MAP & PLAN /REPORT: Ronkonkoma Hub Sewer District

Transcription

1 MAP & PLAN /REPORT: Ronkonkoma Hub Sewer District Suffolk County, New York Suffolk County Sewer District Capacity Study, CP 8189 July 2012

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3 Table of Contents Table of Contents... i List of Figures... ii List of Tables... ii Section 1 Introduction Study Area Location Study Area Description Sewering Objectives Purpose of Feasibility Study & Map and Plan Social Benefits Economic Benefits Environmental Benefits Section 2 Work Plan and Project Development Background Work Plan Project Development Section 3 Technical Information Wastewater Flow Analysis Introduction Proposed Collection and Conveyance System Introduction to Collection and Conveyance System Options Option I - Gravity Sewers Option II - Vacuum Sewers Option III Low Pressure Sewers Selection of Collection and Conveyance System Preliminary Collection System and Conveyance System Design Wastewater Treatment Facility Options Introduction Wastewater Treatment Plant Size, Siting and Effluent Disposal Hydraulic Capacity Organic Capacity Treated Effluent Disposal and Sewage Treatment Plant Siting Treatment Process Selection Treatment Option 1 Modified Ludzack Ettinger (MLE) Process Treatment Option 2 Sequencing Batch Reactor (SBR) Treatment Option 3 Membrane Biological Reactor (MBR) Selected Treatment Process Technology Preliminary Sewage Treatment Plant Design Section 4 Legal Considerations and Map and Plan Sewer District Area Formation Requirements Regulatory Requirements SEQRA Compliance SPDES Permitting i

4 Table of Contents Stormwater Permitting Other Construction Related Permits User Fee Connection Fee Legal Requirements Section 5 Project Cost Opinions and Trends Capital Construction and Soft Costs Collection and Conveyance System Project Cost Opinion Advanced Wastewater Treatment Facility Cost Opinion Estimated Operation and Maintenance Costs Section 6 Financing Considerations Section 7 Schedule Section 8 References List of Figures Figure 1-1 Ronkonkoma Hub Study Area Figure 2-1 Proposed Ronkonkoma Hub Sewer District Boundaries Figure 3-1 Ronkonkoma Hub Collection and Conveyance System List of Tables Table 3-1 Relative Cost Comparison for Treatment Options Table 4-1 Parcels within the Proposed Ronkonkoma Hub Sewer District Table 5-1 Collection and Conveyance System Project Cost Opinion Table 5-2 Sewage Treatment Plant Project Cost Opinion Table 5-3 Annual Operation & Maintenance Costs ii

5 Section 1 Introduction 1.1 Study Area Location The Ronkonkoma Hub study area is consistent with the Town of Brookhaven s Transit Oriented Land Use Implementation Plan Study. Figure 1-1 presents the boundaries of the proposed Ronkonkoma Hub Sewer District and the proposed sewage treatment plant site. The Long Island McArthur Airport has been identified as an out-of-district connectee, as explained in more detail, below. The area to be served by the Ronkonkoma Hub collection system is contiguous and includes properties located within the Town of Brookhaven. The proposed site for the sewage treatment plant (STP) is located in the Town of Islip and is comprised of parcels owned by Suffolk County and the Metropolitan Transit Authority (MTA). 1.2 Study Area Description The Ronkonkoma Hub study area is consistent with the Town of Brookhaven s Transit Oriented Land Use Implementation Plan and the boundaries of the area that the Town of Brookhaven has designated for redevelopment by Tritec Real Estate Company. These parcels are located to the north of the LIRR right-of-way and consist of fifty four (54) individual tax lots covering approximately 58 acres. The Ronkonkoma Hub study area is generally defined by Union Avenue to the north, Village Plaza Drive to the east, the Long Island Railroad (LIRR) to the south and County Route 29, Garrity Avenue and Hawkins Avenue to the west. Existing land uses for the properties located in the Ronkonkoma Hub study area include parking, neighborhood retail, residential, office, automotive, restaurant, and warehouse general services. The proposed STP site located south of the LIRR right-of-way and within the Town of Islip will also be part of the Ronkonkoma Hub Sewer District. The proposed STP site consists of nineteen (19) Suffolk County tax lots and six (6) MTA owned properties. The properties owned by Suffolk County and the MTA comprise 9.2 acres and are generally defined by the LIRR tracks to the north, vacant property located approximately 3,000 linear feet to the east of the intersection of Railroad Avenue and County Route 29, Railroad Avenue to the south and Suffolk County owned municipal parking lots immediately to the west. The Long Island MacArthur Airport consists of four (4) runways, a commercial airline terminal and multiple private airplane enterprises, and is also home to the Suffolk County Police Aviation Section and Stony Brook University Medical Center flight paramedics. It is assumed that only the terminal building will be connected to the sewer system. However, the final sewering plan will be selected by the Town of Islip. Significant changes to the sewering plans for the Airport will require revision to the project cost estimates. 1-1

