater mounding analysis contained in Appendix B. Section 5 discusses alternative uses for the abandoned compost shed. Upgrading needs of the septage facility are presented in Section 6, as a summary of a detailed appraisal contained in Appendix C. Section 7 discusses odor and noise control issues, and Section 8 addresses permitting requirements. Section 9 lists the implementation steps that should guide progress on both the upgrading of the septage facility and planning for possible wastewater-related uses of the site. Section 10 is a summary of the entire report's findings and recommendations. Appendix D contains the current plant discharge permit. This report was prepared under the direction of the Orleans Wastewater Management Steering Committee, with significant input from the staff of the Tri-Town facility and the Orleans Planning Department A 1-3 Wright-Pierce

9 SECTION 2 DESCRIPTION AND APPRAISAL OF EXISTING FACILITIES 2.1 PLANT DESCRIPTION The Tri-Town Septage Treatment Facility was built in the late 1980s following a lengthy and contentious planning period. The planning process included consideration of a limited sewer system for Orleans' downtown area, but this concept was abandoned in favor of a septage-only treatment plant. The facility was originally designed to accomplish its treatment objectives through direct dewatering of lime- and ferric-chloride-conditioned septage solids in plate-and-frame presses, with subsequent treatment of the dewatering filtrate through a secondary treatment process utilizing rotating biological contactors (RBCs). The effluent from the secondary treatment process was subjected to ultraviolet (UV) disinfection prior to discharge to a series of rapid infiltration beds. The residual solids generated by the plate-and-frame presses were originally intended for on-site composting. Construction of the plant was sufficiently complete to allow operations to begin in Completion of the construction was delayed by litigation among the Town of Orleans, the construction contractor and the design engineer. Early operational difficulties resulted in suspension of the on-site composting and the issuance of an Administrative Consent Order (ACO) by the Massachusetts Department of Environmental Protection (DEP). As a result of the ACO, a Corrective Action Report was developed that led to significant plant improvements that were constructed in 1995 to The improvements included additional septage/grease receiving tanks, gravity belt thickeners, a new filtrate equalization tank, secondary clarifiers, and sand filters. Figure 2-1 shows the layout of septage treatment and disposal facilities on the site. A simplified process flow diagram is shown in Figure 2-2, depicting both the original facilities and those added or modified in the mid 1990s. For simplicity, the facilities added in the period of 1995 to 1997 are termed the "1995 upgrade". The Tri-Town facility is designed to treat up to 45,000 gallons per day (gpd) of septage, grease and other trucked wastes under a permit issued in 1986 by the Massachusetts Groundwater Discharge Permit Program (Groundwater Discharge Permit No ). The permit requires that the effluent contain no more than 30 mg/l Biochemical Oxygen Demand, 30 mg/l Total Suspended Solids and 50 mg/l Total Nitrogen. The Tri-Town project was one of three in the Commonwealth that received 50-mg/l nitrogen limits based on the expectation that the local 10461A 2-1 Wright-Pierce

10 receiving waters did not warrant the 10-mg/l standard that all other groundwater discharges must meet. 2.2 APPRAISAL OF CONDITION OF EXISTING FACILITIES The equipment and facilities at the Tri-Town plant have been evaluated several times over the last 15 years, including the Corrective Action Report and the design report for the mid-1990s upgrading. As part of this current study, an updated appraisal was made of each unit process, all major equipment components and systems, and the general superstructure and building systems. Wright-Pierce performed a detailed, multi-disciplined site inspection of the existing septage facility on November 15, This evaluation covers the liquid stream systems, solids handling systems and the effluent disposal system. In attendance for this inspection were five staff members from Wright-Pierce and Jay Burgess and Steve Britto from the District. The inspection was performed in a three-step process that lasted the entire day. The three steps consisted of the following: 10461A 2-2 Wright-Pierce

11 FIGURE A 2-3 Wright-Pierce

12 FIGURE A 2-4 Wright-Pierce

13 1. A group walk-through of the entire facility from "front to back" with a general focus on overall condition, history, and current operational scheme and status. District staff led this tour and provided detailed information for each process, system and area of the facility. 2. A workshop meeting with the District staff to review the findings from the initial tour and discuss current capital improvement plans for the facility, specific needs and equipment preferences, and various other issues related to the facility. This discussion was structured on a technical discipline basis (i.e., unit process operation issues, site issues, architectural issues, HVAC and plumbing issues, structural issues and control issues). 3. A focused second walk-through of the facility. Each area of the facility was again visited with a trained eye toward specific problems or needs. The above noted process was very effective in assessing the current condition of the facility and provided a platform for the operators to clearly articulate any problems or issues that should be included in the evaluation. Potential modifications and/or improvements were discussed by the operators and engineers for each process/area as part of the inspection. The result of the site visit was an effective exchange of current and historical information; data transfer for all processes; photographs of all facility unit process, equipment, buildings and the site; and detailed logs of the condition and status of unit processes, equipment systems and buildings. While the major focus was existing operating systems, an inspection was made of the abandoned compost facility structure, the overall site, as well as the adjacent bike path, radio tower site, Mass Highway property and Route 6 interchange (Exit 12). These investigations were performed with an eye toward potential future effluent disposal areas. Appendix A presents the results of the intensive plant inspection that are summarized in Table 2-1. Appendix A and Table 2-1 present information on the age of the equipment and tankage, their current condition, and considerations for immediate and/or long term modifications and improvements A 2-5 Wright-Pierce

14 TABLE 2-1 EVALUATION OF CURRENT PLANT CONDITIONS Unit Process Structures and Equipment Septage and Grease Receiving and Grit Processing Installation Date Current Condition Mechanical Bar Screen Original Not in operation Grit Cyclone Original Corroded, mixed performance Grit Pump Original Good Grit Wetwell Original Concrete spalling Grease Tank 1995 Good Grease Grit Tank 1995 Good Grease Grit Pump 1995 Good Grease Storage Tank Original Out of service, full of hardened grease Grease Storage Blowers 1995 Very Good Septage Equalization Septage Tank Original Unknown Septage Blowers 1995 Good Septage Thickening Grinders Original Poor performance Septage Pumps Original Good GBT's 1995 Very good Thickened Sludge Pump 1995 Very good Septage Conditioning Septage Conditioning Tanks 1995 Good Lime System Original Fair, cracks in tank walls Permanganate System Original Fair, not in use Polymer System 1995 Good Ferric Chloride System Original Unknown Acid Wash Original Unknown Mixers 1995 Good, currently not used Septage Dewatering Polymer System 1995 Good Ram Press Pumps Original Good Plate & Frame Filter Presses Original Fair Filtrate Equalization Filtrate Tanks 1 & 2 Original Unknown Good Filtrate Blowers 1995 Good Filtrate Pumps 1 & Good 3 & Good 10461A 2-6 Wright-Pierce

15 TABLE 2-1 (Cont.) EVALUATION OF CURRENT PLANT CONDITIONS Unit Process Structures and Equipment Primary Clarification Installation Date Primary Clarifiers Original Poor Sludge Pumps Original Good Secondary Treatment (RBCs) Drives Original Fair Media Original, 2001 Fair to Good Intermediate Pumps 1995 Good Covers Original Fair Secondary Clarification Lamella Clarifiers Original Poor Secondary Clarifiers 1995 Good Scum Pumps 1995 Good Sludge Pumps 1995 Good Tertiary Treatment Current Condition Sand Filters 1995 Good. Not used in winter Backwash Blowers 1995 Good Mudwell Pumps 1995 Good Disinfection Original Good Plant Water Pumps 1995 Good Effluent Pumps 2000 Good Spray Wash Pumps 1995 Good Odor Control Headworks Scrubber Original Fair Headworks Carbon Original Good Thickening Area Scrubber 1995 Good Thickener Area Carbon 1995 Good Instrumentation Original, 1995 Good Composting Original Fair, not used Chemical Building Original Poor Miscellaneous Sump Pumps Original Inadequate Valves Original Poor Compressor Original Poor, excess condensation Water system Original Excessive water hammer The analysis presented in Appendix A and summarized in Table 2-1 leads to the conclusion that the primary areas in need of upgrading are as follows: 10461A 2-7 Wright-Pierce

16 Headworks Area - Mechanical Screening and Grit Handling System. The mechanical screen is currently not working and the degritting system is not operating efficiently. Plate-and-Frame Filter Presses - Solids Dewatering System. The manufacturer is no longer in business, and several components are in need of modifications; consider replacement with more current technology. Rotating Biological Contractors (RBC) - Biological treatment of dewatering filtrate. The media and shafts should be replaced on two of the units. The original Tri-Town construction included on-site composting facilities for the sludge cake generated by septage dewatering, with intended local distribution of the compost product. Since the abandonment of the composting facilities, the District has relied on private contractors to haul sludge cake to off-cape disposal locations. (District staff hauls sludge cake to the Yarmouth septage facility, where a private contractor picks it up and hauls it off-cape.) Reliance on contract disposal makes the plant less self-sufficient than originally planned, but offsite disposal is certainly warranted given the close proximity of the composting shed to residential abutters. An increasing number of small wastewater plants now rely on contractual off-site stabilization and disposal, and a mature industry has developed to satisfy that need. Accordingly, we propose no change in the District's practice of off-site disposal, and we view the risks as small. 2.3 PLANT PERFORMANCE IN NITROGEN REMOVAL While the Tri-Town plant is allowed to discharge up to 50 mg/l total nitrogen, the District staff has worked hard to maximize nitrogen removal, even though there are no formal nitrogen removal processes at the plant. In recent years, the plant effluent has contained, on average, 30 to 40 mg/l of total nitrogen, well below the permit limit. Figure 2-3 was developed to document the actual nitrogen loads discharged from the plant since The loads depicted in Figure 2-3 are computed by multiplying together the plant's discharge flow and the effluent nitrogen concentration with a conversion factor. During most of the 1990s, flows varied significantly 10461A 2-8 Wright-Pierce

17 FIGURE 2-3 EFFLUENT NITROGEN LOADS FIGURE 2-3 5,000 4,500 4,000 Assumed 2 mg/l Organic N Actual Inorganic N ,500 3,000 2,500 2, A 2-9 Wright-Pierce Annual Nitrogen Load (lb/yr)

18 from year to year due to a high degree of price sensitivity in the septage marketplace. Between 1999 and 2005, there was a steady increase in plant flow that was more than offset by improved performance, resulting in a steady decline in nitrogen load. The operational performance from 2001 onward suggests that the current plant can be relied upon to keep effluent nitrogen loads at or below 3,000 pounds per year. (By comparison, the nitrogen load from septic systems and lawn fertilization in the Namskaket Creek watershed is well in excess of 10,000 pounds per year.) 10461A 2-10 Wright-Pierce

19 SECTION 3 ESTIMATES OF SEPTAGE AND LIQUID SLUDGE QUANTITIES To properly determine the upgrading needs of the Tri-Town facility, it is important to make projections of future septage quantities expected from the three District towns, as well as other towns using the plant. This section presents those projections. We have expanded this task to include quantities of liquid sludge produced by decentralized wastewater facilities such as cluster systems and satellite plants. At the request of Barnstable County, this section also considers Cape-wide quantities of septage and liquid sludge. 3.1 DEFINITION OF TERMS The Tri-Town facility receives septage, the liquid sludge periodically removed from individual septic tanks. The broad term "septage" includes such material removed from residential systems as well as that pumped from commercial establishments (including grease traps), institutional facilities and other sources. The Tri-Town plant separates the solids from the liquids, treats the liquids and presses the solids into a sludge "cake" that is transported off-cape for disposal. The treated liquid fraction is discharged to the rapid infiltration basins on site. Centralized wastewater treatment facilities receive sewage (wastewater) that is much more dilute than septage. The solids that are removed or created in the treatment process are typically stabilized and dewatered at the same site, and the resulting sludge cake is then trucked to an offsite disposal location. Off-site disposal options include composting, pelletization, incineration and landfilling. Centralized wastewater facilities also typically receive and treat septage from the unsewered portions of the towns they serve. There are a growing number of so-called "cluster" and "satellite" wastewater treatment facilities on Cape Cod. These facilities serve several properties or a significant development on a single property, such as an apartment complex, shopping center or nursing home. We have used the term "cluster" to describe those facilities that serve multiple lots in a confined area, and fall below the 10,000 gallon-per-day threshold for a DEP groundwater discharge permit. "Satellite" plants are designed for more than 10,000 gpd and are governed by groundwater discharge permits that require a high level of wastewater treatment. Both cluster and satellite plants are typically too small to have on-site sludge dewatering and stabilization, and must rely on trucking of liquid sludge to off-site facilities. If the cluster system is a traditional septic-tank-and-leaching-field system, then the liquid sludge is essentially "septage". When advanced wastewater treatment is provided (some cluster systems and all satellite plants), the biological sludge produced is mixed with and co-disposed with the 10461A 3-1 Wright-Pierce

20 septic tank solids. We call that combined material "liquid sludge" for the purposes of this report. Collectively, septage and liquid sludge are often termed "residuals". 3.2 METHODOLOGY Given these definitions, we have made several assumptions to estimate septage and liquid sludge quantities. The principal assumptions are: 1. Centralized wastewater facilities create sludge that will be processed on-site and disposed of by the owner of the facility. No liquid sludge will be generated that requires capacity at another facility (such as the Tri-Town plant). (The two exceptions are the centralized plants in Provincetown and Falmouth, which do not have dewatering facilities and must haul liquid sludge off site.) 2. Individual, cluster and satellite systems create a liquid sludge that is not processed on site and requires capacity at Tri-Town or elsewhere for proper disposal. 3. Cluster and satellite plants provide a significantly higher level of treatment than individual systems and thus create larger quantities of residuals. We have ignored the relatively small number of individual enhanced treatment systems. 4. We have estimated septage and liquid sludge quantities on a per-capita basis that have been applied to current and build-out populations to predict how these quantities will change, due both to population increases and the implementation of municipal wastewater infrastructure. 5. We have organized our approach to look at three scenarios of possible municipal infrastructure development (ranging from maximum reliance on individual systems to widespread use of cluster/satellite/centralized systems, with one intermediate scenario). Within this broad approach, the specific steps are as follows: 1. Determine the current population in each town that is served by individual, cluster/satellite or centralized systems. 2. Apply per-capita estimates of sludge and septage generation rates to match current quantity estimates. 3. Determine build-out populations. 4. Based on input from Cape Cod Commission staff and municipal officials, formulate three scenarios of municipal wastewater infrastructure at build-out A 3-2 Wright-Pierce

21 5. Apply per-capita estimates of sludge and septage generation rates to arrive at projected future quantities. Figure 3-1 is a schematic representation of this approach. 3.3 CURRENT QUANTITIES OF SEPTAGE AND LIQUID SLUDGE We contacted all of the Cape Cod facilities that receive septage to obtain information on septage quantities over the past several years. We also contacted private off-cape facilities that also receive some Cape Cod septage. A compilation of this information indicates that the 15 Cape Cod towns generate about 59 million gallons of septage per year. These quantities are summarized in Table 3-1. The three District towns are responsible for about one-half of the total volume treated at Tri- Town. The Tri-Town plant handles about 18% of all the septage generated on Cape Cod A 3-3 Wright-Pierce

22 FIGURE A 3-4 Wright-Pierce

23 TABLE 3-1 CURRENT SEPTAGE QUANTITIES Town or Region Septage Quantities (million gallons per year) Orleans 2.62 Brewster 1.94 Eastham 1.12 Subtotal--District towns 5.7 Other towns using Tri-Town plant 5.1 Subtotal--Received at Tri-Town 10.8 Remainder of Cape Cod towns 48.5 Cape-wide Total PER-CAPITA QUANTITIES OF SEPTAGE As a basis for projecting future septage quantities, we have calculated the per-capita generation rate where sufficient data allow that computation. The best data are available from the District staff and indicate the following: Orleans 385 gallons per capita per year Brewster 198 gallons per capita per year Eastham 201 gallons per capita per year It is difficult to compute similar figures from other Cape towns because of cross-town disposal practices and incomplete records. We have estimated figures for certain other towns and they fall in the range of 140 to 385 gallons per capita per year. The Cape-wide average is 270 gallons per capita per year, including the three District towns. It should be recognized that these figures are only rough indicators. Each town has different demographics and development patterns. The per-capita septage figures would be expected to be higher in towns that have: newer development (newer homes have larger septic tanks than older homes); higher-than-average commercial development; more property owners that recognize the benefits of regular septic tank pumping; and a lower percentage of seasonal homes (which are pumped less often than year-round homes) A 3-5 Wright-Pierce

24 The relatively high per-capita figure for Orleans is probably most influenced by Orleans' more intense commercial development compared with Brewster and Eastham, and the Board of Health "reminder letters" to property owners who have not pumped in the last three years. 3.5 PER-CAPITA QUANTITIES OF LIQUID SLUDGE Additional treatment (beyond a simple septic tank) creates more sludge for disposal. We have found very little data to estimate the sludge production from cluster and satellite plants. A theoretical analysis, with some in-the-field data, supports an estimate of about 25% higher than a simple septic-tank-and-leaching-field system. Our projections are based on annual per-capita quantities of 300 gallons for individual systems and 375 gallons for cluster and satellite plants. 3.6 POPULATION PROJECTIONS We began our analysis using build-out projections compiled by the Cape Cod Commission in Each town's projection was submitted to that town's representative to the County Wastewater Implementation Committee (WIC) for review and updating. Table 3-2 shows the build-out population estimates resulting from that process. For "current" populations, we have used the Census figures for 2000 unless a town representative provided more accurate information A 3-6 Wright-Pierce

25 TABLE 3-2 POPULATION PROJECTIONS Town or Region Current Build-Out Orleans 7,000 11,000 Brewster 10,100 12,900 Eastham 5,600 8,900 Subtotal--District towns 22,700 32,800 Other Lower Cape towns 9,600 11,200 Subtotal 32,300 44,000 Remainder of Cape Cod towns 200, ,200 Cape-wide Total 232, ,200 The Lower Cape towns expect a 36% increase in population through build-out, compared with a 20% increase for the remainder of the Cape towns. 3.7 REGIONAL SEWERING SCENARIOS Each town's WIC representative was asked to develop three scenarios of possible future municipal wastewater infrastructure. Scenario A is intended to portray substantial reliance on individual systems. Scenario C is intended to depict an aggressive public sewering program. Scenario B is intermediate to Scenarios A and C. The percentage of build-out population served by public sewerage (cluster, satellite and central) for the three scenarios is summarized in Table FUTURE QUANTITIES OF SEPTAGE AND LIQUID SLUDGE By applying the per-capita figures noted above to the projected population served by individual on-site, cluster/satellite and centralized facilities, we have computed the expected septage and liquid sludge quantities shown in Table A 3-7 Wright-Pierce

26 TABLE 3-3 OVERVIEW OF REGIONAL SEWERING SCENARIOS Town or Region Percentage of population served by public sewerage Scenario A Scenario B Scenario C Orleans Brewster Eastham Subtotal--District towns Other Lower Cape towns Subtotal Remainder of Cape Cod towns Cape-wide Total TABLE 3-4 FUTURE QUANTITIES OF SEPTAGE AND LIQUID SLUDGE Septage and Liquid Sludge Quantities (million gallons per year) Region Scenario A Scenario B Scenario C District towns Other Lower Cape towns Remainder of Cape Cod towns Cape-wide Total For the three District towns, the combined septage and liquid sludge quantities range from 9.9 million gallons per year in Scenario A to 10.8 million gallons per year in Scenario C. If one considers all 6 of the Lower Cape towns, the quantities range from 13.1 to 14.1 million gallons per year for Scenarios A through C, respectively. Cape-wide, the projected increase in population served by centralized wastewater plants (most with their own dewatering capacity and ability to handle their towns' septage) largely offsets the increase in volumes associated with cluster/satellite plants, resulting in only a minor increase in the quantities of septage and liquid sludge across the three scenarios. Most of the increase from 10461A 3-8 Wright-Pierce

27 current conditions through build-out is associated with population growth and assumed more frequent pumping. 3.9 SENSITIVITY ANALYSIS These quantity estimates are based on a number of assumptions. The assumptions that have the most impact on the final quantity estimates are: The degree of sewering to central facilities that have their own sludge dewatering systems, The per-capita liquid sludge quantities from cluster and satellite plants, and Possible changes in pumping frequencies due to better public awareness. To determine the impact of these three factors, we re-computed the Cape-wide quantities for a scenario involving a 10% lower sewered population, a 20% higher per-capita generation rate for cluster and satellite plants, and a 10% increase in per-capita septage generation. The impact of these three factors, combined, is a 11% to 13% increase in the volume of septage and liquid sludge requiring disposal at Tri-Town and other facilities equipped to handle these materials CAPACITY OF EXISTING SEPTAGE AND WASTEWATER FACILITIES The Tri-Town facility is licensed to discharge 45,000 gallons per day. It is not appropriate to compute the annual capacity by multiplying the daily capacity times 365. Due to the seasonal variability in septage flows, plants can be at capacity in the summer and be well below capacity in the winter. This seasonality must be considered in planning for septage management capacity. Given many years of operating experience, the Tri-Town staff believes that the plant can handle about 12 to 14 million gallons per year, considering slow winter periods and the need for major maintenance activities. Managing the seasonal variations, through such measures as pricing incentives, may allow a high annual volume to be received. The current District pricing policies have already been effective in this regard. Cape-wide, the two septage-only treatment facilities and the five centralized wastewater treatment plants have a combined capacity for septage handling of approximately 70 million gallons per year. Private septage facilities in the Taunton area also have capacity that is used by Cape Cod septage haulers POSSIBILITY OF TRI-TOWN EXPANSION Our analysis indicates a build-out septage/sludge volume of about 11 million gallons per year for the three District towns. These projections lead to the conclusion that added capacity is not needed at the Tri-Town facility for some time; see Figure 3-2. The three District towns now account for only 50% of the septage received, and future growth in the quantities from Orleans, Brewster and Eastham can be accommodated by either using current excess capacity or through reductions in volumes received from non-district towns. That being said, with proper planning 10461A 3-9 Wright-Pierce

28 and long-term agreements, an expansion of the Tri-Town facility to handle all of the Lower Cape could be a viable plan that provides benefits to both the District towns and others. Such an expansion would be most attractive if the Town of Orleans, either alone or with one or both District towns, chooses to upgrade the plant to handle wastewater generated from limited sewering. In that case, the existing septage handling processes would be modified and upgraded to be able to treat both sludge from the wastewater process and septage, and added capacity would be achieved quite cost-effectively. While it would not be wise to embark on an expansion at Tri-Town at this time, it is prudent to at least consider the site needs associated with an expansion. Section 4 presents a site layout associated with an increase in capacity from 45,000 gpd to 60,000 gpd A 3-10 Wright-Pierce

29 FIGURE 3-2 ESTIMATES OF SEPTAGE AND SLUDGE QUANTITIES 59 Cape Wide Total Tri-Town Plant Capacity FIGURE 3-2 Wellfleet Truro P-town Orleans Brewster Eastham Current A B C Build-Out Scenario Million Gallons per Year 10461A 3-11 Wright-Pierce

