Water and Sewer Infrastructure

Size: px
Start display at page:

Download "Water and Sewer Infrastructure"

Transcription

1 Chapter 11: Water and Sewer Infrastructure A. INTRODUCTION This chapter evaluates the potential for significant adverse impacts on water and sewer infrastructure that could result from the proposed project. The project would consist of redeveloping the Pier 57 site with open space, retail facilities, a marina, restaurants and other commercial, educational and cultural uses. The redevelopment would increase the project site s water demand and sewage generation from the current condition. The effect on the City s water supply, wastewater treatment and stormwater conveyance infrastructure is discussed in this chapter. Although stormwater from the proposed project site is directly discharged to the Hudson River, sanitary sewage would be conveyed to the City s combined sewer system. Therefore, the size and location of the project (more than 250,000 square feet of commercial development in a combined sewered area) warrants a preliminary sewer analysis per the 2012 City Environmental Quality Review (CEQR) Technical Manual. 1 PRINCIPAL CONCLUSIONS As described more fully below, the proposed project would result in an increased demand on the City s water supply and wastewater treatment infrastructure. The increases in water demand and wastewater due to the proposed project, however, would be minimal and would not significantly impact existing infrastructure. Given that the project site is a pier, stormwater runoff is directly discharged into the Hudson River; therefore the City s stormwater conveyance infrastructure would not be affected. Accordingly, the proposed project would not result in any significant adverse impacts on the City s water supply, wastewater treatment or stormwater conveyance infrastructure. B. METHODOLOGY This analysis follows the methodologies set forth in the CEQR Technical Manual and assesses current conditions, conditions in the future without the proposed project (No Action), and conditions in the future with the proposed project (With Action). Water demands and sewage generation are calculated based on the proposed uses of the project and the generation rates set forth in the CEQR Technical Manual. The ability of the City s water and sewer infrastructure to handle the anticipated demand is determined by comparing With Action conditions to existing conditions for the analysis of stormwater and to No Action conditions for the analyses of water supply and sanitary sewage. The existing and With Action 1 CEQR Technical Manual, May 2012, p

2 Pier 57 Redevelopment stormwater runoff and sanitary flow volumes were calculated using the New York City Department of Environmental Protection (DEP) Flow Calculation Matrix. C. EXISTING CONDITIONS WATER SUPPLY New York City s water supply system is composed of three watersheds Croton, Delaware, and Catskill and extends as far north as the Catskill Mountains. From these watersheds, water is carried to the City via a conveyance system made up of reservoirs, aqueducts, and tunnels. Within the City, a network of underground water pipes distributes water to customers. On average, the New York City water system delivers approximately 1.1 billion gallons per day (bgd) to the five boroughs and Westchester County. The Croton system supplies an average of 22 million gallons per day (mgd), primarily to users in the lower-elevation portions of Manhattan and the Bronx. The Delaware and Catskill systems supply all five boroughs and deliver approximately 98 percent of the City s drinking water. The Delaware and Catskill water systems collect water from watershed areas in the Catskill Mountains and deliver it to the Kensico Reservoir in Westchester County. From the Kensico Reservoir, water is sent to the Hillview Reservoir in Yonkers, which balances the daily fluctuations in water demand and pressure to the system. From there, water is delivered to the City through three tunnels, Tunnel Nos. 1, 2, and 3. Tunnel No. 1 carries water through the Bronx and Manhattan to Brooklyn; Tunnel No. 2 travels through the Bronx, Queens, Brooklyn, and then through the Richmond Tunnel to Staten Island; and Tunnel No. 3 goes through the Bronx and Manhattan, terminating in Queens. City Tunnel No. 1 serves the southern portion of Manhattan where the project site is located. The site is served by a 20-inch diameter ductile iron pipe water main built in 1998 that is located on the west side of Route 9A. 1 The existing building on the Pier 57 site is vacant. Therefore, the Pier 57 site generates no current demand on the local water distribution system. SANITARY SEWAGE Sanitary sewage from the project site is conveyed to a network of combined sewers that convey both sanitary sewage and stormwater to the North River Wastewater Treatment Plant (WWTP). In periods of dry weather, the combined sewer conveys only sanitary sewage. During and immediately after wet weather, the sewers can experience a much larger flow. To control flooding at the North River WWTP, regulators are built into the system to only allow approximately two times the amount of design dry weather flow into the interceptors, which take the flow to the North River WWTP. The excess flow to the regulators is discharged to the nearest waterbody as combined sewer overflow (CSO). The sanitary sewage from the project site is conveyed to a 4 x 2 8 combined sewer in Route 9A, which conveys flow to Regulator 51. CSO from Regulator 51 is conveyed to CSO outfall NR-22. At the North River WWTP, wastewater is fully treated by physical and biological processes before it is discharged into the Hudson River. The quality of the treated wastewater (effluent) is regulated by a New York State Pollution Discharge Elimination System (SPDES) permit issued by the New York State Department of Environmental Conservation (DEC). A maximum daily 1 Information obtained from the DEP Bureau of Water and Sewer Operations Water Maps. 11-2

