Advisory about possible Nacimiento Lake contamination could be lifted Friday

A health advisory regarding possible elevated bacteria levels in Nacimiento Lake could be lifted today, the San Luis Obispo County Department of Public Works and Transportation said Thursday.

The advisory was made Tuesday after thousands of gallons of lake water rushed into the Oak Shores Wastewater Treatment Plant, about six to eight miles west of the lake’s dam.

Divers on Wednesday found a roughly 2-inch-by-2-inch breach in a water line under the lake. A temporary fix was installed to stop the water flow into the treatment plant.

The breach did not cause sewer water to enter the lake, but rather, “the wastewater system was basically draining the lake,” Public Works Director Dave Flynn said. The extra intake water from the break is being treated as a result.

Work is now under way to make a “substantial repair that will be in place for the next two months while the lake level is still high,” Flynn said. A permanent fix will then be sought.

Flynn will meet with the county Public Health Department today to discuss lifting the advisory because water tests are showing normal amounts of bacteria in samples, he said.

But residents of Nacimiento Water Co. at Oak Shores, Lake Nacimiento Resort, and the North Shore Boat and Ski Club are still advised to use bottled water or boil the lake water for a minimum of three minutes before drinking, cooking and bathing with it.

Heritage Ranch is not affected, officials there have said.

People also aren’t allowed to swim or do water sports in the lake.

The break in the water line was pouring about 100 to 200 gallons of water per minute into the sewer plant.

That means the system was running about 300,000 gallons of water per day; it normally treats about 30,000 gallons per day, Flynn said.

The system was built in 1974 and serves the Oak Shores community, adjacent to Nacimiento Lake to the north. The plant is now operating at full capacity and is handling the increased inflow of sewage and lake water, officials said.

Related stories from San Luis Obispo Tribune