30 SECTION 4 SITE CAPABILITY FOR WASTEWATER TREATMENT AND DISPOSAL 4.1 OVERVIEW The evaluation of septage quantities summarized in Section 3 indicates that the undeveloped portions of the Tri-Town site are not likely to be needed for expansion of the septage treatment and disposal facilities. Should the Town of Orleans implement a public sewer system, the significant upland areas of the Tri-Town site may be suitable for wastewater treatment, effluent disposal or both. In general, for a given wastewater flow, the site area needed for effluent disposal is much greater than for wastewater treatment. There are four broad issues to be addressed in determining the capability of the site for expanded effluent disposal: Providing sufficient horizontal area of soils suitable for effluent disposal, Providing sufficient depth to groundwater so that the groundwater mound below the effluent application area is within standards, Determining the direction of flow of the groundwater impacted by the effluent, and Assessing the environmental impacts of the contaminants carried by the groundwater when they reach surface waters. The first three of these issues are addressed in this section of the report. The fourth is the focus of on-going studies performed by the Massachusetts Estuaries Project (MEP). The ability to assess the suitability of the Tri-Town site for effluent disposal has been enhanced by a Barnstable County program. The County has provided funding that allows the application of the regional groundwater model developed by the United States Geologic Survey (USGS) to aid specific effluent disposal investigations by Cape Cod towns. The USGS model was used to help address groundwater mounding and regional flow directions at the Tri-Town site, the second and third issues noted above. 4.2 USGS MODELING OF REGIONAL GROUNDWATER FLOW Modeling Scenarios The USGS model was developed to predict the interaction of groundwater withdrawals (such as pumping of water supply wells) and groundwater recharge from septic systems and municipal wastewater disposal facilities. The model predicts groundwater flow directions and identifies groundwater divides. Earlier model outputs form the basis for the watershed delineations used in the MEP modeling of nitrogen loads and embayment impacts A 3-12 Wright-Pierce

31 The USGS model is regional in nature, and its use is no substitute for site-specific hydrogeologic investigations. Nonetheless, it is useful in broad planning. For the purposes of this study, USGS staff was asked to model four scenarios representing a broad range of uses of the Tri-Town site. We developed a preliminary layout of prospective rapid infiltration beds located all across the higher elevations of the Tri-Town site. We also considered effluent disposal on two nearby parcels to generate a relatively high estimate of future total effluent volume, to try to simulate a "worst case" situation with respect to regional impacts. Figure 4-1 shows the two general application areas: Area A on the Tri-Town site itself and Area B on two adjacent parcels to the south. (We had previously proposed considering the land around the nearby radio tower as a potential effluent disposal site. The depth-to-groundwater mapping provided by the Town indicates that this site is not feasible due to shallow groundwater, and it has been dismissed from further consideration.) The four principal scenarios that were modeled by USGS span a broad range of effluent flow rates in gallons per day (gpd), as follows: Scenario 1 45,000 gpd at the Tri-Town site (Site A) Scenario 2 500,000 gpd at the Tri-Town site (Site A) Scenario 3 330,000 gpd at sites just south of the Tri-Town site (Site B) Scenario 4 830,000 gpd combined at Sites A and B 10461A 3-13 Wright-Pierce

32 FIGURE A 3-14 Wright-Pierce

33 Scenario 1 represents the existing Tri-Town plant discharging year-round at the maximum flow allowed under the District's groundwater discharge permit. The flow rates for Scenarios 2, 3 and 4 are based on relatively high loading rates for rapid infiltration facilities, or alternative methods, fully utilizing the horizontal extent of Sites A and B. As with Scenario 1, the USGS modeling is based on the noted daily flow applied 365 days per year Results The USGS staff produced particle tracking maps to illustrate the model's predicted flow paths and travel times, as well as a tabular summary of the estimated quantities ultimately discharged to each sub-embayment. Figures 4-2 through 4-5 correspond directly to the four scenarios described above. We have noted the USGS scenario designation in the title block of each figure so that the source of this information is clear. We have prepared Table 4-1 to summarize the key results of this modeling. It shows the apparent plume width at the Cape Cod Bay shore, and the distribution of discharge volume among the four watersheds and sub-watersheds that eventually receive the effluent-impacted groundwater. The USGS model indicates that the plume from the existing plant, operating at capacity, will eventually reach Cape Cod Bay along about 3,000 feet of its shoreline. Slightly over half of the impacted groundwater will surface in the Namskaket Creek watershed, with most of that impacting the Upper Namskaket sub-watershed. As the volume of recharged effluent increases, the predicted plume is subject to more spreading as it progresses toward the Bay. With 830,000 gpd discharged at the "expanded" Tri-Town site, the impacted groundwater extends from Namskaket Creek all the way to a point just beyond the outlet of Rock Harbor. Even in this most extreme scenario, all of the impacted groundwater still discharges to the Bay, and not to Town Cove and the Nauset Estuary system A 3-15 Wright-Pierce

34 FIGURE A 3-16 Wright-Pierce

35 FIGURE A 3-17 Wright-Pierce

36 FIGURE A 3-18 Wright-Pierce

37 FIGURE A 3-19 Wright-Pierce

38 TABLE 4-1 SUMMARY OF PRELIMINARY USGS MODELING Scenario Number Effluent Application, gal/day Application Site Mound Height, ft Plume Width at Cape Cod Bay, ft Upper Namskaket Discharge Volume, gal/day, to Lower Little Namskaket Namskaket Cape Cod Bay 1 45,000 A Less than 5 3,000 21,900 2,500 1,400 19, ,000 A Less than 5 5, ,000 37,000 83, , ,000 B Less than 5 3, ,000 27,000 7, , ,000 A Less than 5 330,000 B Less than 5 830,000 A + B 7, ,000 51,000 91, ,000 Notes: Site A Site B Current Tri-Town site Areas adjacent to Tri-Town site, to the south 10461A 3-20 Wright-Pierce

39 Because the adjacent prospective discharge sites (Site B) are closer to the main channel of Namskaket Creek, the Scenario 3 model run predicts a significant increase in the percentage of the total plume going to this watershed. (About 50% of the plume surfaces in the Namskaket Creek watershed in Scenarios 1, 2 and 4. In Scenario 3, that figure rises to 66%.) The added flow at the current site (Scenario 2) causes a drastic increase in the ultimate discharge to the Little Namskaket watershed, while the discharge at Site B alone (Scenario 3) has only a minor impact on the flow to that watershed. Figures 4-2 through 4-5 depict the approximate groundwater travel time. Some of the groundwater impacted by the current plant is predicted to surface in 5 to 10 years, while it will take 50 to 100 years for the plume to reach Cape Cod Bay. Note that the higher effluent application rates increase the groundwater velocity and cause the impacted groundwater to reach specific downgradient points sooner than with the lower application rates Caveats As noted by USGS, it is important to remember that the USGS model is relatively "coarsegrained" with respect to the specific topographic and soil conditions in the vicinity of the Tri- Town site. Therefore, all of these modeling results are quite approximate. Detailed site investigations and site-specific modeling will be needed if the Town or District decides to move ahead with increased effluent loading at this site. As part of the Orleans Comprehensive Wastewater Management Plan (CWMP), studies will be needed to address a number of assumptions used in this analysis, such as the specific loading area and rate. Nonetheless, this work by USGS is helpful to establish a broad framework for these possible later studies. Similarly, the effluent flow rates selected as model inputs represent the likely high end of the loading rates that will be acceptable at these sites, given design setbacks, possible pockets of poor soils and other factors. 4.3 MOUNDING ANALYSIS Under subcontract to Wright-Pierce, GZA Geo-Environmental conducted an analysis of the mound height that can be expected below the effluent disposal areas on the Tri-Town site. These calculations used soil and groundwater characteristics reported by USGS from both the longterm studies of Namskaket Marsh and the more recent regional groundwater modeling. Using the most recent hydraulic parameters developed by USGS, and standard engineering practices as reported in Appendix B, the groundwater mound is expected to be less than 10 feet in height. In the area selected for effluent disposal, the current depth to groundwater is over 30 feet. Given that the water table should not be allowed to rise any closer to the surface than 4 or 5 feet, this analysis indicates that excessive mounding should not be a problem. In preparing the mounding analysis, GZA noted inconsistencies among the information reported from the USGS's Namskaket Marsh studies, the input parameters used in the regional USGS model, and the actual mound from on-going operations. It is not within the scope of this study to address and resolve these issues, but it will be important to address these inconsistencies as part of any detailed hydrogeologic studies at the Tri-Town site A 4-21 Wright-Pierce

40 4.4 SITING OF A WASTEWATER TREATMENT FACILITY Even though no formal wastewater planning has occurred in Orleans, the Town has asked that this study consider the general feasibility of siting a wastewater treatment plant on the Tri-Town site. Figure 4-6 shows a conceptual layout of a wastewater treatment plant sized to handle 0.5 million gallons per day (mgd) and designed to meet tertiary standards (10 mg/l effluent total nitrogen with disinfection). The sludge created in the treatment process would be thickened and dewatered at the existing septage facility and hauled off site with the dewatered septage. We have assumed that treatment would be provided with sequencing batch reactors (SBR) technology, based on an analysis reported in Appendix C A 4-22 Wright-Pierce

41 FIGURE A 4-23 Wright-Pierce

42 The following points should be noted: 1. The SBR technology that is the basis of this layout requires a relatively small amount of space. Most other technologies require more space, but there are others that have a somewhat smaller footprint. 2. We have selected the portion of the site east and north of the existing septage plant for several reasons. The topography of the site here would allow gravity flow to effluent disposal beds, and this location would optimize the set back from adjacent homes north and south of the site. 3. It is possible to site a wastewater treatment plant of this size on the south side of the existing tanks and buildings, but with more site development costs and limited buffer from existing homes. 4. The layout shown would allow the compost shed to remain for other uses. 5. A facility larger than 0.5 mgd could be sited here provided that effluent disposal is elsewhere. These paragraphs of Section 4.4 consider only wastewater treatment and not wastewater disposal. Other part of this report section address effluent disposal. Taken together, these evaluations give us some of the basic building blocks to assemble the optimum mix of treatment and disposal. 4.5 SITE DEVELOPMENT SCENARIOS Possible Uses Of Tri-Town Site The Town of Orleans has identified three possible uses for the Tri-Town site: 1. Septage treatment and disposal, as has been conducted there since 1986; 2. Wastewater treatment and/or disposal; and 3. Public works functions in and around the abandoned compost shed. These uses can be complementary. However, at some scale, the public works functions would limit the amount of wastewater treatment and disposal that the site can accommodate Siting Considerations Many factors must be considered in determining the most appropriate use of the site for the three designated functions. These factors include: 10461A 4-24 Wright-Pierce

43 1. The level of wastewater and septage treatment needed to protect receiving waters (principally Namskaket Creek and Marsh). 2. The capacity of the existing septage treatment and disposal facilities. 3. The size of a wastewater treatment facility that could be located there, as well as the site's ability to receive and disperse the effluent from such a facility. 4. The extent of the public works operations that might be located there. 5. The provisions of buffers between the activities on site and the adjacent (largely residential and commercial) land uses. 6. Availability of nearby sites for either wastewater treatment, wastewater disposal, or both. At Town Meetings in 2004, Orleans, Brewster and Eastham agreed that Orleans could use one or both of two parcels on the Tri-Town site for public works functions. These were called Parcel 1 (at the northerly corner of the site, where the compost shed is located), and Parcel 1A, immediately to the south of Parcel 1 along the Route 6 right-of-way; see Figure 4-6. The Town of Orleans has deferred any decisions on the use of these parcels pending the completion of this investigation Broad Options This investigation has focused on the following broad options for septage and wastewater management: Option 1--Upgrading the existing septage treatment facilities to extend their useful life by 20 years, without any increase in capacity or treatment level. Option 2--Extending the service life by 20 years and providing nitrogen removal to a 10- mg/l limit, without increasing the capacity. Option 3--Extending the service life, proving nitrogen removal, and increasing the capacity from 45,000 gpd to 60,000 gpd. Option 4--Improving and expanding the septage facility as described in Option 3 and building facilities for wastewater treatment and/or disposal. There are many possible sub-options related to wastewater treatment and disposal. These are shown in Table 4-2, along with the septage options. Table 4-2 shows, for each option and suboption, the assumptions with respect to treatment capacity, level of treatment, use of Parcel 1 and 1A for public works functions, and use of adjacent sites for effluent disposal Discussion Of Options Most of our efforts in this study have been directed at determining the feasibility and constraints associated with these options. In the paragraphs that follow, we outline our findings A 4-25 Wright-Pierce

44 Option 1--Upgrading To Extend Life of Existing Facilities. There are no identified plant improvements that require additional land at the site. In this option, Parcels 1 and 1A could be used for public works activities without compromising the value of the site for septage management purposes. Option 2--Upgrading To Extend Life and Meet More Stringent Effluent Limits. The existing septage treatment facilities could be easily upgraded with denitrification filters to meet a 10-mg/l total nitrogen standard. These new facilities would be located in an expansion of the disinfection building, as shown on Figure 4-6. With respect to other uses of the overall site, these new facilities and the building housing them would have no appreciable impact on the use of the remainder of the site for public works functions or for wastewater treatment and disposal. Option 3--Upgrading To Extend Life, Meet More Stringent Effluent Standards and Increase Capacity. Our evaluation of the existing plant indicates that nearly all unit processes have the ability to handle additional septage volumes, with only minor upgrading needs. The only exception is effluent disposal. Figure 4-6 shows an additional set of rapid infiltration basins that should be more than adequate to handle the assumed one-third increase in capacity. (If the Town and District were to proceed with this option, we recommend that a full-scale loading test 10461A 4-26 Wright-Pierce

45 TABLE 4-2 SUMMARY OF SITE DEVELOPMENT SCENARIOS Use of Parcels 1 & 1A for Septage Flow, Wastewater Flow, Effluent N, Treatment or Disposal Effl. Disposal Location No. Description gpd mgd mg/l Parcel 1 Parcel 1A On Site Off Site 1 Upgrade existing plant to extend life 45, No No Yes No 2 Upgrade existing plant to extend life and to meet Class I discharge 45, No No Yes No 3 Option 2 plus added 15,000 gpd flow 60, No No Yes No 4 Option 3 plus new wastewater plant Preserve Parcels? Treatment 1 1A On Site? A Yes Yes Yes 45,000 Not feasible 10 No No Yes No B Yes --- Yes 45, to No Yes Yes No C Yes 45, to Yes Yes Yes No D Yes Yes , to No No Yes No E Yes , to No Yes Yes No F , to Yes Yes Yes No G Yes Yes , to No No Yes Yes H Yes , to No Yes Yes Yes I , to Yes Yes Yes Yes 10461A 4-27 Wright-Pierce

46 be conducted on the existing basins to determine their full capacity. It is conceivable that no additional basins are needed. It is also possible that surface plugging of the existing basins may have reduced their capacity and that more than one third of additional capacity is needed. We have shown a 50% increase in Figure 4-6 to address that conservative assumption.) Option 4--Expand and Upgrade Septage Facilities and Build New Wastewater Facilities. Table 4-2 lists nine sub-options for wastewater treatment and disposal depending on the use of Parcels 1 and 1A, the use of the site for both wastewater treatment and wastewater disposal, and the use of nearby land. Three of these sub-options are illustrated in Figure 4-7. For the feasible options, Table 4-2 lists our estimates of effluent disposal capacity. These estimates are based on the assumption that low permeability soils are not present (or are sufficiently limited in extent to be removed cost-effectively), and that the soils are suitable for application at the rates ranging from 4.0 to 4.75 gpd per square foot. (The higher figure is the design loading rate for the existing rapid infiltration basins.) Options 4A, 4B, and 4C are based on a wastewater treatment plant at the Tri-Town site. From our perspective, the best location on the site for a wastewater treatment plant is the approximate location of Parcel 1A. That location maximizes the distance to the residential developments to the north and to the south. It also allows the effluent disposal to be consolidated to the south of the existing septage treatment facility, and permits gravity flow to them. With the wastewater treatment plant on Parcel 1A, the site would accommodate about 300,000 gpd of effluent treatment and disposal with Parcel 1 set aside for public works uses (Option 4B), or about 500,000 gpd if Parcel 1 were available for effluent disposal (Option 4C). These two sub-options are portrayed in the upper panels of Figure 4-7. In Option 4A, both Parcels 1 and 1A would be set aside for public works functions. The remaining space on site, although technically large enough to site a wastewater treatment plant, is not well located with respect to nearby residential development, and it would be quite limited in effluent disposal capacity. Therefore we view this option as less than ideal, without the use of off-site parcels for effluent disposal A 4-28 Wright-Pierce

47 FIGURE A 4-29 Wright-Pierce

48 The wastewater flow rates shown in Table 4-2 represent the short-term peak flows for which effluent disposal facilities are designed. They do not reflect average flows that might be received from a sewer service area. Logical assumptions on the possible extent of sewering (based on early MEP assessments and experiences of other towns) lead to both average and peak flows above the figures shown for Options 4B and 4C. Therefore we have also included in Figure 4-7 the layout of Option 4F. If Parcels 1 and 1A were made available for effluent disposal, and the wastewater treatment plant were located elsewhere, we estimate that up to 750,000 gpd could be disposed of at the Tri-Town site, subject to all the assumptions listed earlier. Use of nearby lots for effluent disposal is quite conjectural due to ownership issues and lack of soils data. Nonetheless, we have included in Table 4-2 Options 4G, 4H and 4I with effluent disposal capacity of up to 1.0 mgd. These options are based on the disposal areas and assumptions of Options 4D, 4E and 4F, plus an estimated 150,000 to 200,000 gpd of nearby offsite capacity. As noted in other portions of this report section, modeling by USGS shows that use of off-site disposal locations to the south increases the relative flow to the Namskaket Creek watershed, compared with disposal locations on the current Tri-Town site. We have based this evaluation on the use of rapid infiltration beds for effluent disposal, the same technology currently in use at the Tri-Town site. There are other emerging effluent disposal techniques that use less space that should be considered in future site planning. For example, effluent "wicks" are vertical cylinders of highly permeable gravel or crushed stone that require only a fraction of the "footprint" of rapid infiltration beds. If detailed site investigations show suitable soils and depth to groundwater, and with special DEP approval, wicks would allow higher effluent disposal volumes than presented above. Alternatively, use of wicks might allow the site to accommodate about 0.75 mgd (the same as Option 4F) while preserving the compost shed on Parcel 1. Wicks might be particularly applicable on the adjacent sites to the south A 4-30 Wright-Pierce

49 4.5.5 Conclusions We can draw the following conclusions from this analysis: 1. The Tri-Town site is more than adequate for septage treatment and disposal, even if more stringent effluent limits are imposed by DEP and the facility is expanded by one third. 2. If the disposal of wastewater effluent is determined to be the best use of the Tri-Town site, a rapid infiltration system with capacity of about 0.75 million gallons per day could be located there, assuming that the wastewater treatment plant would be sited elsewhere. 3. If the Town of Orleans decides to use Parcel 1 and Parcel 1A for public works functions, the remaining site is not ideal for both wastewater treatment and disposal in addition to the septage facilities. 4. If only Parcel 1 (including the existing composting shed) is used for public works functions, Parcel 1A could be used for a 0.5-mgd wastewater treatment plant, and the remaining site would be adequate for effluent disposal of that volume. 5. Although there are no large suitably-located sites in close proximity to the Tri-Town site, there is some vacant land nearby that might be appropriate to supplement the effluent disposal needs. Conclusions 2 through 5 are based on the assumptions detailed elsewhere in this report. These include the assumption that receiving water impacts are not significant at the flows involved, and that surficial soil characteristics are not limiting. These conclusions stem from this "table-top" evaluation, and must be confirmed or modified by later more detailed investigations. Section 9 of this report outlines important implementation steps the Town and District should undertake to move forward with some or all of the possible uses of the Tri-Town site. 4.6 ORLEANS SEWERING SCENARIOS As one of the principal goals of this study, we have investigated the capacity of the Tri-Town site to accommodate both wastewater treatment and effluent disposal facilities. We have shown that the site might accommodate a wastewater treatment plant of 500,000 gpd capacity (average flow) or expanded rapid infiltration beds of 750,000 gpd capacity (peak flow). These estimates are based on a number of assumptions about site soils and receiving water impacts, and they have not been linked to any specific plan for public sewers in Orleans. While sewering plans must be based on a detailed needs assessment (an early phase of the CWMP which must wait for the completion of the MEP studies), it would be helpful to lay out some hypothetical sewer options to compare with the estimated capacity of the Tri-Town site A 4-31 Wright-Pierce

50 It has been suggested that sewers are needed in the downtown area of Orleans, where the densest development has occurred and where the Town might choose to encourage further "village center" growth. Based on MEP reports on other embayments, and on early discussions with MEP staff, there is also the potential need for sewers to control nitrogen loading, especially in the Pleasant Bay watersheds. With that background, we have outlined three potential future sewering scenarios, and estimated the likely wastewater flows using data from our prior work on Orleans' nitrogen loading model. The three scenarios are as follows: Scenario 1. Sewers in the downtown area. We have assumed that the wastewater flow from this area can be estimated by adding 100% of the commercial flow and 25% of the residential flow in the Town Cove, Rock Harbor and Little Namskaket watersheds. With these assumptions, the build-out average flow would be approximately 490,000 gpd during the summer months, with a short-term peak flow of about 750,000 gpd. These estimates are very close to the capacity of the Tri-Town site. Scenario 2. Sewers to control nitrogen in the upper Pleasant Bay watersheds. We have considered a scenario that involves reducing the nitrogen load from septic systems by 70% in those watersheds that impact the upper Pleasant Bay watersheds (Arey's Pond, Arey's River, Lonnie's Pond, Meetinghouse Pond, Pah Wah Pond, Pochet Inlet and The River). In this case, the summer average flow at build-out would be 490,000 gpd, and the short-term peak flow would be about 660,000 gpd. These estimates are close to the capacity of the Tri-Town site. They do not include any flows from the Brewster portion of the noted watersheds. Scenario 3. Sewers to control nitrogen in the Nauset Estuary system. If sewering were required to provide 40% removal of nitrogen from septic systems in the Town Cove and Nauset Inlet embayments, we estimate an average build-out flow of about 300,000 gpd during the summer months, and a short-term peak flow of about 460,000 gpd. These figures represent about 60% of the capacity of the Tri-Town site. While we have not considered flows from the Eastham portions of these watersheds, it appears that the Tri- Town site might also accommodate the flows from the Eastham portion of the Town Cove watershed. Figure 4-8 shows the watersheds and zoning districts associated with these three scenarios. Note that these three scenarios for sewers in Orleans are unrelated to the regional sewering scenarios presented in Section 3. Many assumptions have been made to compute the figures reported above, just as the Tri-Town site capacity estimates involve numerous assumptions. Therefore, these flow estimates for the selected scenarios should be viewed as rough indicators, not definitive predictions. Nonetheless, it should be helpful to the Town to know that the Tri-Town site may have capacity for treatment and disposal of the wastewater associated with each of these scenarios (individually, but not collectively). This conclusion should help guide the scoping of the upcoming Comprehensive Wastewater Management Plan. The actual need for sewers, and the necessary extent of public sewerage, will be determined by that planning process. The scenarios presented above are not 10461A 4-32 Wright-Pierce

51 intended to predict the outcome of that planning process; instead they merely help frame our conclusions with respect to Tri-Town site capacity. 4.7 COORDINATION WITH LONG-TERM USGS MARSH MONITORING During the course of this study, Wright-Pierce met with the staff of the USGS to coordinate activities with both the County-sponsored use of the regional groundwater flow model, and the long-term USGS monitoring of the Tri-Town plume and Namskaket Marsh. The USGS staff gave us an overview of the findings of USGS s evaluation of the Tri-Town plume, somewhat of a preview of what will later be formally published. USGS has determined that the Tri-Town 10461A 4-33 Wright-Pierce

