CSO Completed Projects History

Click on links for details about each project, including receiving water, cost, water quality benefits and more.

Completed CSO Control Projects 1996-December 2015 (Map)

1996

1. SOMERVILLE BAFFLE MANHOLE SEPARATION

Receiving Water(s):	Alewife Brook, Upper Mystic River	Image
Year Completed:	1996
Cost:	$400,000
Description:	Separated common manholes connecting local sewer and storm drain systems. City of Somerville performed design and construction with MWRA financial assistance.
Water Quality Benefit(s):	Eliminated CSO discharges at three City of Somerville outfalls: SOM001,SOM006, SOM007
Frequency of Discharge (typical year)
	Before project: 2
	With project: 0
Annual Discharge Volume (typical year):
	Before project: 0.04 million gallons
	With project: 0 gallons (discharges eliminated)
CSO Reduction by volume:	100%

2000

2. CONSTITUTION BEACH SEWER SEPARATION

Receiving Water(s):	Boston Harbor/ Constitution Beach	Image
Year Completed:	2000
Cost:	$3,768,888
Description:	Installed approximately 14,000 linear feet of storm drain to separate the combined sewer system, removed stormwater flows from area sewers, and eliminated CSO discharges to Constitution Beach, allowing MWRA to decommission the Constitution Beach CSO treatment facility. BWSC performed design and construction with MWRA financial assistance.
Water Quality Benefit(s):	Eliminated CSO discharges to Constitution Beach to comply with Class B water quality standards. Closed outfalls MWR207(BOS002)
Frequency of Discharge (typical year):
	Before project: 16 treated
	With project: 0
Annual Discharge Volume (typical year):
	Before project: 1.35 million gallons
	With project: 0 gallons (discharges eliminated)
CSO Reduction by volume:	100%

4. HYDRAULIC RELIEF AT OUTFALL B0S017

Receiving Water(s):	BOS017: Mystic River/Chelsea Creek Confluence.	Image
Year Completed:	2000
Cost:	$2,294,549
Description:	BOS017: In Charlestown, 190 feet of 36-inch diameter pipe were installed in Sullivan Square to divert two local (BWSC) combined sewers to a direct connection with MWRA’s Cambridge Branch Sewer. In addition, a 10-foot long restriction between the Charlestown and Cambridge Branch Sewers, adjacent to Sullivan Square, was eliminated.
Water Quality Benefit(s):	Minimized CSO discharges to meet B(cso) water quality standards (>95% compliance with Class B) at CSO Outfall BOS017.
BOS017 - Frequency of Discharge (typical year):
	Before project: 18
	With project: 1
Annual Discharge Volume (typical year):
	Before project: 2.5 million gallons
	With project: 0.02 million gallons
CSO Reduction by volume:	99%

3. HYDRAULIC RELIEF AT OUTFALL CAM005

Receiving Water(s):	CAM005: Upper Charles River Basin.	Image
Year Completed:	2000
Cost:	$2,294,549
Description:	CAM005: In Cambridge, the 40-foot long, 24-inch diameter dry weather connection between the CAM005 regulator and MWRA’s North Charles Metropolitan Sewer was relieved with a 54-inch additional connection.
Water Quality Benefit(s):	Minimized CSO discharges to meet B(cso) water quality standards (>95% compliance with Class B) at CSO Outfall CAM005.
CAM005 - Frequency of Discharge (typical year):
	Before project: 11
	With project: 3
Annual Discharge Volume (typical year):
	Before project: 3.8 million gallons
	With project: 0.84 million gallons
CSO Reduction by volume:	78%

5. NEPONSET RIVER SEWER SEPARATION

Receiving Water(s):	Neponset River	Image
Year Completed:	2000
Cost:	$2,444,394
Description:	Installed approximately 8,000 linear feet of storm drain to separate the combined sewer system, removed stormwater flows from area sewers, and closed CSO regulators, eliminating CSO discharges at the two remaining CSO outfalls to the Neponset River. BWSC performed design and construction with MWRA financial assistance.
Water Quality Benefit(s):	Eliminated CSO discharges from outfalls BOS093 and BOS095 to Neponset River to comply with Class B water quality standards and protect South Dorchester Bay beaches (Tenean Beach.
Frequency of Discharge (typical year):
	Before project: 17
	With project: 0
Annual Discharge Volume (typical year):
	Before project: 5.8 million gallons
	With project: 0 gallons (discharges eliminated)
CSO Reduction by volume:	100%

