Update: The Washington Department of Ecology has received fingerprint analysis of the gasoline samples and is communicating with affected parties to determine next steps.
According to the City of Walla Walla, Washington Department of Ecology has continued to oversee the pumping operation until extraction from the monitoring wells, or other means of source control, are implemented. Three of the monitoring wells drilled around the Chevron station are now being explored as possible candidates for the extraction.
The City adds that an additional sump, containing product, was identified in the basement of the Marcus Whitman Hotel. Clean Harbors began the process of recovering product from that sump.
As of the most recent update from the City of Walla Walla, approximately 20,000 gallons of gasoline/groundwater mixture has been recovered to date. It has been estimated that between 1,500 to 3,000 gallons which have been recovered is gasoline. Again, the City is emphasizing that this is only an estimate, and will likely be revised in the future.
Staff at the Wastewater Treatment Plant have also continued to monitor the wastewater system throughout the incident area and have yet to observe any evidence of gasoline entering the system. Additionally, monitoring of Mill Creek continues to detect no evidence of contaminants entering the waterway.
The response team is discussing possible methods of creating a “cone of depression” for recovering product and directing the potential plume.
Clean Harbors has now mobilized what’s called a “granulated active carbon filtration system” in order to treat the impacted water that has been recovered so far.
Air monitoring also continues to be conducted regularly by the Walla Walla Fire Department at buildings surrounding the affected area. So far WWFD has detected no trace of unsafe conditions, therefore monitoring in these buildings has ended and the owners and/or tenants of those buildings have been notified.
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