EXTREME PRECIPITATION, AGING PIPES, AND SEWAGE OVERFLOWS ARE DRIVING AN EMERGING HEALTH CRISIS: A CASE STUDY FROM SCHENECTADY NY

Increases in annual precipitation and extreme rainfall events in the Northeast are overwhelming aging stormwater and sanitary sewer systems. The increases in precipitation and extreme events in the Northeast are most pronounced in the last two decades, where there has been a ~50% increase in intense or extreme precipitation, mostly during summer months. The Quantitative Precipitation Forecasting (QPF) at National Weather Service (NWS) is partly focused on rainfall probability estimates in the context of annual exceedance probability based on a long Northeast record (70-100 yr), assuming stationarity in the record. However, the assumption of stationarity in the rainfall record is likely incorrect, so that those exceedance probabilities underestimate extreme precipitation events. Significant precipitation events overwhelm stormwater sewer systems, which may end up carrying direct or indirect sewage overflows. While the damages to our waterways from Combined Sewer Overflows (CSOs) are relatively well recognized, a looming threat also exists from aged pipes that leak, effectively acting as CSOs during extreme events. Our work in a Schenectady urban stream that was integrated into the stormwater collection system shows that impaired sanitary sewers directly harm water quality even where storm sewers are supposed to be separate from the sanitary system. The presence of Enterococcus, a common fecal indicator bacteria (FIB), along with nitrates and phosphates, in this impaired urban stream reveals sewage exfiltration and direct leaks from aging sanitary sewers. Pathogen loads in stormwater during high-flow events are orders of magnitude greater than acceptable criteria (i.e., EPA). Gastrointestinal outbreaks have occurred in Schenectady three times in the last two years, which may be linked to sewage contamination. This sewage also ends up in our rivers, including the Mohawk River, where it diminishes water quality and increases nutrient availability that can drive harmful algal blooms (HABs), a public health concern for communities that use the Mohawk as a drinking water source. Our aging infrastructure appears to be underfit to handle the increase in precipitation and extreme events, and without direct intervention we are facing a public health crisis due to rising levels of sewage in our waterways.