2001

6. CHELSEA TRUNK SEWER REPLACEMENT (2000) 7. CHELSEA BRANCH SEWER RELIEF (2001) 8. CHE008 OUTFALL REPAIRS (2001)

Receiving Water(s):	Mystic River/Chelsea Creek Confluence Chelsea Creek	Image
Year Completed:	2000-2001
Cost:	$29,779,319
Description:	Replaced 18-inch diameter city-owned trunk sewer with 30-inch pipe, relieved MWRA’s Chelsea Branch and Revere Extension Sewers with 48-inch to 66-inch diameter pipe, rehabilitated Outfall CHE008, and installed underflow baffles for floatables control at all outfalls.
Water Quality Benefit(s):	Minimized CSO discharges to meet B(cso) water quality standards (>95% compliance with Class B) at outfalls CHE002, CHE003, CHE004, CHE008.
Frequency of Discharge (typical year):
	Before project: 8
	With project: 4
Annual Discharge Volume (typical year):
	Before project: 9.0 million gallons
	With project: 0.58 million gallons

9. UPGRADE COTTAGE FARM CSO FACILITY (2000) 10. UPGRADE PRISON POINT CSO FACILITY (2001) 11. UPGRADE SOMERVILLE MARGINAL CSO FACILITY (2001) 12. UPGRADE FOX POINT CSO FACILITY (2001) 13. UPGRADE COMMERCIAL POINT CSO FACILITY (2001)

Receiving Water(s):	Lower Charles River Basin, Upper Inner Harbor, Upper Mystic River, Mystic River/Chelsea Creek Confluence, South Dorchester Bay	Image
Year Completed:	2001	Image
Cost:	$22,261,200
Description:	Upgraded chlorine disinfection systems, added dechlorination systems, process control and safety improvements.
Water Quality Benefit(s):	Upgrade treatment to meet Class B water quality criteria, including residual chlorine limits for outfalls MWR201, MWR203 MWR205, MWR205A (SOM007A), MWR209 (BOS088/BOS089), MWR211(BOS090) These projects improved treatment performance, but did not affect treated discharges' frequency or volume.

2006

14. PLEASURE BAY STORM DRAIN IMPROVEMENTS

Receiving Water(s):	North Dorchester Bay	Image
Year Completed:	2006
Cost:	$3,200,000
Description:	Stormwater piping and appurtenances to relocate stormwater dischargers from Pleasure Bay to Reserved Channel.
Water Quality Benefit(s):	Eliminated storm water discharges to Pleasure Bay Beach.

15. STONY BROOK SEWER SEPARATION

Receiving Water(s):	Lower Charles River Basin	Image
Year Completed:	2006
Cost:	$44,198,623
Description:	Installed 74,000 linear feet of new storm drain to remove stormwater runoff from local sewers serving a 609-acre area in Jamaica Plain, Mission Hill and Roxbury, and disconnected an already-separated storm drain system serving an adjacent 548-acre area from the sewer system.
Water Quality Benefit(s):	Minimized CSO discharges to meet B(cso) water quality standards (>95% compliance with Class B) at MWR023 (Stony Brook Conduit).
Frequency of Discharge (typical year):
	Before project: 22
	With project: 2
Annual Discharge Volume (typical year):
	Before project: 44.5 million gallons
	With project: 0.13 million gallons
CSO Reduction By Volume:	99.7%