6 Section 1 Introduction 1.3 Sewering Objectives Suffolk County residents depend completely on groundwater for their potable water supply. Consequently, Suffolk County has established a variety of programs to protect the aquifer system that supplies the County s groundwater supply from contaminants that may be introduced by human activity. Sanitary wastewater is one of the most significant sources of nitrogen to the County s groundwater. Throughout most of the County, sanitary wastewater is discharged to on-site wastewater systems, which are usually either septic systems or cesspools. Sanitary wastewater discharged to the groundwater can introduce a variety of contaminants to the environment; pathogens and nitrogen are the two contaminants that have historically been the focus of attention, although other contaminants such as volatile organic compounds (VOCs), phosphates, and pharmaceuticals and personal care products (PPCPs) are also of potential concern. The County has long recognized the importance of protecting the County s groundwater supply from the impacts of sanitary wastewater. In particular, the County has studied the issue of nitrate contamination from wastewater disposal for decades, as reported in documents such as the Comprehensive Public Water Supply Study, Suffolk County, New York (H2M, 1970), the Long Island Comprehensive Waste Treatment Management Plan (Nassau Suffolk Regional Planning Board, 1978), the 1987 Suffolk County Comprehensive Water Resources Management Plan (Dvirka and Bartilucci, 1987) and most recently, the 2010 Suffolk County Comprehensive Water Resources Management Plan (CDM, 2010). Each of these studies considered the nitrogen load that could be introduced to the aquifer from on-site disposal of sanitary wastewater in unsewered areas along with the nitrogen load from turf fertilization and identified the maximum population density (or alternatively, minimum residential lot size) that would result in compliance with the 10 mg/l drinking water standard for nitrate. In response to the need to protect groundwater quality and the County s water supply, the County established sanitary sewer districts in some of the most densely developed parts of the County and constructed systems to collect and treat the wastewater and discharge the treated wastewater to ground or surface waters. In 1980, the County enacted Article 6 of the Suffolk County Sanitary Code to protect groundwater in areas of the County where sewers do not exist. Article 6 establishes minimum lot sizes of ½ acre or 1 acre for properties where residential development utilizing on-site wastewater disposal is planned, depending on the hydrogeological zone where the property is located. Article 6 also establishes population density equivalents (PDEs) for non-residential land use types. Because the cost of land in Suffolk County is high, typical workforce housing developments seek to build more dwelling units per acre than is permitted by Article 6, to maintain the affordability of the units. Similarly, the population density equivalents allowed by Article 6 do not typically provide sufficient capacity to allow establishment of wet businesses such as restaurants that would support economic development in unsewered downtown areas. Recognizing the need to protect the environment, and responding to community requests for more affordable housing and downtown re-development while continuing to protect the County s groundwater supply, the County sought to identify areas where investment in sanitary sewers and treatment facilities could provide environmental, economic and/or social benefits. The Suffolk County Sewer District/Wastewater Treatment Task Force (Task Force) held a series of hearings throughout the County to identify critical areas of need where the potential for implementation of sewerage infrastructure should be evaluated based upon environmental improvement, economic revitalization or construction of workforce housing. 1-2

7 Section 1 Introduction The Ronkonkoma Hub was one of the areas identified for evaluation of sanitary sewering feasibility. The Ronkonkoma Hub study area is located within Groundwater Management Zone 1. The Suffolk County Sanitary Code limits sanitary wastewater in unsewered areas of Zone 1 to a maximum of 600 gallons per day per acre, or the equivalent wastewater generation rate of two single family homes (Standards for Approval of Plans and Construction for Sewage Disposal Systems for Other than Single- Family Residents, Section 7). As described in Section 2.3 below, the Town of Brookhaven has developed a Land Use and Implementation Plan for the proposed Ronkonkoma Hub Transit-Oriented Development (TOD) District to redevelop and revitalize the area surrounding the Ronkonkoma train station. The Town s TOD District would incorporate a mix of land use types including mixed use developments, multifamily housing, professional offices, retail businesses, restaurants, personal and business services, a health club, etc. The redevelopment of the Ronkonkoma Hub study area as planned will result in higher rates of wastewater generation than are permitted by the County s Sanitary Code. Therefore, development plans for the Ronkonkoma Hub include provision of sanitary wastewater collection and treatment facilities to accommodate the wastewater flow generated by the proposed increased density. Providing sewers for the Ronkonkoma Hub area will provide the infrastructure necessary to enable the Town of Brookhaven to redevelop the properties as a transit based gateway to eastern Long Island. 1.4 Purpose of Map and Plan and Report This report was developed to provide a Map and Plan in accordance with the requirements of sewer district formation and to document the feasibility in accordance with the requirements of the County s study of seven currently unsewered areas. The feasibility of sewering the Ronkonkoma Hub area has already been established by the Town of Brookhaven. The social benefits of the Ronkonkoma Hub TOD district as well as the economic feasibility of the Ronkonkoma Hub TOD district have been studied, documented and established by the Town. The Town has identified construction of a sanitary sewage collection system and treatment plant as an essential component of the Ronkonkoma Hub TOD district. This report provides an objective evaluation of the sanitary collection, conveyance and treatment technologies best suited to support the Town of Brookhaven s proposed Ronkonkoma Hub TOD district. The Map and Plan portion of this report details the proposed layout and design of the selected sanitary infrastructure as well as the financial burdens associated with the formation of a new district pursuant to the requirements of New York State County Law. The inclusion of the Map and Plan with this Report enables the document to be used as the basis for the creation of a new County sewer district, herein referred to as the Ronkonkoma Hub Sewer District Social Benefits Installation of sanitary infrastructure will enable properties located in the Ronkonkoma Hub Sewer District to be transformed into a thriving mixed-use commuter-friendly development. This transformation of land use will complement the recent improvements made to the LIRR. The overall intent of the TOD district, as stated in the Generic Environmental Impact Statement for the Proposed Adoption of the Land Use and Implementation Planfor the Ronkonkoma Hub Transit- Oriented Development (TOD), TOD Code and Associated Rezonings to the TOD (VHB Engineering, Surveying and Landscape Architecture, 2010) is to encourage the efficient use of land, be a catalyst for revitalization, and foster a sense of place through development of a new transit- 1-3

