Water: Nonpoint Source Success Stories
Connecticut: Responding to Urban Development - Communities in the Mattabesset River Watershed
The Mattabesset River Watershed Pollution Management Project, initiated in 1992, targets nonpoint source pollution and the restoration of riparian areas along the river and throughout the watershed. Sponsored jointly by the Middlesex and Hartford county soil and water conservation districts, the project is funded primarily by grants under sections 319 and 604(b) of the Clean Water Act, with nonfederal matching contributions from the districts and watershed communities.
The Mattabesset River is a major tributary of the Connecticut River in central Connecticut, flowing 18 miles from its headwaters in New Britain to its confluence with the Connecticut River in Middletown. The watershed's 44,000 acres are highly urbanized and include portions of seven towns. As a result of intense development, water quality is impaired, and important habitats and riparian areas have been lost. The major project objectives, related to these conditions, are to
- develop a constituency for protection and improvement of the river;
- conduct chemical and biological water quality monitoring to establish baseline conditions and measure progress;
- establish critical area treatment sites to demonstrate best management practices;
- develop and implement water quality management programs for the municipalities in the watershed; and
- reduce erosion and sedimentation from urban development sites.
To achieve these objectives, the conservation districts have conducted stormwater management workshops for municipal officials and staff in the watershed communities. The workshops served as a forum for ideas and provided an opportunity for municipal staff from neighboring communities to build working relationships. The districts also have provided "one-on-one" technical training to help municipal staff conduct site plan reviews and field-based problem solving. General workshops were conducted for municipal land use commissioners as part of regular commission meetings.
The Connecticut River Watch Program (CRWP) helps the project identify baseline conditions and water quality problems in the Mattabesset River. CRWP, a volunteer water quality monitoring, protection, and improvement program initiated in 1992, is an integral part of the watershed project. This ongoing monitoring program has helped the watershed project focus its efforts to reduce pollution, especially sediment, nutrients, and bacteria.
Project work in the Mattabesset watershed has focused on remediation and restoration. BMPs for sediment control are incorporated in new developments, municipal maintenance measures have been expanded to preserve riparian values and reduce nonpoint source pollution, and people are becoming more involved through education and outreach programs.
- At Progress Park, an industrial park adjacent to the Mattabesset in Cromwell, a severely eroding site from which the topsoil had been stripped prior to development was stabilized. In addition, a sediment delta that had formed at the site's discharge point to the river was removed, helping to restore the hydrological conditions in that stretch of the river.
- On West Swamp Brook in Middletown, an innovative bioengineering method using coconut fiber rolls and live plants was used to stabilize and restore a section of streambank where loss of riparian vegetation had resulted in severe erosion. The newly stabilized banks protect property and water quality.
- At a public school playing field adjacent to Belcher Brook in Berlin, custodians roped off a 10-foot-wide strip along the water's edge to form a natural vegetative buffer. Previously, the playing field was being mowed right up to the streambank.
- In Cromwell Meadows, a significant tidal marsh in the mouth of the Mattabesset River, junk cars and trash were removed, and cleanup activities have continued on an annual basis.
- The town of Cromwell used bacteria data collected from Coles Brook to help justify a sewer expansion project. A brochure about septic system maintenance was also distributed to help residents deal with this problem.
Street sweeping and catch basin pumping also have decreased sediment and nutrient pollution, and district staff are helping the towns' public works departments develop pollution prevention plans for town garages and parking lots.
The Mattabesset watershed project has improved the quality of the Mattabesset River and its tributaries. It also has been successful at encouraging behavior changes that may ultimately stem the tide of nonpoint source pollution. Degraded areas have been restored and pollution controls designed and implemented for the new development projects.
Town staff and land use commissioners, developers, and contractors are more aware of best management practices to control nonpoint source pollution and are beginning to adopt these best management practices as standard practices. Most promising of all town staff, developers, and contractors have developed stronger working relationships, spurred by a clearer understanding of the necessity for nonpoint source pollution controls. In sum, the project has led to increased communication and cooperation among the watershed towns.
Project managers view the new, grassroots Mattabesset River Watershed Association as an important measure of their success. Citizens from the watershed communities have formally established this organization as a community-based group. The project believes that this new group will maintain its vision of a restored watershed, advocate for its support, and provide services to ensure the long-term protection of the river and its watershed.
|CONTACT: Mel Cote
U.S. Environmental Protection Agency, Region 1
Lake Whitney Artificial Marsh
Treats Urban Runoff
Lake Whitney, in Hamden, Connecticut (about three miles north of New Haven Harbor and Long Island Sound) is a public water supply reservoir owned by the South Central Connecticut Regional Water Authority. The lower portion of the watershed is heavily developed; approximately 70 percent of land use is for commercial, industrial, or high- density residential development. Because of the large amount of impervious surface, the watershed used section 319 funding to demonstrate how constructed, multicelled wetlands (or artificial marshes) can reduce the impacts of urban runoff.
