Other possible sources of PCE contamination identified in South Lake Tahoe
Source: http://southtahoenow.com, March 7, 2019
With a 400 acre plume of tetrachloroethylene (PCE) in some of the South Lake Tahoe groundwater, agencies tasked with protecting the local drinking supply updated the community on cleanup efforts and the status of the plume Wednesday evening.
Authorities originally identified the chemical entered the groundwater at the site of the old Lake Tahoe Laundry Works which was located at the South Y Center that is now home to Raley’s and KMart.
During the meeting, Scott Ferguson of the Lahontan Regional Water Quality Control Board revealed some other points of entry for the chemical are around Tucker and Glorene avenues, near where the former Big O Tire store and the current Napa Auto Parts store are located as well as over at the current site of TJ Maxx where an old dry cleaners was located.
Ferguson said Lahontan, who has been working on the chemical in area water since its discovery in 2009, said they should know by this summer on the exact sources and have a plan in place to remove from the groundwater.
PCE is a man-made chemical that was used from the early 1960s through the mid-1980s as a solvent for dry cleaning clothes and degreasing metal. During the late 1980s, concerns about the toxicity of PCE led Federal and State environmental agencies to list PCE as a probable carcinogen and as a toxic pollutant.
The drinking water in South Lake Tahoe is safe and PCE levels are far below the minimum acceptable amount even though 99 percent of it comes from groundwater. The aquifer holding that water is below sedimentary soil that is great for groundwater, but susceptible to contamination. When the PCE hit the soil, it moved into five wells, three operated by Lukins Brothers and two by Tahoe Keys Property Owners Association (TKPOA).
The plume is deep, from 26 feet to 52 feet deep, 140-180 feet below the surface.
During Wednesday’s meeting, Jennifer Lukins from the Lukins Brothers Water Company and Kirk Woolridge from TKPOA joined Ferguson, Susan Rybarski from Desert Research Institute (DRI) and Ivo Bergsohn and John Thiel from South Tahoe Public Utility District (STPUD).
About 40 residents joined the meeting to learn more about their water and the processes underway to ensure clean water.
TKPOA has spent about $789K of their funds to put in filtration systems in their three remaining wells. Woolridge said they haven’t had grant funding available to reimburse them for their expenses.
Over at Lukins, Jennifer said they are going to apply for grants to get their wells back on line. To supplement water needs they are purchasing water from STPUD to serve their customers.
Rybarski went through four scenarios that are being evaluated as possible plans to remove the PCE. She showed the public the models which were, 1) doing nothing, 2) using 21 shallow extraction wells, 3)replace the Tahoe Keys well #1 and the Lukins well #5, and 4) maximizing current PCE treatment by increasing pumping and Tahoe Keys well #2 and Lukins well #5 up to 90 percent of treatment capacity and reduce pumping at the STPUD wells.
She said doing nothing still reduces the size of the plume over the next 20 years, as does the second scenario though the remaining plume takes on a different shape. Replacement wells would pump water from an uncontaminated aquifer zone but the plume wouldn’t change much from today over the next 20 years and there would be little effect on the PCE. The final scenario from DRI greatly reduces the plume as it has the greatest amount of mass extraction.
Testing on those four scenarios should be completed in April.
As Lahontan moves towards a plan they will hold another public meeting before the summer. So far Ferguson says they have pulled out about 900 pounds of PCE from the ground near the Lake Tahoe Laundry Works site. The heirs to that business are paying for that process but going forward in other areas there will need to be a clear chain of contamination to determine who is responsible for other remediation.
One are of possible concern are the number of private wells left in the Meyers and South Lake Tahoe area. It is unknown if the owners are aware of the PCE issue and if they test their water.
Lukins, TKPOA and STPUD all test their water and it has remained in the safe zone even after the PCE was discovered in the ground water.
The plume of PCE has already reached the canals of Tahoe Keys and most likely all the way into Lake Tahoe, but the size of the lake will further dissipate the chemical and it won’t be noticeable.
In Sacramento around Aerojet Rocketdyne, several chemicals have been found in the groundwater between their location south of US50 and the American River. PCE is just one of them. States across the country have been dealing with PCE in groundwater and it is not limited to Lake Tahoe.