8 Section 1 Introduction oriented, mixed use, pedestrian-friendly community. Provision of a sanitary sewer system is an essential component of the TOD district Economic Benefits Creating the Ronkonkoma Hub TOD will increase tax revenue to the Town of Brookhaven, the Town of Islip and Suffolk County by increasing the tax base as the vacant parcels are developed and by increasing the value of the occupied parcels as they are redeveloped. Providing collection and treatment facilities will attract smart-growth development to the area. This type of development will result in a transit-oriented community consisting of high-density residential usage and downtown businesses desired by both Townships and the County. The high-density residential contingent will attract a young professional commuter population into the area, and the downtown businesses will consist of restaurants and Main Street type store fronts. The Main Street type atmosphere will welcome commuters who currently use the LIRR as well as attract visitors from surrounding areas. Visitors who travel into the re-vitalized Ronkonkoma Hub are likely to use the newly established and redeveloped businesses and restaurants, thus generating economic growth. The revitalized Ronkonkoma Hub will become a desirable destination for not only the LIRR commuter population, but for all visitors who travel into the area. The development and redevelopment of businesses, commercial properties and the Long Island MacArthur Airport will provide additional employment opportunities. Revitalization will also provide a relative increase in the property valuation; resulting in additional property tax revenues, while the increased business activity will create additional sales tax revenues and income taxes, thereby increasing the overall value of the area and ultimately Suffolk County. Implementation of a sanitary sewerage system is an essential component of this project, as it will allow the increased wastewater generation that is required for the development to occur Environmental Benefits Wastewater generated by properties in the proposed sewer district is currently discharged to groundwater either through a septic tank and leaching pools, or directly through leaching pools. These discharges include a variety of contaminants contained in sanitary wastewater, including nitrogen, which can then affect the quality of the underlying groundwater. In fact, existing groundwater quality data indicates that nitrate in at least one private well in the study area has exceeded the 10 mg/l drinking water standard. Discharges from sewage treatment facilities are treated to reduce the levels of objectionable wastewater constituents to permissible levels identified in State Permit Discharge Elimination System (SPDES) permits. Construction and operation of a sanitary sewer system would help to protect groundwater quality by reducing the concentrations of contaminants of concern, such as nitrate, that are discharged to the environment. The environmental benefits and impacts associated with implementation of a sanitary sewer system will be further documented in the Generic Environmental Impact Statement (GEIS) being prepared as part of this project. 1-4

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11 Section 2 Work Plan and Project Development 2.1 Background Recognizing the need to protect the environment, and responding to community requests for more affordable housing and downtown re-development while continuing to protect the County s groundwater supply, Suffolk County sought to identify areas where investment in sanitary sewers and treatment facilities could provide environmental, economic or social benefits. Consequently, the Suffolk County Sewer District/Wastewater Treatment Task Force (Task Force) held a series of hearings throughout the County to identify critical areas of need where the potential for implementation of sewerage infrastructure should be evaluated based upon environmental improvement, economic revitalization or construction of workforce housing. Each critical area of need was identified based on possible growth of businesses, the economy and jobs, provision of work force housing, and/or protection of public health and the environment. The Ronkonkoma Hub was one of the seven currently unsewered areas identified by the Suffolk County Sewer District/Wastewater Treatment Task Force for evaluation of the feasibility of sewering under this capital project. 2.2 Work Plan Suffolk County developed a scope of work for the Suffolk County Wastewater Capacity Study project that includes six tasks, each of which is briefly summarized below. 1. Public Education and Outreach The Public Education and Outreach task includes attendance at stakeholder meetings and establishment and maintenance of a project website to provide project related documents, information and notification of upcoming events to the public. The website established for this project is 2. Feasibility Study Area-specific Feasibility Studies, including the Report/Map & Plan are being prepared to document the sanitary sewerage infrastructure and associated costs that would be required for each of the seven study areas identified by the County. The Work Plan for the Feasibility Study included: Review of background information Coordination with stakeholders identified by SCDPW; i.e., the Town of Brookhaven and their selected developer for the Ronkonkoma Hub, Tritec Real Estate Refinement of Ronkonkoma Hub study area boundaries Establishment of design flows and organic loading for the proposed Ronkonkoma Hub development Selection of appropriate collection system for the Ronkonkoma Hub study area 2-1

12 Section 2 Work Plan and Project Development Identification of effluent limits and selection of treatment technology to achieve the required effluent limits Establishment of the required area for STP and effluent recharge facilities and identification of potential STP location Preliminary design of proposed collection system, STP and effluent recharge facilities Estimate of capital and operational costs Development of an implementation schedule Documentation of the study, map, plan and report. 3. Environmental Tasks A Generic Environmental Impact Statement (GEIS) is being prepared to document the environmental impacts associated with potential future implementation of one or more of the sewering programs identified in the Feasibility Studies. Working together with the SCDPW, the Suffolk County Planning Department and the Suffolk County Legislature, the Council on Environmental Quality (CEQ) first issued a Draft Scoping Document in July, A Public Scoping Hearing was convened on July 26, 2011 at Brookhaven Town Hall to provide an opportunity for public comment on the Draft Scoping Document. In addition, the Draft Scoping Document was posted on both the Suffolk County Planning Department website and the Suffolk County Sewer District Capacity website, and written comments were accepted. The Scope was revised for presentation to CEQ on August 17, Additional written comments were received after the deadline, and members of CEQ offered additional comments at, and after, the August CEQ meeting. The Final Scope includes the relevant issues identified during the public scoping process, including all comments received through August 23, After completion of the GEIS, the project also includes completion of an example long Environmental Assessment Form, and preparation of a scoping meeting agenda and draft and final Environmental Impact Statement table of contents and finding statement templates. 4. Geographic Information Systems (GIS) The GIS task included development of a GIS database structure for the County s sanitary sewage infrastructure, collection of all readily available information characterizing the sanitary sewer infrastructure present within the seven study areas and incorporation of all of this data into the SCDPW s new GIS database. 5. Project Management The Project Management task includes preparation of monthly progress reports, attendance at monthly progress meetings, preparation of subcontracts, preparation of monthly invoices and team coordination. 6. Deliverables The Deliverables task includes printing of all project deliverables. 2.3 Project Development The County s Request for Proposals provided the following description of the Ronkonkoma Hub study area: The service area proposed is consistent with the Town of Brookhaven s Transit Oriented Land Use and Implementation Plan Study and will encompass approximately 330 acres that is generally defined by the Long Island MacArthur Airport to the south, the LIE Express Drive South to the north, Bay Avenue to the 2-2