52 FIGURE A 4-34 Wright-Pierce

53 plume is moving in a northwesterly direction toward Namskaket Creek. There is evidence of a clay layer that dips downward from the Tri-Town site toward the marsh. The plume seems to have taken on a mitten shape. The smaller portion (the thumb ) is above the clay layer, and that portion of the plume has been detected below the marsh and is potentially rising upward toward Namskaket Creek. The hand portion of the mitten seems to be confined below the clay layer, and may eventually pass under the Creek. USGS does not have sufficient information concerning the downgradient extent of the clay layer to be able to predict if the hand will reach surface waters within the Namskaket Creek watershed, in other downgradient watersheds, or in Cape Cod Bay. These findings may be very important to wastewater planning in Orleans. If some of the Tri- Town plume, and perhaps the septic-system-impacted groundwater in the Namskaket Creek watershed, pass below this clay layer to Cape Cod Bay, then the control of nitrogen sources here may be of less importance than in other watersheds. In essence, a portion of the Namskaket watershed, at least as currently mapped, may indeed be part of another watershed, or may be tributary to Cape Cod Bay. Given USGS's position that its regional groundwater model is too coarse-grained to effectively account for the local subsurface conditions near the Tri-Town site, steps should be taken to obtain better information on the Namskaket Creek watershed before the MEP begins its modeling of nitrogen loads and receiving water impacts A 4-35 Wright-Pierce

54 SECTION 5 ALTERNATIVE USES FOR COMPOST SHED As discussed in Section 4, there are three potential uses for the Tri-Town site: septage treatment and disposal; wastewater treatment and/or effluent disposal; and public-works-type functions. In 2004, all three District towns voted in favor of allowing a portion of the overall Tri-Town site to be used by the Town of Orleans for public-works-type functions. That area is actually two separately defined parcels, designated as Parcels 1 and Parcel 1A. These two parcels are shown on Figure 4-6, comprise approximately 6 acres, and are located in the northeast corner of the site. The abandoned compost shed is located in the northeast corner of Parcel 1. Both parcels appear to have significant value for public-works-type functions as well as wastewater treatment and effluent disposal uses. As part of this study, we have considered several options for site development of this overall parcel (including Parcels 1 and 1A) as it relates to wastewater treatment and disposal. This analysis also considered the effects of using these two parcels for public works functions in lieu of septage/wastewater treatment and effluent disposal. The general conclusion of our evaluation is that the overall site could be used for a complementary combination of the above named functions, but use of Parcels 1 and/or 1A for public works functions will ultimately limit the amount of wastewater treatment and disposal that the site can accommodate. The details of that evaluation are presented in Section 4. The abandoned compost shed is a substantial structure that represents a significant capital investment. Serious efforts should be made to use that resource and to avoid the costs of demolition. We have considered specific alternative uses for the compost shed and its adjacent area (both Parcels 1 and 1A), and they fall into two general categories as follows: public works uses and uses related to wastewater/septage treatment Many potential options exist for both categories, but we have listed only the potential uses that we feel may be viable considering many factors related to this site. The following is a list of potential public works uses for the compost shed and its adjacent area: 10461A 5-1 Wright-Pierce

55 Vehicle Storage Facility - Town trucks and large equipment items, such as snowplows, sand/salt trucks, backhoes, etc. Miscellaneous Equipment Storage - lawn mowers, snow blowers, etc. Materials Storage - sand, road salt, yard waste, wood chips, loam, mulch, piping, etc. Maintenance Building - servicing or overhaul of vehicles and equipment Administrative Offices The following is a list of potential functions related to wastewater or septage treatment for the compost shed and its adjacent area: Vehicle Storage Facility - pickup trucks, sludge hauler, sewer vactor truck, etc. Materials Storage - pipe, valves, fittings, hydrants, manholes frames and covers, etc. Equipment Storage - lawn mowers, snow blowers, portable engine-driven pumps and generators, etc. Administrative Offices, Laboratory, Maintenance Facility Sludge Stabilization Facilities - composting, high-alkaline stabilization, thermal drying Shelter for a biofilter odor control system While such a substantial structure as the compost shed could be effectively used on many sites for the sludge stabilization and odor control functions listed above, the proximity of residential development would effectively preclude such uses. Similarly, particularly noisy public works functions may not be suitable here because of the extremely short distances to nearby homes. Any of the above noted potential reuse options for the compost shed will require detailed merit, value and cost-effectiveness evaluations prior to actual implementation. As such, it is recommended that the Town of Orleans conduct a detailed Town-wide evaluation of alternatives for new public-works-type functions which would include the Tri-Town site (Parcels 1 and 1A). This should be an independent effort, but must be closely coordinated with the upcoming comprehensive wastewater planning so that the relative value of Parcels 1 and 1A and specific reuse options for the compost shed can be fairly assessed. The optimum decision can only be made when the relative costs and merits of all potential sites are considered A 5-2 Wright-Pierce

56 SECTION 6 UPGRADING RECOMMENDATIONS AND COSTS Section 2 and Appendix A present an appraisal of the existing equipment and facilities. These documents identify a number of upgrading needs. This section of the report contains specific upgrading recommendations and presents estimates of costs associated with those improvements. 6.1 BROAD OPTIONS This investigation has focused on the following options for septage and wastewater management: Option 1--Upgrading the existing septage treatment facilities to extend their useful life by 20 years, without any increase in capacity or treatment level. Option 2--Extending the service life by 20 years and providing nitrogen removal to a 10- mg/l limit, without increasing the capacity. Option 3--Extending the service life, proving nitrogen removal and increasing the capacity from 45,000 gpd to 60,000 gpd. Option 4--Improving and expanding the septage facility as described in Option 3 and building new facilities for wastewater treatment and/or disposal. 6.2 SPECIFIC RECOMMENDATIONS FOR IMPROVEMENTS We have evaluated the capability of each unit process and associated tanks and equipment, and we have developed recommendations on how each unit process should be upgraded to extend its useful life and to improve operability and reduce maintenance needs. The details of this evaluation and the associated recommendations are contained in Appendix C. Table 6-1 summarizes our recommendations. For each unit process or system, Table 6-1 identifies high priority needs under the heading "must" and lower priority items under the heading "could". Such recommendations are made for each of the first three upgrading scenarios. While there are a large number of potential plant improvements, the major upgrading needs are summarized as follows: Repair of the septage receiving equipment, including screening and de-gritting Major overhaul or replacement of the septage dewatering equipment Replacing the shafts and media on two of the four RBCs A 6-1 Wright-Pierce

57 The major upgrading needs all relate to equipment or tanks installed at the time of the original construction in the late 1980s. It is very important to note that Option 2, upgrading to meet a 10-mg/l nitrogen standard, can be accomplished by converting the existing effluent sand filters to denitrification filters and the addition of a methanol feed system. This represents a relatively straightforward modification, compared to the rather lengthy list of improvements needed to extend the facility life. (With conservative sizing of the denitrification filters, they are probably sufficient to meet a 5-mg/l standard, as a long-term average.) Similarly, Option 3, providing a one-third increase in treatment capacity, can be accomplished through the addition of a single set of new rapid infiltration beds adjacent to the existing beds. Again, this represents a relatively straightforward modification, compared to the rather lengthy list of improvements needed to extend the facility life. (As noted in Section 4, a loading test should be conducted on the existing beds to determine if they have the capacity for the additional flow. If so, no new beds would be needed.) The existing disinfection building has adequate space for denitrification filters that would replace the existing sand filters. This space may not be adequate if the denitrification filters must treat 60,000 gpd A 6-2 Wright-Pierce

58 TABLE 6-1 SUMMARY OF UPGRADING NEEDS Option 1 Option 2 Option 3 Function Extend Facility Life Extend Facility Life and Meet 10 mg/l N Limit Septage and Grease Receiving Grit Removal Septage Equalization Septage Thickening Septage Conditioning Septage Dewatering Filtrate Equalization Primary Clarification Rotating Biol. Contactors Secondary Clarification Effluent Filtration Disinfection Effluent Disposal Odor Control Misc. Items Must: Could: Must: Could: Must: Could: Must Could: Must: Could: Must: Could: Replace bar screen or install septage acceptance plant. Increase bay height, provide external hookup. Repair classifier, repair grit pump discharge piping, refurbish wetwell. Replace classifier, install vortex grit system. Assess tank condition. Refurbish as necessary. No action. Replace with Pipeliner TM grinder. Repair cracks in tank wall, remove unused chemical feed equipment. Upgrade controls, replace with liquid polymer feed system. Refurbish presses, contact vendor to assess piston pump condition. Replace drive with hydraulic drive, replace filters and controls with new plate frame or Fournier press, refurbish piston pumps Inspect tanks. Refurbish as necessary. Replace equipment. Connect to odor control system. Replace remaining shafts and media. Replace RBC drives. Nothing beyond Option 1 Nothing beyond Option 1 Nothing beyond Option 1 Nothing beyond Option 1 Nothing beyond Option 1 Nothing beyond Option 1 Extend Facility Life, Increase Flow and Meet 10 mg/l N Limit Nothing beyond Option 1 Nothing beyond Option 1 Nothing beyond Option 1 Nothing beyond Option 1 Nothing beyond Option 1 Nothing beyond Option 1 Must: Could: Nothing beyond Option 1 Nothing beyond Option 1 Must Nothing beyond Nothing beyond Could: Option 1 Option 1 Must: Nothing beyond Nothing beyond Could: Option 1 Option 1 Could: Remove lamella clarifiers. Nothing beyond Nothing beyond Option 1 Option 1 No action. Must: Replace existing Must: Add third denit. filter with denit. filter. filter in bldg. No action. No action. No action. Must: Add new rapid infiltration beds. Must: Evaluate scrubber condition. Nothing beyond Nothing beyond Could: Replace if necessary. Option 1 Option 1 Must: Replace compressor, replace sump pumps, Nothing beyond Nothing beyond repair/replace gate valves. Option 1 Option 1 Could: Plumbing changes to prevent water hammer. Note: Shading indicates those improvements for which costs have been included in Table A 6-3 Wright-Pierce

59 6.3 COST ESTIMATES Capital Costs Table 6-2 summarizes the capital costs of the improvements listed in Table 6-1. For Option 1, upgrading to extend service life, we have segregated the costs into three categories: high priority, medium priority and low priority. For each unit process, the distinctions among the priorities are described in our detailed assessment in Appendix C. The categories are somewhat subjective and incorporate the preferences of plant staff. The estimates in Table 6-2 are presented as expected construction costs for each item. Within each category, an allowance for engineering and contingencies is added to the total cost. Costs are expressed in current dollars. These estimates lead to the conclusion that upgrading the Tri-Town plant to provide an additional 20 years of service life will cost approximately $1.8 million, with about two-thirds of the cost associated with high priority items. Our estimates have been presented in the form of Table 6-2 so that the District can formulate a phased approach to accomplish the improvement program over a multi-year period. Some of the high priority items are more urgent than others. Table 6-2 also shows the moderate additional costs for nitrogen removal and increased plant capacity. Replacing the existing effluent sand filters with denitrification filters, and installing a methanol feed system, can be accomplished for $200,000 to $250,000, assuming no increase in plant capacity. We have carried an additional $100,000 in construction cost for denitrification filters in case the existing space is inadequate and a building extension is needed for the capacity expansion to 60,000 gpd. The costs for an additional set of rapid infiltration basins, including piping, can be accomplished for less than $100,000. Other than the possible need for an extra denitrification filter, this is the only upgrading item for a one-third increase in treatment capacity. Together, these two items indicate a conservative figure of $200,000 to $250,000 as the incremental costs of Option A 6-4 Wright-Pierce

60 TABLE 6-2 SUMMARY OF UPGRADING COSTS Function Costs for Option 1 Added Costs for: Extend Facility Life Option 2 Option 3 High Priority Medium Priority Low Priority Nitrogen Removal Increased Capacity Septage and Grease Receiving 170,000 Grit Removal 50,000 70,000 5,000 Septage Equalization 10,000 Septage Thickening 30,000 Septage Conditioning 20,000 20,000 10,000 Septage Dewatering 270, ,000 15,000 Filtrate Equalization Primary Clarification 90,000 50,000 10,000 Rotating Biol. Contactors 200, ,000 Secondary Clarification 20,000 Effluent Filtration 175, ,000 Effluent Disinfection Effluent Disposal 70,000 Odor Control 5,000 75,000 Misc. Items 35,000 5,000 Subtotal --Construction 840, , , , ,000 Engineering & Contingency 210, ,000 40,000 45,000 45,000 Total $1,050,000 $540,000 $180,000 $220,000 $215,000 All Priorities Option 1 Total $1,770,000 Option 2 Total $1,990,000 Option 3 Total $2,205, A 6-5 Wright-Pierce

61 In some cases, there are several ways to accomplish the upgrading need. We have described all of the options and presented the cost of the most likely one. More detailed evaluation of these options is warranted when the District decides to proceed with upgrading. The most significant options include alternative dewatering equipment (instead of upgrading the existing plate-andframe presses) and a proprietary "sludge acceptance plant" (instead of improvements to the individual septage receiving and de-gritting processes). Some thought has been given to opportunities for re-using the original chemical building. Costs have not been included for that task, but the opportunities presented by that un-used structure should be considered in any upgrading plan, or if a new wastewater facility is constructed Annual Operating and Maintenance Costs Available records were used to summarize and project forward the District's costs for annual operation and maintenance (O&M). We expect that there should be no significant change in O&M costs in Option 1 where the service life of the facility is increased by 20 years. In Option 2, provision of denitrification facilities, the O&M costs should increase only for chemicals (addition of methanol or other carbon source). This should add only 1 to 2% to the overall O&M budget. If the septage facility is expanded by one third, Option 3, there will be increases in all categories of variable costs (labor, power, chemicals, etc.). We estimate that the overall budget would increase by 15% to 20%. It should be noted, however, that the cost per gallon in Option 3, would actually decline by about 10% due to economies of scale. 6.4 CONCLUSIONS We can draw the following conclusions from this analysis: 6. Although the Tri-Town plant is well operated and maintained, some of the equipment (principally that dating from the original 1980's construction) is nearing the end of its useful life. 7. In the relatively near future, the District should begin to implement our recommendations to extend the facility's useful life. These improvements could be done as a single project, or could be accomplished in a series of phases to spread the cost impact over several years. In the aggregate, these proposed upgrading steps will cost about $1.8 million. An allowance for inflation should be considered for those items deferred for more than one year. 8. When the DEP Groundwater Discharge Permit is renewed in 2007, DEP could impose more stringent limits on effluent nitrogen, which would necessitate the addition of denitrification filters. The costs of this improvement are relatively small (less than $0.25 million, in current dollars) compared to the improvements recommended to extend the facility's useful life A 6-6 Wright-Pierce

62 9. Septage and liquid sludge quantities will increase due to community growth, more frequent pumping, and the installation of cluster and satellite wastewater plants. If these trends, or the formal inclusion of other towns, create the need for a capacity expansion, it can be accomplished through the addition of rapid infiltration beds and expansion of the denitrification filters at moderate cost (less than $0.25 million). The implementation of these upgrading recommendations involves a number of inter-related steps; see Section 9 of this report. While there appear to be no imminent "emergency" repair needs, the systems targeted for upgrading are approaching 20 years old. Given the time needed to design, permit and construct improvements, the Town and District should begin the early steps in the process concurrent with the Town's comprehensive wastewater management planning A 6-7 Wright-Pierce

63 SECTION 7 CONTROL OF ODOR AND NOISE Section 2 of this report summarizes our appraisal of the existing septage treatment facility and Section 6 presents recommendations and costs for plant upgrading. Section 4 outlines site development options, including the siting of a wastewater treatment plant. Proper control of noise and odor is integral to all three subjects: the operation of the existing facilities, the upgrading of those facilities, and the possible construction of a wastewater plant. This section summarizes the odor and noise control issues. 7.1 ODOR CONTROL The Tri-Town facility was originally provided with a two-stage wet chemical scrubber followed by dual activated carbon scrubbers for polishing of the wet chemical scrubber exhaust. Odorous air from the septage receiving tanks, filtrate tanks, receiving garage, dewatering room and sludge garage is collected and discharged into this system. As part of the 1995 upgrading, a new two-stage wet chemical scrubber system was installed, followed by a new carbon adsorption system. This 3,100-cfm system treats odorous air from the new filtrate tanks, the thickener room, the new grease tanks, and the existing septage conditioning tanks. In its early years of operation, the Tri-Town facility received numerous odor complaints. With the cessation of on-site composting, and improved operational control, odor complaints have been significantly reduced. In recent years, odor complaints have become rare, and when odor emissions do occur, they are usually related to equipment malfunction or other un-expected events. Given the good track record, we recommend that the plant staff continue to give the very high priority to odor issues that has been recently successful. The recommended upgrading plan includes an analysis of the existing large wet scrubber, followed by repairs or replacement as necessary. When that work is performed, it would be wise to consider expanding the exhaust air collection system to include the flow distribution structure to the primary clarifiers and the primary clarifiers themselves. The existing system may have the air flow and odor removal capacity to accept the new air flow and odor load that would be generated from these sources. Odor control will be a key component of the potential addition of a wastewater treatment facility. Odor control technologies that should be considered as part of that project for this site include the following: 10461A 7-1 Wright-Pierce

64 Biofilters Wet Packed-Tower Chemical Scrubbers Wet Mist-Type Chemical Scrubbers Carbon Adsorption Scrubbers Biofilter systems are typically operated without the use of chemicals, are "low profile" and represent a reliable system for odor control. Biofilters can be designed and constructed as customized processes, or can purchased and installed as modular pre-engineered systems. With wet scrubbers, both mist and packed-tower arrangements are very effective in odor removal and are also very reliable. These systems come in all shapes and sizes from vertical to horizontal configurations to interior and exterior installations. Carbon adsorption systems can be effective as well and are often used in series as polishing scrubbers following wet chemical systems. A combination of several technologies may be appropriate as well depending on the actual design loading criteria and odor removal efficiency required. The Tri-Town Board of Managers is encouraged to continue to place high priority on effective odor control to extend the record of good performance established over the last few years. Funding for equipment repairs and for carbon replacement should continue to be a high priority. 7.2 NOISE CONTROL Historically, noise has not been a significant issue at the existing Tri-Town facility. Within the last two years, one neighbor has raised a concern to the District regarding truck noise (especially septage haulers) at the facility, as well as possible increased noise levels that might result from future use of the facility and site. Specific to the truck noise concern, a noise barrier has been suggested to the Board as a potential mitigation measure. The current position of the District is that the neighborhood is currently zoned "General Business", and other trucks and equipment that use Bay Ridge Lane, as well as traffic on Route 6, also contribute to the vehicle noise in this area. As such, the District has not implemented any truck noise control mitigation measures at the facility. Our evaluation of noise generation associated with facility operations reveals minimal concerns at this time. The carbon odor control scrubbers and exhaust fans that are located outside, behind the Administration Building, have been the source of a single complaint in the past, but when operating properly, these units should pose no significant noise concerns for the facility and surrounding area. With respect to potential noise problems associated with future uses of the facility and site, the District and Town will need to consider noise generation and abatement strategies for all scenarios, including public works functions, septage handling, and wastewater treatment. Similar to odor control issues, it should be a matter of course that noise issues be considered and factored into any recommended uses for this site. Any facility upgrading, or change in use of the property, will require regulatory approvals (the MEPA process in particular) that will consider noise as one of the many variables in the overall review and approval process A 7-2 Wright-Pierce

65 SECTION 8 REGULATORY AND PERMITTING ISSUES There are a number of permitting and regulatory issues that must be addressed related to upgrading of the Tri-Town plant, or use of the Tri-Town site for wastewater treatment and/or disposal. The nature and scope of the regulatory and permitting issues will depend on the specific intended use of the facility and site. Nonetheless, it is clear that certain regulatory programs must be addressed in any event. This section of the report summarizes the most significant anticipated regulatory and permitting issues as follows: DEP Groundwater Discharge Permit DEP Site Assignment MEPA Review Process 8.1 PERMITS AND APPROVALS DEP Groundwater Discharge Permit Perhaps the most significant permitting issue facing the Tri-Town facility is the renewal of the DEP Groundwater Discharge Permit in The current permit (see Appendix D) allows an effluent total nitrogen concentration as high as 50 mg/l. This is significantly higher than the 10 mg/l limits that are now typical. Should it be decided that the Tri-Town facility will be expanded to receive higher septage volumes (60,000 gpd for example), the permit will almost certainly be modified to the 10 mg/l limit. It is possible that the 50 mg/l limit will be continued if the facility is not expanded to handle an increased septage volume and if the MEP studies determine that there is no significant impact on receiving waters. Conversely, it is also conceivable that the MEP studies could find that an even more stringent total nitrogen standard is necessary (5 mg/l for example). Regardless of the final determinations for the facility, the total nitrogen and other effluent parameters will be reviewed and adjusted as necessary and other new parameters may be added/deleted from the current permit. If a new wastewater treatment facility is constructed on this site (or on any other site for that matter), a DEP Groundwater Discharge Permit will also be required and will likely include a total nitrogen limit of 10 mg/l. The permitting process for a new wastewater plant is a comprehensive process that includes detailed hydrogeological investigations, evaluations and reporting; detailed engineering evaluations; a preliminary design for the treatment and effluent disposal facilities; and the preparation and submittal of a ten-page application A 8-1 Wright-Pierce

66 8.1.2 DEP Site Assignment It is reported that the existing Tri-Town Septage Treatment Facility went through the DEP site assignment process (refer to MGL Ch 83, Section 6) prior to initial construction of the facility, but no written record of such assignment has been located to date. Expansion of the septage treatment facility, or construction of a new wastewater facility, would trigger a site reassignment. It should be noted that DEP policy is evolving toward combining the site assignment process with the groundwater discharge permit process and/or the MEPA process, so this regulatory requirement should not be onerous MEPA Review Process Expansion of the Tri-Town Septage Treatment Facility or construction of a new wastewater treatment plant will require review by the Executive Office of Environmental Affairs (EOEA) under the Massachusetts Environmental Policy Act (MEPA). The MEPA process involves two basic steps. First, an Environmental Notification Form (ENF) is filed to make the project known to the public and various regulatory entities and environmental groups. Second, if potential environmental impacts are deemed significant, then an Environmental Impact Report (EIR) is prepared. Several thresholds under 301 CMR 11.03(5)(b) will be exceeded that will trigger an ENF for the above noted scenarios. Review of the ENF and mandatory EIR thresholds indicates no automatic need for an EIR for the above scenarios, but that actual determination would be made by the EOEA Secretary as part of the ENF review process. An ENF will be filed for Orleans Comprehensive Wastewater Management Plan (CWMP) and it is possible that the entire Orleans CWMP will be subject to the MEPA EIR process. The EIR could cover the implementation of any recommended upgrading of the Tri-Town facility and wastewater management solutions for the Town of Orleans Other Other state and local regulatory issues will need to be addressed and the associated permits procured as part of the implementation of any recommended solution. The specific issues and actions will evolve from the completion of the Orleans CWMP and decisions made by the District regarding the existing Tri-Town facility. Other permitting issues may include, for example, Wetlands Protection Act permitting through the local Conservation Commission, Mass Highway access, DEP plan and specification approvals, and DEP Sewer Extension Permits. 8.2 SCHEDULE A detailed schedule to address all specific permitting issues cannot be prepared until decisions are made by the District regarding any upgrading of the existing Tri-Town facility and the Orleans CWMP is near completion. It is anticipated that the major CWMP tasks will be set into full motion after receipt of the MEP studies which is expected between January and July A 8-2 Wright-Pierce

