ARCHIVED REPORTS_REMEDIAL ACTION PLAN

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Mr. Mark Clardy Page 4 April 3,2006 evaluate the remaining exposure pathways(direct contact and ingestion of soil and inhalation of ' vapor from soil/groundwater) and either evaluate the risk from the complete pathway or eliminate the pathway, thus eliminating the risk. Note that direct contact with soil and ingestion of soil both require essentially a direct exposure to impacted soil. Inhalation of Papor from SoillGroundwater The petroleum hydrocarbons detected at the site are in the crude oil range,which are longer chained hydrocarbons, and therefore relatively non-volatile. Very low levels of BTEX compounds were detected in the soil and groundwater detected at the site. Benzene was not detected in any of the 329 soil samples submitted for analysis. Toluene was detected in the highest number of soil samples, and was detected in only 17 soil samples. The maximum concentration of any BTEX compound detected was 8.7 mg/kg(xylenes). In groundwater, benzene was detected in four out of 41 groundwater samples collected,and only to a maximum of 0.42 pg/L. In groundwater,the highest concentration of BTEX compounds detected was 30 pg/L(toluene). Based on this information, the petroleum hydrocarbons are likely to be non- volatile, and to the extent hydrocarbons are present in the vapor phase,would likely not contain BTEX compounds. Based on the absence of benzene in any soil samples, the low concentrations of other BTEX concentrations in soil, and the low concentrations of BTEX compounds in groundwater,vapor inhalation does not appear to be a complete pathway. Therefore,this ' pathway will not be further evaluated. Direct ContactlIngestion of Soil Impacted soil was observed at relatively shallow depths, and given the anticipated land use over much of the area across which the pipeline alignment runs, direct exposure to soil impacted by petroleum hydrocarbons is a possibility. As noted above, the impacted soil does not contain any benzene,and only very low concentrations of other BTEX compounds and would therefore seemingly not pose a substantial threat with respect to human health. Nonetheless,nuisance ' considerations(i.e.,visual,odors),while not health related are factors in determining a remedial approach. SAIC and Shell propose to eliminate direct contact as a pathway and will present details on the approach below. ' Groundwater Protection The RWQCB has established water quality objectives for crude oil and diesel-range petroleum ' hydrocarbons in groundwater. The RWQCB also uses the maximum contaminant levels(MCLS) for the BTEX compounds as the water quality objectives for BTEX compounds. Groundwater impact was observed in areas B-2,B-3,B-5,B-6,B-8,B-9, and B-12,and SPH was noted in a groundwater sample from Area B-2. Groundwater concentrations in areas B-5,B-8, and B-12 were lower than in the other areas, and below 1,000 pg/L for TPH. A remedial strategy for groundwater protection will be developed in a separate document,based on groundwater data collected from monitoring wells and leachibility of petroleum hydrocarbon constituents in soil.