Dispersion Analysis of the Dartmouth, MA Municipal Sewage Outfall Off Salters Point

The water quality impacts of the existing and proposed upgraded Dartmouth, Massachusetts Wastewater Treatment Plant on the Salters Point region of Buzzards Bay were examined through the use of a computer model system. Included in the study are descriptions of the outfall and physical site, the circulation and transport dynamics of Buzzards Bay in the region off Salters Point, a description of the near and far field computer models used, and a discussion of the water quality impacts. For the latter, attention was focused on the impact of the biochemical oxygen demand (BOD) on the dissolved oxygen (DO) levels near the site and also on levels of fecal coliforms. Results indicated that BOD and DO deficit concentrations due to the facility effluent will be quite small with respect to the surrounding waters off Salters Point. The analysis of fecal coliforms indicated exceedances of state standards at the coast only for the unlikely condition of total plant failure. If chlorination continued, however, the impact will be restricted to the immediate area around the outfall.