Bass Lake Wastewater Treatment Feasibility Report

Transcription

1 Bass Lake Wastewater Treatment Feasibility Report Feasibility Study Prepared for: Town of St. Joseph Prepared by: Thomas Dye, PE

2 Table of Contents EXECUTIVE SUMMARY... I 1.0 INTRODUCTION EXISTING CONDITIONS STUDY AREA WASTEWATER FLOWS EFFLUENT LIMITS COLLECTION SYSTEM TREATMENT ALTERNATIVES CONVEYANCE TO SOMERSET CONVEYANCE TO NEW RICHMOND CONSTRUCT NEW WWTF COST ESTIMATES NON-MONETARY FACTORS Operations Constructability and Implementation Environmental LIST OF APPENDICES PRESSURE SEWER SYSTEM LAYOUT... A.1

3 Executive Summary The area near Bass Lake has slowly developed over the last few decades and contains many permanent homes as well as seasonal cabins. The completion of the Highway 64 bridge is expected to increase development around the Lake. Bass Lake possesses exceptionally clean water, and is one of few lakes in Wisconsin to be designated as an Outstanding Resource Water. As the population near the lake increases and septic systems age, there is greater potential for an increase in the levels of nutrients, such as nitrogen and phosphorus, in the lake. A centralized wastewater collection and treatment system would help protect the water quality of Bass Lake. The Highway 64 Coalition Board approved using mitigation grant money to fund this study. The purpose of this study is to provide budgetary cost estimates for wastewater collection and treatment system options for the development near Bass Lake. For this report two options for wastewater collection, and three options for wastewater treatment were examined. Collection system options evaluated were conventional gravity sanitary sewer system and a pressure sewer system. A pressure sewer system is more cost effective because of the varied terrain surrounding Bass Lake. The collection system is needed regardless of which treatment option is chosen. The three treatment options investigated were conveyance of wastewater to Somerset, conveyance to New Richmond, and the construction of a new wastewater treatment facility (WWTF) near Bass Lake. The cost, constructability, and operational requirements have been considered for the collection system options and each treatment alternative. Of the options evaluated, construction of a pressure sewer system and a new WWTF has the lowest capital cost ($9,600,000) and lowest annual cost per household ($3,300). i

4 INTRODUCTION 1.0 INTRODUCTION This report presents the results of an evaluation of wastewater collection and treatment options for the homes surrounding Bass Lake in St. Joseph, WI. With the construction of the Highway 64 bridge it is likely that development near the lake will increase, which along with deteriorating existing septic tanks, increases the potential for pollution and the threat to groundwater and lake water quality. In light of the potential impact to the Bass Lake area, the Highway 64 Coalition approved using mitigation grant money to fund this study. A central collection and treatment system would help Bass Lake retain its designation as an Outstanding Resource Water by protecting the lake s water quality, sport fishery, and other valued recreational opportunities. For this study, the wastewater collection and treatment system would serve the seasonal and permanent homes nearest the lake, (within the shore zone ), and could be expanded in the future to serve additional homes. Two options for wastewater collection and three options for wastewater treatment were investigated. Wastewater collection could be accomplished with conventional gravity and pump stations, or a pressure sewer system. Treatment alternatives evaluated include neighboring wastewater treatment facility (WWTF) in Somerset or New Richmond, or a new WWTF could be constructed near Bass Lake. fj v:\1938\active\ \reports\feasibility\st joseph feasibility report draft cv.docx 1.1

5 EXISTING CONDITIONS 2.0 EXISTING CONDITIONS 2.1 STUDY AREA The area around Bass Lake includes a variety of topographic features including open farmland, wooded areas, and several small ponds and wetland areas. The topography also can vary greatly in elevation over short distances. Groundwater in the area generally moves from east to west. The study area included 215 homes near Bass Lake. 129 of these homes are within the shore zone and would be served by the wastewater collection and treatment system (see Figure 1). The remaining homes beyond the shore zone could be served by expanding the pressure sewer system and increasing the capacity of the treatment system. The cost estimates are based on providing service to the 129 homes within the shore zone. The project could be constructed in three phases. In the first phase 85 homes would be served, in the second phase an additional 22 homes would be served, and in the third phase another 22 homes. At the completion of Phase 3 all 129 homes nearest Bass Lake would have sewer service. 2.2 WASTEWATER FLOWS Estimated wastewater flows include flow from 129 homes with domestic strength wastewater. Currently there is no commercial or industrial wastewater generated within the study area, and it is not anticipated that there will be in the future. Table 2-1 shows the estimated wastewater flows and characteristics for each of the three potential phases of construction. Table 2-1 Wastewater Flows and Composition Parameter Phase 1 Phase 2 Phase 3 Total Units Average Flow 13,000 3,500 3,500 20,000 gpd Wet Weather Flow 14,500 3,750 3,750 22,000 gpd Peak Hour Flow gpm Total Solids lb/day BOD lb/day Free Ammonia lb/day Total Phosphorus lb/day fj v:\1938\active\ \reports\feasibility\st joseph feasibility report draft cv.docx 2.2

