By Greg Glass
ECAC awaits the formal issuance of a two-year continuation Public Participation Grant from Ecology to cover activities through June 2011. It is typical for the formal grant agreement to take some months past the July 1 initiation date before completion.
A meeting has been scheduled among Ecology, Chevron and its consultant (ARCADIS), and ECAC for October to discuss review comments on two recent reports submitted to Ecology by Chevron: 1) the Phase II As-Built Report for the recent Interim Action cleanup of the Lower Yard (May 13, 2009), and 2) the Additional Site Investigations and Groundwater Monitoring Report (March 27, 2009). The ground water monitoring results to date will also be discussed at that meeting. WSDOT has been hit by budget reductions to address the current revenue problems in Washington and will have limited availability to continue its ongoing project reviews.
The Round 5 ground water monitoring results for June 2009 sampling of 40 monitoring wells at the site were reported to Ecology in mid-August. When the results from Round 6 sampling in August are available, the first year of the planned two-year ground water monitoring program will be complete. A Year 1 ground water evaluation report is scheduled to be submitted to Ecology by Chevron early in 2010.
Two wells installed in the southeast Lower Yard after Interim Action soil excavations were completed (MW-500 and MW-501) continue to show high (mounded) ground water elevations that are atypical for the rest of the site. ARCADIS recently installed 8 piezometers to explore conditions near those wells and provide additional information to support interpretations of the cause of that ground water mounding. The potential effects on ground water flowpaths in the central Lower Yard from the impermeable liner installed along the WSDOT storm drain line are still being discussed.
In the Round 5 sampling event, one well had a small amount (0.01 foot) of LNAPL product detected. That well had a total TPH concentration somewhat above the ground water cleanup level (CUL); quite a few other wells had higher total TPH results but no product detected.
Ecology performed a recalculation of CULs for each well in each sampling round, based on the reported TPH composition at that well. The number of wells among the 40 with analyzed samples that exceeded those sample-specific CULs has been fairly steady (lower in Round 2); for the 5 rounds so far, the number of exceedances are 17, 9, 17, 14, and 15, in sequence. The two areas with notably higher total TPH concentrations – the slops pond (MW-510) and the southeast Lower Yard (MW-129R, MW-510, MW-500, MW-135, and MW-136) remained high in Round 5. In fact, except for a high initial Round 1 measurement at MW-501 of more than 8,000 ug/L, all 6 of those wells had their highest TPH values in Round 5. Well MW-510 at the slops pond exceeded 25,000 ug/L, a concentration approaching 50 times the calculated CUL. The 5 southeast Lower Yard wells exceeded their CULs by factors of about 3.9 to 7.5 in Round 5; 4 of the 5 TPH concentrations were above 2,600 ug/L and the remaining one was almost 2,000 ug/L. The potential source(s) for the continuing TPH observed in the southeast Lower Yard remains a matter of interest; trends at those wells over the continuing sampling rounds will be closely tracked. The source of high TPH contamination at MW-510 is very likely associated with the unremediated former slops pond.
For the other 9 wells exceeding CULs in Round 5, three had their maximum exceedance factor in Round 5. Wells exceeding their CUL in Round 5 included LM-2 at the northwest corner of DB-1; MW-507 and MW-508 at the downgradient extent of the eastern plume wells; MW-514 and MW-517 in the middle plume system; MW-143 at the upgradient end of the west plume system; and 3 wells along the western site boundary, MW-147, MW-104, and MW-518. The CUL exceedance factors for those 9 wells in Round 5 were less than those for the two areas of highest TPH noted above; the range of exceedance factors was about 1.1 to 2.4. The three wells with maximum exceedance factors in Round 5 were MW-507, MW-508, and MW-517. Evaluations of the longer-term trends at all monitoring wells, and any seasonality effects (related to variations in ground water elevations and the infiltration of precipitation), will be supported by data from the total of 12 sampling rounds over two years.
Previously reported high benzene concentrations at well MW-20R did not persist to Round 5, when benzene was not detected. The highest Round 5 benzene result was at the slops pond area well, MW-510, at about one-third of the benzene CUL.
The Round 6 sampling results should be available by mid-October. All questions and comments on these blog postings and the status of the UNOCAL Edmonds site are welcome.
On the left margin of the blog is the Monitoring Well site that can help in giving a visual orientation of the wells discussed.
Feel free to contact: ( HYPERLINK "mailto:gglassenviro@comcast.net" gglassenviro@comcast.net)
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