13 Section 2 Work Plan and Project Development west, and Babcock Avenue to the east. Due to the location in the vicinity of the airport, at grade or underground facilities would be easily sited and is assumed that would be available at cost, though two towns are involved. The study area would include a mix of residential, retail, industrial, and commercial uses within a mix of zoning districts. It is likely that the sewer system would be jacked under the Long Island Railroad going to a wastewater treatment facility on the airport site. An RFP issued by the Town of Brookhaven requires coordination with this capital project. The Town of Brookhaven s Ronkonkoma Hub project proceeded independently throughout the same time period. In 2007, the Town began the two-phased Ronkonkoma Hub Planning Study, with the objective of revitalizing the area around the Ronkonkoma train station. Phase I of the study was completed in 2008, and Phase II of the study, completed in 2009, described a long term vision that included a mix of housing, retail, recreation and office space (Ronkonkoma Hub Transit-Oriented Planning Study, VHB Engineering, Surveying and Landscape Architecture, PC, March 2009). The Town prepared a Generic Environmental Impact Statement (GEIS) on the Proposed Adoption of the Land Use and Implementation Plan for the Ronkonkoma Hub Transit-Oriented Development (TOD), TOD Code and Associated Rezonings to the TOD in This GEIS included a Preliminary Feasibility Study for Sewage Treatment and Disposal (Michael P. Chiarelli, P.C.) that concluded that a STP of 275,000 gallons per day (gpd) would be required to serve the development. Subsequent to the completion of the GEIS, the Brookhaven Town Board adopted the recommended zoning changes and issued a Request for Qualifications (RFQ) for a Master Developer in September Proposals were accepted and in December 2011, the Town s Ronkonkoma Hub Design Committee, consisting of Town Planning and Economic Development staff and members of the Ronkonkoma community recommended Tritec as the Master Developer for the Ronkonkoma Hub project. On February 7, 2012, the Town entered into a Memorandum of Agreement with Tritec Real Estate Company for the Ronkonkoma Hub Transit-Oriented Development. SCDPW held several coordination meetings with the Town of Brookhaven in 2011 that resulted in modifications to the proposed study area, and identification of the properties owned by Suffolk County and the MTA (located south of the Hub site within the Town of Islip) as the proposed location of the new STP. In January 2012, SCDPW, the Town of Brookhaven, and Tritec confirmed the revised Ronkonkoma Hub study area boundaries to be consistent with the Town s Ronkonkoma Hub project, along with the STP location, as shown on Figure 2-1. The proposed capacity of the Ronkonkoma Hub STP was also established as 500,000 gpd, based upon current re-development plans, and Suffolk County Department of Health Services (SCDHS) design standards. 2-3

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15 Section 3 Technical Information 3.1 Wastewater Flow Analysis Introduction Wastewater flow projections for the proposed development within the Ronkonkoma Hub study area were not performed because the County, working in concert with the Town of Brookhaven and their developer, Tritec, established future wastewater flow from the Hub as 400,000 gpd. Working in collaboration with the Town of Islip, the County also established that 100,000 gpd should be allocated for the terminal located at the Long Island MacArthur Airport. Consequently, the total average daily design flow is 500,000 gpd. SCDPW has indicated that the planning for the sewage treatment plant should also consider provision for an additional 250,000 gpd treatment train for future growth or another out-of-district sewer connection such as the un-incorporated area of Holbrook, New York. Commercial wastewater flow rates are generally expressed in gal/acre/day and are based on existing water use records for developed properties or estimated flows for future development based on anticipated zoning. Comparative data from similar areas could also be used to estimate hydraulic loadings. 1 Because the land uses within the Ronkonkoma Hub study area will be dramatically changed in the future, existing water use rates are not reflective of future water use within the Hub area, and it would be inappropriate to utilize them to project future conditions. The Town has adopted a Transit Oriented Development District zoning code for the area based on a Form-Based code for the Hub. This Form-Based code established design guidelines, policies and standards, but does not define a specific land use type. The future wastewater flows from parcels within the Hub could therefore vary widely based on ultimate development. Hence, the future wastewater flow defined by the County, the Town and Tritec based upon development plans is the most appropriate estimate to use to size the sewer system. 3.2 Proposed Collection and Conveyance System Introduction to Collection and Conveyance System Options Sanitary wastewater collection systems are used to convey wastewater generated from individual properties to a centralized location for treatment. The layout and design of collection systems are established in accordance with the 10 States Recommended Standards for Wastewater Treatment Facilities, and SCDHS and SCDPW standards. The main driving force behind the design of a collection system is the local topography, as explained further in section Construction costs and operation and maintenance requirements are also considered during the design of the collection system. The collection system(s) must be sized to handle both the average daily flow and peak hourly flow generated by properties within the sewer district. The three (3) different types of collection systems considered for the Ronkonkoma Hub study area were: 1 Metcalf & Eddy, third edition, Wastewater Engineering, pg

