A property owner’s sewer line backed up and overflowed about 30 gallons of wastewater into a drain near Twain Harte Lake on Sunday, prompting shutdown of the private recreational reservoir for testing.

“We had our water tested yesterday morning,” Lauren Gerber, the general manager and lake director for Twain Harte Lake, said Tuesday in a phone interview. “With the holiday it takes 48 hours to get results. As soon as we hear back we'll be open.”

The popular lake was closed for Memorial Day. None of the 805 dues-paying members of the Twain Harte Lake Association could be reached for comment.

Tom Trott, general manager for Twain Harte Community Services District, said Tuesday the testing lab had some processing delays due to holiday business closures.

“We are hoping for earlier, but it sounds like we should receive confirmed test results by noon on Thursday,” Trott said.

The unidentified property owner’s sewer line blockage was primarily a result of root intrusion and attempting to flush wipes, which are common causes of blockages in the Twain Harte Lake area, Trott said.

Trott is advising Twain Harte Community Services District customers to be aware that primary causes of private sewer lateral back-ups are a combination of roots, grease and non-soluble items flushed down toilets.

Non-soluble items include wipes and swiffers that are not flushable, Trott said.

Trott is reminding Twain Harte Community Services District customers to refrain from flushing anything other than human waste and toilet paper, as well as putting grease down drains. Reducing garbage disposal waste by scraping plates into the trash and using enzyme cleaners to help break down roots are also good ideas, Trott said Tuesday.

“Many of our out-of-town customers experience back-ups because new roots have grown into their laterals over the few months since they last visited their home,” Trott said in a recent announcement. “As soon as the lateral experiences heavy use, toilet paper and other products catch on the roots and cause a clog.”

Twain Harte Lake will remain closed as a precautionary measure until the water is confirmed to be safe for human contact, according to Twain Harte Lake Association and Twain Harte Community Services District staff.

A separate sewage incident reported Sunday west of the Crystal Falls subdivision in the Sullivan Creek watershed was unrelated to the situation at Twain Harte Lake, the general manager for Twain Harte Community Services District said. Tuolumne County health and environmental health officials did not respond to requests for comment on the Sullivan Creek sewage incident.

Trott said he understood the Sullivan Creek incident involved a private septic tank. Crystal Falls subdivision and that part of Sullivan Creek watershed are downstream and downhill from Twain Harte Lake.

The Sheriff’s Office stated in a social media post Sunday that sewage had not reached Sullivan Creek. Sheriff’s staff said “As a precaution the public is advised to not swim, drink, fish or carry out any recreational activities near or in the water. Avoid the area of the Sullivan Creek drainage until further notice.”

Contact Guy McCarthy at gmccarthy@uniondemocrat.com or 588-4585. Follow him on Twitter at @GuyMcCarthy.