An Act relative to further testing after a CSO event

This bill requires Massachusetts environmental agencies to test water for bacteria and pollutants after combined sewage overflow (CSO) events. It mandates testing at multiple downstream locations within a reasonable timeframe, with winter suspensions allowed, and compiles annual reports to create predictive water quality models. Municipalities and utilities (permittees) with bacteria levels exceeding 235 colony forming units per 100 milliliters must develop and get approved mitigation plans for reducing overflows, prioritizing them for state stormwater funding. The law also requires permittees to report discharge volumes and install metering equipment, with public advisories issued based on established timelines.