SITE INFORMATION AND CORRESPONDENCE

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Ms. Jill Jefferson 49 - 2 - 00 13 March 2000 These results suggest one or more releases in the tank farm area, in addition to the already-known source area in the manifold area.',Although bermed, the tank farm is not lined, and it is known to become flooded occasionally during wet weather. Studies in the KMEP facility area and adjacent terminals report that the potentiometric surface in the B-zone is slightly lower than that in the A-zone. This combination of circumstances indicates a potential for downward movement of contaminants and is a source of concern. The groundwater flow direction of generally eastward indicates that the plume probably will go offsite, if it has not already done so. 6Pork Plan: The stated objectives of the proposed work are to assess the nature and extent of the source in the manifold area,to confirm and assess the apparent source in the northern portion of the tank farm near boring B9, and to modify the existing monitoring well array. KMEP proposes a phased approach. In the first phase, dual-tube direct-push techniques will be used to advance borings to a depth of approximately 30 feet. This will-allow for near-continuous soil sampling and PID screening. KMEP proposes to analyze selected soil samples chosen on the basis of visual and PID observations, with at least one soil sample per boring to be analyzed from the interval immediately above the water table. Groundwater grab samples in both the A and B zones are proposed. KMEP proposes to begin this work within six weeks of Board approval of the Work Plan. This schedule may take the work into the dry season. In view of the known seasonal fluctuations of the water table, I suggest that at minimum one additional soil sample be analyzed from the zone of highest known water table elevation or at the to of the capillary fringe. > P P azY g I concur with the proposed Phase I boring locations. In Phase II,KMEP proposes to install an unspecified number of additional A and B zone monitoring wells whose location will be determined by the results of Phase I. Other than using hollow stem auger drilling and installing the casing in the open borehole,the Plan provides little specific information about the well construction. Therefore, before additional wells are installed, KMEP must submit a plan describing the proposed locations and providing more specific information on proposed screen lengths. Justification should be provided for the proposed sand pack based on lithology encountered in the Phase I borings, and the manner of emplacing the pack and bentonite seal (whether by tremie pipe, which is preferred) or free-fall should be specified. A sufficient length of time must be provided to allow complete hydration of the bentonite, whether pellets or powder. If pellets are used, appropriate steps must be taken to avoid bridging. The Work Plan suggests that some existing wells may be proposed for abandonment. We will require KMEP to submit a rationale for each well so proposed. Chemical analyses: The Work Plan proposes to analyze groundwater samples for TPH-gasoline and TPH-diesel using EPA Method 8015 and BTEX and MtBE using EPA Method 8260B. This is acceptable. For this investigation, I request that silica gel wash not be used with the TPH analyses. For the Method 8260 analytes, please report all peaks. Maximum reporting limits for the BTEX compounds and all the oxygenates except TBA should be 0.5 µg/L. For TBA, the lab should achieve 5 gg/L.