16 Section 3 Technical Information Option 1: Gravity Sewers Option II: Vacuum Sewers Option III: Low Pressure Sewers Each of these collection system alternatives has a range of applicability; therefore each alternative was evaluated to identify the most appropriate option for sewering the Ronkonkoma Hub Sewer District Option I - Gravity Sewers Gravity sewers are typically configured with one main sewer line running the length of a street with branch laterals connecting each abutting property to the main line. Gravity sewers are appropriate for areas where the pipe installation can follow the natural inclines of the terrain so that wastewater can flow by gravity to a treatment facility or intermediate pump station strategically located at a low point in the landscape. The gravity sewer main is situated such that wastewater flow follows the pitch of the pipe all the way to the treatment facility and/or intermediate pump station. The major advantage of this collection system option is its autonomous operation once in place, the system does not require pumping or other energy inputs to operate. No on-site wastewater storage or pumping is required to convey flow from the connecting properties to the sewer main. The slope of the gravity sewer must be steep enough to maintain a self-cleansing velocity to prevent clogging and decay of untreated wastewater within the sewer pipe. Periodic cleaning and pipe inspection are the only maintenance necessary. Gravity sewers can also be installed in areas with varying terrain. This is accomplished by locating pump stations at intermediate low points to convey the collected wastewater to another gravity-flow segment of the collection system or directly to a treatment facility via submersible pump and force main. These pump stations are powered by electricity and therefore provisions must be made so that continuous operation can be maintained during periods of power outage. Installing gravity sewers in areas with varying terrain usually adds capital and operational costs, which may reduce the costeffectiveness of the gravity sewer option. Another major disadvantage of gravity sewers is the need to open-cut the entire length of roads where the pipe installation is to occur, potentially posing prohibitive excavation, dewatering and site restoration costs Option II - Vacuum Sewers Vacuum sewers rely on pressure differential to convey wastewater from each property in the district to the collection system. This pressure differential is created by vacuum pumps located at a centralized pump station. The vacuum pumps are connected to an enclosed wet-well (collection tank), which is directly connected to the collection system piping, thereby inducing the negative pressure necessary to convey wastewater flow from all properties. The wastewater generated from each property within the collection system flows by gravity into an individual onsite storage tank. Once a certain fill level is reached within each storage tank, a pneumatic valve opens and the vacuum suction induced within the collection system empties the tank and conveys the wastewater to the enclosed wet well (collection tank). Wastewater collected in the enclosed wet well is then conveyed to a treatment facility via dry-pit sewage pump and force main. Because vacuum sewers do not rely on gravity for operation, they can be installed at shallow depths and do not need to follow the natural grade of the terrain. Directional drilling can be used to install 3-2

17 Section 3 Technical Information vacuum sewers, which is advantageous in developed areas to minimize road excavation and restoration efforts. Typical vacuum sewer collection systems require the installation of at least one vacuum station to sustain the required negative pressure on the sewer line. More than one station may be required depending on size and topography of the collection area. These vacuum stations are powered by electricity and therefore provisions must be made so that continuous operation can be maintained during periods of power outage. Vacuum sewer systems typically incur relatively high capital costs and high operation and maintenance costs. The high capital costs are associated with the vacuum pumps, associated piping and system controls as well as the need for an enclosed wet-well (collection tank). The high operation and maintenance costs are attributed to the vacuum equipment necessary to operate the collection system as well as the issues associated with grease build-up within the individual onsite storage tanks. Grease build-up is a common issue with wastewater generated in high-density developed areas; grease can impede the proper operation of the pneumatic valves causing potential vacuum leaks. These vacuum leaks can directly result in failure of the collection system to convey wastewater to the central vacuum station. Currently, no vacuum sewer systems exist within the County Option III Low Pressure Sewers Low pressure sewer collection systems require each property within the collection area to operate and maintain its own pump station. All pump stations are connected to a common sewer main, which enables all wastewater generated to be conveyed to a centralized wet-well. The wastewater collected at the centralized wet-well is conveyed to a treatment facility via submersible sewage pumps and a force main. The wastewater generated from each property flows by gravity into an onsite storage tank. The onsite storage tank is fitted with level sensing equipment and a submersible positive displacement grinder pump. The positive displacement pumps are able to achieve near constant flow at a wide range of head conditions typical of low pressure sewer collection systems. The grinder pump is turned on when a pre-set fill level is sensed in the storage tank, and turned off after the storage tank is drained to a low level condition. These pump cycles are controlled by the capacity of the onsite wet well, the realtime pressure within the common sewer main and the property s daily wastewater generation rate. The sewer mains used in a low pressure collection system are sized based on capacity requirements and to maintain a self-cleansing velocity. Similar to vacuum sewers, low pressure sewers can also be installed at shallow depths and do not need to follow the natural grade of the terrain. Directional drilling can be used to install low pressure sewers, which is advantageous in developed areas because of the reduced road excavation and restoration requirements. Typical low pressure sewer collection systems require the installation of at least one centralized pump station. More than one station may be required depending on size and topography of the collection area. The function of this pump station is similar to those of pump stations used in a gravity collection system. Several low pressure sewer systems have been installed in Suffolk County. 3-3

