Lake Wildwood returns to normal after sewage spill

It's once again safe to go into the waters of Lake Wildwood.

A mechanical failure at Commodore Park resulted in 878.67 gallons of sewage entering Lake Wildwood last month, according to the Governor's Office of Emergency Services.

The failure happened early March 24.

"The posted signage was related to water entry, letting people know to stay out of the water until water quality improves," said Brad Torres, wastewater operations manager for Nevada County Sanitation District No. 1.

Amy Irani, the director of Nevada County's Department of Environmental Health, said based on fecal coliform numbers from March 28, her agency determined that levels were once again safe for the Lake Wildwood Association to remove any signage regarding the closure of beaches.

Torres said signage was removed Tuesday, with concurrence from Nevada County Environmental Health.

"Timing is usually related to volume spilled, timing of receiving test data back from a lab and in some cases weather," he said.

Torres said an electrical component activated by the well's level sensor failed to relay the signal required to trigger the pumps that prevent overflow.

"When the lift station is functioning properly, the level sensor inside the station detects the level of the wastewater accumulating in the well," Torres said. Once the wastewater reaches a designated depth, "the level sensor sends a signal to the control panel telling it to turn on the pumps and the wastewater is pumped out of the well on its way to the plant."

Torres said once the level sensor indicates the volume of sewage is at the low end of the container's threshold, another signal is sent that directs the control panel to shut down the pumps and avoid damage to the equipment.

"Pumps will have a tendency to burn up if they run without liquid to lubricate and cool them as they work," Torres said. "In this case, when the signal was sent, the relay at the control panel failed to relay the signal and the pump did not turn on, allowing the liquid levels to get too high and overflow."

Torres said Nevada County Sanitation District staff was performing regular checks of the equipment when they discovered the malfunction and identified the spill.

"Staff cleaned up the area removing all debris, and standing water, cleaned the area with fresh water, which was captured and removed as well," Torres said.

Torres’ staff notified the state Office of Emergency Services, Nevada County Department of Public Health and Lake Wildwood Department Of Public Works of the spill. The area was barricaded off and signage posted upstream.

"We also pulled samples for lab testing and continued to do so until the contaminant levels in the lake returned to normal levels," Torres said.

Torres said the sanitation district will add a separate high water float to the system at Commodore Park that will bypass the relays and alert district staff that their in-person troubleshooting efforts are necessary.

"District staff is required to be on site within an hour of any alarm or call out 24 hours a day, 365 days a year, and are generally on site working to correct issues much sooner than that," Torres said.

According to Nevada County's website, there are 10 zones within the Sanitation District with facilities that collect and treat 1.245 million gallons of wastewater each day. The Sanitation District provides sewer service to 5,230 accounts in western Nevada County with a population of 14,000.

"Historically, the district has a very low spill occurrence rate when compared to other municipalities our size," Torres said, noting that the Lake Wildwood district has roughly 45 miles of pipeline, 14 lift stations and 660 manholes maintained by the district's collections team.

"The Sanitation District's field staff does an excellent job of performing preventative maintenance work, as well as responding to call out and emergencies and that is reflected in the low incident rate," Torres said.

Torres said Lake Wildwood is primarily used for recreation, and the community's drinking water is purveyed by the Nevada Irrigation District.

Irani, the Environmental Health director, said her department looks at indicator levels to determine water quality.

Irani said the overall goal of her agency as well as the sanitation district is "to ensure the protection of the Lake Wildwood residents and their guests." The agency recommended the private lake operator close any beaches or areas that test at 200 cfu/100 mL due to the health concern.

WATER SAMPLE RESULTS

For public health and safety, the water samples were grabbed at the spill site, upstream and downstream the day of the spill. The water was tested after the initial samples (day of spill) were taken.

March 24:

Upstream Fecal Coliform: >1,600 mpn/100mL

Downstream Fecal Coliform: >1,600 mpn/100mL

Point of entry Fecal Coliform: >1,600 mpn/100mL

March 25:

Upstream Fecal Coliform: >1,600 mpn/100mL

Downstream Fecal Coliform: 170 mpn/100mL

Point of entry Fecal Coliform: >1,600 mpn/100mL

March 28:

Upstream Fecal Coliform: < 2.0 mpn/100mL

Downstream Fecal Coliform: 8 mpn/100mL

Point of entry Fecal Coliform: < 2.0 mpn/100mL

The difference between reporting as CFU or MPN (Most Probable Number) per unit of measure is due to their respective methods. CFUs or "colony forming units," are determined by directly counting visible colonies of bacterial growth on the plate or film. MPN, or "most probable number," measures growth statistically. In the most probable number method, a sample is added to a series of test tubes with special media at different concentrations. The MPN value is then measured based on the reaction levels in the tubes and the value is then calculated with a 95% confidence interval. CFU is a more precise method than MPN, but MPN is cheaper.

There was another incident with water quality at the lake in 2018 involving E. coli. The cause of the E. coli was never officially determined, although many blamed geese or improperly maintained water ways.

Irani said there could have been high levels of E. coli/enterococci present in the water before a sewage spill that year, but she was not sure because the lake is privately owned.

"If there were high levels before the spill, the samples that the Sanitation District pulled the day of the spill could be influenced by the existing water conditions," Irani said.

Rebecca O’Neil is a staff writer with The Union. She can be reached at [email protected]

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