Beach Monitoring

Swimmers have a choice of three community beaches on beautiful Pine Mountain Lake. Beaches include picnic tables and barbeques. Each swim area is separated from the lake’s open water by a line of buoys and has a floating dock.

Some pathogenic micro-organisms associated with fecal waste can cause a variety of illnesses (such as stomach flu, ear/nose/throat infections, skin rashes) and diseases (such as typhoid, cholera and hepatitis) through the ingestion of contaminated water.

Throughout the lake recreation season, water in each swim area is sampled weekly and analyzed at a certified lab for bacteria that indicate potential fecal contamination:

• Total coliforms—A collection of bacteria that can originate from human and animal waste, although some also originate in soil and plants.
• Fecal coliforms—A kind of coliform found primarily in the guts of mammals.
• Escherichia coli (E. coli)—A specific strain of fecal coliform which has been linked to numerous foodborne illness outbreaks.

Results for year 2024 are posted click here

To recommend posting swim advisories at freshwater beaches with infrequent sampling, the Tuolumne County Division of Public Health uses the following California Department of Health Services “Draft Guidance for Freshwater Beaches” (2006):

• Total coliforms >10,000 colony forming units (CFU) per 100 milliliters (mL)
• Either Enterococcus >61 CFU/100 ml, or E. coli >235 cfu/100 mL

and the United States Environmental Protection Agency’s recommended level for fecal coliform of 200 most probable number (MPN)/100mL.

If such thresholds are exceeded, staff increase the monitoring frequency and investigate potential sources. The most prevalent source is geese, so staff also occasionally monitor geese feces for toxic strains of bacteria. If results continue to indicate potential concerns, staff alert all community members and close the beaches until monitoring results return to normal.