Update: Lake Wildwood Treatment Plant System update and Recent lake water and sediment sampling

August 14, 2017 – Nevada County Public Works (PW) quickly responded to a power failure on Sunday (August 13, 2017) in Lake Wildwood (the failure also affected North San Juan) that affected the power supply to all of the 14 lift/pump stations within the LWW residential community for the wastewater treatment plant. All of the 14 lift stations are equipped with backup generators in case of a power outage. All systems, except Station 22, were working correctly with generator backup and within 30 minutes, the Station 22 issue was rectified. Station 22’s “level sensing equipment” did not reset when the generator kicked in and this resulted in an estimated 1,680 gallons of sewage reaching the lake near 19386 Chaparral Circle.

The overflow had occurred prior to the PW crews’ arrival after which they reset the level sensing equipment, cleaned up the spill, notified the RWQCB and Environmental Health and posted public notices at the location of the spill. Based upon the location of the overflow, and the amount (1,680 gallons), it is highly unlikely that the amount of sewage released would affect the overall quality and condition of the lake with a total capacity of 4,000-acre feet (well over 1.3 billion gallons). However, the spill information will be reported to the CDC and CDPH as well. Meanwhile, the level sensing equipment issue is being addressed.

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The PW Department Staff completed an Electro Scan of the gravity sewer lines located around Commodore Park and Meadow Park today (August 14, 2017). The Electro Scan provides a detailed view of the sewer lines to detect any cracks or faults and the results of the scanning have shown all lines are intact with no evidence of failure. Additionally, the PW staff continues to evaluate the gravity sewer lines and flows upstream and downstream of the beaches.

On August 13, 2017, Environmental Health Department collected water from Commodore and Meadow Park swimming areas using Field Dead-End Ultrafiltration (DEUF) filters and equipment supplied by the CDC. Sediment samples were also collected from Commodore Beach swimming area. The water and sediment samples were shipped back to the Centers for Disease (CDC) Control in Atlanta, Georgia and results from testing are anticipated within 2 weeks. Public Works continues to test the lake water twice a week at eight different points in the water near Commodore, Meadow Park, and Hideaway Park Beaches for the Environmental Health Department, and will continue to do so until results indicate the issue has been resolved.

Results from the August 11, 2017 samples warrant continued beach closures, as results at six of the sites near the three beaches indicate elevated levels of fecal coliforms (these are bacteria, some of which may cause illness), with the highest levels being measured near both Commodore Park and Meadow Park at >2,419.2 MPN per 100 mL. Levels above 200 MPN per 100 mL warrant beach closure. The seventh and eighth sample site at Hideaway Park tested at 66.3 MPN per 100mL and 113.7 MPN per 100 mL respectively. Though only three beaches are being tested regularly, all five beaches are closed as a precautionary measure to ensure public health and safety and to prevent further illness.

The Nevada County Environmental Health and Public Health Departments are in continual communication with representatives from the California Department of Public Health and the Centers for Disease Control (CDC) and Prevention. According to their recommendations, the public beaches should remain closed until contamination levels in the lake water have dropped to a safe level and until after three E. coli incubation periods have passed since the last known exposure of those who have become ill.

In order to determine the source of contamination, numerous samples have been collected (wildlife scat, sediment and water) and tests have been conducted, including multiple tests of the wastewater system and at the NID canals along Deer Creek. The contamination source, however, has still not been identified. The investigation continues, and the results of testing of wildlife scat, sediment, and other tributaries is in process. The Environmental Health, Public Works and Public Health Departments continue to work closely with one another and with the Lake Wildwood Association, sharing test results, reviewing past data, and discussing closures and notices.