67 Preliminary Town estimates indicate completion of the CWMP two years after receipt of the MEP studies (resulting in a mid-2008 completion milestone). Some planning guidance on permit scheduling is as follows: The Tri-Town facility's Groundwater Discharge Permit is up for renewal in 2007 which requires the District to submit a renewal application six months prior to the actual permit lapse date. Permitting tasks should therefore commence in 2006 or early 2007 at the latest. If a new Groundwater Discharge Permit is required for either an expansion in capacity at Tri-Town or for a new wastewater plant, a new application will be required. The timeframe for completion of a new Groundwater Discharge Permit is typically 6 to 8 months. Discussions with DEP on site assignment should commence as soon as decisions are made regarding future use of the Tri-Town site (continued septage treatment and disposal, wastewater treatment and/or disposal, and public works functions, or some combination thereof). We believe that DEP will seek to combine the site assignment process with the Groundwater Discharge Permit process and perhaps the MEPA review. If so, the schedule for those approvals will dictate the site assignment schedule. The MEPA process will be project-specific. The ENF process typically takes 3 to 4 months depending on project details and the degree of public involvement and opposition. (This timeframe includes the mandatory 45-day public comment period.) The EIR process is of longer duration and is difficult to predict. An EIR associated with a CWMP will typically take 9 to 15 months and the schedule can often times be greatly affected by the public and regulatory review process. In summary, the schedule for permitting will be significantly impacted by the schedule and specifics of the Orleans CWMP and decisions made by the District for the Tri-Town facility. The District and Town of Orleans are encouraged to stay abreast of the potential regulatory and permitting issues and start the permitting process for specific projects as soon as possible to ensure that permitting delays do not impact the overall implementation schedule A 8-3 Wright-Pierce

68 SECTION 9 IMPLEMENTATION STEPS Section 4 of this report presents our evaluation of development alternatives of the Tri-Town site. Section 6 presents a detailed plan for upgrading the septage facilities. This overall evaluation should be considered "conceptual", meaning it is based on broad assumptions and standard practices without detailed surveys, soils analyses and groundwater modeling. As such, it is intended to establish a framework for later more detailed investigations. There are several tasks that could and should be undertaken by the District and/or the Town regarding this facility and associated site; however none of them requires "emergency" action at this time. This Section 9 lays out the implementation steps to move forward on both fronts. To summarize, our evaluations have focused on the following broad options: Option 1--Upgrading the existing septage treatment facilities to extend their useful life by 20 years, without any increase in capacity or treatment level; Option 2--Extending the service life by 20 years and providing nitrogen removal to a 10- mg/l limit, without increasing the capacity; Option 3--Extending the service life, proving nitrogen removal and increasing the capacity from 45,000 gpd to 60,000 gpd; and Option 4--Improving and expanding the septage facility as described in Option 3 above and building new facilities for wastewater treatment and/or disposal. Options 1, 2 and 3 are specific to septage treatment and disposal at the Tri-Town facility. Option 4 is dramatically different in that it relates to potential new wastewater treatment and/or effluent disposal facilities. Option 4 includes many sub-options that involve the potential use of the site for public works functions as well as wastewater treatment and effluent disposal. The general conclusion that can be drawn from this evaluation is that the District can proceed with Options 1, 2 or 3 noted above, somewhat independently from Option 4. In fact, the District has some plans for capital improvements at the facility and has already begun to develop a 5-year capital improvement plan. Options 2 and 3 are dependent on the effluent total nitrogen limit set in the renewed Groundwater Discharge Permit and the District's decision whether or not to increase capacity at the facility. If the Town of Orleans needs this site for wastewater treatment and/or effluent disposal, that project could proceed somewhat independently of Options 1, 2 and 3. It is also possible that the upgrading of the Tri-Town plant could be included into the Town's wastewater project. The following are recommended implementation steps specific to upgrading of the existing septage facility: 10461A 9-1 Wright-Pierce

69 1. Continue to fund and implement the District's capital improvement plan which will specifically address necessary upgrading needs. Of the three major upgrading needs identified at the facility (dewatering system improvements; septage receiving, screening, and de-gritting equipment; and RBC shaft and media replacement for two RBC trains), the District's current plan will address two of three of these needs, which should be amended to include the important upgrading of the dewatering system. 2. Determine from DEP if the Groundwater Discharge Permit conditions will become more stringent when the permit is renewed in 2007; specifically if a 10-mg/l total nitrogen limit will be imposed. (This information may not be available until the MEP report on the Cape Cod Bay watersheds is issued, now scheduled for mid 2006.) 3. Decide whether or not to increase treatment facility capacity to allow for long-term receipt of septage from Lower Cape communities. 4. Undertake negotiations with the three District towns (and perhaps the other Lower Cape towns) regarding sharing of upgrading costs and amend the inter-municipal agreements accordingly. 5. Once the capacity, management and cost sharing decisions are in place, design the prioritized improvements. 6. Apply for the necessary permits. 7. Apply for SRF low interest loan and other grant or loan funding for the upgrading project(s). 8. Construct the recommended improvements and place into operation. The above summarized implementation steps are applicable to the three broad options for the existing septage treatment facility. Option 4 is much more complex as it is dependent on numerous factors and many potential sub-alternatives that could be implemented. As such, it is difficult to summarize the implementation steps that the District and/or Town should take at this time. The bottom line is that many of the above identified steps can and should be taken within the next couple of years starting immediately, but the implementation of site development alternatives that include potential public works functions and/or wastewater treatment and/or effluent disposal must await the results of the CWMP and a detailed town-wide evaluation and analysis of public works type facilities. Below we have summarized key implementation steps that should be taken to better determine the feasibility of the alternative site development scenarios: 1. Based on MEP studies and other investigations, determine the needs for public sewers in Orleans and in the other District towns A 9-2 Wright-Pierce

70 2. Through the MEP, determine the assimilative capacity of nearby water resources to see if the indicated wastewater flows will have a significant impact, and if so, at what lower level of discharge the impacts are acceptable. 3. Investigate other potential treatment and effluent disposal sites in Orleans (and other District towns as appropriate) and rate them against the Tri-Town site for such factors as cost, public acceptability, environmental impact, etc. 4. If Steps 1, 2 and 3 indicate the need to use the Tri-Town site for wastewater facilities, conduct the appropriate site-specific investigations to confirm or fine-tune the assumptions made in this analysis. 5. Determine in more detail the specific needs of the Town of Orleans for public works functions, and decide if those needs can be provided for elsewhere in town. 6. Consider all feasible options for siting of wastewater facilities and for siting of public works facilities, and determine if pubic works functions should be located at the Tri- Town site. 7. It Step 5 yields favorable results, and based on the results of Step 6, design and construct facilities for the Tri-Town site and any adjacent lands as may be appropriate, apply for applicable permits and funding and initiate operations of new or modified facilities. Most of these steps will be integral to the upcoming CWMP or performed concurrently and coordinated closely with the CWMP. Item 5 (detailed public works use evaluations) should also be performed concurrently and closely coordinated with the CWMP. Town officials and the Board of Manager of the District should meet periodically throughout the CWMP to coordinate their efforts A 9-3 Wright-Pierce

71 SECTION 10 SUMMARY OF FINDINGS AND RECOMMENDATIONS Significant findings of this study are presented in each of the sections of this report. In this Section 10 we summarize all of the principal findings and associated recommendations FINDINGS Condition of Existing Facilities (Section 2) 1. The Tri-Town Septage Treatment Facility is well run. It routinely meets the requirements of its DEP Groundwater Discharge Permit. Due to close control of costs, the fees charged by the facility are competitive. 2. Most of the plant's tankage and equipment were placed in service in the late 1980's. A significant upgrading occurred in the mid 1990's to correct a number of design and construction deficiencies. The original facilities are over 15 years old and are showing signs of wear. The facilities added in 1995 have little need for upgrading at this time. 3. The principal areas that need attention are: a) septage and grease receiving (including screening and grit removal); b) septage dewatering; and c) the rotating biological contactors. Quantities of Septage and Liquid Sludge (Section 3) 4. Over the past three years, the three District towns have produced 5.7 million gallons of septage per year on average. Non-District towns have delivered an average of 5.1 million gallons per year over the same period, with most of that volume coming from Wellfleet, Truro and Provincetown. For the remainder of Cape Cod, septage quantities have been about 50 million gallons per year. Cape-wide totals are about 60 million gallons per year A 10-4 Wright-Pierce

72 5. There are factors that will increase septage production in future years and other factors that will reduce septage volumes. It is expected that the future quantities of septage will be greater than current production due to growth in the number and size of septic systems and due to increased pumping frequency as more property owners understand the need for regular pumping. As septic tanks are abandoned and properties connect to public infrastructure, septage quantities will decline; however most cluster and satellite wastewater plants will not have sludge dewatering facilities and instead will rely on trucking of liquid sludge to facilities such as the Tri-Town plant. Based on assumptions on the extent of new public wastewater infrastructure developed by each of the 15 towns, it is estimated that the combined annual volume of septage and liquid sludge will grow to approximately 90 million gallons Cape-wide. Projections for septage and liquid sludge volumes in the three District towns range from 10 to 11 million gallons per year. For the six Lower Cape towns, the projections range from 13 to 14 million gallons per year. 6. The Tri-Town plant has sufficient capacity for the projected quantities of septage and liquid sludge from the three District towns through build-out. If the increase in volume occurs as predicted, the District may need to turn away some of the septage and liquid sludge from the other Lower Cape towns during certain times of the year. 7. Cape-wide, there will be a shortage of capacity for septage and liquid sludge before build-out is reached. That shortfall may be as much as 20% to 25% of the expected total volume. 8. The true capacity of the Tri-Town plant is difficult to determine. If the plant were to receive the permitted daily maximum volume of 45,000 gallons for 365 days, the annual capacity would be 16.4 million gallons. Unfortunately, there is a marked seasonal variation in septage generation rates, such that the plant runs below capacity in the winter and must turn away septage trucks in the summer. Given the current seasonal trends, the actual capacity is about 12 to 14 million gallons per year. Managing the seasonal variations may allow a higher annual volume to be received and treated A 10-5 Wright-Pierce

73 Capability of Site for Effluent Disposal (Section 4) 9. There is significant unused land at the Tri-Town site that could accommodate a much higher volume of effluent application than is currently discharged. A conventional layout of additional rapid infiltration beds indicates the capacity to discharge a sustained peak flow of about 750,000 gallons per day (gpd), or about 15 times the current permitted volume. This estimate is based on the design application rate of the existing beds (4.75 gpd per square foot of bottom area). The actual capabilities of the entire site would be more than 750,000 gpd if a higher application rate could be used. Conversely, the presence of less suitable soils would dictate a lower application rate and a smaller daily volume. (On an average daily basis, the wastewater flow associated with a 750,000 gpd peak flow would be about 450,000 to 550,000 gpd.) 10. There is vacant land near the Tri-Town site that may also be suitable for effluent disposal. Without consideration of ownership or acquisition issues, it is estimated that there may be as much as 200,000 gpd of additional effluent disposal capacity nearby. That additional capacity may be greater if innovative high-rate disposal systems can be implemented. 11. One limitation to high rates of effluent application is the generation of a mound in the water table below the application area that rises closer to the ground surface than the minimum 4 feet required by DEP. An analysis based on the soil properties at the Tri- Town site indicates a mound height of less than 10 feet at the 500,000-gpd application rate. In that the depth to groundwater is 30 to 40 feet over large areas of the site, excessive mounding is not expected to be a problem. 12. Barnstable County has provided the services of the US Geological Survey (USGS) to investigate several effluent disposal scenarios at the Tri-Town site using the regional model that is the basis for the Massachusetts Estuaries Project (MEP). These investigations indicate that increased effluent application at the Tri-Town site and vicinity will broaden the plume of effluent-impacted groundwater and increase the geographic extent of the potentially impacted area. The largest portion of increased application at the current site will eventually reach the Namskaket Creek and Little 10461A 10-6 Wright-Pierce

74 Namskaket Creek watersheds. Use of sites adjacent to and south of the current site will result in proportionally more flow to the Namskaket Creek watershed. 13. At the highest effluent application rates considered, the USGS model predicts that the effluent-impacted plume will be confined to the Cape Cod Bay watersheds, and not impact the Nauset Estuary system. 14. This study has considered effluent disposal in terms of areal application rates, mounding and direction of groundwater flow. The receiving water impacts of effluent application have not been evaluated. This study is based on "table-top" evaluations, and detailed site-specific analyses are required to confirm these generalized findings. Capability of Site for a Wastewater Treatment Facility (Section 4) 15. It is possible to locate a wastewater treatment facility of 500,000 gpd capacity (expressed as average daily flow) at the Tri-Town site. Several candidate treatment technologies can fit within the optimum footprint. 16. The Tri-Town facilities can be easily adapted to handle the liquid sludge generated from a wastewater treatment plant at the site. This capability, along with the existing roadway, utilities and office/lab facilities, would allow a less expensive wastewater plant here than at other sites where these amenities do not exist. 17. The use of a portion of the Tri-Town site for a wastewater plant would reduce the land available for effluent disposal. The optimum footprint for a wastewater plant would take away about 200,000 gpd of peak rapid infiltration capacity. Options for Compost Shed (Section 5) 18. In 2004, Town Meeting actions in all three District towns provided for a portion of the Tri-Town site (Parcels 1 and 1A) to be used by the Town of Orleans for public works functions. The 6 acres involved appear to represent a convenient and cost-effective location for such functions, particularly considering the former compost shed that sits on Parcel A 10-7 Wright-Pierce

75 19. From a wastewater management perspective, Parcel 1A is very nearly the optimum footprint for the 500,000-gpd wastewater treatment plant discussed above. Parcel 1 is too close to residential development to the north for that function, but it could be used for effluent disposal. Use of Parcel 1 for public works functions takes away about 200,000 gpd of peak effluent disposal capacity. Use of both Parcel 1 and Parcel 1A for public works functions takes away about 400,000 gpd of peak effluent disposal capacity. 20. Parcels 1 and 1A have potential value for both public works functions and wastewater treatment and disposal. No conclusions can be drawn about the relative value for these competing uses until alternatives are identified and evaluated. Any such evaluation should take into account the value of the substantial compost shed and the cost of demolishing it. Upgrading Needs and Costs (Section 6) 21. A program of capital improvements has been developed to extend the useful life of the Tri-Town plant. The total cost, in current dollars, is approximately $1.8 million. The recommended improvements have been assigned a relative priority to facilitate a phased program of upgrading. The cost of the highest priority items is about $1.1 million. 22. The current discharge permit requires that the effluent nitrogen concentration be no higher than 50 mg/l. If DEP imposes the typical standard of 10 mg/l at the time of permit renewal (2007), the plant should be upgraded to include denitrification filters that could be installed for about $0.25 million. Depending on how the permit limits are set, a 5 mg/l limit could also be met for a similar cost. 23. While the plant has capacity for the three District towns through build-out, an expansion to add one-third more capacity (to 60,000 gpd) would also provide capacity for the entire Lower Cape. The plant upgrading would include an extra denitrification filter and more effluent disposal beds. The costs for this upgrading option are about $0.25 million. 24. If the Tri-Town site were to be used for a new 500,000 gpd wastewater treatment plant, the cost could be in the range of $7 to $9 million A 10-8 Wright-Pierce

76 Control of Odor and Noise (Section 7) 25. The addition of new odor control equipment in the mid 1990s has been very effective in significantly reducing odor complaints to those associated with plant upsets or other emergency circumstances. Technology similar to the existing systems is also capable of providing effective odor control for a 500,000-gpd wastewater facility at this site. 26. Equipment and truck noise at the site are consistent with the business/industrial nature of the plant and vicinity. Permitting Requirements (Section 8) 27. The principal permitting issue facing the Tri-Town plant is the renewal of the DEP Groundwater Discharge Permit in The current permit allows an effluent nitrogen concentration as high as 50 mg/l, much higher than the 10 mg/l limits that are now typical. If the Tri-Town plant is expanded to receive higher septage volumes, the DEP permit will certainly be modified to the 10 mg/l limit. Similarly, a new wastewater treatment facility will also be required to meet the 10 mg/l standard. It is possible that the 50 mg/l limit will be continued if the plant is not expanded to handle more septage and if the MEP studies determine that there is no significant impact on receiving waters. It is also conceivable that the MEP studies could find that an even more stringent standard, say 5 mg/l is necessary. 28. Although it is reported that the Tri-Town facility underwent DEP site assignment (under MGL Ch 83, Section 6) before the original construction, no written record of that assignment has been located. Expansion of the septage facility, or construction of a new wastewater facility, would trigger a re-assignment. DEP policy is evolving toward the combining of the site assignment process with the groundwater discharge permit process and/or the MEPA process, so that this requirement should not be onerous. 29. Expansion of the septage treatment facility or construction of a new wastewater facility will require state review under the Massachusetts Environmental Policy Act (MEPA). It 10461A 10-9 Wright-Pierce

77 is likely that the entire Orleans Comprehensive Wastewater Management Plan (CWMP) will be subject to MEPA review that could include any actions to be taken at Tri-Town. Implementation Steps (Section 9) 30. The upgrading of the Tri-Town plant can proceed somewhat independently from the studies needed to determine if the Town needs wastewater facilities and, if so, where they might be located. However, there may be advantages to combining the upgrading with the implementation of wastewater infrastructure under certain circumstances. Until wastewater planning in Orleans has progress further, the high priority upgrading needs can proceed RECOMMENDATIONS 1. The Tri-Town staff should continue its excellent record-keeping program that tracks the source of all septage loads received at the plant. Annual review of this information is warranted to monitor any trends toward higher quantities in any of the District towns or other towns served. 2. Barnstable County should develop a program for receiving and analyzing data from all regional septage facilities to track similar trends Cape-wide. To be effective, this program may require plant operators to keep more complete records than is now the case. That effort should include a close analysis of septage capacity and should lead to a longrange program to expand existing facilities if and when necessary. 3. The Board of Managers could embark on a multi-year phased program of capital improvements to address the upgrading recommendations of this report. In so doing, consideration should be given to maintaining the flexibility for the plant to receive and treat liquid sludge from a co-located or nearby wastewater plant or plants. 4. The Board of Managers should consider offering long-term contracts to other Lower Cape towns to receive and treat their septage. These contracts would commit the Board of Managers to expand the plant if and when necessary, and would provide for capital payments from those towns to assure that capacity. By expanding the plant concurrent 10461A Wright-Pierce

78 with addressing other upgrading needs, economies of scale can accrue to all participating parties. 5. Either as part of inter-municipal agreements or through pricing policies, the Board of Managers should provide incentives to level the normal seasonal peaks in septage generation. 6. As the Towns of Orleans, Eastham and Brewster undertake comprehensive wastewater management planning, the Tri-Town site should receive serious consideration as one of the possible sites for a wastewater treatment plant, as well as a site for effluent disposal. 7. The Town of Orleans should monitor the availability of land near the Tri-Town site as possible effluent disposal locations. 8. Both the Board of Managers and the Town of Orleans should provide close coordination, input and oversight of the MEP studies of the Cape Cod Bay watersheds to ensure that a fair appraisal is made of the assimilative capacity of Namskaket Creek and other impacted watersheds. This must involve the incorporation of past and ongoing USGS studies of Namskaket Marsh. 9. The Town of Orleans should be prepared to undertake detailed hydrogeologic evaluations of the Tri-Town site as part of the CWMP consistent with the MEP study results. 10. The Town of Orleans should conduct a cost-effectiveness analysis of options for new public-works-type facilities, including the Tri-Town site. This effort should be coordinated with the CWMP so that the relative value of Parcels 1 and 1A can be fairly assessed. If wastewater treatment and disposal needs can be handled elsewhere and/or if other potential public works sites are difficult to acquire or develop, than the reuse of the compost shed at the Tri-Town site may be a very desirable option. Conversely, if the CWMP shows that the Tri-Town site is particularly valuable for wastewater treatment and disposal, and/or the public works function are easily accommodated elsewhere, it may be in the overall best interests of the Town to locate the public works facilities elsewhere. The right decision can only be made when the relative costs and merits of other sites are considered A Wright-Pierce

79 11. The Board of Managers should be prepared to add denitrification facilities in the event that the plant is expanded or if the MEP studies show that the current 50 mg/l standard is not sufficiently protective. 12. The Board of Managers should continue to place high priority on effective odor and noise control to extend the record of good performance established over the last few years. Funding for equipment repairs and for carbon replacement should continue to be a high priority A Wright-Pierce

80 APPENDIX A Evaluation of Existing Facilities

81 APPENDIX A EVALUATION OF EXISTING FACILITIES BACKGROUND The Cape Cod communities of Orleans, Brewster and Eastham maintain and operate a septage treatment facility located in Orleans, known as the Tri-Town Septage Treatment Facility. The facility is owned and operated by the Orleans, Brewster, Eastham Groundwater Protection District (District). The facility was designed to treat an average of 45,000 gallons per day of raw septage and grease trap waste. The facility was originally designed to accomplish its treatment objectives through direct dewatering of lime and ferric chloride conditioned sludge, with subsequent treatment of the generated filtrate through a secondary treatment process utilizing rotating biological contactors (RBCs). The effluent from the secondary treatment process is subjected to ultraviolet (UV) disinfection prior to discharge to a series of rapid infiltration beds. The residual solids generated by the plate and frame press were originally intended for on-site composting. The facility operates under a permit issued by the Massachusetts Groundwater Discharge Permit Program (Groundwater Discharge Permit No ). Since initiation of operations in 1989, the facility was plagued with difficulties and was the subject of numerous reports and studies associated with these deficiencies. These difficulties resulted in the suspension of the on-site composting operation with the resulting need for contract disposal of the solids generated at an off-site location. The difficulties further resulted in an Administrative Consent Order from the Massachusetts Department of Environmental Protection stemming from the failure to consistently meet the discharge limitations. A comprehensive performance evaluation was performed by the District, and a corrective action report (CAR) was prepared. As a result of the CAR, on-site pilot studies and bench scale studies were performed to further refine recommended process improvements. The culmination of the efforts was a September 1994 report entitled "Report on Results of Studies Recommended in Corrective Action Report." This report was prepared by the current operators of the Tri-Town facility. This report presented the final recommendations for corrective actions at the Tri-Town facility. In 1994, the District retained Wright-Pierce to prepare a preliminary design of the improvements necessary to accomplish the recommendations in the September 1994 report. The preliminary design report was issued in February 1995 and was used as the basis for the final detailed design of the remedial actions. The final design plans and specifications were completed by Wright- Pierce in 1995 and contractors then prepared bids for the construction. Construction began in 1995 and was completed in During construction, Wright-Pierce provided complete construction administration, resident inspection, start-up and operational assistance services. Since the new upgrade was completed in 1997, the plant has continuously met its groundwater discharge permit conditions. According to the Chief Operator, the upgrade work was very effective in correcting the deficiencies with the original design and the plant has operated extremely well A A - 1 Wright-Pierce

