10/13/2011 ENVIRONMENTAL OVERSIGHT COMMITTEE Minutes

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Johns Pond Dissolved Oxygenm Temperature( g/1) or Tem P (C) Mashpee 0 5 10 15 20 25 MA-818 2 Acreage: 337.7 4 — Maximum Depth: 62 ft 6 2001 Secchi Dip: 12.7 ft 8 10 Lake Association:None 12 14 ♦—Temperature OVERVIEW 16 - — DO 8 ' Johns Pond is located in -` ., T. . western Mashpee just southeast ofAshumet Pond and the Mas- Dissolved Oxygen and Temperature sachusetts Military Reservation Johns Pond,2001 (MMR). Apublic paved boat ramp with an accompanying small parking lot is located on the northwest corner of the pond off of Hooppole Road. The pond drains into the Childs and Quashnet Rivers. Fish- eries surveys conducted during 1991 and 1992 recorded 11 species present and the pond is stocked annually in the spring and fall with brook and rainbow trout. WATER QUALITY Johns Pond was sampled in 1948, 1980, 1993, 1994, 1998,2001, and 2002. The 7/23/48 temperature profile showed stratification around 35 ft,with depressed dissolved oxygen(DO)concentrations below_50 ft and a minimum DO concentration of 6.4 ppm. hi 8/13/80 and the summer of 1994,temperature stratifica- tion occurred around 30 ft and DO concentrations'less than 1 ppm (i.e., anoxic conditions) were measured below 36 ft. The 2001 PALS readings are consistent with the 1980 and 1994 samplings, but DO and temperature concentrations were not measured below 10 in(33 ft). Surface TP concentrations from the 2001 PALS snapshot(see below)are below the current Cape Cod"impacted" threshold,while the chlorophyll a and TN concentrations exceed their thresholds. A Carlson TSI based on a surface chlorophyll a concentra- tion places the pond in the middle of the mesotrophic category. Although the surface concentrations do not indicated impacts,it is clear from a comparison of historic and recent DO profiles that deep water quality has become impaired over the last 50 years. The rise in TN, TP, and alkalinity concentrations observed in the deep samples (see below)are consistent with anoxic con- ditions allowing sediment -bound nutrients to be released into overlying waters. Monitoring from MMR studies(HAZWRAP, 1994)suggests that anoxic conditions develop early in the summer,but additional DO monitoring on a biweekly schedule during the surnmer or two is recommended to resolve how persistent the anoxia is. It is also recommended that annual monitoring of the pond continue, and that more refined monitoring and a characterization of nutrient loads to and within the lake be considered in the future. Johns Pond presents as an impacted lake with existing water quality problems. 2001 PALS Snapshot Results Depth pH Chlorophyll a Alkalinity Total Phosphorus Total Nitrogen _ meters µg/L as m CaCO3/L µ mg/L 0.5 6.8 3.67 8.0 4.0 0.32 3 6.75 3.20 8.0 4.0 0.36 91 6.431 6.65 1 8.11 7.4 0.32 _181 6.441 3.851 26.71 26.9 1.20