3 Chapter 11: Water and Sewer Infrastructure capacity for each treatment facility in the City is set to ensure that the quality of effluent is acceptable to discharge into surrounding water bodies; the maximum capacity for the North River WWTP is 170 million gallons per day (mgd). Table 11-1 lists the monthly flows to the North River WWTP. The average monthly flow over a recent 12 month period was 124 mgd, well below the maximum permitted level of 170 mgd. Table 11-1 Monthly Flows at North River WWTP Month Flow (mgd) July August September October November December January February March April May June Month Average 124 Notes: Permitted Limit: 170 mgd Source: DEP Monthly Reports: Operating Efficiency Citywide Bubble STORMWATER The project site is located on a pier in the Hudson River. Stormwater is discharged directly into the Hudson River and therefore does not affect CSO conditions in the City s combined sewer system. The project site is approximately 3.80 acres. It is estimated that approximately 3.16 acres (83 percent) of the site is covered by impermeable building roof and 0.64 acres (17 percent) is paved. Table 11-2 describes the project site surfaces and surface areas, and how stormwater runoff is currently discharged from the project site. Table 11-2 Project Site Surface Coverage: Existing Conditions Surface Type Surface Areas (sf) Discharge Method Building Roofs 137,775 Direct Drainage Paved Surfaces 27,800 Direct Drainage Total 165, Note: sf = square feet Sources: Data provided by Hudson Eagle LLC The weighted runoff coefficient of the project site is calculated to be 0.97, which corresponds to the percentage of precipitation that becomes surface runoff. 11-3

4 Pier 57 Redevelopment D. THE FUTURE WITHOUT THE PROPOSED PROJECT In the No Action condition, the existing pier structure on the project site is expected to remain vacant. Water consumption, sanitary sewage generation, and stormwater runoff would not be expected to change from existing conditions. E. PROBABLE IMPACTS OF THE PROPOSED PROJECT WATER SUPPLY Table 11-3 summarizes the estimated water consumption of the proposed project under the With Action condition. The proposed uses on the project site are estimated to have a water demand of 132,603 gallons per day (gpd). Table 11-3 Projected Water Consumption Size (Square feet) Consumption (gallons per day) Use Rate Retail 1 Domestic 261, gpd/sf 62,856 Air Conditioning 261, gpd/sf 44,523 Commercial 2 Domestic 83, gpd/sf 8,370 Air Conditioning 83, gpd/sf 14,229 Rooftop Open Space Domestic 525 visitors 3 5 gpd/visitor 4 2,625 TOTAL 345, ,603 Notes: sf = square feet 1. Retail uses include: Work/Sell Marketplace Center, Food Market and Restaurants, Restaurant Terrace, Flexible Retail Space, and General Retail 2. Commercial uses include: Technical Art School and Ancillary Facilities, Theater/Cultural Use and Gallery/Spa/Storage/Other Uses 3. Number of visitors is based on the Saturday trip generation for the rooftop open space and rooftop exhibit space. 4. Rate obtained from NYSDEC Design Standards for Wastewater Treatment Works for Intermediate Size Sewage Facilities, last revised Source: Rates from 2012 CEQR Technical Manual. The projected water consumption for the proposed project of 132,603 gpd represents a small increase in demand on the New York City water supply system. The incremental demand due to the proposed project would be approximately 0.01 percent of the 1.1 bgd typically distributed within New York City and Westchester County. As described above, an existing 20-inch diameter water main is located on the west side of Route 9A. According to the Hudson River Park Trust, there are currently no reported issues with low water pressure within the Hudson River Park. The proposed project does not represent an exceptionally large water demand and is not located in an area that experiences low water pressure. Therefore, the proposed project would have no significant adverse impacts on the City s water supply. 1 1 CEQR Technical Manual, May 2012, p

