WSSC flags infiltration-and-inflow as key driver of wet-weather stress; offers rehab, storage or expansions

Tom Hilton described infiltration and inflow (noted in the transcript as "INI") as extraneous wet-weather flow that enters the collection system and drives peak loading at treatment plants.

"INI is essentially extraneous flow that enters our wastewater collection system," Hilton said, outlining I&I sources such as groundwater entering through deteriorated joints, stormwater entering through manholes, and illegal roof-leader connections.

WSSC said it has over 100 wastewater meters and rain gauges tied to calibrated hydraulic models and is using genetic-algorithm optimizations to identify cost-effective solutions. Hilton explained that in some basins it may be more cost-effective to build storage to attenuate wet-weather peaks or to rehabilitate collection-system elements rather than expand plants, and that facility plans will evaluate alternatives before recommending CIP projects.