photo by Will Campbell

water quality projects

past

In 1974, California State Department of Health Services (DHS) directed the Los Angeles Department of Water and Power (LADWP) to begin studies on how to improve water quality, including the protection of 15 open distribution reservoirs. Treated water in these reservoirs is subject to degradation due to algae, small aquatic organisms, microbes, airborne particles, and birds. This results in taste and odor problems for customers. It also requires LADWP to increase the use of disinfectants (chlorine) in order to comply with health-based drinking water regulations.

In addition to the normal environmental exposures faced by open bodies of water, several open distribution reservoirs were determined by DHS in 1991 as having the potential for contamination by surface runoff according to the Surface Water Treatment Rule. LADWP was required to mitigate this potential threat at four reservoirs by December 1993. The reservoirs are Encino, Lower Stone Canyon, and Upper and Lower Hollywood. Each reservoir project was developed with significant involvement from surrounding communities to meet this drinking water standard.

present

LADWP has taken action by covering, abandoning, or replacing open distribution reservoirs with tanks that provide better protection and quality assurance for customers. To date, 9 of the 15 reservoirs that were open to the environment in 1974 have been bypassed, replaced, or covered. Improvements are under way to address the 6 remaining open reservoirs using a site-specific approach. Improvements being made to meet customers' expectations for taste and appearance, and those for regulatory compliance, are closely related.

LADWP recognized that substantial time and capital improvements would be necessary to meet the Surface Water Treatment Rule, which meant that the compliance deadline of December 1993 would not be met. LADWP formally requested and received an extension of the compliance deadline.

LADWP's compliance with the Surface Water Treatment Rule is governed by an agreement with DHS entered into July 1993. Negotiated compliance deadlines are November 1, 2001 for Upper and Lower Hollywood Reservoirs; January 1, 2003 for Encino Reservoir; and January 1, 2005 for Lower Stone Canyon Reservoir. To ensure the safety of the water until compliance is achieved, LADWP developed specific operations plans for each reservoir that included increased reservoir outlet chlorination, daily calculations for disinfection efficacy, continuous turbidity monitoring, and daily bacteria monitoring at the outlet of each reservoir.

future

The six remaining open reservoirs are the Upper Stone Canyon Reservoir, Santa Ynez Reservoir, Silver Lake Reservoir, Ivanhoe Reservoir, Los Angeles Reservoir, and Elysian Reservoir. For these 6 open reservoirs, a variety of projects and activities to improve water quality have been implemented. Additional improvements at these reservoirs are necessary in the next decade to meet new regulations, primarily the Disinfection By-Products (DBP) Rule and enhancements to the Surface Water Treatment Rule, and to improve the taste and appearance of water coming out of these reservoirs. To meet the requirements of the DBP Rule, LADWP has made the decision to change disinfection using chlorine to disinfection using chloramines. In order to convert to chloramines all remaining open distribution reservoir must be covered or removed from service. It will take approximately 6 years to convert the water distribution system to chloramines.

(Source: LADWP Website)