6 LEGEND Phase 1 Homes 129 Shore Zone Homes 85 Phase 1 Homes 22 Phase 2 Homes 22 Phase 3 Homes Phase 2 Homes Phase 3 Homes Homes Beyond Shore Zone Phase Boundaries City Border Proposed WWTF Proposed Infiltration Basins " 215 Total Homes Phase 3 Phase 1 85 Homes Beyond Shore Zone " Proposed Treatment Facility Phase 2 ± Stantec Consulting Services 2335 Highway 36 West Saint Paul, MN Miles Sources: Esri, HERE, DeLorme, USGS, Intermap, INCREMENT P, NRCan, Esri Japan, METI, Esri China (Hong Kong), Esri Korea, Esri (Thailand), MapmyIndia, NGCC, OpenStreetMap contributors, and the GIS User Community FIGURE 1 - BASS LAKE STUDY AREA CITY OF ST. JOSEPH May 2017 The information on this map has been compiled by Stantec staff from a variety of sources and is subject to change without notice. Stantec makes no representations or warranties, express or implied, as to accuracy, completeness,timeliness, or rights to the use of such information. V:\1938\active\ \GIS\Projects\Bass Lake Project\Bass Lake Study Area.mxd

7 EFFLUENT LIMITS 3.0 EFFLUENT LIMITS Bass Lake and the St. Croix River are designated as Outstanding Resource Waters (ORW). Of Wisconsin s 15,000 lakes and impoundments, fewer than 1% are designated as ORWs. To maintain this superior water quality, effluent limits for treated wastewater discharge into these waters are prohibitively stringent. Limits for ammonia, chloride, chromium, copper, lead and zinc are far below Wisconsin s drinking water limits, thereby eliminating discharging into nearby surface waters as a feasible option. A similar investigation into wastewater treatment options was completed for the Houlton area within St. Joseph Township. Table 3-1 presents surface water and soil absorption discharge limits that were obtained for the Houlton area study and would apply to the Bass Lake area as well. Because these extremely low contaminant levels for surface water discharge cannot be met with conventional wastewater treatment methods, wastewater must either be transported to a neighboring facility or a newly constructed WWTF would need to utilize a soil absorption system. Table 3-1 Surface Water vs Soil Absorption Effluent Limits Effluent Limits Wastewater Parameter St. Croix River Apple River Willow River Soil Absorption Biochemical Oxygen Demand (BOD) 2.0 mg/l 2.0 mg/l 2.0 mg/l 50 mg/l Total Dissolved Solids (TDS) Limit Not Given Limit Not Given Limit Not Given 500 mg/l Fecal Coliform 24#/100 ml 24#/100 ml 24#/100 ml Limit Not Given Total Phosphorous mg/l mg/l mg/l Limit Not Given Nitrogen, Ammonia mg/l mg/l mg/l Limit Not Given Total Nitrogen Limit Not Given Limit Not Given Limit Not Given 10 mg/l Chloride 6 mg/l 6 mg/l 6 mg/l 250 mg/l Chromium ug/l ug/l ug/l Limit Not Given Copper ug/l ug/l ug/l Limit Not Given Lead ug/l ug/l ug/l Limit Not Given Zinc 0.75 ug/l 0.75 ug/l 0.75 ug/l Limit Not Given fj v:\1938\active\ \reports\feasibility\st joseph feasibility report draft cv.docx 3.3

