Still River Study Sponsored by Friends of the Lake Presented by Curtis Read November 17th, 2005

2 Background From its headwaters in the Housatonic River in New Milford, Lake Lillinonah extends 12 miles to the Shepaug Dam Lake covers 1900 acres to a maximum depth of 110 feet with 45 miles of shoreline. Connecticut Light and Power created Lake Lillinonah in 1955 as a source of hydroelectricity and flood control. The dam's 57,000-horsepower turbine drives a 43,000- kilowatt generator in what is Connecticut's newest and largest hydroelectric plant.

3 Determination of Influence by the Still River Tributary to the Water Quality & Algae Blooms in Lake Lillinonah Lake Lillinonah suffers algae blooms due to infusion of nutrients (primarily phosphorus and nitrogen compounds) from both non-point stormwater and point source pollution. It was postulated that a significant loading of nutrients to the lake is the result of the Still River contribution directly into Lake Lillinonah. The Friends of the Lake contracted Hydro Technologies, Inc. to design and perform the comprehensive Still River Study to pinpoint the source(s) of nutrient loading in the urban watershed that includes Danbury and the narrow corridor flowing north along Route 7 through Brookfield and New Milford to enter the top of Lake Lillinonah at Lovers Leap.

4 Upper Still – Site 1 Below STP –Site 4 Lovers Leap

5 Water Sampling Sites Site 1 - Still River above Limekiln Brook Site 2 - Limekiln Brook at Bennet Park above Sewage Treatment Plant Site 3 - Limekiln Brook below Sewage Treatment Plant Site 4 - Confluence of Still River and Limekiln Brook Site 5 - Harry Brook Park Site 6 - Lovers Leap Gorge Site 7 - Housatonic River at Addis Park Site 8 - Housatonic River at Boardman Bridge above New Milford

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8 Danbury Sewage Treatment Plant (STP) DEP permit issued Feb, 2003, Valid for 5 years Design capacity = 15.5 mgd. Typical discharge = 10 At 10 mgd = 15.5 cfs flow for 24 hours every day Permit allows STP to discharge daily avg of 1.0 mg/L T-Phos in season (April 1 – September 30), no limit other 6 months Nitrogen credits (fine) bought by Danbury (highest or 2 nd most $ in CT) = $378,000 in 2003

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10 Site 7 Addis ParkSite 8 – Boardman Bridge Still River Inlet Housatonic - New Milford Site 6 - Lovers Leap

11 GIS Mapping and AVI by Northwest Conservation District

12 USGS Gage in Brookfield records flows constantly. There appears to be a daily variance of discharge of approx. 10 cfs. Note the spikes on this graph showing storm effects in urban watershed of Danbury. This is a result of a high % of impervious cover.

13 Flow in Cubic Ft/Sec Site 3 – Below STPSite 5 – Harrybrook Park

Data

Data

Data used for Fertilizer Equivalent

17 Comparison of Data from 2004 & 2005 Data sets for four summer months only May - August

18 Recommendations Year round removal of phosphorus, not just seasonal. Lower the phosphorus level of 1.0 mg/L allowed by the Danbury STP discharge permit to a Technology-Based Permit Limit achieved now by sewage treatment plants in other states (0.3 mg/L) Look at Lake Champlain, Chesapeake Bay and others where Sewage Treatment Plants have invested in infrastructure where mandated by regulating agencies.

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