82 DESCRIPTION OF THE CURRENT TREATMENT FACILITIES A summary follows of the major unit processes at the Tri-Town facility. (See Figure 2-1 and 2-2 for the site plan and process flow diagram): Septage and Grease Receiving and Treatment Septage and grease from grease traps are delivered to the facility in both traditional 2,500-gallon tank trucks, as well as larger 5,000-gallon tanker trucks. Prior to and after discharge into the treatment facility, septage and grease delivery trucks are weighed on either a 30-foot-long, 30- ton scale in the southern truck bay and a 60-foot-long, 60-ton scale in northern truck bay. Weighing and discharge of incoming loads of grease are carried out in the southern truck bay due to the location of the grease discharge point. Septage is discharged via a quick connect hose fitting at the septage receiving station after which it flows through a manually cleaned bar rack and into the grit wetwell. The Chief Operator indicated that some haulers are now using larger aluminum tank trucks that are too high for the 11' - 4" bay doors. A mechanically screened bar rack was installed as part of the original plant construction however; it has not been used for some time. According to the Chief Operator, the bar screen was sized inappropriately to handle the surges from a septic truck resulting in material being forced through the screens. In an attempt to capture more material, the plant staff attempted to modify the rake and bars to a finer spacing. However, this caused excessive rag buildup and backup of incoming septage flow due to insufficient cleaning capability of the mechanical bar screen. The bar screen cycle time is too slow to keep pace with the power discharges from the haulers. Other potential options include replacement of the bar screen with new unit, installation of a step screen, Rotamat fine screen, etc. This would most likely require extensive modifications to the headworks area. The grit wetwell was constructed as part of the original plant and according, to the Chief Operator, the condition of the grit wetwell concrete is poor and is in need of repair. From the grit wetwell, septage is pumped through an inclined grit classifier which removes and dewaters grits prior to discharge into two septage equalization tanks (discussed later). The grit wetwell is in need of repair. Spalling on the underside of the slab near the hatch is extensive, and may be compromising integrity of the slab. The original grease system consisted of a 10,000-gallon grease tank with gravity discharge of decanted liquid into the grit wetwell. The original system had no provisions for pumping the contents of the tank and was too small for the quantity of grease delivered to the facility. The upgraded grease treatment system includes: grease-grit tank; grease-grit pump; grease storage tanks; grease tank aeration system; grease pumps; grease sodium hydroxide pumps; a potassium permanganate feed system; and an antifoam feed system. The grease-grit tank, with a volume of approximately 5,000 gallons, allows grit and heavy solids to settle to the bottom of the steeplysloped tank and allow floatables and liquid to overflow into either grease storage tank. Removal of accumulated solids from the bottom of the grease-grit tank is accomplished by the grease-grit pump. Downward opening weir gates have been provided between the grease-grit tank and 10461A A - 2 Wright-Pierce

83 grease storage tanks to allow the operators to direct the flow of grease into either, or both, of the adjacent grease storage tanks. Figure A-1 - Grease Blowers The grease-grit pump can discharge the accumulated material into either the grit cyclone, located in the Grit and Screenings room, or to either grease storage tank. If the majority of the settled material in the grit tank is inorganic solids (grit), the material is pumped to the grit cyclone. If the settled material contains a significant organic fraction, such as grease balls which may foul the grit cyclone, the material is discharged into one of the grease storage tanks for treatment. The grit cyclone installed as part of the original project shows signs of corrosion and wear, and may be approaching the end of its useful service life. Although the unit is still performing well, maintenance has become a problem due to the difficulty in obtaining replacement parts. In fact, during the on site tour, part of the inclined classifier screw broke off and was discharged into the grit hopper. The accumulated grit is heavily laden with sludge and organics. The operators indicated that grit removal is a problem. Upgrading recommendations include a grit separator to precede the classifier, such as an enclosed vortex grit unit. The condition of the WEMCO grit pumps is good, although the units are obsolete, parts are still available. The operators questioned the integrity of the discharge piping, suspecting that the pipe may be worn due to the severe duty. According to the operators, the sump pumps in the grit area and blower room are undersized, and in need of replacement A A - 3 Wright-Pierce

84 Figure A-2 - Grit Cyclone and Classifier Two grease storage tanks were provided, each with a usable storage and treatment volume of approximately 30,000 gallons. The purpose of these tanks is to allow for the biological pretreatment of the grease prior to discharge into the rest of the treatment system. The tanks operate using the fill, treat and draw concept. That is, while Tank No. 1 is being filled and aerated over a period between 5 days (summer months with weekly grease flow of 40,000 gallons) and 6 weeks (winter months with weekly grease flow of 5,000 gallons), the grease in Tank No. 2 is being aerated and discharged into the septage receiving tanks as flows and loads allow. The dissolved oxygen (DO) level and ph level in each grease tank are continuously monitored through in-tank DO and ph probes. The mixing and oxygen requirements are met by a fine bubble membrane aeration system and positive displacement rotary lobe blowers. Each grease tank is supplied with an air flow range of 22 cfm to 132 cfm per tank. Two double disc pumps each with a capacity of 95 gpm are used to feed the pretreated grease into the septage receiving tanks. The condition of these pumps is good, and they move the grease very well, which is a notoriously difficult stream to handle A A - 4 Wright-Pierce

85 Figure A-3 - Double Disc Grease Pump Grease trap pumpings consist of fats, oils, waxes and other similar constituents that can be readily acidified to volatile organic acids. The ph of grease trap pumping is regularly less than 4 and sometimes as low as 1, which seriously hinders microbial degradation of grease. The grease tank ph control system consists of a ph probe in each tank and two NaOH feed pumps located in the Odor Control Room to keep the ph in a more neutral range to allow for biological decomposition. Because of the potential to generate odors, particularly in the unaerated grease grit tank, potassium permanganate solution can be added to the grease-grit tank and grease storage tanks as necessary. Furthermore, a chemical feed pump can be run manually to pump antifoam solution to the grease storage tanks to minimize the formation of foam during aeration. Air from the headspace of the grease and grit tanks is ventilated to an odor control system installed as part of the 1995 upgrade. Details on the odor control system are presented at the end of this section. Septage Equalization and Aeration Degritted septage, pretreated grease and wastewater treatment recycle flows are all pumped to the two Septage Equalization Tanks. Each tank has a capacity of 135,000 gallons, which provides a holding time of approximately 3 days per tank at design flow. The septage equalization tanks are equipped with a coarse bubble aeration system and positive displacement rotary lobe blowers installed as part of the 1995 upgrade. The aeration system and blowers are regularly utilized to mix the contents of the equalization tanks and maintain solids in suspension prior to thickening. Lime is added to the septage on a daily basis to raise the ph, such that the resulting filtrate will be within an acceptable range for the biological treatment system. The lime also suppresses the formation of sulfides, which helps control odors A A - 5 Wright-Pierce

86 The septage receiving equipment (screens, grit wetwell, grit pumps, grit classifier) represent the most problematic areas for the plant staff, which is not unexpected. These facilities are part of the original plant construction and have been in service for 15 years. They are also subject to the greatest wear and most corrosive conditions. Septage Thickening The majority of the septage thickening and transfer system was installed as part of the 1995 upgrade and consists of the three original recessed impeller centrifugal feed pumps with antecedent grinders, two gravity belt thickeners (GBTs), two polymer feed systems, two spray wash pumps, and two positive displacement, double disc thickened septage transfer pumps. The purpose of the septage thickening and transfer system is to reduce the amount of water in the septage before dewatering using the plate and frame filter presses to minimize press run times. Facilities for injection of permanganate for odor control and polymer to enhance thickening are provided. Septage in the septage equalization tanks is pumped to the GBT's by one of three original recessed impeller pumps, located in the Operations Building basement. The operators requested that the existing grinder system be replaced with a Moyno Pipeliner grinder. The pumps were upgraded with supplemental sheaves and VFDs to provide a range of flows from 240 to 400 gpm. The Chief Operator stated that the grinders are not providing adequate maceration of material, and may need to be replaced. The GBT's were installed as part of the 1995 upgrade. Each GBT has a capacity of 150 gpm at 400 lb/hr dry solids, depending on the septage solids content. Only one GBT is intended for operation at a time, while the other unit is a standby. Although the GBT's can thicken the septage to a solids content of as high as 10%, a solids content of approximately 3 to 4% is targeted which facilitates handling by the double disc pumps. Each GBT is provided with two chemical feed systems, for permanganate and polymer addition. After thickening, two double disc pumps, each with a capacity of 20 gpm, transfer the thickened septage to the septage conditioning tank. Odors from the GBT area are treated by a two-stage scrubber installed as part of the 1995 upgrade. Odor control systems will be discussed later in this section. Septage Conditioning The conditioning of the septage prior to thickening is accomplished with a polymer solution and potassium permanganate that is injected into the septage by two chemical feed systems before thickening. The polymer feed system and potassium permanganate feed system are used to allow effective thickening and to minimize the odors in the GBT Room, respectively. The permanganate system is not used, and can probably be decommissioned. There was discussion of the possibility of switching from a dry polymer system to the latest generation of "polyblend" drum blending units. This suggestion was not deemed a critical need, but may be worth investigating A A - 6 Wright-Pierce

87 The conditioning of septage prior to dewatering is conducted in two conditioning tanks. During the 1995 upgrade, each conditioning tank was retrofitted with a new mixer to allow for better mixing of the thickened septage. In addition to injecting polymer upstream of the thickening process, the polymer feed system allows polymer injection into the septage conditioning tank for mixing prior to dewatering. This treatment step replaces the original lime and ferric chloride conditioning system. Potassium permanganate can also be added directly into the septage conditioning tank to minimize release of odors in the dewatering room. The sludge is also conditioned with lime slurry. The operators expressed their desire to have unused or obsolete equipment removed from the process area, such as the ferric chloride and acid wash system. The reaction tank mixers are no longer used, and the operators requested that they be removed. Septage Dewatering The septage dewatering system is essentially the original system that was installed and it has been in operation since The only changes to the system as part of the 1995 upgrade include the use of polymer for thickened septage conditioning and the fact that the presses now dewatered thickened septage instead of raw septage. The dewatering system consists of three hydraulic ram press pumps, and two plate and frame filter presses. The ram presses each have a capacity of approximately 200 gpm. The ram presses have been performing satisfactorily, although the condition of the pistons should be checked. The filter presses are each rated for approximately 1,220 lb/hr (wet basis), and are designed to produce a cake with 20 to 40% solids. The filter presses have performed satisfactorily, although the original equipment manufacturer, Edwards-Jones, is no longer in business. The Edwards-Jones line of equipment has been acquired by US Filter, but they no longer provide parts or service for this equipment. As such, all maintenance and repairs on the presses must be completed by the plant staff. The Chief Operator indicated that the most critical component on the ram press is the wear strip, which he diligently keeps lubricated. Cloth filter media is available, however the frames are not. Replacement frames made of synthetics (polyester?) may be available from a firm in Massachusetts. The Chief Operator expressed interest in having the screw drives replaced with a hydraulic system. At a minimum, he requested that the press be refurbished to the extent possible. We discussed the possibility of replacing the existing presses with a Fournier type press. The Fournier is a low-speed dewatering system that is completely enclosed, which would help minimize odors, and would be much easier to maintain and operate. The monorail over the two presses does not provide adequate clearance for plate removal. This requires manual plate removal and maintenance which presents a serious risk of injury to the operators. The safety light curtains for each press have recently been replaced A A - 7 Wright-Pierce

88 Figure A-4 - Plate and Frame Press Figure A-5 - Ram Press The District hauls dewatered septage to Yarmouth using a single District-owned dump truck, which will need replacement in the near future. Solids production from the plant is approximately 6 wet tons per day in the summer, with an average solids content of 30%. Filtrate Equalization and Pumping The original filtrate equalization system consisted of two 80,000-gallon storage tanks (located adjacent to the two septage equalization tanks) with submersible mixers. As part of the 1995 upgrade, a new 200,000-gallon filtrate equalization tank complete with fine bubble membrane 10461A A - 8 Wright-Pierce

89 aeration system complete with two blowers was constructed. Additionally, a coarse bubble aeration system complete with two blowers was installed for aeration of the two existing 80,000-gallon filtrate equalization tanks. Four new 50-gpm progressive cavity filtrate pumps and piping to allow pumping from the three tanks into the primary clarifier distribution box were also installed. Figure A-6 - Progressive Cavity Filtrate Pumps 1 and 2 Figure A-7 - Progressive Cavity Filtrate Pumps 3 and 4 The intended mode of operation is for all filtrate from the thickening operation to flow to the new filtrate tank, and all the filtrate from the dewatering operation to flow to the existing filtrate tanks. In addition to providing equalization for the filtrate prior to discharge into the liquid 10461A A - 9 Wright-Pierce

90 treatment process, the filtrate tanks and aeration systems allow for reduction in the biochemical oxygen demand (BOD) of the filtrate as loads to the facility increase and the tanks could be used as part of a nitrogen removal process in the future. Primary Clarification After equalization, the filtrate is pumped by the filtrate pumps through a reaction tank and flow splitter which directs flow to the two 16-foot-diameter primary clarifiers. The original design required the reaction tank to allow hydrochloric and phosphoric acid to be added for ph reduction and nutrient addition, respectively, but the filtrate now passes through the reaction tank without acid addition. The primary effluent from the clarifiers flows to the RBC flow splitter. Primary sludge is pumped to the septage equalization tanks by three original progressive cavity pumps, each with a capacity of 50 gpm. The primary clarifiers were part of the original plant construction, and show signs of corrosion and wear. The plant staff recently repaired the drives and gearboxes, and replaced the walkways. The weirs have corroded in place such that vertical adjustment is no longer possible. The operators requested that all metalwork in the clarifiers be replaced. The primary sludge pumps have been in service for approximately 15 years, and may be nearing the end of their useful service life. The operators suggested that the primary splitter and clarifiers should be connected to an odor controls system. The splitter should be provided with an enclosure from which the headspace from there and the clarifiers could be piped to an odor control system. Rotating Biological Contactors (RBCs) Figure A-8 - RBC The RBC flow splitter directs flow from the primary clarifiers to one of the four RBCs, which are operated as four separate parallel units. Each of the four RBCs has four stages, and 10461A A - 10 Wright-Pierce

91 approximately 100,000 square feet of plastic media per shaft. The RBCs are the heart of the secondary treatment process and are responsible for the majority of the BOD removal in the treatment process. The facility is operated such that the primary effluent is directed to three of the RBC's, while the fourth serves as a polishing step for the recycle flows. The RBCs are capable of converting 100% of the ammonia in the primary clarifier effluent to nitrate (complete nitrification). Although the facility was not designed for total nitrogen removal (nitrification followed by denitrification), some denitrification is provided by recycling flow to the anaerobic portion of the septage equalization tanks. After biological treatment in the RBCs, flow is pumped by the intermediate pump station to the secondary clarifiers. The intermediate pump station consists of two new progressive cavity pumps that were installed as part of the 1995 upgrade, each with a capacity of 80 gpm. While the pumps are identical, one of the new pumps was designed to recycle RBC effluent back to either the septage or filtrate equalization tanks while the second pump was designed to pump the RBC effluent to the secondary clarifier splitter box. In 2002, the District retained Wright-Pierce for the design of a project to replace the shafts and media on two of the RBC's, which were put into service in The new media was provided by US Filter while the remaining original media was manufactured by Lyco. The Chief Operator requested that the drives on all RBC's be replaced. No odor control is provided for the primary clarifiers and RBCs, however all processes are covered. If the facility were to begin taking municipal wastewater, the staff expressed the likelihood that odor control for these processes would be required. An MLSS recycle for the RBC's is not used. The recycle pump is sometimes used to send flow to one of the RBC's as a polishing step. Secondary Clarification Two new secondary clarifiers were installed as part of the 1995 upgrade project to replace the original Lamella-type clarifiers which were ineffective at secondary solids removal. The Lamella-type clarifiers currently receive gravity flow from the RBCs and effluent is withdrawn from these units by the new intermediate pump station pumps discussed above. The operators suspect that the lamella clarifiers are corroded, and believe they should be removed. (The Lamellas were retained in the flow train during the upgrading to avoid having to reconfigure the piping.) The upgrade included the addition of two 16-foot-diameter enclosed circular secondary clarifiers to match the existing 16-foot-diameter enclosed primary clarifiers. A liquid polymer blending and injection system was also added to inject polymer into the RBC effluent prior to clarification. Each clarifier is provided with a flocculation-style center feed well to allow for mixing and flocculation of the solids to aid in settling A A - 11 Wright-Pierce

92 Figure A-9 - Secondary Clarifier Drive One clarifier is adequate to provide good settling and the second clarifier serves as a standby unit. The secondary clarifiers have been very effective at removing both total suspended solids (TSS) and BOD from the RBC effluent. Two progressive cavity secondary sludge pumps convey sludge from the clarifier underflow to the septage equalization tanks. These progressive cavity pumps were installed as part of the 1995 upgrade and each has a capacity of 10 gpm. Sand Filtration As part of the 1995 upgrade project, the Department of Environmental Protection (DEP) required that two, 19-square-foot upflow sand filters be installed to ensure the TSS discharge limit of 30 mg/l is always met. As Wright-Pierce anticipated during the design, with proper operation of the secondary clarifiers, the sand filters are not used for TSS removal. In the summer months, the filters are used to denitrify the effluent prior to discharge. In the winter months, the filters are taken out of service. The sand filters are backwashed/cleaned with an air compressor with the backwash or "mud" overflowing to the mudwell pump station. The mudwell pump station consists of two submersible pumps which recycle the "mud" back to the septage equalization tank. Disinfection and Discharge Effluent from the sand filters flows by gravity through two banks of enclosed UV disinfection units, each with a capacity of 100 gpm. The after UV disinfection, the final effluent flows into an effluent dosing tank. Two submersible effluent dosing pumps, each with a capacity of 55 to 85 gpm, discharge treated effluent to one of four sand beds for rapid infiltration into the ground. In 2000, Wright-Pierce worked with the plant operators to size and select two new effluent dosing pumps to replace the original pumps. The two new pumps were installed and became operational in A A - 12 Wright-Pierce

93 As part of the 1995 upgrade project, a new plant water system was installed which draws treated effluent from the effluent dosing tanks and pumps it to various locations throughout the plant where treated effluent is needed such as for tank cleaning and gravity belt thickener spray water. Instrumentation The 1995 upgrade project included the installation of 21 new control panels to control the new equipment included in the upgrade. Table A-1 lists the new control panels installed. TABLE A-1 CONTROL PANEL SUMMARY Panel No. Panel Name Panel Function P1 Filtrate Pump Panel Controls two filtrate pumps P2 Pump Panel Controls two filtrate pumps, two spraywash pumps, two grease pumps, one grease-grit pump and display tank levels P3 Blower Panel Controls septage, grease and filtrate tank blowers P4 Secondary Clarifier No. 1 Panel Controls Secondary Clarifier No. 1 P5 Secondary Clarifier No. 2 Panel Controls Secondary Clarifier No. 2 P6 Sand Filter Room Panel Controls secondary sludge pumps and polymer system P7 Scum Pump Panel Controls secondary scum pump P8 RBC Pump Panel Controls intermediate pump station pump and recycle pump P9 GBT Polymer Panel Controls new GBT polymer system P10 GBT Main Panel Controls thickening process including septage feed pumps, GBT, spraywash pumps and thickened sludge pumps P11 GBT Control Station Controls polymer system at the GBTs P12 Plant Water Panel Controls plant water system P13 Septage Pump Panel Controls septage feed pumps at the pumps P14 Permanganate System Panel Controls permanganate batch and feed system P15 Sand Filtration Panel Controls sand filter system P16 Remote Blower Panel Controls filtrate tank blowers P17 Grease ph Panel Controls grease ph adjustment pumps P18 Odor Control Panel Controls odor control system P19 Reserved for future use N/A P20 Mudwell Pump Panel Controls mudwell pump station P21 Underdrain Pump Station Panel Controls building underdrain pump station P22 Chemical Fill Station Panel Provides status of odor control chemical tank levels and alarms for delivery truck 10461A A - 13 Wright-Pierce

94 Seven of the 21 control panels were provided with programmable logic controllers (PLCs) which control many of the new processes and provide information on each unit process to a Supervisory Control and Data Acquisition (SCADA) System. Five of the seven PLCs form a distributed control system (DCS) and local area network (LAN) which allows for control of numerous processes, communication of key information from the unit processes to the SCADA system and communication of key information from the SCADA system to individual unit processes. The SCADA system consists of two personal computers and a specialized software program (Wonderware) which has graphical depictions of all of the new unit processes and the ability to collect and store data, as well as modify process control variables with a keystroke. Since the upgrade in 1995, the District has upgraded the SCADA system to allow some of the original unit processes to be controlled from the SCADA system. Emergency Power A second diesel generator was added to the facility as part of the 1995 upgrade project. The emergency power capacity is sufficient to maintain full operational capability including solids processing and handling for the treatment system, but not for receiving. During an extended blackout period, the plant is able to treat septage previously delivered to the facility but is not able to receive flow. The new generator may have spare capacity that could be used to power the receiving area equipment. Odor Control The Tri-Town facility was originally provided with a two-stage wet chemical scrubber followed by dual activated carbon beds for polishing of the scrubber exhaust. Odorous air from the septage receiving tanks, filtrate tanks, receiving garage, dewatering room and sludge garage is collected and discharged into this system. The system is still operated, but limited work has been done to determine the effectiveness of the odor removal and the balance of the ductwork system to ensure sufficient air is being withdrawn from each space. The plant operators think that the scrubber may be approaching the end of its useful service life. The pumps have been refurbished, however the condition of the fiberglass is suspect. The media for the carbon system was recently switched from permanganate-impregnated to Centaur-brand media. The life of the media is estimated to be 4 to 5 years. The permanganate carbon was prone to exothermic reaction, which at times caused overheating posing a danger to the structures and staff A A - 14 Wright-Pierce

95 Figure A-10 - Receiving Area 2 Stage Wet Scrubber Figure A-11 - Receiving Area Carbon Odor Control Tanks As part of the 1995 upgrade, a new two stage wet chemical scrubber system, followed by a carbon adsorption system, was installed. This 3,100-cfm system treats odorous air from the new filtrate tanks, GBT Room, new grease tanks, and the existing septage conditioning tanks. This new odor system is operating satisfactorily A A - 15 Wright-Pierce

96 Compost Building The original aerated static pile composting process was shut down shortly after startup in the early 1990's due to odor complaints from neighbors. The composting area was covered with a pre-engineered metal roof which is still in place. The structure consists of a reinforced concrete slab with push walls. A small enclosed building houses the former sludge and wood chip mixing conveying equipment as well as a small office, electrical room and lavatory. The area also has a buried diesel fuel tank and fuel pump. The composting area is no longer used, but consideration should be given to possible other District or Town uses. Chemical Feed Building The Chemical Feed Building was built as part of the original treatment facility construction. The building included a 6,000-gallon bulk hydrochloric acid tank and two hydrochloric acid feed pumps to lower the ph of the filtrate prior to the biological process. Additionally, a containment area for storage of phosphoric acid drums and two phosphoric acid feed pumps were constructed in the building. The phosphoric acid was used to raise the phosphorus level in the septage prior to biological treatment. In the early 1990's, the 6,000-gallon storage tank failed. Even though the failure was contained in the secondary containment structure, the acid fumes caused significant damage in the space including doors, control panels, and equipment. For a period in 1997, access to the building was restricted by the Orleans Building Inspector, Electrical Inspector and Fire Chief because of structural and electrical concerns. In 1997, Wright-Pierce conducted a structural and electrical evaluation of the Chemical Building. The evaluation found the building to be structurally sound and suitable for entry. All of the electrical equipment was determined to be damaged beyond the point where it could be considered safe to use and complete removal and replacement was recommended prior to restoring power to the building. Additionally, it was recommended that access doors to the facility, which are severely corroded, be replaced. In 2001, Wright-Pierce conducted another brief evaluation of options for the Chemical Building but, to date, no upgrades have been conducted. The Chemical Building is no longer needed for chemical storage and addition. The building could make an ideal cold storage space, or may be needed for future treatment processes. Upgrades to the building should be postponed until after the evaluation of the Tri-Town Septage Facility is completed. The Chief Operator suggested that a drive through bay be installed to connect the chemical storage building to the main process building. This would allow adequate space to consolidate the maintenance shop. The operators consider the various scattered maintenance areas to be one of the primary shortcomings of the facility A A - 16 Wright-Pierce