5 Chapter 11: Water and Sewer Infrastructure SANITARY SEWAGE The estimated amount of sanitary sewage generated by the proposed project would be 73,851 gpd. This estimated amount conservatively includes all water demand except that consumed by air conditioning (as shown in Table 11-3 above), which is not discharged into the sewer system. The sanitary sewage generated by the proposed uses on the project site would be conveyed to the 4 x 2 8 combined sewer in Route 9A and treated at the North River WWTP. The volume of sanitary sewage generated would be 0.04 percent of the permitted average daily flow of 170 mgd at the North River WWTP and would not result in an exceedance of the North River WWTP s capacity. Therefore, the proposed project would not result in a significant adverse impact on the City s sanitary sewage treatment system. Additionally, per the New York City Plumbing Code (Local Law 33 of 2007) low-flow fixtures are required to be implemented and would help to reduce sanitary flows from the project site. STORMWATER Based on the proposed site plan, approximately 83 percent (137,775 square feet) of the site would be roof surfaces and 17 percent (27,800 square feet) of the site would be occupied by paved surfaces. Based on this information, the weighted runoff coefficient was calculated to be 0.97 (no change from the existing condition). 1 A small area of landscaping may be included on the roof, however it is conservatively assumed for this analysis that there would be no landscaped surfaces. As a part of the proposed project, the circulation space in front of the pier from West 14th Street to West 16th Street would be reconfigured. The surface coverage of this area in the existing condition is paved and would remain predominately paved in the With Action condition; therefore it is excluded from the project site area calculations. Using the existing and proposed site data, the DEP Calculation Matrix was completed for the existing and With Action conditions. The summary tables, taken from the DEP Flow Matrix are included in Table Table 11-4 DEP Flow Matrix Existing and With Action Comparison Rainfall (in.) Rainfall Duration (hr.) Direct Drainage Existing With Action 165,575 sf / 3.80 Acres 165,575 sf / 3.80 Acres Sanitary Total To River Sanitary Total Notes: sf = square feet CSS = Combined Sewer System; MG = Million Gallons 1 The repair of the existing perimeter walkway and its extension to connect with the public esplanade to the east of the pier was previously assessed in the Final Environmental Impact Statement (FEIS) for Hudson River Park, and permits and subsequent renewals were issued to the Hudson River Park Trust (HRPT). As this work was evaluated in the FEIS for the Hudson River Park and has been permitted, it will not be re-evaluated in this EIS. 11-5

6 Pier 57 Redevelopment The calculations from the flow volume matrix help to determine the change in wastewater volumes to the combined sewer system from existing conditions to the With Action condition. volumes were calculated for four rainfall volume scenarios with varying durations; however, all stormwater runoff would be directly discharged to the Hudson River. The overall increase in sanitary sewer discharge from the project site for the above rainfall volume-duration scenarios would be 0.01MG, 0.01MG, 0.03MG and 0.06MG, respectively. The increase in flows would be the result of sanitary sewer discharge from the proposed project since there would be no sanitary sewage discharged from the site in the No Action condition. Per the New York City Plumbing Code (Local Law 33 of 2007) low-flow fixtures are required to be implemented and would help to reduce sanitary flows from the project site. The water and sediment quality of the lower Hudson River due to stormwater from the project site is assessed in Chapter 9, Natural Resources. Stormwater from the project site is directly discharged to the Hudson River and is not conveyed to the City s combined or separate sewers; therefore the proposed project would have no impact on the City s stormwater conveyance infrastructure. 11-6