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Sheridan staff outline plan to measure and reduce sewer inflow and infiltration
Summary
Utilities director Dan Roberts told city council the city will deploy flow monitors, expand CCTV inspections and prioritize pipe and manhole repairs to reduce unwanted water entering the sewer system that can raise treatment costs and risk overflows.
Dan Roberts, Sheridan utilities director, told the City Council on May 19 that staff plan to intensify measurement and targeted repairs to reduce inflow and infiltration (I&I) into the municipal sewer system. The council heard that surges of rain and groundwater entering sewer pipes and manholes can double daily flows at the treatment plant and increase treatment costs and sanitary-sewer overflow risk.
Roberts said the city will deploy continuous flow monitors in priority areas, increase CCTV inspections and then pursue spot repairs, manhole linings and pipe lining where the data show the best return on investment. “To accurately quantify it, it’s gonna require a thorough monitoring and measurement on our part,” Roberts said. “A reasonable level is below 10% for a system.”
Why this matters: excess I&I occupies sewer capacity that could be used for new connections and development, raises treatment costs and increases the chance of overflows that must be reported to the Department of Environmental Quality. Councilmembers asked whether I&I has previously limited development; staff said design assumptions typically include peaking factors that account for some I&I but stressed the need to “truth up” the model with field data.
Key details from staff presentation: - The system is divided into eight sewer sheds; staff propose flow monitoring at 13 locations identified in the city master plan. The budget includes six smart-cover monitors this year and seven more anticipated in fiscal year 2027 to reach those 13 locations. - Sheridan’s sewer network: about 137 miles of pipe and more than 3,000 manholes; roughly 48 miles are clay pipe and an estimated 366 manholes date from 1960 or earlier—areas likely more prone to I&I. - Typical corrective tools: targeted spot line repairs, cured-in-place pipe lining (the city has completed about five miles of lining historically; the most recent lining work was in 2022), manhole lining (city cited about $2,000 per manhole lining versus full replacement), and sealing low-lying manholes (staff identified 65 manholes in low-lying areas for potential gasket/tray treatment). - Current equipment needs: the city’s CCTV inspection van dates to 1999 and is budgeted for replacement.
Roberts said current best estimates are inconclusive but generally put I&I below 30% citywide; he emphasized the need for monitoring to determine how much is actionable and where repairs will deliver the greatest benefit. The utilities director said staff will return with findings and recommended capital work once monitoring and inspections produce clearer data.
Council response and next steps: Council members thanked Roberts for the overview and pressed for clarity about development impacts; staff reiterated that the proposed flow monitoring is intended to provide the empirical basis for capacity and planning decisions. No formal action was taken; the report was received as a staff update.
