The city of Sedona and state of Arizona are continuing to monitor a sewer spill in Sedona created by heavy rains.
According to a city press release, at around 4 p.m. on Friday, July 23, rainwater inundated the city of Sedona’s El Camino Lift Station at 700 El Camino Road and overwhelmed the pump system, causing a sewage spill. The spill was stopped within 30 minutes.
Water quality counts taken between 8:50 a.m. and 11:18 a.m. the following day showed E. coli levels at all test sites above the state and federal water quality E. coli limit of 235 Colony Forming Units per 100 mL of water for recreational swimming. City officials believe this is due to the heavy rain this weekend, after almost no 2020 monsoon rainfall.
The city estimates approximately 1,500 gallons of untreated liquid effluent spilled into a nearby wash that flows into Carroll Canyon Wash, which ultimately drains into Oak Creek near the Crescent Moon Ranch Day Use Area, approximately 2.7 miles downstream.
E. coli Counts
Water quality counts taken between 8:50 and 11:18 a.m. on Saturday, July 24, show E. coli levels at all test sites above the state and federal water quality E. coli limit of 235 Colony Forming Units/100mL of water. The measurement is Most Probable Number/100 mL.
Location on Oak Creek/E. coli Results
Poco Diablo (upstream from spill), 1,575
Red Rock State Park, 2,966
Deer Pass Trail, 7,308
Page Springs Bridge, 3,583
Page Springs Bridge Duplicate, 4,487
Windmill Park, Cornville, 12,976
“There isn’t anything we could have done to prevent this from occurring,” Wastewater Director Roxanne Holland said on Monday, July 26. “This was Mother Nature at play. The amount of rain that fell in such a short amount of time was able to find its way into our sewer system and ultimately overwhelmed the pumps where they could not pump water out fast enough.”
The untreated liquid effluent entering Oak Creek was highly diluted by the rain occurring at the time of the spill, the release stated.
“For context, the volume of effluent translates to approximately 0.11 cubic feet per second,” the release said. “For comparison, Oak Creek’s rate of flow during this rain event was just under 900 cubic feet per second.”
Oak Creek’s average annual flow is 65.5 cubic feet per second.
City staff sent these results to the Arizona Department of Environmental Quality.
The release stated that residents should take extreme caution when recreating in Oak Creek, especially after storms when E. coli levels are highest.
The immediately-affected areas near Crescent Moon Ranch swimming area have signage posted warning of high levels of E. coli. The city also hand-delivered information on this spill to residents near Crescent Moon Ranch with direct creek access located downstream from the spill.
Holland said each of the city’s 17 lift stations are fully automated and have alarms that alert an on-call operator when the pump systems are not working properly.
“On Friday afternoon, a few of our lift stations were in alarm conditions because the water level in the wet wells where the pumps are located was getting high, due to stormwater runoff entering our sewer system,” she said.
“Operators responded to each of the alarms and were able to prevent any spills, except at El Camino. When the operator arrived at El Camino, sewage was bubbling out of the manhole that feeds the lift station. We immediately took action to stop the overflow and were able to do so within 30 minutes of the alarm.”
For sewer spill emergencies, call the city’s sewer emergency hotline at 203-5180.