2007

16. SOUTH DORCHESTER BAY SEWER SEPARATION

Receiving Water(s):	South Dorchester Bay	Image
Year Completed:	2007
Cost:	$118,394,583
Description:	Installed 135,700 linear feet (25.7 miles) of storm drain to remove stormwater runoff from local sewers serving a 1,750-acre area in Dorchester. Closed all CSO regulators, allowing decommissioning of MWRA’s Fox Point and Commercial Point CSO facilities.
Water Quality Benefit(s):	Eliminated CSO discharges to Savin Hill, Malibu and Tenean beaches, in compliance with Class B water quality standards at outfalls MWR209(BOS088/BOS089), MWR211(BOS090)
Frequency of Discharge (typical year):
	Before project: 20 (treated)
	With project: 0
Annual Discharge Volume (typical year):
	Before project: 30 million gallons
	With project: 0 gallons (discharges eliminated)
CSO Reduction By Volume:	100%

17. FORT POINT CHANNEL SEWER SEPARATION

Receiving Water(s):	Fort Point Channel	Image
Year Completed:	2007
Cost:	$11,866,775
Description:	Removed stormwater runoff from local andMWRA combined sewers by installing 4,550 feet of new storm drains serving 55 acres in the Fort Point Channel area. Also overflow weirs were raised, at BOS072 & BOS073. At both locations new tide gates were installed, and underflow baffles were constructed for floatables control.
Water Quality Benefit(s):	Minimized CSO discharges to meet B(cso) water quality standards (>95% compliance with Class B).
Frequency of Discharge (typical year):
	Before project: 9
	With project: 0
Annual Discharge Volume (typical year):
	Before project: 3.0 million gallons
	With project: 0 gallons (discharges eliminated)
CSO Reduction By Volume:	100%

18. REGIONWIDE FLOATABLES CONTROL (2007) 19. MWRA FLOATABLES CONTROL AND OUTFALL CLOSING PROJECTS (2000)

Receiving Water(s):	Regional Application	Image
Year Completed:	2007
Cost:	$2,469,970
Description:	Projects involved floatables controls and regulator or outfall closings that are independent of the larger projects. The project affected various outfalls system-wide. In March 2000, MWRA closed Outfalls MWR021 and MWR022 to CSO discharges.
Water Quality Benefit(s):	Complied with EPA Policy Nine Minimum Controls requirement to control solid and floatable material. Eliminated CSO discharges at select outfalls. The floatables controls did not affect CSO discharge frequency or volume.

20. UNION PARK DETENTION/TREATMENT FACILITY

Receiving Water(s):	Fort Point Channel	Image
Year Completed:	2007
Cost:	$49,583,406
Description:	Added CSO treatment facility to existing BWSC Union Park Pumping Station with fine screens, chlorine disinfection, dechlorination, and 2 million gallons of detention storage.
Water Quality Benefit(s):	Provided treatment of Union Park pumping station discharges to Fort Point Channel at BOS 070 to meet Class B water quality criteria, including residual chlorine limits, and lowered discharge frequency and volume with on-site detention basins.
Frequency of Discharge (typical year):
	Before project: 25 (untreated)
	With project: 17 (treated)
Annual Discharge Volume (typical year):
	Before project: 132.0 million gallons
	With project: 71.4 million gallons/year
CSO Reduction By Volume:	46%

21. BOS019 CSO STORAGE CONDUIT

Receiving Water(s):	Upper Inner Harbor (Little Mystic Channel)	Image
Year Completed:	2007
Cost:	$14,287,800
Description:	Installed twin-barrel 10’x17’box conduit to provide 670,000 gallons of off-line storage, between Chelsea St. and the Mystic Tobin Bridge, Charlestown. Included above ground dewatering Pump Station.
Water Quality Benefit(s):	Minimized CSO discharges at BOS019 to meet B(cso) water quality standards (>95% compliance with Class B).
Frequency of Discharge (typical year):
	Before project: 13
	With project: 2
Annual Discharge Volume (typical year):
	Before project: 4.4 million gallons
	With project: 0.6 million gallons
CSO Reduction By Volume:	86%

