Worcester DPW&P Sewer Operations is responsible for the operation and management of sewer infrastructure, which includes three components: the sanitary sewer system, the surface sewer or stormwater system and the combined sewer system.
The sanitary sewer system conveys wastewater (sewage) from homes and businesses to the Upper Blackstone wastewater treatment plant. The surface sewer or stormwater system collects rainfall from City streets and pipes it to the nearest waterway. The combined sewer system collects both sewage and stormwater and conveys it to the Upper Blackstone plant for treatment before it discharges to the Blackstone River.
Worcester's combined sewer system covers some 4 square miles of the City including downtown, Shrewsbury Street, Green Island and parts of Main South. Some of the oldest pipes in the City are combined sewers with many constructed of brick in the mid to late 1800's.
Some of these brick combined sewers are enormous with diameters up to 96 inches (8 feet). Decades ago, when heavy rains caused combined sewer overflows (CSOs), the mix of stormwater and sewage would flow untreated to the Blackstone River. In the 1980s, Worcester became one of the first cities in New England to construct a CSO treatment facility designed to provide some level of wastewater treatment to the combined sewer flow before it entered the River.
The Quinsigamond Ave Combined Sewer Overflow Treatment Facility (QACSOTF) functions as a sewer pumping station during dry periods or small rain storms when only sewage or sewage mixed with moderate amounts of runoff is flowing through the combined sewers.
The facility pumps this sewage to the Upper Blackstone plant for treatment. When heavy rains occur the facility switches to treatment mode. After treatment, the flow moves into the former Mill Brook, then eventually discharges into the Blackstone River. Since the QACSOTF discharges to the Blackstone River, it is regulated by the USEPA and MassDEP under the National Pollution Discharge Elimination System (NPDES) permitting program under the Clean Water Act.
The DPW&P regularly evaluates cost-effective solutions to sewer-related problems facing the City of Worcester.
Options to reduce the amount of stormwater entering the combined sewer system were explored and the most cost-effective were identified in the 2004 CSO Long-term Control Plan. DPW&P also completed modifications to the old Mill Brook conduit upstream of the QACSOTF so that greater volumes of combined sewage can be stored underground for slow, controlled release to the QACSOTF.