Sign warning of sewer overflow. Courtesy

Ever curious what happens when it rains really hard in DC?  Well, DC has what’s called a combined sewer system in most of the city- that is, storm water is combined with sanitary waste in the same sewer pipes and sent to the Blue Plains treatment plant. 

When a lot of rain occurs quickly, some parts of the system cannot handle the capacity, so there exist a network of sewer outflow points located alond DC’s rivers and creeks.  When the system overflows, the sewer water pours into the waterways.  Or, in the case of recent flooding in Bloomingdale, sewers can back up into the streets:


DC Water has some great maps showing the locations of sewer outflow points:

For those new to the site, we’ve covered sewage pumping before.