Administered by the SWRCB-DDW, the Surface Water Treatment Rule (SWTR) is a set of drinking water regulations that establish specific treatment requirements for surface water to reduce the risk of waterborne diseases.
The last update to the SWTR is the Long Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR). This rule protects treated water reservoirs from microbiological contamination by requiring one of three actions: 1) covering, 2) removing from service, or 3) providing additional treatment. LT2ESWTR applied to the six remaining uncovered reservoirs at the time: Los Angeles, Upper Stone Canyon, Santa Ynez, Ivanhoe, Silver Lake, and Elysian.
LADWP has implemented several projects over the past 25 years at a cost of over $1.5 billion to comply with LT2ESWTR. Several uncovered finished storage facilities and open reservoirs were either covered, removed from service, or provided with additional treatment. The Los Angeles Reservoir was brought into compliance through a combination of shade balls deployed in 2015 and the completion of the Los Angeles Reservoir Ultraviolet Disinfection Plant (LARUVDP) in January 2022. The LARVUDP was the final step in meeting all the conditions set forth by the 2009 compliance agreement with DDW and ensures that water provided by LADWP complies with all primary state and federal requirements.
Visit LADWP’s Water Quality webpage to learn more about water quality projects and issues.