The Lahontan Regional Water Quality Control Board (Lahontan Water Board) announced it has received a $4.6 million grant to investigate regional perchloroethylene (PCE) groundwater contamination in South Lake Tahoe affecting drinking water wells.
Multiple drinking water supply wells, including those operated by three different water suppliers, have been affected or are threatened by the PCE contamination. In spite of these impacts, South Lake Tahoe water purveyors continue to provide a safe water supply for South Lake Tahoe residents, businesses, and visitors.
“While Lake Tahoe’s beauty and clarity remains a worldwide attraction, our drinking water supplies are at risk of further contamination unless prompt action is taken,” said Patty Kouyoumdjian, Executive Officer for the Lahontan Regional Water Board. “This grant gives us the critical funds to fully investigate the regional PCE groundwater contamination, track down all potential sources of pollution, expedite cleanup and protect our remaining drinking water sources.”
Funds from the grant award, issued by the State Water Resources Control Board’s Site Cleanup Subaccount Program (SCAP), will be used for investigating an area referred to as the “South Y area” of South Lake Tahoe in El Dorado County (generally surrounding the intersection of Highways 50 and 89 and extending north and northeasterly).
The project will investigate the horizontal and vertical extent of regional PCE groundwater contamination, including potential sources of the regional contamination. “Sentry” groundwater monitoring wells will also be installed to monitor groundwater near several water supply wells, providing information water suppliers can use to better protect their water supply systems from the PCE contamination.
Several businesses in the South Y area are known or suspected to have used, stored, or disposed of PCE or PCE-containing products. PCE is a common ingredient in many drycleaning and metal degreasing products.
PCE has been detected in groundwater in the South Y area at concentrations as high as approximately 1,700 parts per billion (ppb) and in individual supply wells as high as approximately 60 ppb. The drinking water maximum contaminant level for PCE is 5 ppb. The water supply wells with detections exceeding 5 ppb PCE were shut down to ensure customers continue receiving safe drinking water.
PCE is a colorless liquid that can be harmful when ingested, inhaled or touched. Short-term exposure can cause acute effects, such as dizziness, headaches, and nausea, among other things, while prolonged exposure is known to cause cancer and neurological problems.
In 2017, the Lahontan Water Board issued a Cleanup and Abatement Order (CAO) requiring multiple responsible parties to investigate and cleanup the full lateral and vertical extent of PCE contamination originating from a property in the South Y area that formerly operated a drycleaning facility. In addition, there have been several other investigations that have occurred over many years in the South Y area. However, the investigations have been site-specific or localized investigations and have failed to evaluate the full extent of the regional PCE contamination.
“This will be the first comprehensive regional investigation of the South Y area PCE contamination and should provide valuable information allowing the Lahontan Water Board, water suppliers, and other parties to better address the contamination through water treatment and cleanup,” Kouyoumdjian said. “We are pleased to lead this effort and are looking forward to a very productive investigation.”
The Lahontan Water Board received the grant money from SCAP, a relatively new program established by Senate Bill 445 (Hill, 2014) authorizing grants for projects to investigate sources of surface water and groundwater contamination, and to remediate the harm to human health, safety, or the environment caused by existing or threatened surface or groundwater contamination.
The Lahontan Water Board will coordinate with its contractor and oversee implementation of the grant-funded work, which is expected to begin in early summer 2019. The Lahontan Regional Water Quality Control Board is a California state agency responsible for the preservation and enhancement of the quality of California’s water resources in eastern California. For more information about the Lahontan Water Board visit its website.