Published Date Written by Roger AmsdenSANBORNTON — The final report of the Black Brook Watershed Management plan, which was received recently by the town, calls for a combination of steps, including new culverts and sediment traps in critical areas, as well as zoning ordinance and site plan regulation changes, in order to combat non source point pollution (NPS), which poses a major threat to the water quality of Lake Winnisquam.
Don Foudriat, who coordinated the $40,000 study for the town, says that the plan, which was developed by AECOM Environment, ''projects a significant increase in future NPS pollution that will likely occur as the watershed gradually moves from forests, agriculture, and low density housing toward more intensive residential housing.''
He said NPS pollution sources come from naturally occurring rain water that becomes contaminated from atmospheric impurities during rainfall and then acquires impurities found in or on the soil from sources such as septic systems, animal feces and fertilizer chemicals as it flows over and through the soil. These water borne contaminants enter brooks and streams and eventually into lakes and other water bodies.
Foudriat said the phosphorus discharge from Black Brook already exceeds the limit for maintaining high water quality in Winnisquam and will eventually lead to degradation of the lake, creating ideal conditions for algae blooms and the growth of water milfoil.
The Black Brook area became a major problem for the town in 2006 when culverts and catch basins failed in a storm during July and tons of silt were washed into Lake Winnisquam. The state Department of Environmental Services then mandated repairs to the roads and infrastructure along Maple Circle, Dr. True Road and Gray Road to prevent future incidents.
The town completed a comprehensive drainage report in 2007 which estimated that repairs would cost up to $1 million. Lacking funds to complete the entire project, the town installed three new culverts in the area.
Foudriat said that when federal stimulus funds became available in 2009 the town had a shovel ready project which qualified and was able to obtain $918,280 in funding, half of which was forgiven and the remaining $459,140 repaid at a low interest rate.
The grant allowed the town to repair the drainage through the Sanbornton Town Beach, Maple Circle, Gray Road and Shute Road and some $238,000 left over from the project was used over last summer to construct a box culvert at the intersection of Black Brook and Black Brook Road.
But some $650,000 in work remains to be done in the Black Brook watershed area, which encompasses some 3,000 acres, according to Foudriat.
He said that non-point source pollution has been largely ignored in the past but has emerged as a major threat to the water quality of New Hampshire lakes. Foudriat says that unlike pollution from municipal sewage sources and industrial discharges, NPS pollution control will involve "hands on" actions from communities and many individual citizens to deal with a myriad of little pollution sources to be effective.
AECOM identified 38 sites in the watershed for remedial action and suggested means for sediment control at each of these sites. A multiyear schedule for implementation and the use of available grants to supplement local tax money was suggested as well.
Foudriat said that since the watershed is projected to see increasing phosphorus discharge over time as residential development increases, reductions in the current level of phosphorus will be needed just to offset increasing residential development.
He said the plan also addresses the need for land use planning in the watershed and that zoning ordinance and site plan regulations will need to be revised with a goal of retaining sediments on new development sites before drainage is permitted to exit the site. Steps will also need to be taken to avoid soil erosion during construction and landscaping will need to be designed to prevent soil erosion from storm waters, eliminating the future need for expensive sediment traps and devices. Planners will also
provide for educating existing land owners with information and in some cases, volunteer assistance, to identify and control sediment originating on their sites.
And plans for reviewing public works projects, particularly those involving road construction and maintenance, will need to be put in place to ensure that road drainage is free of sediments before it enters watercourses.
''We'll have to follow Best Management Practices (BMPs) in order to reduce the sediment runoff and protect the lake,'' says Foudriat, who notes that one interested party in the Black Brook area is the state's Fish and Game Department, which would like to see Black Brook, currently choked with sediment, restored as a breeding area for smelt.