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Big Oak Flat Sanitary Sewer Overflow

Staff received a report of a possible Sanitary Sewer Overflow Tuesday, August 22nd @ 1:06pm. Upon inspection, staff found an active spill running at approximately 1 gallon per minute entering a drainage channel that leads to a local creek. Staff began documentation and restoration of service . The spill appearance point was a vacant building's lateral service that was severed beneath the building. Once service was restored, staff investigated the cause of the spill via camera and found a softball wedged in the mainline. Upon excavation, the mainline was found to be blocked with a large piece of firewood and the softball. Repairs were made and the spill area had the contaminated soil removed and the area was disinfected.  Tuolumne County Environmental Health was contacted at 2:24pm. As there is very little flow within the creek,  the standing water was vacuumed and returned to the wastewater plant for treatment.

The spill area is very remote, discovered by a passing local motorist who had pulled off the highway. Based on volume and observations of bio film growth, staff is estimating the spill was occurring for 5.3 to 10.6 days at 1 gpm for a total volume of 7,680 to 15,361 gallons. Staff estimate that they were able to recover 4,521 gallons of the spill.

The District is considering this an act of vandalism as these items could only have entered the collections system via a manhole.  Staff will continue to sample the creek area and report results to the Tuolumne County Environmental Health Department. 


May contain: monitor, screen, display, electronics, television, tv, and lcd screen
May contain: ball, tennis, tennis ball, sports, sport, team sport, team, clothing, apparel, baseball, and softball