Richmond, California, enjoys 32 miles of coastline, the most of any city in the San Francisco Bay Area, but this geography has its downside.

“During heavy or prolonged rain events, our treatment plant flow can increase from 5 mgd to 40 mgd,” says Dan Duffield, source control inspector for the Richmond Municipal Sewer District.

The I&I comes from direct tidal inflow in the southern basin near the Bay, groundwater infiltration from tidal saturation, storm runoff inflow...