Gay Cemetery Pond Dam Removal

A design-build dam removal project restores fish passage, habitat, and water quality to a 7.5-acre pond, setting the stage for improved ecological function in a local watershed.

Once a source of cooling water for a nearby factory, Gay Cemetery Pond in Uncasville, Connecticut is a 7.5-acre open water impoundment with a remnant concrete dam near the headwaters of Horton Cove, the confluence of the Oxoboxo and the Thames Rivers. The 19-foot dam and associated impoundment presents water quality and habitat issues including the degradation of fish passage for critical species including alewife (Alosa pseudoharengus) and blueback herring (Alosa aestivalis). To improve water quality and restore ecological function to the pond and the Oxoboxo River, EnviroAnalytics Group (EAG) turned to Biohabitats to assess the dam and evaluate removal versus repair options.

Biohabitats reviewed existing information before conducting a detailed sampling and analysis of sediment quality and quantity that could be impacted by the dam removal. This initial step is often critical to the advancement toward dam removal and river restoration. The quantity and quality of sediment within an artificial impoundment can have significant cost implications for a project.

Biohabitats concluded that approximately 48,000 cu yd of sediment are entrained in Gay Cemetery Pond and that several legacy pollutants were present. Should some form of dam removal or lowering of the spillway be pursued, the entrained sediment would need to be managed. However, the extent of sediment to be managed is likely to be less than the total volume. Only sediment that is susceptible to mobilization, following the alteration of the Dam, would need to be actively managed (i.e., dredged and relocated). This sediment would be removed from any proposed, restored stream channel. For Gay Cemetery Pond, this stream channel restoration would yield an estimated 6,000 cu yd of sediment. The remainder of sediment adjacent to the restored stream channel could be regraded and stabilized in place.