The goal of the Clean Water Act (cwa) is to restore and maintain the chemical, physical, and biological integrity of the Nation’s waters
WMA water withdrawal and NPDES wastewater discharge summarY
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- Use Assessment
- Shellfish Harvesting
- Primary and Secondary Contact RECREATION and aesthetics
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WMA water withdrawal and NPDES wastewater discharge summarYThere are no permitted direct water withdrawals or NPDES discharges to Plymouth Bay. The Entergy Nuclear Generation Company (ENGC) - Pilgrim Nuclear Power Station is located just south of Rocky Point. ENGC operates Pilgrim Nuclear Power Plant in accordance with NPDES Permit MA0003557, issued in 29 April 1991 (modified 30 August 1994) and transferred to Entergy Nuclear from Boston Edison on 22 September 1999. This permit is still in effect since the renewal application received in March 1996 is under review. The Pilgrim Nuclear Power Station, which began operation in December 1972, is a 670 MW electric generating station. Once-through cooling water is withdrawn from an intake embayment from Cape Cod Bay via two circulating water pumps with a capacity of approximately 345 cfs (223 MGD) each. There are also five service water pumps with a combined capacity of 23 cfs (14.9 MGD). Water is drawn under a skimmer wall, through vertical bar racks, and finally through vertical traveling water screens prior to passing through the condensers. There are two traveling water screens for each water pump (Anderson 1987). Impinged organisms washed from the screens are directed into a sluiceway that directs them south (approximately 320’ away) of the intake. The permit authorizes discharges from 10 outfalls as described below. Main Discharge Canal into Cape Cod Bay: Outfall 001: 447 MGD average monthly (510 MGD maximum daily) condenser cooling water discharged via a 900’ discharge canal. The maximum daily temperature is limited to 102ºF with a ΔT of 32ºF between intake and discharge. Total residual oxidants 0.1 mg/L when in use. Boron and sodium nitrite limited to <1.0 mg/L and 2.0 mg/L, respectively, above background levels. Outfall 010: 19.2 MGD average monthly discharge of chlorinated plant service cooling water; Total residual oxidant monthly average limit of 0.5 mg/L (1.0 mg/L maximum daily). Outfall 011: 0.015 MGD (0.06 MGD daily max) makeup water and demineralizer wastewater; average monthly TSS 30 mg/L (100 mg/L daily maximum). Although subject to an annual review, the barrier net near the end of the discharge canal required to minimize entrainment of fish, primarily flounder, menhaden, and migrating rainbow smelt was removed in November 1994 (Alexander 1999). As an alternative to the physical barrier, the EPA and MassDEP can require the Permittee maintain an average dissolved nitrogen level of 115% in the canal to minimize gas bubble disease in finfish. Intake Embayment area into Cape Cod Bay: Outfall 002: 255 MGD maximum daily of thermal backwash for bio-fouling control (limited to 3 hours/day twice weekly when necessary, maximum temperature 120ºF. This thermal backwash generally occurs about four to five times a year, for a period of about 1.5 to 2 hours. During a thermal backwash, heated water from the downstream end of the steam condensers is re-routed back through the system and out through the intake embayment. This is done to control macro-fouling, primarily from mussels. To accomplish this, the facility shuts down one of the two intake pumps and pushes hot water back through half the system. During this period (about 35-45 minutes) the water within the half of the system receiving the backwash is typically heated to between 105F and 110F, but may reach as high as 120F. The second half of the system is then treated in the same manner. Because the facility has to reduce load during these times, which is expensive, the duration and number of backwashes per year is kept to a minimum. In summary, during a thermal backwash about 155,000 gpm of heated water (>105F) is sent into the intake embayment for a period of about 1.5-2 hrs. Outfall 003: 4.1 MGD intake screen wash water (fish sluice water). This discharge can be made up of 3.2 MGD of Cape Cod Bay water and when necessary 0.9 MGD potable fresh water (Fire Station Water). The marine water will be dechlorinated before injection. Outfall 008: 0.73 MGD potable water for sea foam suppression (sprayed directly in front of intake structure) when necessary to reduce buildup of sea foam. Periodic testing of fire pumps is also conducted. Outfalls 004, 005, 006, and 007: Yard drain runoff; average monthly/daily maximum limit for total suspended solids 30/100 mg/L, respectively and oil and grease daily maximum limit 15 mg/L (sampling required twice year in April and September during first hour of significant storm). It should be noted that the potential for re-entrainment of fish is of concern due to the nearness of the fish-return to the intake. Use AssessmentAquatic LifeEelgrass Bed Habitat MassDEP’s Wetlands Conservancy Program (WCP) identified the presence of eelgrass in Plymouth Bay from historic 1951 black and white aerial photography (Costello 2003). In 1998 MassDEP WCP performed field verification of 1995 aerial photography and