10/13/2011 ENVIRONMENTAL OVERSIGHT COMMITTEE Minutes

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E s 'z k Y-' Mashpee/Walceby Dissolved Oxygen (mg/1) or Temperature (C) Pond 0 5 10 15 20 Mashpee, Sandwich 0 MA-634 5 Acreage: 725.8 10 Maximum Depth: 83 ft 2001 Secchi Dip: 9 ft 15 Lake Association: None 4 20 Temperature DO OVERVIEW 25 ` Mashpee Wakeby Pond is com- posed of two connected kettlehole Dissolved Oxygen and Temperature basins located in both Mashpee and Mashpee/Wakeby Pond,200 i Sandwich, east of Route 130. The northern basin is deeper with a maximum depth of 95 ft,while the upper basin has a maximum depth of 65 ft. Shallows between the two basin have.a maximum depth of approximately 20 ft. The pond is recharged by groundwater flow from the northwest and contributes surface flow to groundwater along its eastern shoreline. A controlled surface water outlet and herring run connects to the Mashpee River at the southern tip. The shoreline is heavily developed with seasonal and year-round single family homes, several town beaches and summer camps. Public access is available at the Sandwich town beach at the Ryder Property, and at the Mashpeepublic beach and boat ramp,north of Route 130. The pond is stocked with brook,brown and rainbow trout twice a year. Other species include large and smallmouth bass, chain pickeral and white catfish. WATER QUALITY The lake was sampled in 1948, 1980,2001, and 2002. The 7/29/48 temperature profile showed strati- fication around 30 ft,with depressed DO concentrations below 40 ft and a minimum DO concentration of 2.6 ppm. In both 1980 and 2001, DO concentrations of less than 1 ppm (i.e., anoxic conditions) were measured below 45 ft. Surface chlorophyll a,TP,and TN concentrations from the 2001 PALS snapshot(see below)are all above the current Cape Cod"impacted"thresholds,with the TP concentration nearly ten times the threshold. A Carlson TSI based on a surface chlorophyll a concentration places the pond at the high end of the mesotrophic category. It is clear from a comparison of historic and recent DO profiles that deep water quality has become more impaired over the last 50 years. Additional DO monitoring on a biweekly schedule during the summer is recommended to resolve whether the anoxia develops at the onset of stratification or whether it only occurs during the late summer. It is also recommended that annual monitoring of the pond continue,and that more refined monitoring be considered in the future, along with a characterization of nutrient loads to and within the lalce. Mashpee Walceby 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 mg CaCO3/L µg/L mg/L 1 6.89 6.34 12.6 72.8 0.34 2 6.51 6.72 12.4 14.1 0.34 9 6.40 2.96 12.4 10.8 0.35 141 6.261 7.401 25.3 149.6 0.60 261 6.411 0.041 30.6 370.1 1.52 samples also collected at: 4, 5, 6, 8, and 10 m