Describing the new system
The South Central Connecticut Regional Water Authority's design called for redirecting a stormwater outfall draining about 20 acres of primarily small residential lots (with 45 percent impervious cover) into a new multicell treatment system. The new system consists of a sediment forebay, a sediment basin, and an artificial marsh and wet pond. The cost was reasonable (less than $50,000) and the system was compact, covering only about a half-acre or 2.6 percent of the contributing drainage area.
Multi-celled systems have many advantages. The sediment forebay effectively traps coarse sediments and trash, is easy to clean, and preserves system storage volumes. Subsequent treatment stages are easily accommodated in the other cells, including further sediment removal in the sediment basin, and biological treatment, filtration, and other pollutant removal mechanisms in the marsh and wet pond cell. Long, narrow shapes were used in both the sediment basin and wet pond to maximize detention time and pollutant removal. The system is visually attractive, provides habitat for wildlife, and effectively removes a variety of pollutants from urban runoff.
Monitoring of the system indicates that while the sediment basin has variable removal rates, the combined sediment basin and wet pond removes conventional pollutants and heavy metals in excess of 50 percent. Minimal maintenance is needed, and with the exception of some nuisance wildlife problems, no serious functional problems have arisen.
Although better water quality is the primary objective, multicell systems with artificial marshes and wet ponds are also visually attractive and valuable habitat for wildlife. Additional benefits include the simplicity of their design and low maintenance requirements. Publicity generated by the Lake Whitney project has increased awareness of urban runoff issues within local government as attested by several recent land-use decisions within the watershed. For example, a 30-acre shopping center has been approved, at least in part because its developers included plans for a comprehensive stormwater management system designed to minimize adverse impacts to water quality.
Planning a stormwater management system
This project identified a number of issues that should be considered during the planning, design, construction, and operation of multicelled stormwater management systems:
- Incorporate multicell concepts in the treatment design, with each cell having its own primary function. Sediment forebays are effective, preserve system storage volumes, and simplify maintenance. Subsequent stages can be designed to serve many physical and biological treatment needs.
- Consider water quality goals, the quality of incoming runoff, available land, and costs during the design phase. The detention volume should be sufficient to treat at least one-half inch of runoff over the impervious areas; however, additional volume and by-pass/overflow provisions may be desirable for winter thaw and rain storms that can overwhelm a system of this size.
- Increase the potential for pollutant removal by maximizing overland flow and buffering vegetation. When using buffers to detain flow, flows should be distributed across the buffers as evenly as possible.
- Enhance visual attractiveness by using curvilinear pond shapes, peninsulas, and wetland and flowering plants; by substituting vegetation for riprap; and by retaining existing trees where practicable.
- Consider in advance possible nuisance wildlife that could damage vegetation and affect the appearance, structural integrity, and function of the system. At Lake Whitney, for example, the project was plagued by muskrat burrows and Canada geese droppings. Three-to-one side slopes, wire mesh barriers, riprap in certain areas, winter drawdown, and trapping, grates, and screens over outlet pipes are possible countermeasures. Selecting less palatable plant species may also discourage nuisance wildlife.
- Design to facilitate maintenance. Ramps allow heavy equipment access to sediment removal areas.
- Design inflow and outflow structures with adjustable water levels and flows. Removable weir boards can be used to adjust water levels or temporarily bypass flows. A high-flow bypass serves as an emergency spillway and can be used to lower water levels for maintenance.
- Project managers should communicate with local officials early in the planning process to facilitate local zoning approval. A stormwater management project may be a new concept to local boards or may not fit existing land-use regulations. In some cases, amending local regulations may be necessary to expedite the process.
- Reuse stripped topsoil on basin side slopes and bottoms. In some places, it may be necessary to place topsoil over excessively stony or gravel bottoms to ensure successful wetland planting.
- Establish a permanent inspection and maintenance program to monitor system performance and vegetative cover and plantings. Maintenance and landscaping crews should be educated about how each component functions and how to maintain it; for example, these personnel should be instructed on whether vegetation should be mowed, removed, or left undisturbed. Crews should also check system structures for erosion and subsidence, and look for wildlife damage, sediment and debris accumulation, and vandalism. Sediment forebays should be cleaned every two to three years, although local conditions, such as excessive soil disturbance, may require more frequent cleaning.
|CONTACT: Mel Cote
U.S. Environmental Protection Agency, Region 1