8 COLLECTION SYSTEM 4.0 COLLECTION SYSTEM Before wastewater can be treated, it must be collected from individual homes and transported to a treatment facility. Two options were investigated for the proposed collection system: conventional gravity sewer and a pressure sewer system. A conventional gravity system works with the existing terrain to convey flows to one of several lift stations, located at low points, which then pump the wastewater to a higher elevation so that it can continue to travel by gravity until eventually reaching the treatment facility. The terrain surrounding Bass Lake is varied, with frequent and relatively sudden elevation changes. A gravity system would be less desirable because it would require the construction of several large lift stations and a great deal of earthwork to lay pipes. This would significantly increase the initial construction cost. With a pressure sewer system, each home has its own small grinder pump station approximately the size of a sump pump. The pumps then pressurize the sewer system and wastewater flows are able to overcome elevation changes en route to the treatment facility. The pressure sewer system is comprised of 1.25-inch diameter to 4-inch diameter piping that is installed by horizontal directional drilling methods. This is a trenchless method of installation that reduces the amount of disturbance to roads, driveways, and yards. This style of collection system is more cost effective for the terrain surrounding Bass Lake than the conventional gravity sewer system. fj v:\1938\active\ \reports\feasibility\st joseph feasibility report draft cv.docx 4.4

9 TREATMENT ALTERNATIVES 5.0 TREATMENT ALTERNATIVES Once the wastewater has been collected from individual homes and conveyed to a central point it must be treated. Three treatment alternatives have been examined: conveyance to an existing WWTF at either of two neighboring towns, or construction of a new WWTF. For each of these treatment options, the collection system remains the same. If the wastewater was transported through a forcemain to a neighboring WWTF, in either Somerset or New Richmond, it would be brought by the collection system to a central pump station located near the intersection of 150th Ave and 78th St. Both of these existing WWTFs have the capacity to treat the additional wastewater flows from the Bass Lake area. If a new WWTF was constructed in the Bass Lake area, the pressure sewer system would convey the wastewater directly to the treatment facility. For the purpose of this study, it was assumed that the new WWTF would be between 140th Ave and Aushegun Trail, but it could be located elsewhere around Bass Lake (see Figure 2). 5.1 CONVEYANCE TO SOMERSET The conveyance system to transport wastewater to the Somerset WWTF would require about 6.5 miles of forcemain. The system would travel north along County Road I, cross Highway 64, cross the railroad, and then travel northwest to the WWTF (see Figure 2). The forcemain requires air release valves (ARV) at each high point to allow gasses to escape from the system and cleanouts are located at low points to provide access for cleaning the pipe. Topography determines the amount of ARVs and cleanouts that are necessary. The conveyance system to Somerset would require approximately 12 ARVs and 12 cleanouts. 5.2 CONVEYANCE TO NEW RICHMOND The system transporting wastewater flows to New Richmond would require approximately 7 miles of forcemain and would travel mostly along 150th Ave, 95th St, and 170th Ave (see Figure 2). It would not be necessary to cross any major highways or railroads. Approximately 19 ARVs and 17 cleanouts would be required. 5.3 CONSTRUCT NEW WWTF The proposed WWTF would utilize a membrane bioreactor (MBR) process. An MBR facility uses both biological processes and a membrane filter to produce high quality effluent. The biological component consists of an activated sludge process, which is a reliable, established method for treating wastewater. In the activated sludge process, microorganisms consume contaminants as fuel for their growth and the treatment facility fosters conditions ideal for microorganism growth in order to maximize contaminant reduction. The facility would discharge treated effluent into three infiltration basins with sand bottoms, allowing the treated effluent to infiltrate into the ground. The infiltration basins would have a fj v:\1938\active\ \reports\feasibility\st joseph feasibility report draft cv.docx 5.5

10 LEGEND Phase 1 Homes 129 Shore Zone Homes 85 Phase 1 Homes 22 Phase 2 Homes 22 Phase 3 Homes Phase 2 Homes Phase 3 Homes # Proposed Pump Station 85 Homes Beyond Shore Zone Homes Beyond Shore Zone 215 Total Homes Bass Lake to New Richmond Bass Lake to Somerset " " New Richmond WWTF Somerset WWTF " " Route to Somerset Route to New Richmond # ± 0 Stantec Consulting Services 2335 Highway 36 West Saint Paul, MN Miles Sources: Esri, HERE, DeLorme, USGS, Intermap, INCREMENT P, NRCan, Esri Japan, METI, Esri China (Hong Kong), Esri Korea, Esri (Thailand), MapmyIndia, NGCC, OpenStreetMap contributors, and the GIS User Community FIGURE 2 - CONVEYANCE ROUTES CITY OF ST. JOSEPH May 2017 The information on this map has been compiled by Stantec staff from a variety of sources and is subject to change without notice. Stantec makes no representations or warranties, express or implied, as to accuracy, completeness,timeliness, or rights to the use of such information. V:\1938\active\ \GIS\Projects\Bass Lake Project\Bass Lake Conveyance Routes.mxd

