Reversing a Force Main: EBMUD’s Cost-Effective Plan to Decrease Wet Weather Facility Discharges through Operational Modifications

The East Bay Municipal Utility District (EBMUD) conveys and treats an average dry weather daily flow of 50 million gallons per day (mgd) [2.2 m3/s]. During major wet weather events, when excessive collection system infiltration and inflow (I/I) cause peak flows of up to 13 times the dry weather average, a portion of the interceptor flows is diverted to EBMUD’s three wet weather facilities (WWFs), which have a combined capacity of over 300 mgd [13.1 m3/s]. EBMUD identified a relatively low-cost infrastructure project that would significantly decrease discharges from its Point Isabel WWF by operating EBMUD’s 24-mgd [1.1 m3/s] capacity pump station force main in a reverse-flow, gravity mode under certain conditions, while maintaining its original force main function.