The City of Cambridge has issued an advisory that Combined Sewer Overflow (CSO) CAM401B has discharged to Alewife Brook on August 22, 2011. During heavy or prolonged rain events, CSOs can discharge stormwater mixed with untreated sewage. Discharges from CSOs contain levels of bacteria, viruses, raw sewage and other pollutants that may pose health risks to people who come in direct or indirect contact (e.g. contact with pets swimming in contaminated water). Contact with CSO-contaminated water should be avoided. Click the link here for more information about CSO's.