11 TREATMENT ALTERNATIVES total footprint of approximately two acres, would be constructed with earthen dikes, and would have specific Wisconsin DNR requirements such as: 1000 feet set back distance from community drinking water supply wells 250 feet setback from private wells 10 feet vertical separation from absorption basin bottom to bedrock 5 feet vertical separation from absorption basin bottom to high groundwater 3 absorption basins are required A minimum of 3 monitoring wells must be provided near the basins Soils must have soil properties meeting specific requirements Soil must be natural in-place soils and cannot be replaced with engineered soil material 5.4 COST ESTIMATES Table 4-1 shows estimated costs for a pressure sewer system for the three possible phases. Costs shown in each column are cumulative and represent the estimated total costs for service those phases. Table 4-1 Estimated Collection System Capital Cost Component Phase 1 Phase 1, 2 Phase 1, 2, 3 Mobilization $129,000 $164,000 $203,000 *1.25" HDPE Service Lateral $189,000 $239,000 $290,000 2" HDPE Forcemain $100,000 $156,000 $195,000 3" HDPE Forcemain $270,000 $374,000 $272,000 4" HDPE Forcemain $100,000 $100,000 $267,000 E-one Grinder Pump Stations $1,008,000 $1,272,000 $1,548,000 Booster Station $0 $62,000 $124,000 ARVs $80,000 $112,000 $168,000 Restoration $51,000 $70,000 $100,000 Valves & Flushing Connections $51,000 $70,000 $100,000 Subtotal $1,980,000 $2,620,000 $3,270,000 Contingency (20%) $400,000 $530,000 $660,000 Construction Total $2,380,000 $3,150,000 $3,930,000 Engineering, Admin, Finance $590,000 $790,000 $980,000 Estimated Collection System Cost $2,970,000 $3,900,000 $4,900,000 *Assumed 150 feet of service lateral required for each home fj v:\1938\active\ \reports\feasibility\st joseph feasibility report draft cv.docx 5.6

12 TREATMENT ALTERNATIVES Table 4-2 shows the estimated capital costs for the three wastewater treatment options available for the Bass Lake area. Table 4-2 Estimated Wastewater Treatment Capital Costs Item Option 1 Somerset Option 2 New Richmond Option 3 Construct WWTF Force Main $2,400,000 $2,680,000 Maintenance Structures $390,000 $520,000 Pump Station $250,000 $250,000 Sewer Access Fees $300,000 $200,000 Facility & Equipment $860,000 Building $230,000 Infiltration Basins $100,000 Contingency $600,000 $700,000 $230,000 Engineering, Admin, Finance $760,000 $850,000 $280,000 Estimated Treatment Cost $4,700,000 $5,200,000 $1,700,000 The project to serve the Bass Lake area would include capital cost for the collection system and the capital cost for wastewater treatment. In Table 4-3 below, the collection system capital cost for the Phase 1, 2, 3 project is included and added to the capital costs for the treatment options. Table 4-3 Estimated Wastewater Treatment System Capital Costs Item Option 1 Somerset Option 2 New Richmond Option 3 Construct WWTF Collection Construction Cost $4,900,000 $4,900,000 $4,900,000 Treatment Construction Cost $4,700,000 $5,200,000 $1,700,000 Estimated Total Capital Cost $9,600,000 $10,100,000 $6,600,000 Capital costs include equipment, materials, and installation. The cost of operation, maintenance, and replacement (O, M & R) was estimated to determine the cost per household. O, M & R costs include electricity, chemicals, sludge disposal, and labor. Once total project costs were estimated, annual debt service was determined based on a Wisconsin s Rural Development Loan with 3.375% interest and a 40-year repayment period. fj v:\1938\active\ \reports\feasibility\st joseph feasibility report draft cv.docx 5.7

