Water-quality modeling of combined sewer overflow effects on Newtown Creek

Thr upstream branches of Newtown Creek, which receive major combined sewer overflow (CSO) discharges, exhibit stratification of salinity, anoxic conditions below the pycnocline, and emission of hydrogen sulfide (H2S) odors throughout the summer. As high sediment oxygen demand (SOD) levels were coincident with these upstream branches, the modeling approach focused on the mechanisms of solids settling, organic carbon flux, and sediment diagenesis for CSO as well as other sources of solids. Extensive field measurements of the CSOs and the water and sediments within Newtown Creek and the adjoining East River were performed to evaluate model parameters and calibrate/verify the models. Continuous simulations of a 4-mon summer period for existing (baseline) conditions and CSO abatement alternatives projected the water-quality improvements that could be expected in the Creek. Because of the extremely low dissolved oxygen (DO) in Newtown Creek, the response to CSO abatement is inhibited, as the model's reaction kinetics would indicate; however, measures that would relieve these conditions and increase DO would also enhance the change in DO achievable through CSO abatement.