Heavy April storms drove seven sanitary sewer overflows, utilities presenter says

Scott Murphy, a representative of InfoMark that manages the city's wastewater plants and lift stations, told the Fayetteville City Utilities Committee on May 13 that two extreme rain events in April produced unusually high flows that strained treatment and collection facilities.

"April for us was a really tough month," Murphy said. "We had 7 sanitary sewer overflows at the lift station. Bear in mind, we have 60 lift stations." He told the committee the two large storms produced about 8.5 inches of rain in early April and roughly 5 inches in a second event later in the month.

Why it matters: the excess flows pushed some plant processes past operational limits, producing three NPDES permit exceedances and damage to electrical equipment. Murphy said two of the permit violations were for coliform limits and one was a phosphorus exceedance during the same high-flow week. "The phosphorus violation was the exact same week... the limit there was a 2, and we were at a 2.4 for that flow period," he said.

Murphy and other staff described how the combination of very high rainfall and aged collection infrastructure created the problem. Murphy said peak flows reached about 34,500,000 gallons per day at the Westside plant and about 19,000,000 gallons per day at the Nolan plant, well above those facilities' typical peaks. He also noted lightning strikes and an arc flash at a motor control center that damaged wiring during the first storm.

Discussion and next steps: staff said their response plan has both immediate and longer-term elements. Short-term actions described to the committee include repair of damaged motor control equipment, replacement or repair of damaged pumps, deployment of an additional auto-sampler for industrial monitoring, and weekly/biweekly generator exercising. Medium-term work includes targeted inflow and infiltration (I&I) investigations using smoke testing to locate ground-level inflow points and point repairs to broken or leaking sewer mains.

Murphy summarized the investigative approach: "that's an inexpensive way to identify those points of inflow...we'll start forcing that smoke in the areas that we know are contributing to the problem." He explained crews will use flow and run-time data from lift stations to prioritize areas for inspection and repair.

Staff emphasized that portions of the system are old and are more prone to infiltration and inflow during high river and groundwater conditions. Committee members asked about seasonal permit limits and whether the state might adjust compliance periods; Murphy said permit terms are set in the renewal process and that municipalities can request changes at the five-year renewal but that regulators rarely relax limits.

No formal committee vote was taken on corrective work at the meeting. Murphy said upgrades and maintenance actions are planned through the summer and staff will return with further operational reports.