One of the most popular sites for Tuolumne County Recreation Department swim classes and recreational swim programs, the Sonora High School Memorial Pool, has experienced intermittent closures throughout the summer season due to an unacceptable chlorine balance in the water.

Tuolumne County Recreation Department Supervisor Eric Aitken acknowledged that because of health code regulations, the pool must be closed when the proper chlorine levels drop below one part per million.

The Recreation Department tests the water however, and must report the issues to Sonora High School maintenance staff to fix the problem.

“Then they respond,” he said over a phone message.

His staff does not know the maintenance staff’s schedule, he said.

Aitken indicated that the department's testing procedure begins with a chlorine test before anyone enters the water, and continues every hour after the opening until the swim times are closed.

Chlorine is used as a water disinfectant, killing bacteria that may result from urination or any other chemical or organic compound in the pool system.

A chlorine balance inside a pool is just one of many features of public health, equipment safety within the pool system. A pool’s saturation index and water chemistry is determined by water temperature, pH reading, calcium hardness and alkalinity level, and often maintained through a series of filtration and piping systems.

The Sonora Memorial Pool hampered with maintenance issues for many years, with underground plumbing at the site dating back to the 1950s, even though 1994 repair work extended the life of the facility for 20 years.

A Sonora High School fact sheet on the pool also indicates that the pool’s “mechanical systems i.e. pumps, heater, filtration, drains are outdated and inadequate for a large public use pool.”

The Memorial pool’s piping, filtration system and pump are limited in size and take 10 hours to filter water. Current health standards require that the filtration time take 6 hours, the document notes.

The Sonora High School district spends about $37,000 annually for heating, chemical costs and equipment repairs, the document says.

Sonora High School superintendent Pat Chabot or Maintenance Director Gilbert Hammerbeck could not be reached for comment.

Aitken did not have dates and times readily available for when Memorial Pool had been closed over the summer season, but classes are held in three sessions over June, July and August, and are held before and after t he swim drop-in program.

The Sonora Memorial pool is typically open on Monday through Thursday for classes and recreational swim between 10:00 a.m. and 7 p.m.

The recreational swim is open to all members of the public and held from 1 to 5 p.m. There is a fee to swim.

For the 2017 summer swim season, the recreation department is fully staffed with about 75 total employees over the pool programs at Sonora High School, Tuolumne, Twain Harte and Columbia.

Aitken said in June that he was anticipating a full program at all four pools over the summer with at least 1,200 to 1,500 total registrations.

When the new Sonora High School Aquatic Center opens on Aug. 1, the old pool will be decommissioned at the conclusion of the recreation season.

The new Aquatic Center pool is about 25 yards across, or 75 feet, with an external gutter to continually process water overflowing over the interior pool area. A downward-sloped access point into the pool bordering the Sonora High School football field begins at 1 foot and continues to four-foot-six-inches before reaching the maximum pool depth of seven feet.

Additional improvements have also been made to improve on the filtration and heating deficiencies of the current site, with an extraneous mechanical room filled with boilers, filtration tanks, and an assortment of devices, gauges, components and equipment to maintain an operative saturation index.

The new Sonora High School Aquatic Center was constructed after Sonora High School District voters approved the Measure J bond in November 2012. Measure J called for issuance of $23 million in general obligation bonds to finance the renovation, construction and modernization of Sonora High School facilities.

Of that $23 million, nearly $6 million was budgeted for the construction of the pool facility.

A project expenditures report ending on Oct. 31 noted that nearly $500,000 was contributed to that budget from non-bond funds.

Contact Giuseppe Ricapito at (209) 588-4526 or . Follow him on Twitter @gsepinsonora.