18 Section 3 Technical Information Selection of Collection and Conveyance System Figure 3-1 depicts the collection and conveyance systems for the Ronkonkoma Hub Sewer District and the Long Island MacArthur Airport connection. Based upon local topography, relative depth to groundwater and the current redevelopment plans for the area, gravity sewers are the recommended option to provide wastewater collection for the Ronkonkoma Hub Sewer District. The topography in the Ronkonkoma Hub gradually slopes towards the southeastern corner of the area where a pump station would be located. Groundwater in the area is estimated to be approximately 60 feet below grade, so that dewatering will not be required during the construction activities. The traffic disturbances typically associated with the installation of gravity sewers are also negligible for this project since the local traffic patterns are going to be already impacted by the planned redevelopment activities. The redevelopment of the area will require roads to be closed and the area to be detoured, thereby eliminating the benefits associated with the installation of vacuum and low pressure sewers. The gravity sewers proposed to service the properties located within the Ronkonkoma Hub area consist of 8-inch and 10-inch diameter sewers with manholes located approximately 300 feet apart. The sewers will be located within the roadways and will be pitched towards the southeast corner of the re-development area. The collection system will drain into a submersible pump station that will pump the wastewater under the LIRR tracks via force main to the proposed wastewater treatment facility. The gravity sewers proposed to service the out-of-district Long Island MacArthur Airport property will re-route the existing on-site gravity flow from the sub-surface leaching pools to a new submersible pump station. This pump station will convey all wastewater collected from the airport to the proposed wastewater treatment facility via force main routed around the east side of the airport property Preliminary Collection System and Conveyance System Design Wastewater generated by the Ronkonkoma Hub Sewer District will be collected by gravity sewers and conveyed to the treatment facility by a pump station and force main. The Ronkonkoma Hub sanitary collection system will consist of approximately 3,800 linear feet of 8-inch diameter gravity sewer and approximately 1,530 linear feet of 10-inch gravity sewer as shown by Figure 3. Approximately 3,200 linear feet of the 8-inch gravity sewer will be located at depths ranging from 3 feet to 10 feet below grade, and the rest of the 8-inch and 10-inch gravity sewers will be located at depths ranging between 10 feet and 15 feet below grade. Manholes for both areas will be spaced approximately 300 feet apart. All gravity sewer piping is assumed to be SDR-35 PVC and all manholes are assumed to be constructed in accordance with H-20 load ratings and SCDPW approved castings. The pump station handling the wastewater generated within the Ronkonkoma Hub area has been sized based on an average daily flow equal to 400,000 gallons per day. This pump station will consist of two submersible type pumps sized to handle both the average daily and peak hourly flows expected from the area. The pumps will be variable speed controlled and capable of passing 3-inch diameter solids. The pumps operate one duty and one standby in accordance with the requirements of the SCDPW and SCDHS. The force main located between this pump station and the treatment facility will be constructed out of 6-inch diameter ductile iron class-53 pipe. This force main will be approximately 250 linear feet in length with 100 linear feet jacked under the LIRR tracks. The portion of the pipe that is jacked under the LIRR tracks will be encased inside a 30-inch diameter steel pipe, with the annular 3-4

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20 Section 3 Technical Information space filled entirely with non-shrink grout per SCDPW requirements for jacked pipe. A permit to jack the pipe must be obtained from the MTA (LIRR). The control panel for this pump station will be located inside a common building with the emergency back-up power generator. The generator will be fueled by natural gas, and the building will be designed to blend in with the surrounding residential area. Since this pump station is located within a residential area, an odor control system will also be provided to prevent nuisance odors from impacting the surrounding residents. A lot size of approximately 2,500 square feet should be reserved by Tritec for the pump station in the general facility directly north of the STP site. The pump station handling the wastewater generated by the Long Island MacArthur Airport property is sized based on an average daily flow of 100,000 gallons per day. This pump station will consist of two submersible type pumps sized to handle the average daily flow from the airport. The pumps will be variable speed controlled and capable of passing 3-inch diameter solids. The pumps operate one duty and one standby in accordance with the requirements of SCDPW and SCDHS. The force main connecting this pump station to the treatment facility will be constructed of 6-inch diameter DR-18 PVC pipe. This force main will be approximately 11,000 linear feet in length with the majority of it installed beneath the open field area of the airport. Approximately 2,500 linear feet of the force main will be installed within a paved roadway. This preliminary layout assumes that only the terminal building will be connected for sanitary service. The control panel for the pump station will be located inside a common building with the emergency back-up power generator. The generator will be fueled by natural gas, and the building will be designed to blend in with the surrounding area. No odor control system is anticipated for this pump station since it will be located in an open area far from public access. As of the writing of this report, the as-built sanitary site plan has been requested from SCDHS and the department is in the process of obtaining this information. The preliminary layout may be refined based upon input from the Town of Islip. 3.3 Wastewater Treatment Facility Options Introduction The design of the proposed treatment facility for the Ronkonkoma Hub Sewer District includes consideration of the treatment plant size, treatment plant location, the technology required to meet the target effluent concentrations based on influent loadings and flow, and disposal of the treated effluent Wastewater Treatment Plant Size, Siting and Effluent Disposal The size of the wastewater treatment plant is based on average daily and peak hourly flow estimates for the sewer district. The peak hourly flow is determined based on the 10 States Recommended Standards for Wastewater Treatment Facilities. These standards associate the peak hourly flow to the projected population of the sewer district. The location of the treatment plant is contingent on the area required for the selected technology and effluent discharge conditions Hydraulic Capacity The wastewater treatment facility for the Ronkonkoma Hub Sewer District must be large enough to handle an average daily flow equal to 500,000 gallons per day. All structures and mechanical 3-6

