Sanitary Sewer Overflows
Boston Water and Sewer Commission maintains a vast system of sanitary sewers and
stormwater drains designed to properly convey sanitary flows to the MWRA's Deer
Island Treatment Facility and stormwater to receiving waters. Over the past two
decades, the Commission has invested heavily in upgrading the system to increase
capacity as well as separate combined sewers, resulting in far reaching environmental
benefits. As the Commission's work progresses, BWSC carefully monitors Sanitary
Sewer Overflows (SSOs). Some SSOs occur when wet weather events cause inflows to
exceed the collection capacity of the system, producing an overflow of sanitary
sewerage. SSOs can also occur during dry weather events due to a variety of causes,
including blockages and structural failures. The map below displays the location
of SSO events throughout the city based on a selected timeframe.
- Click on the layer list icon in the upper-right corner to open it. Under Operational
Layers, check one box for the desired time frame from the options listed. SSOs that
occurred during that period will be indicated by caution symbols on the map.
- To view detailed information from a specific event, click on a caution symbol, then
the arrow button on the right of the pop-up. To go back to the map, click the down
arrow in the upper-right corner. To clear all selections and go back to the map,
click the X in the upper-left corner.
- To view all SSO events in the current map extent, click the up arrow at the bottom
of the map to make the attribute table visible. Table columns can be sorted by clicking
on the headings and widened by clicking and dragging on the borders.
- Click the plus and minus buttons in the upper-left to zoom in and out.
- Click the House button in the upper-left, below the minus button, to return to a
full view of the city.
- To export SSO event data to an Excel table, select the events you'd like to export
in the attribute table, click the Options drop-down button, and click Export to
CSV. This button will be grayed out if no data is selected.