The City of Lomita takes water quality seriously, and the oversight and guidance provided by the State Water Resources Control Board on this matter is valued and appreciated. Everyone in the City depends on clean and healthy drinking water and adherence to water quality standards is our top priority. The City also believes in transparency in the process–this website, along with easy access to City Staff, is intended to provide Lomita water users with the information they need to understand their water supply.
In August of 2016, the City received notification from the State of California that, based on a four-quarter average, we exceed the Maximum Contaminant Level (MCL) for a disinfection byproduct (DBP) known as Total Trihalomethanes (TTHM) at two locations. The rolling average test results showed 81.5 ppb and 82.1 ppb (the MCL is 80 ppb) at the 2450 247th St. and 1948 252nd St. sampling locations, respectively. The elevated average is due to a single sample in February 2016 that showed an increased level of TTHM for that month of 182.6 ppb.
The elevated count of disinfectant was a result of Lomita Water implementing a routine change to free chlorine disinfection in order to combat elevated nitrate levels in the water. Once the nitrate levels were stabilized, the use of chloramine disinfection was resumed and the system was returned to normal operations. All previous and subsequent tests have shown TTHM levels are averaging between 30 and 60 ppb, well below the Federal guidelines.
As seen in this graph, the elevated level of TTHM was a temporary situation resulting from the planned use of free chlorine. This process to combat nitrate levels is routinely done by water agencies across the nation and is considered a best practice. Temporary changes to disinfection treatments will naturally lead to elevations in TTHM. The Federal guidelines note that sustained exposure over a long period of time can have negative health consequences, but brief periods of elevated levels pose no health risks.
While the State requires quarterly monitoring of DBPs, the City has increased the frequency of sampling for TTHM in order to more aggressively monitor this MCL and ensure continued and ongoing compliance. These values will be reported to the State, as they were in the case of this citation, and to our customers. To view a copy of the public notice, click here.