ARCHIVED REPORTS_PETITION FOR REVIEW OF ACTION; REQUEST FOR STAY HEARING

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Mr. Mike Bauer -2- 7 September 2010 Chevron Banta Terminal The Keylock area bio-sparge system became operational on 21 August 2009 to clean up TPHd concentrations in groundwater. Groundwater Monitoring of the cleanup in this area is conducted in two wells, MW-34UA and MW-35UA, These wells are not sampled during the second quarter. During the first quarter, TPHd concentrations in MW-34UA were within historical variations observed since monitoring was initiated during the third quarter of 2004. Compared to historical concentrations, TPHd concentrations in MW-35UA increased sharply during the third quarter of 2009, but decreased again during the first quarter of 2010. Remedial activity in the greater Site area consists of operation of a groundwater oxygenation system that was initiated in April 2004, The system consists of 65 oxygenation well points (OW-1 to OW-85)that are about 25 feet in total depth. The well points are connected to a compressor capable of delivering 41 standard cubic feet per minute of.air at 21 pounds per square inch. Chevron is conducting a dissolved oxygen (DO) monitoring study in all on-site and off- site monitoring wells. DO monitoring is conducted before and after purging. The results -of-Do-sarnpling-conductedsiu.ring six quarters are tabulated in Table 5 and displayed in figures. They show that some monitoring wells in the loading rack and former UST area generally have the lowest DO concentrations at about 0 milligrams per liter (mg/Q. DO concentrations in monitoring wells adjacent to the perimeter oxygen injection wells and at the edges of the off-site plume are generally on the order of one to two mg/L. During the second quarter, the highest DO concentrations were generally observed in B-zone wells. Our 23 April 2010 letter required Chevron to submit a Work Plan by 14 June 2010 to delineate the plume to the west and south and to remediate the off-site plume to the north. In response, Chevron submitted the 14 June 2010 Response to Comments (Response), which stated that remediation to the north of the Site is technically infeasible due to current agricultural land use. However, the Response proposed to submit a remedial action plan (RAI') that would propose increasing the delivery of oxygen in the perimeter oxygenation system. As memorialized in our 23 June letter, that date expired without Chevron submitting a Work Plan. Thus, a meeting was convened on 25 August to discuss submission of the RAP and other Site issues. During the meeting, Chevron presented chromatograms of previous TPHd detections in select off-site wells and a chromatogram of a diesel standard. Chevron stated that it believes the chromatograms of the detections do not match the diesel standard. Chevron requested to submit, by 30 September 2010, a proposal to produce additional chromatograms from a future quarterly sampling event. The additional chromatograms would be evaluated to identify other =- -npeunds, such as pesticides, that possibly are being interpreted as TPHd. In addition, Chevron requested that we contact the owner of the card lock facility at 22904 Kasson Road and ask them to evaluate the possibility that a 24 July 2008 diesel release at that facility may be affecting wells at Chevrons eastern --property-boundary-such-as-MW 7A-and-MW-7.5 --_____ During the meeting, Chevron also briefly discussed the 19 July 2010 evidence of a gasoline release that was observed in the soil overlying a 1-inch fuel line originating