21 Section 3 Technical Information equipment must be sized large enough to treat both the average daily flow and the peak hourly flow expected from the sewer district. The peak hourly flow is estimated based on the equivalent population for the sewer district. The equivalent projected population for the sewer district is based on the re-development plans for the Ronkonkoma Hub area. Assuming an average water consumption rate of 100 gpd/capita, the equivalent population served by the plant will be approximately 5,000. The peaking factor derived from Figure 1 within the Ten State Standards is 3.2. Consequently, only the headworks of the sewage treatment plant must be capable of treating a peak hourly flow rate of 1,600,000 gpd, because a flow equalization basin will be provided downstream of the headworks and prior to the process tankage Organic Capacity The design of the sewage treatment and sludge processing facilities is based on the strength of the wastewater being treated. Anticipated wastewater strength has been established as: BOD: 350 mg/l TSS: 350 mg/l Total Nitrogen: 110 mg/l Alkalinity: 100 mg/l One factor that helps to predict wastewater strength is the age of the collection system. The older the system, the more likely the system will be subject to extraneous water entering the system, thus diluting the wastewater to a weaker strength. The sewers serving the Ronkonkoma Hub Sewer District will be new and built to rigorous standards, inspections and testing. Therefore, groundwater infiltration and rainwater inflow into the system will be minimized, and the wastewater will not be diluted. The Ronkonkoma Hub development is expected to include a large percentage of restaurants, bars, and other wet uses. The organic content in this type of waste, because of the sugar, alcohol and other organic compounds substantially increases the wastewater strength. There is a possibility that a brewery may become part of the development. Brewery waste is highly concentrated and will significantly increase organic concentrations. The selected waste strength also reflects trends in the United States of declining water use. Declining water use is attributed to: Customer conservation and awareness, Installation of low flush toilets and water saving devices, and Decreasing average household size Treated Effluent Disposal and Sewage Treatment Plant Siting The proposed wastewater treatment facility requires area for treatment plant tankage and equipment, subsurface recharge, and space buffers between adjacent properties as required by SCDPW and SCDHS. The overall area required for treatment plant tankage and equipment is based on the selected technology and room for 100 percent future expansion. SCDPW requires subsurface leaching pools to 3-7

22 Section 3 Technical Information have an 8 foot buffer between one another and not exceed an effective depth of 16 feet. The SCDPW also requires the leaching area to accommodate 200 percent of the design flow. Space buffers between the treatment facility, leaching pools and adjacent properties must also be in accordance with SCDPW requirements, and account for the remaining area required to construct the wastewater treatment facility for the Ronkonkoma Hub Sewer District. Based on SCDPW and SCDHS requirements, the total area required for subsurface recharge is approximately 1.2 acres out of the 9.2 available acres for the treatment facility. This area includes the land needed to handle 200 percent of the design flow, leaving 8 acres of land for the construction of the treatment facility, 100 percent future expansion of the treatment facility, and the required buffer. The calculations for the leaching area are based on effluent filtering and a loading rate of 10 gpd/sq. ft. with a 10 foot leaching pool diameter, an effective depth of 16 feet per pool and an 8 foot separation distance between pools Treatment Process Selection Three different treatment processes were evaluated for the Ronkonkoma Hub wastewater treatment plant. During the course of the development of the Sewer Capacity Study regular progress meetings were held with the SCDPW Division of Sanitation. In consultation with the Division, it was determined that three process options would be considered for any new sewage treatment plant: Treatment Option 1 Modified Ludzack Ettinger (MLE) Process Treatment Option 2 Sequencing Batch Reactor (SBR) Process Treatment Option 3 Membrane Biological Reactor (MBR) Process Treatment alternatives were evaluated based on the anticipated study area-specific requirements for effluent nitrogen levels. Option 1, the MLE process, is capable of achieving an effluent Total Nitrogen concentration of 10 mg/l which is the typical State Permit Discharge Elimination System (SPDES) permit limit for groundwater recharge; Option 2, the SBR process can reduce effluent nitrogen to 4-6 mg/l, and Option 3, the MBR process represents the limit of technology for nitrogen removal, which is currently 3 to 5 mg/l. A relative comparison of the total project cost for a typical 200,000 gpd facility was performed. The relative cost comparison was performed, so common facility components that are required for all treatment options were not included. For instance, a control building is required regardless of the treatment option. Consequently, the cost for the control building is not included in the relative cost analysis. The results of the cost comparison are summarized in Table

23 Section 3 Technical Information Process Table 3-1 Relative Cost Comparison for Treatment Options Effluent Concentration Total Construction Cost Total Soft Cost Total Project Cost Percent Difference MLE 10 mg/l $9,321,000. $945,000. $10,266, SBR 4-6 mg/l $10,780,000. $1,195,000. $11,975, % MBR 3-5 mg/l $10,786,000. $1,195,000. $11,982, % For effluent requirements of 10 mg/l Total Nitrogen, Option 1 was selected as being the most cost effective in terms of capital cost. As background information, the following describes each of the treatment options Treatment Option 1 Modified Ludzack Ettinger (MLE) Process The modified Ludzack-Ettinger (MLE) process is a suspended growth type activated sludge treatment process used for nitrogen removal. This process requires an oxygen deficient pre-anoxic zone for denitrification followed by an oxygen rich aeration zone for nitrification and a secondary clarifier for sludge removal. Denitrification occurs in the pre-anoxic zone because nitrate is readily consumed in the absence of oxygen. Flow into the pre-anoxic zone is comprised of screened treatment plant influent and recycled process flow from the downstream aeration zone and secondary clarifier. The recycle flows maintain a stable carbon source and nitrate feed to the process while increasing the overall nitrogen removal efficiency. The aeration required for the MLE process can be achieved through the use of blowers or other mechanical means. The method of aeration analyzed in this study is through use of an STM-Aerotor mechanism. The STM-Aerotor is an Integrated Fixed-Film Activated Sludge (IFAS) system, which combines attached and suspended growth to maximize biomass concentration. The STM-Aerotor configuration is an energy efficient option in terms of nitrogen reduction with minimal operation and maintenance needs. When used as part of the MLE process, the STM-Aerotor system can deliver a total effluent nitrogen concentration of 10 mg/l. The STM-Aerotor is a relatively new treatment technology. The major advantage of this equipment is the operational energy savings realized over time. Aeration blowers are not required for aeration or mixing in the process tank because a series of rotating wheels provide the fixed film growth surface, aeration, and mixing needed for biological treatment Treatment Option 2 Sequencing Batch Reactor (SBR) The sequencing batch reactor (SBR) is another suspended growth type activated sludge process used for nitrogen removal. Similar to the MLE process, the SBR process also achieves pre-anoxic denitrification using BOD in the influent wastewater. The SBR combines anoxic, aeration and clarification within one common basin thereby eliminating the need to recycle process flow between tanks. Parallel process trains are also used to maintain constant flow conditions. The ability to 3-9

