What is a Combined Sewer Overflow (CSO)?

When Lowell developed in the early 1900s a single pipe was installed to carry both wastewater (sewage collected from homes and businesses in the City) and stormwater (runoff from rainfall or snowmelt collected from city streets through catch basins). This is known as a combined sewer system and was commonly used in older New England mill cities. Combined sewers serve more than 60 percent of the City. However, during rainstorms, stormwater can exceed the capacity of the sewer pipes causing a mixture of stormwater and wastewater to be discharged to the Merrimack and Concord Rivers. These CSO discharges occur at 8 locations in the City. Lowell is required by a federal mandate to start eliminating these discharges.

Request for Catch Basin Cleaning

CSO Reports

• 2008 First Quarter Diversion Summary Report
  
• 2007 Diversion Summary Reports
  
• 2006 Diversion Summary Reports