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City of Manchester, N.H. Clean Water Act Settlement Information Sheet

(BOSTON – July 13, 2020) In a settlement with the U.S. Environmental Protection Agency (EPA) and the State of New Hampshire, the City of Manchester, N.H., has agreed to implement a comprehensive set of corrective measures and improvements to the city’s sewer system that will result in significant reductions of sewage.


The City of Manchester owns and operates a publicly owned treatment works (POTW), including a wastewater treatment facility (WWTF), that serves the City of Manchester and portions of Bedford, Londonderry, and Goffstown, New Hampshire and approximately 155,000 people. The wastewater collection system tributary to the treatment plant has six interceptors totaling over 23 miles in length, 11 pump stations, four inverted siphons, 13 miles of force mains, approximately 385 miles of sewer pipe (of which 45 percent are combined sewers), 15 combined sewer overflow (CSO) outfalls, and over 10,000 manholes.

Pursuant to the City’s National Pollutant Discharge Elimination System (NPDES) permit, Manchester’s sewer collection system is authorized to convey wastewater to the WWTF for treatment and discharge to the Merrimack River, and, when capacity in the system is reached, to discharge through CSO outfalls into receiving waters including the Merrimack River, Piscataquog River, Ray Brook and Tannery Brook.

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The Complaint alleges that the City of Manchester violates Section 301 of the Clean Water Act and terms and conditions of its NPDES permit by discharging from its CSO outfalls combined sewage, which contains pollutants in excess of the amounts allowed under New Hampshire water quality standards.

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Injunctive Relief

The proposed settlement includes a 20.5-year plan to control and significantly reduce overflows of its sewer system, which will improve water quality of the Merrimack River. The plan is estimated to cost $231 million to implement. The settlement addresses problems with Manchester’s combined sewer system, which when overwhelmed by rain and stormwater, frequently discharges raw sewage, industrial waste, nitrogen, phosphorus and polluted stormwater into the Merrimack River and its tributaries.

The two major CSO abatement controls will disconnect Cemetery Brook in Manchester, the largest of the local five significant connected brooks, from the city’s combined sewer system. Manchester will design and construct a new 2.5 mile drain for Cemetery Brook from Mammoth Road to the Merrimack River to convey both the brook’s and storm drainage flows, ranging in size conceptually from 6-foot-wide by 5-foot-tall box culvert to 12-foot-wide by 10-foot-tall at the downstream terminus. The city will also design and construct projects to separate the combined sewers for areas adjacent to the Cemetery Brook drain. These drainage and sewer separation projects will together address the largest drainage basin in the city and produce the greatest volume of CSO reduction.

The work under the proposed consent decree also includes the construction of a new drain and sewer separation in the Christian Brook drainage basin, which will remove the third largest brook from the wastewater collection system.

The proposed consent decree also requires the city to implement a CSO discharge monitoring and notification program, which will include direct measurement of all discharges from six CSO outfalls estimated to be more than 99 percent of all of the city’s total CSO discharge volumes. The city will be required to provide initial and supplemental notification to the public, including public health departments and downstream communities, with notification made through electronic means such as posting to the city’s publicly available website and reasonable efforts to provide other notification.

The proposed settlement also requires upgrades to improve the handling of solid waste at the wastewater treatment plant to reduce discharges of phosphorous.

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Pollutant Impacts

The Merrimack River is a drinking water source for more than 500,000 people, is stocked with bass and trout for fishing, and is used for kayaking and boating and other recreational opportunities. Many of the communities in the Merrimack River watershed are environmental justice communities with large numbers of minority and low-income residents.

The volume of combined sewage that overflows from Manchester’s combined sewer system is approximately 280 million gallons annually, which is approximately half of the combined sewage discharge volume from all communities to the Merrimack River. Under the proposed consent decree, Manchester will install CSO control projects and upgrades at its wastewater treatment facilities that are expected to reduce the city’s total annual combined sewer discharge volume by approximately 74 percent from approximately 280 million gallons to 73 million gallons. Data over the past nine years reveal levels of E. coli colonies ranging from 1,250 to 560,000 colonies per 100 milliliters, in excess of the amounts allowed under New Hampshire water quality standards and the city’s NPDES permit of 1,000 colonies per 100 milliliters.

Through the implementation of the proposed consent decree, the following estimated annual pollutant reductions will result:

  • 1,814,450 pounds of total suspended solids;
  • 535,695 pounds of biochemical oxygen demand;
  • 881,304 pounds of chemical oxygen demand;
  • 16,416 pounds of total nitrogen; and
  • 3,283 pounds of total phosphorus.

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Health and Environmental Effects 

  • Total Suspended Solids (TSS) – TSS indicates the measure of suspended solids in wastewater, effluent or water bodies. High levels of TSS in a water body can diminish the amount of light that penetrates the water column and reduce photosynthesis and the production of oxygen.
  • Biological Oxygen Demand (BOD) – BOD is an indirect measure of the biologically degradable material present in organic wastes. High BOD means there is an abundance of biologically degradable material that will consume oxygen from the water during the degradation process. It may take away oxygen that is needed for aquatic organisms to survive.
  • Chemical oxygen demand (COD) – COD is a measure based on the chemical decomposition of organic and inorganic contaminants, dissolved or suspended in water. As with BOD, high levels of COD indicate high levels of pollutants are present in the wastewater that will consume oxygen from the water and may take away oxygen that is needed for aquatic organisms to survive.
  • Nutrients – Excess levels of nitrogen and phosphorus in waters can produce harmful algal blooms. These blooms contribute to the creation of hypoxia or “dead zones” in water bodies where dissolved oxygen levels are so low that most aquatic life cannot survive

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State Partner

The State of New Hampshire, acting through its Department of Environmental Services, has joined as a co-plaintiff and brings its own parallel claims under the New Hampshire Water Pollution and Waste Disposal Act, NH RSA 485-A.

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Comment Period

The proposed consent decree is subject to a 30-day public comment period and court approval after it is published in the Federal Register.   Information on submitting comment is available at the Department of Justice.

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Contacts for Further Information

Sarah Rae
Water Enforcement Division
U.S. Environmental Protection Agency
1200 Pennsylvania Ave., NW (Mail Code 2243A)
Washington, DC, 20460
(202) 564-2841

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