CLE Engineering, Inc. was retained by the Town of Mattapoisett to provide surveying, engineering and consulting services relating to the improvements to Eel Pond. Several studies were conducted from 1992 to 2001, stating increasing concern over the condition of Eel Pond, which at least one report concluded was among the most eutrophic embayments within the Buzzards Bay Monitoring Program. CLE was tasked with developing plans to increase salt-water flow, restore salt marsh on the fringe of the pond and improve the water quality within Eel Pond. In order to accomplish this goal, CLE began with developing existing conditions plans included detailed topographic mapping of the pond and adjacent resource areas, and an investigation of the existing 12” sewage force main that crosses both the railroad embankment and the West Channel. This investigation revealed that in general, the sewer line was buried about five feet below existing grade, however the portion of the pipe beneath the West channel was found to have only 18” of cover at the deepest point of the channel. This is a matter of serious concern, as a major storm event (such as a hurricane) could uncover and possibly rupture the pipe.
CLE recommended that to meet the project goals without disturbing the sewer line, that plans be made to close the West Channel by filling and restoring the original beach grades. However, in order to perform this closure, plans had to be developed to enlarge the East Channel and increase the size of the railroad culvert to still meet the goals of the project.
CLE developed a computer model of the Eel Pond watershed and connecting channels. A number of programs were run evaluating the existing conditions as well as various potential improvements, along with the effects of rainstorms and tidal conditions ranging from minor to extremely severe. Findings were that if the west channel was closed, the east channel required dredging and an increased culvert under the railroad crossing to improve flows. CLE worked with the Town to develop cost estimates and supporting documents for permit applications to regulatory agencies (Conservation Commission, Executive Office of Environmental Affairs, Coastal Zone Management, Department of Environmental Protection, US Army Corps of Engineers). CLE’s ability to promptly respond to the Town’s needs and thoroughly evaluate this complex, critical environmentally sensitive area will have far reaching benefits. The program greatly improved the tidal exchange of Eel Pond as well as restored the fringe salt marsh areas.