2008

22. PRISON POINT CSO FACILITY OPTIMIZATION

Receiving Water(s):	Upper Inner Harbor	Image
Year Completed:	2008
Cost:	$50,000
Description:	Minimized treated CSO discharges at MWR203 to the Inner Harbor by optimizing the operation of existing facility gates and pumps to maximize in-system storage and convey more flow to Deer Island
Water Quality Benefit(s):	Reduced treated CSO discharges into the Upper Inner Harbor.
Frequency of Discharge (typical year):
	Before project: 30 (treated)
	With project: 17 (treated)
Annual Discharge Volume (typical year):
	Before project: 335 million gallons
	With project: 243 million gallons
CSO Reduction By Volume:	27%

2009

23. COTTAGE FARM BROOKLINE CONNECTION AND INFLOW CONTROLS

Receiving Water(s):	Lower Charles River Basin	Image
Year Completed:	2009
Cost:	$3,326,823
Description:	Optimized the combined conveyance capacity of the two MWRA sewers that carry flows across the Charles River by interconnecting overflow chambers outside the Cottage Farm CSO facility; increased this conveyance capacity by bringing into service a parallel, previously unutilized 54-inch diameter sewer (the “Brookline Connection”)
Water Quality Benefit(s):	Minimized treated CSO discharges to the Charles River Basin at MWR201.
Frequency of Discharge (typical year):
	Before project: 7 (treated)
	With project: 7 (treated)
Annual Discharge Volume (typical year):
	Before project: 44.5 million gallons
	With project: 24 million gallons
CSO Reduction By Volume:	46%

24. MORRISSEY BOULEVARD STORM DRAIN

Receiving Water(s):	North Dorchester Bay	Image
Year Completed:	2009
Cost:	$36,405,252
Description:	Installed 2,800 linear feet of 12-foot by 12-foot box conduit for stormwater conveyance, with gated connection to North Dorchester Bay CSO Storage Tunnel at upstream end, new outfall to Savin Hill Cove, and pollution prevention measures.
Water Quality Benefit(s):	Increased level of stormwater control along the South Boston beaches by redirecting some stormwater to Savin Hill Cove in large storms.

2010

25. BULFINCH TRIANGLE SEWER SEPARATION

Receiving Water(s):	Charles River	Image
Year Completed:	2010
Cost:	$9.6 million
Description:	Installed 4,500 linear feet of of new storm drain and and special structures. Performing TV inspections and sewer cleaning.
Water Quality Benefit(s):	Reduces CSO discharges to the Charles River, especially at MWRA’s Prison Point CSO facility, and allows BWSC to eliminate CSO discharges at Outfall BOS049. When the isolation of the outfall is complete, BOS049 will no longer discharge to the Charles River Basin.

26. EAST BOSTON BRANCH SEWER RELIEF

Receiving Water(s):	Boston Harbor and Chelsea Creek	Image
Year Completed:	2010
Cost:	$85.2 million
Description:	Upgrade of MWRA’s 115-year-old interceptor system serving most of East Boston, using a combination of construction methods: microtunneling, pipebursting, open-cut excavation and pipe relining.
Water Quality Benefit(s):	Reduces CSO discharges to Boston Harbor and Chelsea Creek through outfalls BOS003 and BOS014.

27. INTERCEPTOR CONNECTION RELIEF AND FLOATABLES CONTROL AT CAM002 AND CAM401B AND FLOATABLES CONTROL AT CAM001

Receiving Water(s):	Alewife Brook	Image
Year Completed:	2010
Cost:	$2,904,569
Description:	Upgraded the hydraulic capacities of City of Cambridge connections to MWRA interceptors and installed underflow baffles for floatables control.
Water Quality Benefit(s):	Together with other Alewife Brook CSO projects (not yet complete), minimizes CSO discharges and their impacts to meet “fishable/swimmable” criteria 98% of the time

2011

28. CAM400 COMMON MANHOLE SEPARATION

Receiving Water(s):	Alewife Brook	Image
Year Completed:	2011
Cost:	$4.7 million
Description:	Replaced common storm drain and sewer manholes with separate manholes and associated piping in the local, mostly residential streets bounded by Alewife Brook Parkway, Massachusetts Avenue, Magoun Street and Whittemore Avenue, as well as a portion of the WR Grace property off Whittemore Avenue.
Water Quality Benefit(s):	Eliminated CSO discharges to Alewife Brook at Outfall CAM400.

