By Charles (Pony) Ellingson
Summary of activities since last blog update. Since my last blog update in October of 2013, Chevron has completed the following work:
- Continued quarterly monitoring of groundwater
- Performed a field investigation of soil vapor
- Developed a groundwater model
- Submitted a stakeholder-review draft Feasibility Study report
- Continued to manage and sample onsite stormwater
The following paragraphs describe Chevron’s work on the first four topics above, and ECAC’s participation in the project.
Groundwater Monitoring Results. Data from three additional rounds of quarterly sampling are now available. Sampling occurred in September 2013, December 2013, and March 2014. The December round included both point of compliance (POC) and interior wells whereas the September and March rounds included only the POC wells. ECAC occasionally observes Chevron’s field work to collect samples; however, our primary activity is to review the written data reports and provide interpretations in this blog. When appropriate, we also inform Ecology of our interpretations.
Of the 52 wells sampled in December 2013 (POC plus interior wells), TPH was detected in 14 wells which is slightly greater than the 11 (of 50) wells with detectable TPH in June 2013. The locations of the detections are consistent with contamination that is known to remain in soils. Recently installed interior well MW-525, near the WSDOT storm drain line where contamination was not removed, appears to have the highest remaining TPH concentration at 4,175 ug/L in December.
Of the 23 POC wells, only MW-510 had a TPH concentration above its respective cleanup level in September and March; and 2 wells (MW-510 and MW-518) had TPH concentrations above their respective cleanup levels in December. Monitoring well MW-510 has consistently exceeded its CUL whereas prior to December, MW-518 had been below its CUL since March 2011 (ten consecutive quarterly rounds below the CUL). The high December concentration in MW-518 appears to be a large spike in an otherwise downward trend. Although TPH is still detected in several other POC wells, the concentrations have been below the CUL for six or more consecutive quarterly sampling rounds.
The overall trend in groundwater TPH continues to be encouraging; however, as shown by the spike in concentration at MW-518, even after many rounds with concentration below the CUL, concentrations can spike upward.
Soil Vapor Field Study. Petroleum product contamination in the ground can contaminate soil, groundwater, and the vapor that exists between the soil grains. Vapor can enter buildings placed over contaminated soil at concentrations that pose a threat to human health. Therefore Washington State Department of Ecology has recently begun requiring evaluation of this risk pathway at MTCA cleanup sites. Chevron tested soil vapor at three locations on the former UNOCAL site and included results in the Feasibility Study report draft submitted in January 2014. They installed probes in areas of the highest remaining contamination. The results of the work will be reported in the FS report, which will be provided for ECAC evaluation and public comment.
Groundwater Model. A report on the groundwater model was originally scheduled for submittal by Chevron to Ecology in September, 2013. ECAC intended to review the model development and report at that time, prior to use of the model in the Feasibility Study. Although the model report was completed on November 8, 2013, it was not submitted until January 30, 2014 (as Appendix G to the Draft Feasibility Study Report also submitted at that time). Ecology approved that delay but did not inform ECAC until we asked about the missing modeling report via email in October. Chevron and Ecology’s decision to delay submittal of the modeling report by two and half months after its completion, and after it had already been used within the i draft Feasibility Study, may result in ECAC’s comments on the model being ignored. Our concerns about the reporting process and the model itself have been submitted to Ecology and they forwarded our comments to Chevron. Ecology may or may not require Chevron to address our concerns about the model. We will provide a summary of our comments and Ecology’s direction to Chevron in a future blog post.
Feasibility Study. A stakeholder-review Draft Feasibility Study Report was submitted for a review by stakeholders on January 30, 2014. The Feasibility Study provides information about the effectiveness, implementability, and cost of a select set of alternatives for final remediation. It recognizes the extensive removal of contaminated soil and groundwater that were performed as “interim actions”. When the report is finalized, Ecology will use it as part of its basis for selecting a final remedy. Ecology will publish its requirement for the final action in a Cleanup Action Plan (CAP). Both the FS report and CAP will be available for public review.
ECAC provided Ecology many comments on the stakeholder-review draft FS report. Ecology is scheduled to release its own comments, and its requirements for Chevron to complete the FS report, late in May 2014. Although Ecology provided Chevron ECAC’s comments, Ecology may or may not require Chevron to address ECAC’s comments. Ecology could decide that improvements to the FS are required in order to provide Ecology a sufficient basis for selecting the final remedy. Washington State Department of Transportation also provided comments on the stakeholder-review draft report. We will provide a summary of our comments and Ecology’s direction to Chevron in a future blog post.
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This product was funded through a grant from Washington State Department of Ecology. While these materials were reviewed for grant consistency, this does not necessarily constitute endorsement by the Department.