mapped the extent of eelgrass bed habitat in Plymouth Bay. Total areal coverage in Plymouth Bay from the 1998 survey was approximately 2%. In 2001 MassDEP WCP performed field verification of 2001 aerial photography and mapped the extent of eelgrass bed habitat in Plymouth Bay. There was almost no change in the total coverage of eelgrass beds between 1998 and 2001. There are no apparent changes in eelgrass beds since 1951. Biology Scattered populations of blue mussels (Mytilus edulis) are found along the entire shoreline. The Warren Cove area has a small population of soft shelled clams (Mya arenaria). Surf clams (Spisula solidissima) are found in waters between the 10 and 30-foot contour with ocean quahogs (Arctica islandica) beyond the 60-foot depth (Churchill 2003f). As part of their NPDES permit, ENGC is required to conduct environmental surveillance and monitoring programs to determine whether the operation of the Pilgrim Nuclear Power Station results in measurable effects on the marine ecology in the Western Cape Cod Bay ecosystem and in the Rocky Point area and to evaluate the significance of any observed effects (Environmental Protection Group 2005). A technical review of intake and discharge effects to finfish can be found in Appendix H. Although impingement effects to winter flounder populations appear to be fairly small, estimated entrainment effects vary from being minimal to a 20% loss to the population at large (the Plymouth/Kingston/Duxbury Bay (PKDB) and adjacent waters areas are thought to be the primary spawning ground that produced the larvae and eggs entrained by the Plymouth Nuclear Power Station). Whether or not these levels of impact are a “significant” detriment to the population, and will result in slowing the return of much higher population densities, is currently unknown. The Aquatic Life Use is assessed as support for Plymouth Bay based primarily on best professional judgment, the apparent stability of the eelgrass bed habitat, and the high water quality conditions documented in the adjacent inner segment of Duxbury Bay. Shellfish HarvestingThe DMF Shellfish Status Report of July 2000 indicates that Areas CCB41.0 and CCB41.2 (which contain this entire segment) are approved (MA DFG 2000 and Appendix G, Table G3). Based on the DMF shellfish growing area status, the Shellfish Harvesting Use is assessed as support. Primary and Secondary Contact RECREATION and aestheticsWeekly testing for Enterococci bacteria during the swimming season was conducted at five locations along the Plymouth public beach in Plymouth. No postings were reported in either of the 2002/2003 beach seasons (MDPH 2003 and MDPH 2004b). There have been no visual observations of aesthetically objectionable conditions (e.g., oils, odors, deposits, etc.) in Plymouth Bay (DeCesare 2005). The Primary and Secondary Contact Recreational and Aesthetics uses are assessed as support in Plymouth Bay since the beach was open all of the 2002 and 2003 bathing seasons and the lack of aesthetically objectionable conditions. Furthermore, the entire area of Plymouth Bay is approved for shellfishing - indicative of low bacteria levels. Plymouth Bay (MA94-17) Use Summary Table
RecommendationsImplement recommendations in the DMF shellfish management plans for Areas CCB41.0 and CCB41.2. Support DMF efforts to improve availability/access (electronic or web site) to water quality and biological monitoring data collected from DMF shellfish sampling stations to assess the status of the Primary and Secondary Contact Recreational uses. Support passage of the federally approved boat sewage No Discharge Area (NDA) for the entire Plymouth/Kingston/Duxbury Bay so the Bay is designated as an NDA by the 2006 boating season. Based on a review of intake and discharge effects to finfish associated with the Pilgrim Nuclear Power Station the following recommendations were suggested (Appendix H): 1. The resource agencies in concert with the permit agencies should consider further evaluation of the intake effects to winter flounder. If effects are found to be substantial, these agencies should determine what steps need to be taken to reduce the impacts of the facility on the winter flounder population. 2. Because impinged fish from the intake screens are shunted back into the intake embayment, there is a concern that these fish, weakened from impingement, will simply be re-impinged. An assessment of re-impingement rates, especially during large-scale events, should be considered by the permitting and resource agencies. These studies should also include an evaluation of the best point for locating the screen-wash discharge such that it would have the smallest negative impact on the populations of impinged species. South Shore Coastal Watersheds 2001 Water Quality Assessment Report 94wqar.doc DWM CN 93.0 Directory: eea -> docs -> dep -> water -> resources -> 71wqar09 dep -> Charles D. Baker Governor dep -> Charles D. Baker Governor dep -> Charles D. Baker Governor dep -> Index of Photographs dep -> Department of environmental protection one winter street, boston, ma 02108 617-292-5500 water -> Water Resource Management Planning 71wqar09 -> 2004 water quality assessment report Download 3.32 Mb. Share with your friends:
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