The Impact of Rochester Storm Sewers on the Water Quality of the Lower Genesee River: A Modeling Approach Using PCSWMM

Abstract

The lower Genesee River suffers from beneficial use impairments from the mouth of the river at Lake Ontario to the New York State Barge Canal due to industrial and municipal sources, storm sewers, and urban runoff. In urban areas, nonpoint source pollution from stormwater runoff is known to be a dominant factor in water quality. An assessment of the lower Genesee River was initiated to determine impacts from the canal, storm sewers, combined sewer overflows, and a wastewater treatment plant. To accomplish this, an integrated approach combining water quality sampling, statistical analysis, and modeling was employed. A cluster analysis was performed on samples taken during hydrometeorologic events to determine natural groupings in storm sewer sites based on water quality. These events and results of the cluster analysis were used to calibrate and validate a model of the Rochester storm sewer network (ROCSWMM) using hydrologic modeling tool PCSWMM (Storm Water Management Model). Model-predicted flows, total phosphorus (TP) loads, and total suspended solid (TSS) loads to the Genesee River for 2012 were 19,197,116 m3, 2,277 kg P, and 625,694 kg, respectively. More than 50% of the total flow and 27% of the TP load discharged to the Genesee River from the storm sewer network came from the Merrill sewershed. The Irondequoit sewershed was the second largest contributor of stormwater (2,659,179 m3) and TP load (481 kg), and over half of the TSS load was contributed by the Merrill (29%) and KenElm (24%) sewersheds. Precipitation events resulted in four combined sewer overflows (CSOs) in 2012. Water from these discharges have extremely high concentrations of nutrients (727 ?g P/L to 4,180 ?g P/L), sediment (156 mg/L to 810 mg/L), and E. coli (282,720 MPN/100mL to 483,920 MPN/100mL.) Kodak King’s Landing Wastewater Treatment Plant (WWTP) was a large point source of water and pollutant loads to the Genesee River accounting for 0.5% of the total flow and 1.3% of the TP load of the Genesee River. Low impact developments (LIDs) were simulated in ROCSWMM to determine theoretical reductions in flows and loads to the Genesee River from the storm sewer network. Converting 25% of subcatchment impervious area to porous pavement reduced flow and TP and TSS loads by up to 15% and treating ten percent of impervious roof runoff with rain barrels could reduce flows and loads up to eight percent. Further research should be conducted to determine the placement of LIDs within subcatchments that will achieve the greatest reduction of inputs into the sewer system.