12/16/2024 SELECT BOARD Minutes - Laserfiche WebLink

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12 Segect Board. Minutes December 16,, 2024 APPOINTMENTS & HEARINGS WaW.. duality. Update and Presentation , Ed Eichner,, School of Marine Sciencennnand _Technoio sy _($MAST),,, UMass Dartmouth: (continued) Mashpee Wakeby Pond Man all,ement Plan and Diagnostic Assessment: Ed Eichner, School of Marine Science and Technology updated the Board and interested public on the Mashpee Wakeby Pond Management Plan and Diagnostic Assessment. After reviewing the data Mr. Eichner presented the following summary of the impaired Wakeby and Mashpee Ponds; The sediments are the largest source of summer phosphorus in both basins, High TP and CHL levels and regular deep anoxia, Deep anoxia often extends throughout the hypolimnion and transition zone, Temperature stratification is often shallower in June especially in Wakeby than in summer, Sediment cores showing anoxic conditions cause a rapid release of phosphorus, Shallow sediments have greater amounts of phosphorus, Phosphorus management is the key to achieving acceptable water quality conditions. Management Options include; In -pond sediment phosphorus management; Alum applications, Hypolimnetie aeration and dredging. The alum application with monitoring is estimated to cost: $725,000 in Wakeby and $960,000 in Mashpee. Hypolimnetic aeration treatment with monitoring; Wakeby V. 5 million, Mashpee $2 million (20 yrs.) Dredging; Wakeby $21 million, Mashpee $28 million. The following was recommended; Alum treatment be implemented in Wakeby Pond, A post -alum treatment implemented in Wakeby and Mashpee Ponds with water quality monitoring, Continued review of updated data, and alum treatment details, Implement an alum treatment in Mashpee Pond, Continued monitoring, Propose phosphorus TMDL to Mass DEP if water quality goals are achieved. Discussion followed with respect to the conditions of the ponds and the setting of goals. Due to costs and logistics, the alum treatment is recommended. It was disclosed that 80% of the groundwater/wastewater in emanating from Wakeby Pond. Mashpee Pond groundwater/wastewater is 8%. 68% of the flow derives from Wakeby Pond from individual parcels upgradient to the pond. Mr. Eichner indicated that fertilizer does not have a role in phosphorus conditions as most of the fertilizer is used directly by the lawns adding that cranberry bogs are small contributors to the overall phosphorus conditions. Although other studies have reported that bogs contribute 13% of the phosphorus impairment.