by Richard Uhlhorn
“We think the lake is protected,” said Russ Shropshire, a project manager with Leidos, the technology company retained by RELLC (Resource Environmental) to examine and address the release of petroleum products in the downtown Chelan area.
First documented in 1987 when a leak was discovered from a gasoline underground storage tank at the Chevron Service Station located at the corner of Sanders and Woodin Avenue, Chevron entered into an agreement with the Department of Ecology (Ecology) to complete remedial investigations.
A summary and status of the environmental investigation activities at the Chelan Chevron Site were shared with Chelan City Council at its August 3 City Workshop.
The Chevron site is approximately 10 acres in size in the downtown area and is being conducted under the direction of Ecology which has been an open Cleanup Site within Ecology’s Toxic Cleanup Program.
Fifty groundwater monitoring wells have been installed over the years and 36 currently exist to evaluate soil conditions for on-going assessment of groundwater conditions up to 75 feet below the surface.
The investigation has also determined the existence of diesel fuel or #2 heating oil in the vicinity of the property at 136 E. Johnson Avenue. Other possibilities included abandoned heating oil tanks or other undocumented underground storage tanks.
Frontier Communications has additionally been named as a potential liable person for the site.
There are two aquifers that lie under the surface. the first is a perched aquifer with contaminated water. Called a Perched Aquifer (Groundwater that is separated from the underlying main body of groundwater (aquifer) by unsaturated rock (aquiclude). Also known as perched groundwater, perched water table.). This aquifer sits on top of a glacial deposit which is dry in its upper portion. This aquifer is heavily impacted b dissolved-phase petroleum consitituents and LNAPL (A Light Non-Aqueous Phase Liquid (LNAPL) is a groundwater contaminant such as petroleum oil, gasoline or diesel fuel that is less dense than water and is not very soluble in water.).
This water bearing zone is pinched out and wells installed to the left of this termination have historically been dry.
The second aquifer is much deeper and occurs in a sand-silt-gravel zone with a depth to water at 62 to 92 feet below the surface. This is a regional water table which flows southeast towards Chelan Falls and appears to be contaminant free which is why the investigation has concluded that contaminants are not reaching the lake or river.
“Everything that will leak has leaked,” said Shropshire.
Mayor Bob Goedde reminded the everyone that over the years there were a number of gas stations, old grocery stores and other businesses that had heating oil tanks.
Shropshire stated that they wanted public participation and whatever clean-up activities that take place are done without negative impact to the community.
- On-going work will include:
Continued LNAPI gauging and groundwater monitoring;
Further investigation of diesel/heating oil sources in the work vicinity:
Preliminary development of potential cleanup alternatives this year and next year;
Development of a soil management plan:
Underground storage tank and soil removal action at 221 E. Woodin Avenue in 2022; and
Feasibility studies for future testing, selection of cleanup options and implementation of future cleanup remedies.
Restoration timeframe for the site is expected to be on the order of 50 or more years to achieve final cleanup goals.