97 Miscellaneous Building Systems The operators indicated that the air compressor accumulates excessive moisture, requiring monthly changing of the oil, and water in the air line. The compressor is provided with an air dryer, however its performance is questionable (the manufacturer is not familiar to Wright-Pierce). The service reps for the compressor have advised the staff that the problems with excessive moisture may be related to having the unit mounted too low in the facility, which is exacerbated by the proximity of marine ambient conditions. The operators expressed frustration with the phone system The gate valves on the plant water system are corroded. The staff also mentioned that the water piping systems experience severe water hammer. The lime pumps can be started but not deactivated at the unit. This limitation occurred when the lime system was incorporated into the new SCADA system. SPECIFIC UPGRADING RECOMMENDATIONS Appendix C builds on the information presented above, in the same process-by-process format, to identify specific upgrading recommendations A A - 17 Wright-Pierce

98 APPENDIX B GZA Report on Groundwater Mounding 10461A A - 18 Wright-Pierce

99 A. EXISTING CONDITION AND UPGRADING FOR 20 YEAR LIFE Below is a summary of the function and condition of each of the facility's major unit processes, as well as recommendations for each unit process to extend the life of the facility for another 20 years. Also presented for each unit process is a relative priority of the recommended upgrading to extend the existing equipment for a 20-year design life, as well as the estimated installation cost (i.e. equipment plus contractor's installation cost). Septage and Grease Receiving and Treatment Septage and grease from grease traps are delivered to the facility in both traditional 2,500-gallon tank trucks, as well as larger 5,000-gallon tanker trucks. Prior to and after discharge into the treatment facility, septage and grease delivery trucks are weighed on either a 30-foot-long, 30- ton scale in the southern truck bay and a 60-foot-long, 60-ton scale in northern truck bay. Weighing and discharge of incoming loads of grease are carried out in the southern truck bay due to the location of the grease discharge point. Septage is discharged via a quick connect hose fitting at the septage receiving station after which it flows through a manually cleaned bar rack and into the grit wetwell. A mechanically screened bar rack was installed as part of the original plant construction; however, it has not been used for some time. According to the staff, the bar screen was sized inappropriately to handle the surges from a septic truck, resulting in material being forced through the screens. Also, the cycle time is too slow to keep pace with the pressurized discharges from the haulers. Also, to accommodate the larger tankers used by some of the haulers, increasing the bay height or providing an external hookup should be considered. Priority High High Description Replace bar screen with a new unit, or consider installation of a step screen, Rotamat fine screen, etc. This would most likely require extensive modifications to the headworks area. OR Consider installation of a septage acceptance plant. (This unit would accomplish both screening and grit removal) Estimated Cost $170,000 $310,000 Grit Removal The septage receiving equipment (screens, grit wetwell, grit pumps, grit classifier) represent the most problematic areas for the plant staff, which is not unexpected. These facilities are part of the original plant construction and have been in service for 15 years. They are also subject to the greatest wear and most corrosive conditions A B - 2 Wright-Pierce

100 The grit cyclone installed as part of the original project shows signs of corrosion and wear, and may be approaching the end of its useful service life. Although the unit is still performing well, maintenance has become a problem due to the difficulty in obtaining replacement parts. The accumulated grit is heavily laden with sludge and organics. Priority Description Estimated Cost High Repair, or (preferably) replace the grit classifier. $50,000 Medium Consider installation of a grit separator to precede the classifier, $70,000 such as an enclosed vortex grit unit. (Septage acceptance plant as recommended above would include grit removal). Low Evaluate wear on grit pump discharge piping, and replace as $5,000 necessary. High Replace sump pumps in the grit area and blower room. $10,000 Septage Equalization and Aeration Degritted septage, pretreated grease and filtrate treatment recycle flows are all pumped to the two Septage Equalization Tanks. Each tank has a capacity of 135,000 gallons, which provides a holding time of approximately 3 days per tank at design flow. The septage equalization tanks are equipped with a coarse bubble aeration system and positive displacement rotary lobe blowers installed as part of the 1995 upgrade. The aeration system and blowers are regularly utilized to mix the contents of the equalization tanks and maintain solids in suspension prior to thickening. Lime is added to the septage on a daily basis to raise the ph, such that the resulting filtrate will be within an acceptable range for the biological treatment system. The lime also suppresses the formation of sulfides, which helps control odors. The staff suspects that the condition of the equalization tanks is poor, and confirmed that their condition has never been assessed. Inspection of the tanks is therefore recommended to ensure their integrity for the next 20 years. Estimated Priority Description Cost Medium Evaluate condition of the septage equalization tanks. $10,000 Septage Thickening The majority of the septage thickening and transfer system was installed as part of the 1995 upgrade and consists of the three original recessed impeller centrifugal feed pumps with antecedent grinders, two gravity belt thickeners (GBTs), two polymer feed systems, two spray wash pumps, and two positive displacement, double disc thickened septage transfer pumps. The purpose of the septage thickening and transfer system is to reduce the amount of water in the septage before dewatering using the plate and frame filter press to minimize press run times A B - 3 Wright-Pierce

101 Facilities for injection of permanganate for odor control and polymer to enhance thickening are provided. Septage in the septage equalization tanks is pumped to the GBT's by one of three original recessed impeller pumps, located in the Operations Building basement. The pumps were upgraded in 1995 with supplemental sheaves and VFDs to provide a range of flows from 240 to 400 gpm. The Chief Operator stated that the grinders are not providing adequate maceration of material, and may need to be replaced. The GBT's were installed as part of the 1995 upgrade. Each GBT has a capacity of 150 gpm at 400 lb/hr dry solids, depending on the septage solids content. Only one GBT is intended for operation at a time, while the other unit is a standby. Although the GBT's can thicken the septage to a solids content of as high as 10%, a solids content of approximately 3 to 4% is targeted which facilitates handling by the double disc pumps. Each GBT is provided with two chemical feed systems, for permanganate and polymer addition. After thickening, two double-disc pumps with a capacity of 20 gpm each transfer the thickened septage to the septage conditioning tank. Odors from the GBT area are treated by a two-stage scrubber installed as part of the 1995 upgrade. Odor control systems is discussed later in this section. Estimated Priority Description Cost Medium Replace existing grinders with a Moyno Pipeliner grinder. $30,000 Septage Conditioning The conditioning of the septage prior to thickening is accomplished with a polymer solution and potassium permanganate that is injected into the septage by two chemical feed systems before thickening. The polymer feed system and potassium permanganate feed system are used to allow effective thickening and to minimize the odors in the GBT Room, respectively. The conditioning of septage prior to dewatering is conducted in two conditioning tanks. During the 1995 upgrade, each conditioning tank was retrofitted with a new mixer to allow for better mixing of the thickened septage. In addition to injecting polymer upstream of the thickening process, the polymer feed system allows polymer injection into the septage conditioning tank for mixing prior to dewatering. This treatment step replaces the original lime and ferric chloride conditioning system. Potassium permanganate can also be added directly into the septage conditioning tank to minimize release of odors in the dewatering room. The staff requested that unused equipment for the chemical feed systems and the reaction tank mixers be decommissioned. Also, the lime storage silos have some minor cracking, which allows some seepage of product into the lime feed area A B - 4 Wright-Pierce

102 Priority Description Estimated Cost High Decommission the unused reaction tank mixers $10,000 High Decommission the permanganate and ferric systems. $10,000 Medium Repair cracks in lime storage silos. $20,000 Low Upgrade lime feed controls $10,000 Septage Dewatering The septage dewatering system is essentially the original system and it has been in operation since The only changes to the system as part of the 1995 upgrade include the use of polymer for thickened septage conditioning and the fact that the presses now dewatered thickened septage instead of raw septage. The dewatering system consists of three hydraulic ram press pumps, and two plate and frame filter presses. The ram presses each have a capacity of approximately 200 gpm. The filter presses are each rated for approximately 1,220 lb/hr (wet basis), and are designed to produce a cake with 20 to 40% solids. The filter presses have performed satisfactorily, although the original equipment manufacturer, Edwards-Jones, is no longer in business. The Edwards-Jones line of equipment has been acquired by US Filter. The monorail over the two presses does not provide adequate clearance for plate removal. This requires manual plate removal and maintenance which presents a serious risk of injury to the operators. The safety light curtains for each press have recently been replaced. A representative from US Filter visited the site to assess the condition of the presses and pumps, and to make recommendations for refurbishing both unit processes for a 20-year life. In addition, the operators requested at a minimum, that the existing press closure mechanism be replaced with a hydraulic mechanism, and that standby capacity for the ram press pumps be provided. The ram press pumps showed signs of wear and leaking oil, and should be refurbished as outlined in the US Filter scope. The US Filter representative stated that the existing press frames are in acceptable condition and do not need to be replaced, however a cost per plate is provided as requested by the Chief Operator. Some of the equipment recommended for replacement could not be observed directly without disassembly. Consequently, a portion of the cost proposal for upgrading work is an assessment based on the representative's experience on parts that would need replacement due to the equipment's age. The US Filter representative also recommended that the condition of the existing ram press pump pistons should be evaluated. An alternative to refurbishing the existing presses would be to consider the installation of two Fournier Rotary Presses. Fournier presses are gaining acceptance at many wastewater treatment plants and are also being retrofit to replace other dewatering mechanisms, due to their distinct design advantages. Fournier presses are totally enclosed to prevent fugitive odors, operate at slow rotational speeds and low noise, efficient solids removal (although not as high as the existing plate and frame presses), and have very low power consumption. A Fournier press would not require the high pressure and power cost of the existing ram press pumps. Typically progressive cavity or hose pumps are used A B - 5 Wright-Pierce

103 The costs presented below are total costs to refurbish or replace equipment for two units: Priority Description Estimated Cost Medium Refurbish ram press pumps, provide spare capacity $130,000 High Provide new ram press pump control panels $10,000 High Upgrade plate separator mechanisms $110,000 Low Replace plate (cost per plate) $4,000 Medium Replace Drip flap/launder sub assemblies $20,000 High Replace press control panels with PLC-based control panel $40,000 Option 1 High Replace existing screw closure mechanism in kind $210,000 OR Option 2 High Replace screw closure mechanism with hydraulic system $110,000 Alternative Replace existing plate presses with Fournier Presses $500,000 Filtrate Equalization and Pumping The original filtrate equalization system consisted of two 80,000-gallon storage tanks (located adjacent to the two septage equalization tanks) with submersible mixers. As part of the 1995 upgrade, a new 200,000-gallon filtrate equalization tank was constructed complete with fine bubble membrane aeration system complete with two blowers. Additionally, a coarse bubble aeration system complete with two blowers was installed for aeration of the two existing 80,000- gallon filtrate equalization tanks. Four new 50-gpm progressive cavity filtrate pumps and piping were also installed to allow pumping from the three tanks into the primary clarifier distribution box. The condition of the existing filtrate tanks should be inspected. Estimated Priority Description Cost Low Inspect filtrate equalization tanks $5, A B - 6 Wright-Pierce

104 Primary Clarification After equalization, the filtrate is pumped by the filtrate pumps through a reaction tank and flow splitter which directs flow to the two 16-foot diameter primary clarifiers. The primary effluent from the clarifiers flows to the RBC flow splitter. Primary sludge is pumped to the septage equalization tanks by three original progressive cavity pumps, each with a capacity of 50 gpm. The primary clarifiers were part of the original plant construction, and show signs of corrosion and wear. The plant staff recently repaired the drives and gearboxes, and replaced the walkways. The weirs have corroded in place such that vertical adjustment is no longer possible. The primary sludge pumps have been in service for approximately 15 years, and may be nearing the end of their useful service life. Priority Description Estimated Cost High Replace all metalwork in the clarifiers. $90,000 Low Refurbish primary sludge pumps $10,000 Medium Provide enclosure over primary splitter structure. Connect primary clarifiers and splitter structure to odor control system. $50,000 Rotating Biological Contactors (RBCs) The RBC flow splitter directs flow from the primary clarifiers to one of the four RBCs, which are operated as four separate parallel units. Each of the four RBCs has four stages, and approximately 100,000 square feet of plastic media per shaft. The RBCs are the heart of the secondary treatment process and are responsible for the majority of the BOD removal in the treatment process. The facility is operated such that the primary effluent is directed to three of the RBC's, while the fourth serves as a polishing step for the recycle flows. The RBCs are capable of converting 100% of the ammonia in the primary clarifier effluent to nitrate (complete nitrification). Although the facility was not designed for total nitrogen removal (nitrification followed by denitrification), some denitrification is provided by recycling flow to the anaerobic portion of the septage equalization tanks. After biological treatment in the RBCs, flow is pumped by the intermediate pump station to the secondary clarifiers. The intermediate pump station consists of two new progressive cavity pumps that were installed as part of the 1995 upgrade, each with a capacity of 80 gpm. While the pumps are identical, one of the new pumps was designed to recycle RBC effluent back to either the septage or filtrate equalization tanks while the second pump was designed to pump the RBC effluent to the secondary clarifier splitter box. In 2002, the District retained Wright-Pierce for the design of a project to replace the shafts and media on two of the RBC's, and that work was completed in The new media was provided by US Filter while the remaining original media was manufactured by Lyco A B - 7 Wright-Pierce

105 No odor control is provided for the primary clarifiers and RBCs, however all processes are covered. If the facility were to begin taking municipal wastewater, the staff expressed the likelihood that odor control for these processes would be required. Priority Description Estimated Cost High Replace shafts and media on two remaining RBC's. $200,000 Medium Replace drives on all RBC's $100,000 Low Consider odor control for RBC's N/A Secondary Clarification Two new secondary clarifiers were installed as part of the 1995 upgrade project to replace the original Lamella-type clarifiers which were ineffective at secondary solids removal. The Lamella-type clarifiers currently receive gravity flow from the RBCs and effluent is withdrawn from these units by the new intermediate pump station pumps discussed above. The upgrade included the addition of two 16-foot diameter enclosed circular secondary clarifiers to match the existing 16-foot diameter enclosed primary clarifiers. A liquid polymer blending and injection system was also added to inject polymer into the RBC effluent prior to clarification. Each clarifier is provided with a flocculation-style center feed well to allow for mixing and flocculation of the solids to aid in settling. One clarifier is adequate to provide good settling and the second clarifier serves as a standby unit. The secondary clarifiers have been very effective at removing both total suspended solids (TSS) and BOD from the RBC effluent. Two progressive cavity secondary sludge pumps convey sludge from the clarifier underflow to the septage equalization tanks. These progressive cavity pumps were installed as part of the 1995 upgrade and each has a capacity of 10 gpm. Although the existing Lamella clarifiers are no longer used, they were left in place to minimize piping revisions that would have been necessary as part of the 1995 upgrade. However, the staff have indicated that the clarifiers are beginning to show signs of corrosion, and should therefore be decommissioned, and the piping revised as necessary. Priority Low Description Decommission lamella clarifiers and reconfigure intermediate pump piping accordingly. Estimated Cost $20, A B - 8 Wright-Pierce

106 Sand Filtration As part of the 1995 upgrade project, the Department of Environmental Protection (DEP) required that two, 19-square-foot upflow sand filters be installed to ensure the TSS discharge limit of 30 mg/l is always met. As Wright-Pierce anticipated during the design, with proper operation of the secondary clarifiers, the sand filters are not used for TSS removal. In the summer months, the filters are used to denitrify the effluent prior to discharge. In the winter months, the filters are taken out of service. The sand filters are backwashed/cleaned with an air compressor with the backwash or "mud" overflowing to the mudwell pump station. The mudwell pump station consists of two submersible pumps which recycle the "mud" back to the septage equalization tank. No action required Disinfection and Discharge Effluent from the sand filters flows by gravity through two banks of enclosed UV disinfection units, each with a capacity of 100 gpm. The after UV disinfection, the final effluent flows into an effluent dosing tank. Two submersible effluent dosing pumps, each with a capacity of 55 to 85 gpm, discharge treated effluent to one of four sand beds for rapid infiltration into the ground. In 2000, Wright-Pierce worked with the plant operators to size and select two new effluent dosing pumps to replace the original pumps. The two new pumps were installed and became operational in As part of the 1995 upgrade project, a new plant water system was installed which draws treated effluent from the effluent dosing tanks and pumps it to various locations throughout the plant where treated effluent is needed such as for tank cleaning and gravity belt thickener spray water. No action required Odor Control The Tri-Town facility was originally provided with a two-stage wet chemical scrubber followed by dual activated carbon beds for polishing of the scrubber exhaust. Odorous air from the septage receiving tanks, filtrate tanks, receiving garage, dewatering room and sludge garage is collected and discharged into this system. The system is still operated, but limited work has been done to determine the effectiveness of the odor removal or to balance the ductwork system to ensure sufficient air is being withdrawn from each space. The media for the carbon system was recently switched from permanganate-impregnated to Centaur brand media. The life of the media is estimated to be 4 to 5 years. As part of the 1995 upgrade, a new two-stage wet chemical scrubber system, followed by a carbon adsorption system, was installed. This 3,100-cfm system treats odorous air from the new filtrate tanks, GBT Room, new grease tanks, and the existing septage conditioning tanks. This new odor system is operating satisfactorily A B - 9 Wright-Pierce

107 Priority Description Estimated Cost High Evaluate condition of wet scrubber. $1,000 Low Replace as necessary. $75,000 Chemical Feed Building The Chemical Feed Building was built as part of the original treatment facility construction. The building included a 6,000-gallon bulk hydrochloric acid tank and two hydrochloric acid feed pumps to lower the ph of the filtrate prior to the biological process. Additionally, a containment area for storage of phosphoric acid drums and two phosphoric acid feed pumps were constructed in the building. The phosphoric acid was used to raise the phosphorus level in the wastewater prior to biological treatment. In the early 1990's, the 6,000-gallon storage tank failed. Even though the failure was contained in the secondary containment structure, the acid fumes caused significant damage in the space including doors, control panels, and equipment. For a period in 1997, access to the building was restricted by the Orleans Building Inspector, Electrical Inspector and Fire Chief because of structural and electrical concerns. In 1997, Wright-Pierce conducted a structural and electrical evaluation of the Chemical Building. The evaluation found the building to be structurally sound and suitable for entry. All of the electrical equipment was determined to be damaged beyond the point where it could be considered safe to use and complete removal and replacement was recommended prior to restoring power to the building. Additionally, it was recommended that access doors to the facility, which are severely corroded, be replaced. In 2001, Wright-Pierce conducted another brief evaluation of options for the Chemical Building but, to date, no upgrades have been conducted. The Chemical Building is no longer needed for chemical storage and addition. The building could make an ideal unheated storage space, or may be needed for future treatment processes. Upgrades to the building should be postponed until after the evaluation of the Tri-Town Septage Facility is completed. Possible Action Demo and rehab chemical building. Provide drive through maintenance area A B - 10 Wright-Pierce

108 Miscellaneous Building Systems The plant operators commented on various minor issues throughout the plant, some of which should be addressed as routine maintenance. However, two items were considered to be more than nuisance, and could affect the operation of the plant, the condition of the air compressor, and the operation of water system gate valves. The air compressor is located in a room in the lower pump gallery. The operators indicated that the air compressor accumulates excessive moisture, requiring monthly changing of the oil, and water in the air line. The compressor is provided with an air dryer, however its performance is questionable. The service reps for the compressor have advised that the problems with excessive moisture may be due to the unit's location in the facility, which is exacerbated by the proximity of marine ambient conditions. The operators indicated that the gate valves on the plant water system are corroded and are subject to water hammer. Priority Description Estimated Cost High Provide new air dryer for compressor system $15,000 High Relocate compressor. $10,000 Low Refurbish gate valves on the plant water system. Address water $5,000 hammer. B. UPGRADING TO MEET 10 MG/L N STANDARD The discharge permit for the Tri Town facility is due to be re-issued in 2007 (Steve/Jay--please confirm). Based on current trends, it is possible that the new permit will impose a nitrogen limit of 10 mg/l, which is a common limit in southeastern Massachusetts. Accordingly, Wright- Pierce evaluated the ability of the existing facility to be upgraded for a 20-year service life, and to meet an effluent discharge limit of 10 mg/l N. Based on conversations with the plant's operations staff and a review of recent operating data, the plant is able to fully nitrify (conversion of TKN to nitrates) at the existing loading conditions. A recycle stream from one of the RBC's is seasonally directed to the septage holding tanks to achieve partial denitrification (conversion of nitrates to nitrogen gas) for total nitrogen reduction. However, this is an uncontrolled process, and will not consistently meet a discharge N limit of 10 mg/l. Therefore, the existing plant will not be able to meet a 10 mg/l N limit by modifying the existing process train without new equipment. For the scale of the Tri-Town facility, and in consideration of the existing process, two treatment modifications appeared feasible for consideration: 1) install anoxic RBC's; and 2) modify or upgrade existing sand filters to denitrification filters. Anoxic RBC's would be located immediately downstream in series with the existing RBC's. Denitrification requires anoxic conditions (i.e. presence of nitrates with little or no dissolved oxygen), and an organic carbon source. Anoxic RBC's are similar to aerobic RBC's except that 10461A B - 11 Wright-Pierce

109 the entire RBC media is submerged to preclude exposing the denitrifying bacteria to oxygen, which can poison the denitrification process. The process flow scheme to provide anoxic RBC's is typically achieved in one of two ways, either by a pre-anoxic or post-anoxic arrangement. In a pre-anoxic scheme, the anoxic RBC's are located ahead of the aerobic RBC's to utilize the influent wastewater as a carbon source, and recycle nitrified effluent to the anoxic RBC's. The post-anoxic scheme locates the anoxic RBC's downstream of the aerobic RBC's; the organic carbon requirement is typically achieved through methanol addition. Although the pre-anoxic scheme offers several advantages, the existing site constraints are not considered to be amenable to installing a pre-anoxic configuration. Installation of post-anoxic RBC's at the Tri-Town facility would require relatively deep excavations, as the existing hydraulic grade at the effluent of the existing RBC's would need to be maintained. The difficulty of construction due to the limited space available and proximity to the disposal beds, in concert with the high expected equipment costs, were considered to be less favorable than installation of denitrification filters. Denitrification filters are a well-established technology commonly used to achieve denitrification at a wide range of plant sizes. Denitrification filters achieve two functions, suspended solids removal and denitrification. In concept, a denitrification filter is similar to a conventional sand filter, with the exception that the pore size is larger to allow for biological growth, and that a supplemental carbon source is fed, typically methanol. Denitrification filters are always used on clarified secondary effluent to reduce the solids loadings to the filters. In a properly performing secondary process, the majority of TKN in the wastewater will be converted to nitrates, or removed from the wastewater in the biological sludge. However, since the effluent will be low in a carbon source (i.e. BOD), a supplemental carbon source such as methanol is necessary to promote denitrification. Denitrification filters (commonly abbreviated as "denite filters") take up less space than an anoxic RBC. Since the Tri Town facility is already equipped with a building to accommodate the existing sand filters, the most feasible option to provide denitrification would be to either convert the existing filters to denite filters or replace them with a new denite filter system. Wright-Pierce evaluated the feasibility of converting the existing Andritz filters to sand filters. Unfortunately, Andritz has no experience with this process, and the existing media and equipment are unsuitable for conversion. Therefore, various other manufacturers and vendors were contacted to determine the scope and supply to demolish the existing filters for replacement with a new denite filter system. The two new filters would be 5 feet in diameter, by 13 feet high, with 5 feet of media. The cost for the filters would be approximately $175,000. From a preliminary review of the proposed equipment dimensions, it appears that the new filters could be retrofit into the existing Filter Building, without requiring significant modification to the UV system. The existing chemical feed system would be converted to a methanol feed system. A 25% methanol solution would be recommended to avoid NFPA regulations, and would allow the drums and pumping equipment to be located in the existing room. To upgrade the existing facility for a 20-year design life, and meet a 10 mg/l N, Wright-Pierce recommends that the following action be considered: 10461A B - 12 Wright-Pierce