29. NORTH DORCHESTER BAY STORAGE TUNNEL AND RELATED FACILITIES

Receiving Water(s):	North Dorchester Bay	Image
Year Completed:	2013
Cost:	$224.7 million
Description:	Constructed a 10,832-ft., 17-ft. diameter soft-ground tunnel, drop shafts and CSO and stormwater diversion structures along outfalls BOS081-BOS087; 15-mgd tunnel dewatering pump station at Massport’s Conley Terminal; 24-inch force main; and below-ground tunnel ventilation and odor control facility at the upstream end of the tunnel. More information
Water Quality Benefit(s):	Eliminated CSO and separate stormwater discharges up to the 25-year storm and 5-year storm, respectively.

2013

30. BROOKLINE SEWER SEPARATION

Receiving Water(s):	Lower Charles River Basin
Year Completed:	2013
Cost:	$24,889,000
Description:	Over 70 acres separated, total. Installed over 9,448 linear feet of storm drain, and 5840 linear feet of sewer. MWRA outfalls cleaned.
Water Quality Benefit(s):	Supports attainment of long-term CSO control at the Cottage Farm CSO facility.

31. CAM004 STORMWATER OUTFALL AND WETLAND BASIN

Receiving Water(s):	Alewife Brook
Year Completed:	2015
Cost:	$13,825,000
Description:	Constructed a new 4-foot by 8-foot box culvert storm drain to convey the separated stormwater to a new 3.4 acre wetland in the Alewife Brook Reservation. The wetland will provide 10.3 acre-feet of detention storage of stormwater flows and the attenuation of stormwater flow rate to the Little River and Alewife Brook.
Water Quality Benefit(s):	Supports the CSO benefits of CAM004 Sewer Separation.

32. SOM01A INTERCEPTOR CONNECTION RELIEF/FLOATABLES CONTROL

Receiving Water(s):	Alewife Brook
Year Completed:	2013
Cost:	$0.8 M
Description:	Upgraded the size of the local sewer connection between City of Somerville’s Tannery Brook Conduit and MWRA’s interceptor system and installed an underflow baffle to control the discharge of floatable materials.

2015

33. CONTROL GATE AND FLOATABLES CONTROL AT OUTFALL MWR003 AND MWRA RINDGE AVE. SIPHON RELIEF

Receiving Water(s):	Alewife Brook
Year Completed:	2015
Cost:	$3.7 M
Description:	MWRA replaced the original static overflow weir with an automated weir gate; replaced the 30-inch diameter Rindge Avenue Sewer overflow siphon with a 48-inch diameter siphon; and installed an underflow baffle for floatables control. The project improves the balance of flows in MWRA’s twin interceptors and provides greater system relief in large storms, in part to compensate for the closing of Outfall CAM004.
Water Quality Benefit(s):	Together with other Alewife Brook CSO projects, minimizes CSO discharges and their impacts to meet Class B “fishable/ swimmable” criteria >95% of the time.

34. RESERVED CHANNEL SEWER SEPARATION

Receiving Water(s):	Reserved Channel
Year Completed:	2015
Cost:	$70.5 M
Description:	BWSC installed 81,200 linear feet of new sewer and storm drain to separate the combined sewer systems serving a 365-acre area of South Boston tributary to four CSO outfalls along the Reserved Channel.
Water Quality Benefit(s):	Minimizes CSO discharges to meet Class SB(cso) water quality standards (>95% compliance with Class SB).

35. CAM004 SEWER SEPARATION

Receiving Water(s):	Alewife Brook
Year Completed:	2015
Cost:	$0.8 M
Description:	Cambridge installed 55,300 linear feet of new or rehabilitated sewer and storm drain to separate the combined sewers serving a 211-acre area of Cambridge east of Fresh Pond Parkway. With the project, the City of Cambridge permanently closed Outfall CAM004.
Water Quality Benefit(s):	Together with other Alewife Brook CSO projects, minimizes CSO discharges and their impacts to meet Class B “fishable/ swimmable” criteria >95% of the time.