Water: Nonpoint Source Success Stories
New Hampshire: Section 319 Success Stories, Vol. III
North County RC&D Area Council
719 North Main Street
Laconia, NH 03246-2772
|Primary Sources of Pollution:|
|urban storm water runoff|
|Primary NPS Pollutants:|
|installed system of berms|
|settling and filtering basins|
|82 percent reduction in phosphorus|
The Chocorua Lake Association (CLA) has been monitoring Chocorua Lake for more than 20 years. Recent trends showing declining water clarity prompted the CLA to request designation of the watershed as "Category I," a priority waterbody in need of restoration. Working with the Carroll County Conservation District, the North Country Resource Conservation and Development Area, Inc., and Natural Resources Conservation Service, a 319 project was developed and the New Hampshire Department of Environmental Services awarded grant funds in April 2000.
The Chocorua Lake watershed is 13.2 square miles in extent and well protected except for a few vulnerable areas. The U.S. Forest Service manages the south side of Mount Chocorua as a scenic view area. This management decision helped maintain more than half of the watershed as uncut forest. As a result of work begun in 1969 by the Chocorua Lake Conservation Foundation, about 95 percent of the land in the watershed is protected by conservation easements written into the property deeds of about 60 landowners. These easements have preserved woodland buffers all around the lake, except for a portion of the Route 16 highway corridor. The easements also require setbacks for housing and septic systems, beyond state regulation, and low-density housing. North of the lake are conservation lands owned by The Nature Conservancy and the Chocorua Lake Conservation Foundation. There are also several large wetlands in the watershed that act as natural filters to help treat the water before it enters the lake. Although the lake is protected in most areas of its watershed, it is a fragile lake. It has a maximum depth of 29 feet and an average depth of 12 feet. Because the lake is so shallow, sunlight reaches most of the water column. Even low concentrations of nutrients are readily available to algae and other plant life.
The CLA participates in the University of New Hampshire's Lakes Lay Monitoring Program, which determined that 15 percent of phosphorus input to the lake was coming from direct runoff from Route 16, a heavily traveled tourist road adjacent to the lake. Watershed surveys found several eroded ditches adjacent to Route 16 and across land providing beach access to the lake owned by the Chocorua Lake Conservation Foundation and the Town of Tamworth. In addition to the water quality problems, the CLA was interested in addressing traffic safety and noise problems caused by the highway.
Route 16 has grown enormously since it began as a dirt road next to the lake in the 1890s. In the early 1900s the road was tarred but left very close to the lake. In the 1950s the road was widened, straightened, and moved slightly away from the lake; however, Route 16 still runs close to the lake for about 1 mile. The width and length of this impermeable surface next to the lake play a doubly negative role. First, the road's surface collects particulates from partially burned gas and diesel fuel, oil, and sand and salt. These residues typically contain high amounts of phosphorus, which are diluted and flushed into the lake. Second, during spring runoff and storm events, runoff from the impermeable surface creates surges of water, which flow to the ditches and culverts. High volumes and velocities of runoff scour the soil, adding to the phosphorus loading of the lake. Neither the highway residues nor the eroded soils have time to settle and filter before entering the lake.
The groups mentioned previously, along with the New Hampshire Department of Transportation (DOT) and the Town of Tamworth, initiated the "Berms and Swales Project." The best management practices (BMPs) installed include a system of berms, swales, and settling and filtering basins to control runoff, improve safety, and reduce noise.