13 TREATMENT ALTERNATIVES Table 4-4 shows a breakdown of the annual costs for debt service and O, M &R into costs per household for the different collection system phases and treatment options. The figures reflect the fact that it is more expensive per household to provide collection to the houses that are further from the treatment facility. Table 4-4 Estimated Annual Per Household (HH) Costs Option 1 - Option 2 New Somerset Richmond Option 3 Construct WWTF Phase 1 Collection Debt Service $1,600 $1,600 $1,600 Treatment Debt Service $2,500 $2,800 $900 Total Debt Service $4,100 $4,400 $2,500 Annual O, M & R Cost $1,400 $1000 $1,200 Total Annual Cost per HH $5,500 $5,400 $3,700 Phase 1,2 Collection Debt Service $1,700 $1,700 $1,700 Treatment Debt Service $2,000 $2,200 $700 Total Debt Service $3,700 $3,900 $2,400 Annual O, M & R Cost $1,300 $1,000 $1,000 Total Annual Cost per HH $5,000 $4,900 $3,400 Phase 1,2,3 Collection Debt Service $1,800 $1,800 $1,800 Treatment Debt Service $1,700 $1,900 $600 Total Debt Service $3,400 $3,600 $2,400 Annual O, M & R Cost $1,300 $900 $900 Total Annual Cost per HH $4,700 $4,500 $3, NON-MONETARY FACTORS Operations Regardless of which treatment option is selected, a part-time worker will be needed to maintain and operate the collection system, complete administrative work, and process the individual bills for residents. If a new WWTF is constructed, one part-time employee would be needed to operate the facility and complete administrative tasks. Conversely, if wastewater is conveyed to a neighboring town the existing WWTF staff will operate the plant Constructability and Implementation Building a conveyance system to a neighboring WWTF would require moving a great deal of earth to install 6 to 7 miles of forcemain. Any driveways or roads damaged in the process would need to be repaired. Laying forcemain across a highway or railroad presents additional complications. Permits from the Wisconsin DOT, County and City would be required for the work within road right-of-ways. The project including design, construction, and startup would take about two years to complete. fj v:\1938\active\ \reports\feasibility\st joseph feasibility report draft cv.docx 5.8

14 TREATMENT ALTERNATIVES Similarly, design and construction of a new WWTF with infiltration basins would take about two years to complete. The initial construction would require permits, and the WWTF would require a discharge permit from the Wisconsin DNR that describes facility requirements and effluent limits. The facility would also require regular maintenance. Infiltration basins are considered lowmaintenance systems but they require groundwater monitoring, which would involve collecting and analyzing samples. After 15 to 20 years the WWTF would likely require upgrades Environmental Any of the three proposed treatment options will help to protect the environmental and ecological health of Bass Lake. As the population surrounding the lake increases and septic systems age, the potential for pollution to affect the water quality in the lake also increases. Plants need phosphorus to grow, and it is the limiting nutrient for algae blooms in most Wisconsin lakes. High phosphorus levels lead to greater algal blooms and lower water quality. Over the past 30 years, phosphorus levels in Bass lake have gradually increased. Implementing a centralized wastewater collection and treatment system would help limit total phosphorus loads, among other pollutants, and help ensure Bass Lake retains high water quality for fishing, wildlife, and recreation. fj v:\1938\active\ \reports\feasibility\st joseph feasibility report draft cv.docx 5.9

15 Appendix A Pressure Sewer System Layout PRESSURE SEWER SYSTEM LAYOUT A.1

16 LEGEND Shore Zone Homes Homes Beyond Shore Zone " Pump House Discharge Piping City Border Potential Facility Locations Shore Zone Homes 98 Homes Beyond Shore Zone 215 Homes Total # - ZONE NUMBER - FLOW DIRECTION/ZONE DIVIDER " 4 ± Miles Sources: Esri, HERE, DeLorme, Intermap, increment P Corp., GEBCO, USGS, FAO, NPS, NRCAN, GeoBase, IGN, Kadaster NL, Ordnance Survey, Esri Japan, METI, Esri China (Hong Kong), swisstopo, MapmyIndia, OpenStreetMap contributors, and the GIS User Community FIGURE 1 - BASS LAKE HOMES CITY OF ST. JOSEPH April 2017 Document Path: V:\1938\active\ \GIS\Projects\Bass Lake Project\Bass Lake Project.mxd