110 Make all the improvements stated in Section 4.1 Demolish the existing Andritz filters, and replace them with new denitrification filters. Provide new methanol feed system. C. UPGRADING TO MEET INCREASED SEPTAGE LOAD As part of the evaluation, Wright-Pierce determined that the facility might be upgraded to meet a septage flow of 60,000 gpd, with a nitrogen limit of 10 mg/l. This increased capacity would allow acceptance of septage from Lower Cape towns through build-out. All of the existing unit processes have the capability of meeting this increased load, with the exception of the denite sand filters. As above, two new denite filters would be required to meet the existing septage flow and to provide denitrification to achieve a total nitrogen limit of 10 mg/l. However, the filters recommended above would not have adequate additional capacity to meet a septage flow of 60,000 gpd. To meet the increased septage flow, an additional filter unit would be required, which would also require a small addition to the existing filter building to accommodate the third filter unit. The total cost for these additional features would be approximately $100,000, above the cost upgrading for two filters discussed above. In addition to the capital costs, the operating and maintenance costs to provide treatment for 60,000 gpd must also be considered, to include labor, power and chemicals. In addition to denite filters, there may be a need for additional effluent disposal facilities to handle 60,000 gpd. We have considered a site layout that includes an additional set of rapid infiltration basins that should be more than adequate to handle the assumed one-third increase in capacity. (If the Town and District were to proceed with this option, we recommend that a fullscale loading test be conducted on the existing basins to determine their full capacity. It is conceivable that no additional basins are needed. It is also possible that surface plugging of the existing basins may have reduced their capacity and that more than one third of additional capacity is needed.) For planning purposes, we propose that the project budge include $70,000 for new infiltration basins and piping. D. NEW WASTEWATER FACILITY The Town's Comprehensive Wastewater Management Plan will consider options to provide public sewers in portions off the Town, and to provide a new wastewater treatment facility to accommodate wastewater flows and septage. The evaluation that follows was based on constructing a new wastewater treatment facility near the existing septage treatment plant with an summer capacity of 0.5 million gallons per day (mgd) and an annual average flow of about 0.3 mgd. Part of the existing plant would remain operational for solids and residuals handling. Waste sludge from the new plant would be pumped to the existing septage storage tanks, from which solids thickening and dewatering processes would be carried out similar to existing operations A B - 13 Wright-Pierce

111 The primary selection criteria for the technologies to be considered must be able to achieve the following objectives: Reliability The system must be designed to consistently and efficiently achieve the discharge standard. Process Control The system must provide sufficient process flexibility to address varying influent flows and loads and to achieve the stringent discharge criteria without increasing process complexity. Maintenance The equipment must be designed to maximize equipment life, to minimize maintenance requirements, and to maximize serviceability when maintenance is recommended or required. For the alternative to provide a new wastewater treatment facility, a broad range of treatment technologies was considered. Two candidate technologies emerged: sequencing batch reactors (SBR's) and membrane bioreactors (MBR's). Both technologies have demonstrated performance at other facilities with characteristics and design issues similar to those anticipated for Orleans. Some of the aspects of these technologies that make them favorable for consideration in Orleans include: Compact design to minimize the land area required for installation High effluent quality to meet stringent discharge limits typical of Cape Cod Enclosed unit processes to minimize odor impacts to nearby receptors Highly automated process control to reduce operational costs Ability to adapt to widely varying seasonal loadings Sequencing Batch Reactor (SBR) The sequencing batch reactor (SBR) alternative would be designed for nitrification and denitrification, with the option to provide biological phosphorus removal. The SBR process does not use separate clarifiers, since the tanks are decanted and sludge wasted directly from the settled tank volumes. This reduces the amount of space required for the process, which is a major advantage in cases where a limited amount of room is available. One disadvantage of the batch process is that the flows usually must be equalized after decanting in order to avoid the need to oversize all downstream processes, and the outfall sewer. Construction of multiple SBR basins can often minimize the necessary equalization volume. In the SBR process, each reactor undergoes a cyclical operation including the following steps: "fill", "mix and fill", "aerate", "settle", and "decant". SBRs have the capability, through adjusting aeration levels, throughout the different cycles, to nitrify and denitrify, and to biologically remove phosphorus (with the addition of anaerobic selector tanks). A typical SBR facility for the Tri Town facility would consist of the following processes: Preliminary treatment using a bar screen or comminutor, and a vortex grit removal system. Influent equalization and sludge recycle tanks A B - 14 Wright-Pierce

112 SBR tanks with aeration and decanting equipment. SBR effluent equalization tanks. Aeration system blowers. SBR effluent filtration using traveling bridge sand filters or cloth media. UV disinfection. Pump liquid sludge to the existing septage facility for waste sludge thickening, storage, and dewatering. Effluent disposal via rapid infiltration or subsurface leaching. Membrane Bioreactor (MBR) Membrane technology was originally developed primarily for industrial wastewater treatment. However, in the last few years, membrane technology has been gaining wide acceptance for municipal wastewater treatment. The technology has been adapted for municipal use with the development of high permeability hollow fiber membranes that need only a low vacuum to draw the wastewater through the fiber into the collection manifolds. The membrane rack modules are typically inserted directly into an aeration tank, or into an existing aerated lagoon that has been modified in order to accept the MBR modules. Flat plate membranes are also coming onto the market. In the MBR process, a vacuum is applied to a header that is connected to the membranes. The vacuum draws the treated wastewater through the hollow fiber membranes, and the effluent is then disinfected and discharged. Air is introduced into the bottom of the MBR in order to create turbulence that scours the external surface of the membranes. One of the limitations of membrane technologies is the inability of the membranes to accommodate variations in load above the design average. The manufacturers concede that a membrane system will not be cost competitive if the ratio of peak to average flows is greater than 2.5 to 3.0. However, this limitation may be accommodated by providing equalization volume. The very small filtration pore size that has extremely high capture efficiencies for total suspended solids (TSS), biochemical oxygen demand (BOD), phosphorus, nitrogen and metals. The small pore size also allows high concentrations of biomass with long sludge ages. This allows for high levels of nitrification and denitrification, while also minimizing space requirements. The effluent from MBR plants often meets the stringent regulatory requirements for direct reuse applications, such as landscape irrigation, or California Title 22 Standards for Recycled Water or Mass DEP Reclaimed Water Guidelines. The long sludge age of a membrane system allows for endogenous respiration and thus reduced sludge production. In addition, the complete mix tanks allow for the introduction of chemicals to precipitate and then capture high levels of phosphorus in the sludge if necessary. At times the membrane pores can fill with fine particulates and become coated with biomass, thus becoming clogged and reducing hydraulic capacity. The membranes require periodic backwash with a chlorine solution to regain hydraulic capacity. Since some of the units will 10461A B - 15 Wright-Pierce

113 always be in the backwash mode, the system needs to be sized to provide for one or more units to be off line at a time. The clogging issue is still the biggest uncertainty for MBRs in the municipal wastewater market; clogging problems have limited the use of many filter systems in the past, and may prevent the MBR technology from being cost effective in the municipal market. It should be noted that the MBR process is not fully proven in the municipal wastewater market at sizes proposed for Orleans. Small units and pilot units have published histories, but full scale long-term operational data is not yet available. In addition, replacement frequency of the membranes is not well established as yet; this can possibly result in substantial unforeseen costs. Annual power costs associated with the MBR technology may be higher when compared with other biological and physical treatment processes. A typical MBR facility would consist of the following processes: Preliminary treatment using a bar screen or comminutor, and a vortex grit removal system. MBR equipment building. MBR tankage and equipment. Permeate pump system and equipment. Membrane air scour blower and appurtenances. Sludge recirculation and wasting system. UV disinfection system. Pump liquid sludge to the existing septage facility for waste sludge thickening, storage, and dewatering. Effluent disposal via rapid infiltration or subsurface leaching. Either of the candidate technologies would be capable of producing a high quality effluent to meet the expected discharge permit. However, it should be noted that for a given wastewater, the MBR technology will most likely produce the highest quality effluent. Although the Massachusetts DEP considers MBR's to be a relatively new technology, there are several membrane plants currently in operation in Massachusetts, all of which have consistently met permit requirements A B - 16 Wright-Pierce

114 The relative advantages and disadvantages of SBR and MBR technologies are presented in Table 4-X: Table 4-X - Relative Advantages and Disadvantages of SBR's and MBR's Technology Advantages Disadvantages SBR MBR Extensive performance record Familiar technology Smaller building area Less equipment High effluent quality Complete package process service and support Operator experience Structural requirements Larger building Higher equipment maintenance costs Less extensive operating history Higher equipment capital costs Only 1 or 2 proven manufacturers Unknown long-term life cycle costs Limited ability to accommodate peak to average flow ratio > 2.5 Detailed costs estimates were not performed for this study that could conclusively state one technology as being more cost effective than the other. However, based on Wright-Pierce's experience with plant's of similar size and technology, the total expected project cost for either technology including construction, engineering, contingency would be expected to be approximately $7 to 9 million, based on a 2006 bid date. Operations and Maintenance Costs Estimates of future O&M costs were based on information provided by the plant staff. The data included the budgetary O&M data, adopted budget, and the actual expenditures for years 2002, 2003, and Actual expenditures for only years 2002 and 2003 were available. A review of the costs revealed a disparity between the budgeted O&M costs compared to the actual costs. To project future O&M costs, only the actual expenditures were used as a basis. Each of the actual O&M cost items as provided by the District were grouped into the following general categories: salaries, administrative, electrical, fuel, utilities, lab, Chemicals, maintenance, sludge, and miscellaneous. The costs for fiscal years 2002 and 2003 for this grouping are presented in Table. The table indicates that salaries and benefits comprise the largest O&M expenditure. Some of the costs reveal an unexpected decrease in amount from 2002 to 2003, such as salaries, electrical, and sludge disposal. The reason for this is unknown, and was beyond the scope of this study. The costs from FY '03 and '04 were then used to develop costs for each of the four upgrading options presented as part of the evaluation, namely Upgrading for a 20 year life with no change in discharge limits, 10461A B - 17 Wright-Pierce

115 Upgrading for a 20 year life, and a 10 mg/l N limit Upgrading for a 20 year life, 10 mg/l N limit and increase in flows to 60,000 gpd Provide a new 0.5 mgd treatment plant for sewered flows. O&M costs for upgrading for a 20 year life were estimated based on a qualitiative assessment of the cost categories for '03 and '04. Due to the disparity in the costs between the two years, and the lack of supporting data, other methods of projection such as calculating the average of the two years was not considered to be as relevant for projections. The resulting costs were increased by a nominal amount, to represent the projected O&M costs for FY 2006, and are presented in Table. These costs for 2006 represent the expected costs to upgrade the facility for a 20 year design life, while maintaining the same level of treatment and flow. O&M costs for future years would be projected at the selected rate of inflation. As discussed in Section, the capital improvements for the second scenario, upgrading for 20 year design life, and treatment capability to meet 10 mg/l N, would consist of installation of denitrification filters. The proposed denitrification filters are a low energy consumption process system, and the labor, electrical and maintenance requirements would be expected to present only a marginal increase in these costs. Therefore, O&M costs to provide treatment capability to 10 mg/l N would not be expected to increase significantly beyond the projected costs to upgrade for a 20 year design life as presented in the first scenario. The third scenario consists of the same criteria as the second scenario, while also increasing capacity of the facility to meet 60,000 gpd. For this evaluation, the O&M costs established in Table for FY '06 were used as a starting condition. However, under this scenario, two factors would be expected to inflate costs for future years, the rate of inflation, and the increased O&M to accommodate additional flow, essentially a 33% increase of existing design flows. The starting year for treating an increasing flow volume was projected to begin in FY '07, or 4 years from the latest available actual operating data. Thus all costs from FY'06 were inflated at 3% annually. In addition to the annual inflation, some costs would be expected to increase proportionally to an increase in flow, while othwer costs would not be expected to do likewise. A summary of these cost considerations due to increasing flow capacity is provided below: Salaries and benefits - Salaries and benefits would not be expected to increase proportional to taking more flow. However, if the workload for existing staff is found to justify adding personnel, this would increase salary costs accordingly. For this evaluation, no increase in personnel was presumed. Administrative - Administrative costs would not be expected to increase; Electrical - Electrical costs would be expected to increase to accommodate additional flow, however, not uniformly. Some electrical demands would see no increase, such as lights, computers, instrumentation, while other process electrical demands would increase, such as pump run times, etc. Furthermore, other electrical demands for process equipment would not increase, such as RBC's, UV, etc. Therefore, to project electrical costs to accommodate increasing flow volume, an arbitrary inflation rate of 33% was applied to half of the FY '06 electrical costs; Fuel - Fuel costs would not be expected to increase; 10461A B - 18 Wright-Pierce

116 Utilities - Utility costs would not be expected to increase; Laboratory - Laboratory costs would not be expected to increase; Chemicals - Chemical costs would not be expected to increase Maintenance - Equipment maintenance costs would be expected to increase proportional to the increased flow rate; Miscellaneous - costs would not be expected to increase. The resulting O&M costs are provided in Table. The fourth scenario involves providing a new 0.5 mgd treatment facility. For this scenario, existing cost data would be irrelevant. Accordingly, Wright-Pierce reviewed O&M cost estimates prepared for other projects of similar size and scope. Using these sources of information, approximate O&M costs for a new wastewater treatment facility were estimated as shown in Table A B - 19 Wright-Pierce

117 APPENDIX C Upgrading Needs 10461A B - 20 Wright-Pierce

118 APPENDIX C UPGRADING NEEDS Appendix A contains a detailed appraisal of the existing condition of the Tri-Town Septage Treatment Facility. Sections 4 and 6 of the report define four broad options for upgrading the septage facility and for other uses of the site. This Appendix C provides the technical basis for each of the four broad options. UPGRADING TO EXTEND USEFUL LIFE BY 20 YEARS Below is a summary of the function and condition of each of the facility's major unit processes, as well as recommendations for each unit process to extend the life of the facility for another 20 years. Also presented for each unit process is a relative priority of the recommended upgrading, as well as the estimated installation cost (that is, equipment cost plus contractor's installation cost). Septage and Grease Receiving and Treatment Septage and grease from grease traps are delivered to the facility in both traditional 2,500-gallon tank trucks, as well as larger 5,000-gallon tanker trucks. Prior to and after discharge into the treatment facility, septage and grease delivery trucks are weighed on either a 30-foot-long, 30- ton scale in the southern truck bay and a 60-foot-long, 60-ton scale in northern truck bay. Weighing and discharge of incoming loads of grease are carried out in the southern truck bay due to the location of the grease discharge point. Septage is discharged via a quick connect hose fitting at the septage receiving station after which it flows through a manually cleaned bar rack and into the grit wetwell. A mechanically screened bar rack was installed as part of the original plant construction; however, it has not been used for some time. According to the staff, the bar screen was sized inappropriately to handle the surges from a septic truck, resulting in material being forced through the screens. Also, the cycle time is too slow to keep pace with the pressurized discharges from the haulers. Also, to accommodate the larger tankers used by some of the haulers, increasing the bay height or providing an external hookup should be considered. Priority High High Description Replace bar screen with a new unit, or consider installation of a step screen, Rotamat fine screen, etc. This would most likely require extensive modifications to the headworks area. - or - Consider installation of a Septage Acceptance Plant. (This unit would accomplish both screening and grit removal) Estimated Cost $170,000 $310, A C - 2 Wright-Pierce

119 Grit Removal The septage receiving equipment (screens, grit wetwell, grit pumps, grit classifier) represent the most problematic areas for the plant staff, which is not unexpected. These facilities are part of the original plant construction and have been in service for 15 years. They are also subject to the greatest wear and most corrosive conditions. The grit cyclone installed as part of the original project shows signs of corrosion and wear, and may be approaching the end of its useful service life. Although the unit is still performing well, maintenance has become a problem due to the difficulty in obtaining replacement parts. The accumulated grit is heavily laden with sludge and organics. Estimated Priority Description Cost High Repair, or (preferably) replace the grit classifier. $50,000 Medium Low Consider installation of a grit separator to precede the classifier, such as an enclosed vortex grit unit. (Septage Acceptance Plant as recommended above would include grit removal). Evaluate wear on grit pump discharge piping, and replace as necessary. $70,000 $5,000 High Replace sump pumps in the grit area and blower room. $10,000 Septage Equalization and Aeration Degritted septage, pretreated grease and filtrate treatment recycle flows are all pumped to the two Septage Equalization Tanks. Each tank has a capacity of 135,000 gallons, which provides a holding time of approximately 3 days per tank at design flow. The septage equalization tanks are equipped with a coarse bubble aeration system and positive displacement rotary lobe blowers installed as part of the 1995 upgrade. The aeration system and blowers are regularly utilized to mix the contents of the equalization tanks and maintain solids in suspension prior to thickening. Lime is added to the septage on a daily basis to raise the ph, such that the resulting filtrate will be within an acceptable range for the biological treatment system. The lime also suppresses the formation of sulfides, which helps control odors. The staff suspects that the condition of the equalization tanks is poor, and confirmed that their condition has never been assessed. Inspection of the tanks is therefore recommended to ensure their integrity for the next 20 years. Estimated Priority Description Cost Medium Evaluate condition of the septage equalization tanks. $10, A C - 3 Wright-Pierce

120 Septage Thickening The majority of the septage thickening and transfer system was installed as part of the 1995 upgrade and consists of the three original recessed impeller centrifugal feed pumps with antecedent grinders, two gravity belt thickeners (GBTs), two polymer feed systems, two spray wash pumps, and two positive displacement, double disc thickened septage transfer pumps. The purpose of the septage thickening and transfer system is to reduce the amount of water in the septage before dewatering using the plate and frame filter presses to minimize press run times. Facilities for injection of permanganate for odor control and polymer to enhance thickening are provided. Septage in the septage equalization tanks is pumped to the GBT's by one of three original recessed impeller pumps, located in the Operations Building basement. The pumps were upgraded in 1995 with supplemental sheaves and VFDs to provide a range of flows from 240 to 400 gpm. The Chief Operator stated that the grinders are not providing adequate maceration of material, and may need to be replaced. The GBT's were installed as part of the 1995 upgrade. Each GBT has a capacity of 150 gpm at 400 lb/hr dry solids, depending on the septage solids content. Only one GBT is intended for operation at a time, while the other unit is a standby. Although the GBT's can thicken the septage to a solids content of as high as 10%, a solids content of approximately 3 to 4% is targeted which facilitates handling by the double disc pumps. Each GBT is provided with two chemical feed systems, for permanganate and polymer addition. After thickening, two double-disc pumps with a capacity of 20 gpm each transfer the thickened septage to the septage conditioning tank. Odors from the GBT area are treated by a two-stage scrubber installed as part of the 1995 upgrade. Odor control systems is discussed later in this section. Estimated Priority Description Cost Medium Replace existing grinders with a Moyno Pipeliner grinder. $30,000 Septage Conditioning The conditioning of the septage prior to thickening is accomplished with a polymer solution and potassium permanganate that is injected into the septage by two chemical feed systems before thickening. The polymer feed system and potassium permanganate feed system are used to allow effective thickening and to minimize the odors in the GBT Room, respectively. The conditioning of septage prior to dewatering is conducted in two conditioning tanks. During the 1995 upgrade, each conditioning tank was retrofitted with a new mixer to allow for better mixing of the thickened septage. In addition to injecting polymer upstream of the thickening process, the polymer feed system allows polymer injection into the septage conditioning tank for mixing prior to dewatering. This treatment step replaces the original lime and ferric chloride 10461A C - 4 Wright-Pierce

121 conditioning system. Potassium permanganate can also be added directly into the septage conditioning tank to minimize release of odors in the dewatering room. The staff requested that unused equipment for the chemical feed systems and the reaction tank mixers be decommissioned. Also, the lime storage silos have some minor cracking, which allows some seepage of product into the lime feed area. Priority Description Estimated Cost High Decommission the unused reaction tank mixers $10,000 High Decommission the permanganate and ferric systems. $10,000 Medium Repair cracks in lime storage silos. $20,000 Low Upgrade lime feed controls $10,000 Septage Dewatering The septage dewatering system is essentially the original system and it has been in operation since The only changes to the system as part of the 1995 upgrade include the use of polymer for thickened septage conditioning and the fact that the presses now dewater thickened septage instead of raw septage. The dewatering system consists of three hydraulic ram press pumps, and two plate and frame filter presses. The ram presses each have a capacity of approximately 200 gpm. The filter presses are each rated for approximately 1,220 lb/hr (wet basis), and are designed to produce a cake with 20% to 40% solids. The filter presses have performed satisfactorily, although the original equipment manufacturer, Edwards-Jones, is no longer in business. The Edwards-Jones line of equipment has been acquired by US Filter. The monorail over the two presses does not provide adequate clearance for plate removal. This requires manual plate removal and maintenance which presents a serious risk of injury to the operators. The safety light curtains for each press have recently been replaced. A representative from US Filter visited the site to assess the condition of the presses and pumps, and to make recommendations for refurbishing both unit processes for a 20-year life. In addition, the operators requested, at a minimum, that the existing press closure mechanism be replaced with a hydraulic mechanism, and that standby capacity for the ram press pumps be provided. The ram press pumps showed signs of wear and leaking oil, and should be refurbished as outlined in the US Filter scope. The US Filter representative stated that the existing press frames are in acceptable condition and do not need to be replaced, however a cost per plate is provided as requested by the Chief Operator. Some of the equipment recommended for replacement could not be observed directly without disassembly. Consequently, a portion of the cost proposal for upgrading work is an assessment based on the representative's experience on parts that would need replacement due to the equipment's age. The US Filter representative also recommended that the condition of the existing ram press pump pistons should be evaluated. An alternative to refurbishing the existing presses would be to consider the installation of two Fournier Rotary Presses. Fournier presses are gaining acceptance at many wastewater treatment plants and are also being retrofit to replace other dewatering mechanisms, due to their distinct 10461A C - 5 Wright-Pierce

122 design advantages. Fournier presses are totally enclosed to prevent fugitive odors, operate at slow rotational speeds and low noise, efficient solids removal (although not as high as the existing plate and frame presses), and have very low power consumption. A Fournier press would not require the high pressure and power cost of the existing ram press pumps. Typically progressive cavity or hose pumps are used. The costs presented below are total costs to refurbish or replace equipment for two units: Priority Description Estimated Cost Medium Refurbish ram press pumps, provide spare capacity $130,000 High Provide new ram press pump control panels $10,000 High Upgrade plate separator mechanisms $110,000 Low Replace plate (cost per plate) $4,000 Medium Replace drip flap/launder sub assemblies $20,000 High Replace press control panels with PLC-based control panel $40,000 Option 1 High Replace existing screw closure mechanism in kind - or - $210,000 Option 2 High Replace screw closure mechanism with hydraulic system $110,000 Alternative Replace existing plate presses with Fournier Presses $500,000 Filtrate Equalization and Pumping The original filtrate equalization system consisted of two 80,000-gallon storage tanks (located adjacent to the two septage equalization tanks) with submersible mixers. As part of the 1995 upgrade, a new 200,000-gallon filtrate equalization tank was constructed complete with fine bubble membrane aeration system complete with two blowers. Additionally, a coarse bubble aeration system complete with two blowers was installed for aeration of the two existing 80,000- gallon filtrate equalization tanks. Four new 50-gpm progressive cavity filtrate pumps and piping were also installed to allow pumping from the three tanks into the primary clarifier distribution box. The condition of the existing filtrate tanks should be inspected. Estimated Priority Description Cost Low Inspect filtrate equalization tanks $5, A C - 6 Wright-Pierce