BMP performanceInstallation of the BMPs was completed on September 5, 2000. Since then the BMPs have been performing to design specifications. Water quality monitoring has shown an 82 percent reduction in phosphorus entering the lake. The CLA continues to monitor the BMPs, and the project team is now beginning Phase II of the Chocorua Lake project, which will address additional phosphorus sources in the watershed. The success of the project is mainly the result of the resources and energy brought to it by the numerous project partners. The project team hopes to formalize one aspect of the project in a Memorandum of Agreement drafted between the CLA and the New Hampshire DOT. The CLA will inspect the BMPs and report on their condition annually to DOT so that long-term maintenance can be planned. DOT will invite CLA's participation in planning future highway improvements in the Chocorua Lake watershed.
|Story 1 | Story 2 |State Water Quality Site [BROKEN]|
Lake Opechee Watershed Project:
City-State Partnership Takes on Multiple Pollutants
Planning and Community Development
City of Laconia
45 Beacon Street, E
Laconia, NH 03246
simpsona@ city.laconia. nh.us
|Primary Sources of Pollution:|
|urban storm water runoff|
|Primary NPS Pollutants:|
|oil and grease|
|redesigned boat-launch ramps|
|regraded surface away from lake|
|monitoring in progress|
Lake Opechee has a very high use and visibility in the city of Laconia. The watershed is one of the city's smallest but most urbanized watersheds, with the heavily developed Lakeport and Union Avenue to the southeast, the fringes of downtown to the south, and residential development surrounding most of the westerly, northern, and easterly sides of the lake. The city's principal beach and recreation complex, Opechee Park, is located on the south westerly shore of this water body, and one of the city's best public beaches, Bond Beach, is located on its northeasterly shore.
Lake Opechee suffered from multiple nonpoint sources of pollution related to the use of land in the public domain. Opechee Cove is a particularly sensitive area in the lake because very little exchange or flushing takes place. Storm water discharge from adjacent streets, as well as several boat launching ramps around Lake Opechee, had been identified as contributing significant sediment and urban runoff to the lake. The city's uncovered sand and salt storage facility, as well as a nearby private parcel used as a snow dump site, were also significant contributors of pollutants to Lake Opechee.
These sources were determined to contribute significant pollutant loads to the lake and the connecting Winnipesaukee River system, including salt, fertilizer, phosphorus, sediment, and the wide gamut of pollutants contained in urban runoff, such as oil and grease, heavy metals, bacteria, phosphorus, and nitrogen. In addition, boat trailers would become mired in the ramps, which had inadequate base preparation, thus stirring up large quantities of bottom sediment.
To address these issues, in 1996 the New Hampshire Department of Environmental Services initiated a 3-year project with the City of Laconia. To provide overland treatment before storm water entered the lake, the city implemented diversion and swale improvements, creating a 0.5-acre wetland in Opechee Cove to treat and settle out pollutants before the storm water entered the lake. The city also wanted to prevent run off and sediment from leaving the boat-launching ramps and discharging into the lake. To accomplish this, the city selected two boat-launching ramps to test the construction and maintenance of innovative best management practices (BMPs). The city installed a prefabricated mat and cellular block system as part of each ramp. Vegetated swales and diversions were also installed along the lake edge of the boat-launching parking lot to prevent runoff from discharging directly into the lake.
To prevent the direct overland flow of sand and salt from the public works yard to the lake, the city installed a vegetated buffer strip along the shore, regraded the public works yard surface away from the lake, installed a sediment basin to trap salt brine and sediment from the work bays, and guttered all building outlets to a newly installed catch basin. To prevent runoff of salt- and sediment-laden snowmelt from directly entering Lake Opechee, the city constructed a berm with a 25-foot setback from the lake and regraded the site such that runoff flows away from the lake at the city's snow storage facility. The city also constructed a 150-foot-long sediment basin along the toe of the berm to trap any sediment before it was discharged into the lake.
Successful as project and as learning experienceOfficials from the City of Laconia expressed that this project has been a great learning experience for them, from the design issues to the construction and maintenance of each BMP. The project involved five different city departments working together to meet the water quality goals. The design and implementation process raised the city's awareness of the water quality and land use issues that face the community. The city has also expressed how pleased it is with the physical outcomes of the project, including the bioengineered wetland in Opechee Cove and the resulting modern boat ramps.