24 Section 3 Technical Information denitrify, nitrify and clarify within a single tank allows for process optimization of the overall nitrogen removal efficiency. The SBR technology has been documented to achieve effluent nitrogen concentrations of 4 to 6 mg/l. Sequencing batch reactors are widely used on Long Island and throughout the world; in addition to providing highly effective wastewater treatment, they are advantageous in that the entire biological process occurs in one tank, eliminating the need for a separate clarifier thereby reducing capital costs associated with tankage construction. It is relatively energy intensive as compared to Option 1. The SBR operates based on a sequence of five (5) steps to achieve total effluent nitrogen concentrations down to permitted levels. The five (5) process steps are: Fill Cycle utilizes mechanical mixing to contact the mixed liquor from previous cycles with new influent wastewater to remove the nitrate remaining in the mixed liquor (denitrify). React Cycle utilizes aeration to nitrify the process water after the fill cycle to complete the biological treatment process. Settle Cycle allows the suspended growth portion of the wastewater to settle and become waste sludge following the react cycle. Decant Cycle allows the clarified process water to be drained from the surface of the SBR basin after the solids have been given ample time to settle during the settle cycle. Idle Cycle is the period between the decant cycle finish and the beginning of the next fill cycle. A pre-specified cycle time is established for each of these five (5) steps based on influent wastewater strength and sludge settleability characteristics Treatment Option 3 Membrane Biological Reactor (MBR) The membrane biological reactor (MBR) is another suspended growth type activated sludge process used for nitrogen removal. The MBR process requires pre-anoxic, aeration and membrane filtration to achieve total nitrogen removal. Flow into the pre-anoxic zone is comprised of screened plant influent and recycled process flow from the downstream MBR basin(s). These recycle flows, similar to those described for the MLE process, are necessary to maintain a stable carbon source and nitrate feed while increasing the total nitrogen removal efficiency of the process. The MBR treatment option is capable of reliably producing an effluent nitrogen concentration of 3 to 5 mg/l; commonly described as the limit of technology for nitrogen reduction. MBR technology eliminates the need for secondary clarification and effluent filtration. This process can also operate at higher mixed-liquor suspended solids (MLSS) concentrations when compared to those of an MLE or SBR. The ability to eliminate secondary clarification and operate at higher MLSS concentrations provides the following advantages: (1) higher volumetric loading rates and thus shorter reactor hydraulic retention times; (2) longer sludge retention times (SRTs) resulting in less sludge production; (3) operation at low dissolved oxygen (DO) concentrations with potential for simultaneous nitrificationdenitrification in long SRT designs; (4) high-quality effluent in terms of low turbidity, bacteria, total suspended solids (TSS), and biological oxygen demand (BOD); and (5) less space required for wastewater treatment. 3-10

25 Section 3 Technical Information A vacuum differential created by permeate pumps extracts clarified water through the membranes. This filtration process results in solids concentrations typically ranging from 1 percent to 3 percent in the MBR tank(s). Routine membrane fouling, or the embedding of solids within the membrane pores and onto the membrane surface, is a disadvantage of using this technology. Membrane fouling must be mitigated to maintain proper MBR function. As such, aeration is used to mechanically scrape solids from the membrane surfaces, while periodic backwashing and chemical cleaning is required to loosen particles lodged within the pores. It is relatively energy intensive as compared to Option Selected Treatment Process Technology Taking into account expected effluent quality, the most cost effective process option for the Ronkonkoma Hub Sewage Treatment Plant is the Modified Ludzack-Ettinger (MLE) Process using the STM-Aerotor. Photographs of the STM- Aerotor for the Village of Patchogue facility are shown. Photograph 1 - STM Aerotor Being Installed Typically final clarifiers are used for solids separation and return of the mixed liquor. In lieu of final clarifiers the use of membrane-bioreactor (MBR) filtration is warranted to allow the use of the treated effluent to be discharged at the rate of 10 gpd/sq. ft. for final effluent recharge to groundwater. Membrane-bioreactor (MBR) filtration will be used to combine solids separation with effluent filtering. The use of MBRs results in lower capital cost because of the savings associated with the covered tank, smaller footprint than a clarifier and elimination of the need to construct a building as is required for effluent polishing filters. The STM-Aerotor is a relatively new treatment technology; Long Island currently has only three installations. The first installation has been in operation since 2003 and is located at the Newsday facility in Melville, and the second installation has Photograph 2 - STM-Aerotor Clean Water Testing been in operation since mid-2011 and is part of a newly upgraded Village of Patchogue Advanced Wastewater Treatment Facility (AWTF). The Village of Greenport has also recently implemented this process. Sludge thickening will be provided in conjunction with this process to increase the solids concentration to 3 percent prior to liquid sludge disposal at the Bergen Point Wastewater Treatment Plant. Measures in the design must consider a future thickened sludge concentration of 5 percent per SCDPW requirements. Sludge thickening will also be achieved through the use of Membrane Bioreactor Thickening or MBT thickening. MBT does not require a building and polymer system as is required for a gravity belt thickener (GBT). 3-11