Stanislaus County officials said additional water testing is being conducted at Woodward Reservoir following reports that visitors became sick after swimming at the park north of Oakdale.
In a press release Wednesday, the county’s Parks and Recreation division said the extra testing for bacteria levels was out of “an abundance of caution.” The results are expected today.
Officials are reacting to reports that a Stockton man who swam at the lake earlier this month was hospitalized for days with an intestinal illness caused by a campylobacter infection. Other park visitors who posted on social media or spoke to the press said they suffered from diarrhea, fever and rashes after swimming at the reservoir.
Routine tests showing higher-than-normal total coliform bacteria in the reservoir prompted the county last month to post signs just before Memorial Day weekend. The signs say bacteria levels are higher than usual and advised people to swim at their own risk.
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Jami Aggers, county environmental resources director, said the additional tests will provide a current reading on bacteria levels. The South San Joaquin Irrigation District, which owns the reservoir, arranges for periodic testing of the reservoir water, checking for E. coli and coliform bacteria.
“If any additional action is warranted based on the water testing, appropriate action will be taken,” the press release said.
A San Joaquin County public health nurse interviewed the Stockton man, Luis Lopez, finding the reservoir was only a possible source of the campylobacter infection, said Alvaro Garza, health officer for San Joaquin County.
“We are not going to know exactly where he got it,” Garza said. The bacterial illness may originate from tainted water, but a common source is contaminated food.
“There is no food to test,” Garza said, adding the health department would not do more investigating unless there’s an outbreak of illness.
Aggers said information on the water quality at Woodward Reservoir will be given to visitors at the regional park’s entrance. Notices will explain that swimming in lakes and rivers is not the same as using a chlorinated pool. Besides exposure to naturally occurring bacteria in the water, the literature says, people with sensitivities may have a skin reaction from the untreated water.
The lake water is tested for E. coli, which comes from human and animal wastes, and coliform, a bacteria that lives in the intestines of people and animals. Testing for the bacteria can suggest that other germs such as campylobacter are present.
Aggers said park attendance is down about 25 percent this week, but she thought that was due to cooler temperatures.
The county expects to allow water recreation at the park for some time beyond July 7. The SSJID filled the reservoir for a shortened season because of the drought, but won’t start reducing the water level July 8 as planned. The extra time for water recreation will be subject to further notice from the district, Aggers said.