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I lie 18 February 1997 AGE-NC Project No 95-0104 Page 6 of 22 total volume from 30 to 45 feet bsg Petroleum hydrocarbon-impacted soil volume assumptions and calculations are also included in Appendix D I Ground water has been sampled at the site on fourteen occasions Increasing petroleum hydrocarbon concentrations have been detected in ground water samples collected from VW-1, which has been monitored during the last two monitoring events Petroleum hydrocarbon concentrations have I declined in ground water samples collected from monitoring wells MW-1 through MW-4 However, ground water has been above the screened intervals in wells MW-2 through MW-4 since April 1994, therefore, samples collected from these wells during this time may not be representative of actual ground water conditions ' 5.0. POTENTIAL IMPACT ON NEARBY SURFACE AND GROUNDWATER Typically, ground water would represent the migi ation medium for contaminants over significant horizontal distances Sites that are located in up-gradient or cross-gradient directions from the subject -� property are not likely to be negatively impacted by the subject pi operty The nearest surface water I feature to the site is the Stockton Diverting Channel located approximately 3,500 feet cross-gradient from the site Based upon the distance from the site, it is very unlikely that impacted ground water at the Marlowe site represents a threat to the integrity of water in the Diverting Channel IDrinking water near the site is supplied by the City of Stockton (California Water Service CWS) from municipal wells First encountered ground water is not used for drinking of irrigation, although ' all ground water in the State of California is coiisidei ed to be of potential beneficial use CWS well 979 is located between Cherokee Road and Waterloo Road approximately 2,000 feet north of the site and therefore is not likely to be affected by site conditions Furthermore, there does not appear to be any down-gradient municipal city wells within a one-mile radius of the site 6.0 SOIL REMEDIATION ALTERNATIVES 6 1 SOIL. VAPOR EXTRACTION ISoil vapor extraction (SVE) is a well accepted method of treatment for hydrocarbon-impacted soil and has been used at numerous sites with an excellent rate of success The method is most effective Ion volatile hydrocarbons in permeable soil 611 PRINCIPLES • Y For most SVE systems, Y a vacuum blower is used to volatilize hydrocarbons in the vadose I I