123 Primary Clarification After equalization, the filtrate is pumped by the filtrate pumps through a reaction tank and flow splitter which directs flow to the two 16-foot-diameter primary clarifiers. The primary effluent from the clarifiers flows to the RBC flow splitter. Primary sludge is pumped to the septage equalization tanks by three original progressive cavity pumps, each with a capacity of 50 gpm. The primary clarifiers were part of the original plant construction, and show signs of corrosion and wear. The plant staff recently repaired the drives and gearboxes, and replaced the walkways. The weirs have corroded in place such that vertical adjustment is no longer possible. The primary sludge pumps have been in service for approximately 15 years, and may be nearing the end of their useful service life. Priority Description Estimated Cost High Replace all metalwork in the clarifiers. $90,000 Low Refurbish primary sludge pumps $10,000 Medium Provide enclosure over primary splitter structure. Connect primary clarifiers and splitter structure to odor control system. $50,000 Rotating Biological Contactors (RBCs) The RBC flow splitter directs flow from the primary clarifiers to one of the four RBCs, which are operated as four separate parallel units. Each of the four RBCs has four stages, and approximately 100,000 square feet of plastic media per shaft. The RBCs are the heart of the secondary treatment process and are responsible for the majority of the BOD removal in the treatment process. The facility is operated such that the primary effluent is directed to three of the RBC's, while the fourth serves as a polishing step for the recycle flows. The RBCs are capable of converting 100% of the ammonia in the primary clarifier effluent to nitrate (complete nitrification). Although the facility was not designed for total nitrogen removal (nitrification followed by denitrification), some denitrification is provided by recycling flow to the anaerobic portion of the septage equalization tanks. After biological treatment in the RBCs, flow is pumped by the intermediate pump station to the secondary clarifiers. The intermediate pump station consists of two new progressive cavity pumps that were installed as part of the 1995 upgrade, each with a capacity of 80 gpm. While the pumps are identical, one of the new pumps was designed to recycle RBC effluent back to either the septage or filtrate equalization tanks while the second pump was designed to pump the RBC effluent to the secondary clarifier splitter box. In 2002, the District retained Wright-Pierce for the design of a project to replace the shafts and media on two of the RBC's, and that work was completed in The new media was provided by US Filter while the remaining original media was manufactured by Lyco. No odor control is provided for the primary clarifiers and RBCs, however all processes are covered. If the facility were to begin taking municipal wastewater, the staff expressed the likelihood that odor control for these processes would be required A C - 7 Wright-Pierce

124 Priority Description Estimated Cost High Replace shafts and media on two remaining RBC's. $200,000 Medium Replace drives on all RBC's $100, Consider odor control for RBC's -- Secondary Clarification Two new secondary clarifiers were installed as part of the 1995 upgrade project to replace the original Lamella-type clarifiers which were ineffective at secondary solids removal. The Lamella-type clarifiers currently receive gravity flow from the RBCs and effluent is withdrawn from these units by the new intermediate pump station pumps discussed above. The upgrade included the addition of two 16-foot-diameter enclosed circular secondary clarifiers to match the existing 16-foot-diameter enclosed primary clarifiers. A liquid polymer blending and injection system was also added to inject polymer into the RBC effluent prior to clarification. Each clarifier is provided with a flocculation-style center feed well to allow for mixing and flocculation of the solids to aid in settling. One clarifier is adequate to provide good settling and the second clarifier serves as a standby unit. The secondary clarifiers have been very effective at removing both total suspended solids (TSS) and BOD from the RBC effluent. Two progressive cavity secondary sludge pumps convey sludge from the clarifier underflow to the septage equalization tanks. These progressive cavity pumps were installed as part of the 1995 upgrade and each has a capacity of 10 gpm. Although the existing Lamella clarifiers are no longer used, they were left in place to minimize piping revisions that would have been necessary as part of the 1995 upgrade. However, the staff have indicated that the clarifiers are beginning to show signs of corrosion, and should therefore be decommissioned, and the piping revised as necessary. Priority Low Description Decommission lamella clarifiers and reconfigure intermediate piping accordingly. Estimated Cost $20,000 Sand Filtration As part of the 1995 upgrade project, the Department of Environmental Protection (DEP) required that two, 19-square-foot upflow sand filters be installed to ensure the TSS discharge limit of 30 mg/l is always met. As Wright-Pierce anticipated during the design, with proper operation of the secondary clarifiers, the sand filters are not used for TSS removal. In the summer months, the filters are used to denitrify the effluent prior to discharge. In the winter months, the filters are taken out of service. The sand filters are backwashed/cleaned with an air compressor with the backwash or "mud" overflowing to the mudwell pump station. The mudwell pump station 10461A C - 8 Wright-Pierce

125 consists of two submersible pumps which recycle the "mud" back to the septage equalization tank. No action required Disinfection and Discharge Effluent from the sand filters flows by gravity through two banks of enclosed UV disinfection units, each with a capacity of 100 gpm. The after UV disinfection, the final effluent flows into an effluent dosing tank. Two submersible effluent dosing pumps, each with a capacity of 55 to 85 gpm, discharge treated effluent to one of four sand beds for rapid infiltration into the ground. In 2000, Wright-Pierce worked with the plant operators to size and select two new effluent dosing pumps to replace the original pumps. The two new pumps were installed and became operational in As part of the 1995 upgrade project, a new plant water system was installed which draws treated effluent from the effluent dosing tanks and pumps it to various locations throughout the plant where treated effluent is needed such as for tank cleaning and gravity belt thickener spray water. No action required Odor Control The Tri-Town facility was originally provided with a two-stage wet chemical scrubber followed by dual activated carbon beds for polishing of the scrubber exhaust. Odorous air from the septage receiving tanks, filtrate tanks, receiving garage, dewatering room and sludge garage is collected and discharged into this system. The system is still operated, but limited work has been done to determine the effectiveness of the odor removal or to balance the ductwork system to ensure sufficient air is being withdrawn from each space. The media for the carbon system was recently switched from permanganate-impregnated to Centaur brand media. The life of the media is estimated to be 4 to 5 years. As part of the 1995 upgrade, a new two-stage wet chemical scrubber system, followed by a carbon adsorption system, was installed. This 3,100-cfm system treats odorous air from the new filtrate tanks, GBT Room, new grease tanks, and the existing septage conditioning tanks. This new odor system is operating satisfactorily. Priority Description Estimated Cost High Evaluate condition of wet scrubber. $5,000 Low Replace as necessary. $75,000 Chemical Feed Building The Chemical Feed Building was built as part of the original treatment facility construction. The building included a 6,000-gallon bulk hydrochloric acid tank and two hydrochloric acid feed 10461A C - 9 Wright-Pierce

126 pumps to lower the ph of the filtrate prior to the biological process. Additionally, a containment area for storage of phosphoric acid drums and two phosphoric acid feed pumps were constructed in the building. The phosphoric acid was used to raise the phosphorus level in the wastewater prior to biological treatment. In the early 1990's, the 6,000-gallon storage tank failed. Even though the failure was contained in the secondary containment structure, the acid fumes caused significant damage in the space including doors, control panels, and equipment. For a period in 1997, access to the building was restricted by the Orleans Building Inspector, Electrical Inspector and Fire Chief because of structural and electrical concerns. In 1997, Wright-Pierce conducted a structural and electrical evaluation of the Chemical Building. The evaluation found the building to be structurally sound and suitable for entry. All of the electrical equipment was determined to be damaged beyond the point where it could be considered safe to use and complete removal and replacement was recommended prior to restoring power to the building. Additionally, it was recommended that access doors to the facility, which are severely corroded, be replaced. In 2001, Wright-Pierce conducted another brief evaluation of options for the Chemical Building but, to date, no upgrades have been conducted. The Chemical Building is no longer needed for chemical storage and addition. The building could make an ideal unheated storage space, or may be needed for future treatment processes. Upgrades to the building should be postponed until after the evaluation of the Tri-Town Septage Facility is completed. Possible Actions Demo and rehab chemical building. Provide drive-through maintenance area. Miscellaneous Building Systems The plant operators commented on various minor issues throughout the plant, some of which should be addressed as routine maintenance. However, two items were considered to be more than nuisance, and could affect the operation of the plant, the condition of the air compressor, and the operation of water system gate valves. The air compressor is located in a room in the lower pump gallery. The operators indicated that the air compressor accumulates excessive moisture, requiring monthly changing of the oil, and water in the air line. The compressor is provided with an air dryer, however its performance is questionable. The service reps for the compressor have advised that the problems with excessive moisture may be due to the unit's location in the facility, which is exacerbated by the proximity of marine ambient conditions. The operators indicated that the gate valves on the plant water system are corroded and are subject to water hammer A C - 10 Wright-Pierce

127 Priority Description Estimated Cost High Provide new air dryer for compressor system $15,000 High Relocate compressor. $10,000 Low Refurbish gate valves on the plant water system. Address water hammer. $5,000 UPGRADING TO MEET 10 MG/L NITROGEN STANDARD The discharge permit for the Tri-Town facility is due to be re-issued in Based on current trends, it is possible that the new permit will impose a nitrogen limit of 10 mg/l, which is a common limit in Massachusetts. Accordingly, Wright-Pierce evaluated the ability of the existing facility to be upgraded for a 20-year service life, and to meet an effluent discharge limit of 10 mg/l N. Based on conversations with the plant's staff and a review of recent operating data, the plant is able to fully nitrify (conversion of TKN to nitrates) at the existing loading conditions. A recycle stream from one of the RBC's is seasonally directed to the septage holding tanks to achieve partial denitrification (conversion of nitrates to nitrogen gas) for total nitrogen reduction. However, this is an uncontrolled process, and will not consistently meet a discharge N limit of 10 mg/l. Therefore, the existing plant will not be able to meet a 10 mg/l N limit by modifying the existing process train without new equipment. For the scale of the Tri-Town facility, and in consideration of the existing process, two treatment modifications appeared feasible for consideration: 1) install anoxic RBC's; and 2) modify or upgrade existing sand filters to denitrification filters. Anoxic RBC's would be located immediately downstream in series with the existing RBC's. Denitrification requires anoxic conditions (i.e. presence of nitrates with little or no dissolved oxygen), and an organic carbon source. Anoxic RBC's are similar to aerobic RBC's except that the entire RBC media is submerged to preclude exposing the denitrifying bacteria to oxygen, which can poison the denitrification process. The process flow scheme to provide anoxic RBC's is typically achieved in one of two ways, either by a pre-anoxic or a post-anoxic arrangement. In a pre-anoxic scheme, the anoxic RBC's are located ahead of the aerobic RBC's to utilize the influent wastewater as a carbon source, and recycle nitrified effluent to the anoxic RBC's. The post-anoxic scheme locates the anoxic RBC's downstream of the aerobic RBC's; the organic carbon requirement is typically achieved through methanol addition. Although the pre-anoxic scheme offers several advantages, the existing site constraints are not considered to be amenable to installing a pre-anoxic configuration. Installation of post-anoxic RBC's at the Tri-Town facility would require relatively deep excavations, as the existing hydraulic grade at the effluent of the existing RBC's would need to be maintained. The difficulty of construction due to the limited space available and proximity to 10461A C - 11 Wright-Pierce

128 the disposal beds, in concert with the high expected equipment costs, were considered to be less favorable than installation of denitrification filters. Denitrification filters are a well-established technology commonly used to achieve denitrification at a wide range of plant sizes. Denitrification filters achieve two functions, suspended solids removal and denitrification. In concept, a denitrification filter is similar to a conventional sand filter, with the exception that the pore size is larger to allow for accumulation of biological growth, and that a supplemental carbon source is added, typically methanol. Denitrification filters are always used on clarified secondary effluent to reduce the solids loadings to the filters. In a properly performing secondary process, the majority of TKN in the wastewater will be converted to nitrates, or removed from the wastewater in the biological sludge. However, since the effluent will be low in a carbon source (i.e. BOD), a supplemental carbon source such as methanol is necessary to promote denitrification. Denitrification filters (commonly abbreviated as "denite filters") take up less space than an anoxic RBC. Since the Tri-Town facility is already equipped with a building to accommodate the existing sand filters, the most feasible option to provide denitrification would be to either convert the existing filters to denite filters or replace them with a new denite filter system. Wright-Pierce evaluated the feasibility of converting the existing Andritz sand filters to denite filters. Unfortunately, Andritz has no experience with this process, and the existing media and equipment are unsuitable for conversion. Therefore, various other manufacturers and vendors were contacted to determine the scope and supply to demolish the existing filters for replacement with a new denite filter system. The two new filters would be 5 feet in diameter, by 13 feet high, with 5 feet of media. The cost for the filters would be approximately $175,000. From a preliminary review of the proposed equipment dimensions, it appears that the new filters could be retrofit into the existing Filter Building, without requiring significant modification to the UV system. The existing chemical feed system would be converted to a methanol feed system. A 25% methanol solution would be recommended to avoid NFPA regulations, and would allow the drums and pumping equipment to be located in the existing room. To upgrade the existing facility for a 20-year design life, and meet a 10 mg/l N, Wright-Pierce recommends that the following action be considered: Make all the improvements stated in Section 4.1 Demolish the existing Andritz filters, and replace them with new denitrification filters. Provide new methanol feed system. UPGRADING TO TREAT INCREASED SEPTAGE VOLUMES As part of this evaluation, Wright-Pierce determined that the facility might be upgraded to meet a septage flow of 60,000 gpd, with a nitrogen limit of 10 mg/l. This increased capacity would allow acceptance of septage from Lower Cape towns through build-out. All of the existing unit processes have the capability of meeting this increased load, with the exception of the denite sand filters. As above, two new denite filters would be required to meet the existing septage flow and to provide denitrification to achieve a total nitrogen limit of A C - 12 Wright-Pierce

129 mg/l. However, the filters recommended above would not have adequate additional capacity to meet a septage flow of 60,000 gpd. To meet the increased septage flow, an additional filter unit would be required, which would also require a small addition to the existing filter building to accommodate the third filter unit. The total cost for these additional features would be approximately $100,000, above the cost upgrading for two filters discussed above. In addition to the capital costs, the operating and maintenance costs to provide treatment for 60,000 gpd must also be considered, to include labor, power and chemicals. In addition to denite filters, there may be a need for additional effluent disposal facilities to handle 60,000 gpd. We have considered a site layout that includes an additional set of rapid infiltration basins that should be more than adequate to handle the assumed one-third increase in capacity. (If the Town and District were to proceed with this option, we recommend that a fullscale loading test be conducted on the existing basins to determine their full capacity. It is conceivable that no additional basins are needed. It is also possible that surface plugging of the existing basins may have reduced their capacity and that more than one third of additional capacity is needed.) For planning purposes, we propose that the project budget include $70,000 for new infiltration basins and piping. CONSTRUCTION OF A NEW WASTEWATER FACILITY The Town's Comprehensive Wastewater Management Plan will consider options to provide public sewers in portions of the Town, and to provide a new wastewater treatment facility to accommodate wastewater flows and septage. The evaluation that follows was based on constructing a new wastewater treatment facility near the existing septage treatment plant with an summer capacity of 0.5 million gallons per day (mgd) and an annual average flow of about 0.3 mgd. Part of the existing plant would remain operational for solids and residuals handling. Waste sludge from the new plant would be pumped to the existing septage storage tanks, from which solids thickening and dewatering processes would be carried out similar to existing operations. As primary selection criteria, the technologies to be considered must be able to achieve the following objectives: Reliability The system must be designed to consistently and efficiently achieve the discharge standard. Process Control The system must provide sufficient process flexibility to address varying influent flows and loads and to achieve the stringent discharge criteria without increasing process complexity. Maintenance The equipment must be designed to maximize equipment life, to minimize maintenance requirements, and to maximize serviceability when maintenance is recommended or required. For the alternative to provide a new wastewater treatment facility, a broad range of treatment technologies was considered. Two candidate technologies emerged: sequencing batch reactors (SBR's) and membrane bioreactors (MBR's). Both technologies have demonstrated performance at other facilities with characteristics and design issues similar to those anticipated for Orleans A C - 13 Wright-Pierce

130 Some of the aspects of these technologies that make them favorable for consideration in Orleans include: Compact design to minimize the land area required for installation High effluent quality to meet stringent discharge limits typical of Cape Cod Enclosed unit processes to minimize odor impacts to nearby receptors Highly automated process control to reduce operational costs Ability to adapt to widely varying seasonal loadings Sequencing Batch Reactor (SBR) The sequencing batch reactor (SBR) alternative would be designed for nitrification and denitrification, with the option to provide biological phosphorus removal. The SBR process does not use separate clarifiers, since the tanks are decanted and sludge wasted directly from the settled tank volumes. This reduces the amount of space required for the process, which is a major advantage in cases where a limited amount of room is available. One disadvantage of the batch process is that the flows usually must be equalized after decanting in order to avoid the need to oversize all downstream processes, and the effluent disposal beds. Construction of multiple SBR basins can often minimize the necessary equalization volume. In the SBR process, each reactor undergoes a cyclical operation including the following steps: "fill", "mix and fill", "aerate", "settle", and "decant". SBRs have the capability, through adjusting aeration levels, throughout the different cycles, to nitrify and denitrify, and to biologically remove phosphorus (with the addition of anaerobic selector tanks). A typical SBR facility for Orleans would consist of the following processes: Preliminary treatment using a bar screen or comminutor, and a vortex grit removal system. Influent equalization and sludge recycle tanks. SBR tanks with aeration and decanting equipment. SBR effluent equalization tanks. Aeration system blowers. SBR effluent filtration using traveling bridge sand filters or cloth media. UV disinfection. Pump liquid sludge to the existing septage facility for waste sludge thickening, storage, and dewatering. Effluent disposal via rapid infiltration or subsurface leaching. Membrane Bioreactor (MBR) Membrane technology was originally developed primarily for industrial wastewater treatment. However, in the last few years, membrane technology has been gaining wide acceptance for municipal wastewater treatment. The technology has been adapted for municipal use with the development of high permeability hollow fiber membranes that need only a low vacuum to draw the wastewater through the fiber into the collection manifolds. The membrane modules are typically inserted directly into an aeration tank, or into an existing aerated lagoon that has been 10461A C - 14 Wright-Pierce

131 modified in order to accept the MBR modules. Flat plate membranes are also coming onto the market. In the MBR process, a vacuum is applied to a header that is connected to the membranes. The vacuum draws the treated wastewater through the hollow fiber membranes, and the effluent is then disinfected and discharged. Air is introduced into the bottom of the MBR in order to create turbulence that scours the external surface of the membranes. One of the limitations of membrane technologies is the inability of the membranes to accommodate variations in load above the design average. The manufacturers concede that a membrane system will not be cost competitive if the ratio of peak to average flows is greater than 2.5 to 3.0. However, this limitation may be accommodated by providing equalization volume. The very small filtration pore size that has extremely high capture efficiencies for total suspended solids (TSS), biochemical oxygen demand (BOD), phosphorus, nitrogen and metals. The small pore size also allows high concentrations of biomass with long sludge ages. This allows for high levels of nitrification and denitrification, while also minimizing space requirements. The effluent from MBR plants often meets the stringent regulatory requirements for direct reuse applications (such as landscape irrigation), California Title 22 Standards for Recycled Water, or Mass DEP Reclaimed Water Guidelines. The long sludge age in a membrane system allows for endogenous respiration and thus reduced sludge production. In addition, the completely mixed tanks allow for the introduction of chemicals to precipitate and then capture high levels of phosphorus in the sludge, if necessary. At times the membrane pores can fill with fine particulates and become coated with biomass, thus becoming clogged and reducing hydraulic capacity. The membranes require periodic backwash with a chlorine solution to regain hydraulic capacity. Since some of the units will always be in the backwash mode, the system needs to be sized to provide for one or more units to be off line at a time. The clogging issue is still the biggest uncertainty for MBRs in the municipal wastewater market; clogging problems have limited the use of many filter systems in the past, and may prevent the MBR technology from being broadly cost-effective in the municipal market. It should be noted that the MBR process is not fully proven in the municipal wastewater market at sizes proposed for Orleans. Small units and pilot units have published histories, but full scale long-term operational data is not yet available. In addition, replacement frequency of the membranes is not well established as yet; this can possibly result in substantial unforeseen costs. Annual power costs associated with the MBR technology may be higher when compared with other biological and physical treatment processes. A typical MBR facility would consist of the following processes: Preliminary treatment using a bar screen or comminutor, and a vortex grit removal system. MBR equipment building A C - 15 Wright-Pierce

132 MBR tankage and equipment. Permeate pump system and equipment. Membrane air scour blower and appurtenances. Sludge recirculation and wasting system. UV disinfection system. Pump liquid sludge to the existing septage facility for waste sludge thickening, storage, and dewatering. Effluent disposal via rapid infiltration or subsurface leaching. Either of the candidate technologies would be capable of producing a high quality effluent to meet the expected discharge permit. However, it should be noted that for a given wastewater, the MBR technology will most likely produce the highest quality effluent. Although the Massachusetts DEP considers MBR's to be a relatively new technology, there are several membrane plants currently in operation in Massachusetts, all of which have consistently met permit requirements. The relative advantages and disadvantages of SBR and MBR technologies are presented in Table C-1: TABLE C-1 RELATIVE ADVANTAGES AND DISADVANTAGES OF SBR'S AND MBR'S Technology Advantages Disadvantages SBR MBR Extensive performance record Familiar technology Smaller building area Less equipment High effluent quality Complete package process service and support Operator experience Structural requirements Larger building Higher equipment maintenance costs Less extensive operating history Higher equipment capital costs Only 1 or 2 proven manufacturers Unknown long-term life cycle costs Limited ability to accommodate peak to average flow ratio > 2.5 Detailed costs estimates were not performed for this study that could conclusively state one technology as being more cost effective than the other. However, based on Wright-Pierce's experience with plants of similar size and technology, the total expected project cost for either technology including construction, engineering, contingency would be expected to be approximately $7 to 9 million, based on a 2006 bid date. COST ESTIMATES Capital Costs 10461A C - 16 Wright-Pierce

133 Estimated equipment and installation costs are presented above for each broad option on a process-by-process basis. Table 6-2 in Section 6 summarizes these costs and includes expected engineering costs and contingencies. Operation and Maintenance Costs Available records were used to summarize and project forward the District's costs for annual operation and maintenance (O&M). We expect that there should be no significant change in O&M costs in Option 1 where the service life of the facility is increased by 20 years. In Option 2, provision of denitrification facilities, the O&M costs should increase only for chemicals (addition of methanol or other carbon source). This should add only 1 to 2% to the overall O&M budget. If the septage facility is expanded by one third, Option 3, there will be increases in all categories of variable costs (labor, power, chemicals, etc.). We estimate that the overall budget would increase by 15% to 20%. It should be noted, however, that the cost per gallon in Option 3, would actually decline by about 10% due to economies of scale A C - 17 Wright-Pierce

134 APPENDIX D DEP Groundwater Discharge Permit 10461A C - 18 Wright-Pierce

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