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IAWGR <br /> �WNFM J.OPCW aerarfam <br /> August 20, 2010 <br /> Mr. Michael Infurna <br /> San Joaquin County Environmental Health Department <br /> 600 East Main Street <br /> Stockton, CA 95202-3029 <br /> SUBJECT: RESPONSE TO JULY 30, 2010 SAN JOAQUIN COUNTY LETTER <br /> UST Site#3 <br /> Port of Stockton <br /> Port Road 13 at G Street <br /> Stockton, California <br /> WGR Southwest, Inc., Project No. 704.PRI.03 <br /> SJCEHD Site Code#1282124 <br /> Dear Mr. Infurna: <br /> On behalf of the Port of Stockton (The Port), WGR Southwest, Inc (WGR) has <br /> received the San Joaquin County Environmental Health Department's (EHD) <br /> response letter, dated July 30, 2010, which approved the pilot test work plans <br /> submitted in the Updated Site Conceptual Model and In-Situ Chemical Oxidation <br /> (ISCO) Pilot Test Work Plans (SCM-WP), dated May 10, 2010. Since submittal of <br /> the SCM-WP, the Semi-Annual Monitoring Report — Second Quarter 2010, dated <br /> June 22, 2010, has been submitted. Review of results from this report strongly <br /> indicate a declining trend in petroleum hydrocarbons from wells MW3-6 and MW3-9. <br /> These wells are located in the residual zone of the plume, where injection of <br /> compressed oxygen has been approved by the EHD for pilot scale remediation. We <br /> feel that it would be prudent to postpone initiation of the compressed oxygen <br /> injection phase of the pilot test and, instead conduct monitoring and sampling of <br /> wells MW3-6 and MW3-9 on a quarterly basis. If downward trends in these wells <br /> continue, oxygen injection may not be necessary and natural attenuation may prove <br /> to be sufficient in mitigating contaminants of concern and moving the case towards <br /> closure status. We feel that this approach would potentially save unnecessary costs <br /> and time to the client, as well as the State Cleanup Fund. Attached are time trend <br /> charts of these two wells (MW3-6 and MW3-9) illustrating how concentration levels <br /> appear to be nearing the targeted levels for case closure. A site map has also been <br /> included for your reference. <br /> Please bear in mind that although the dissolve oxygen phase of the pilot test would <br /> be temporarily postponed, pending well monitoring results, the proposed Ozone- <br /> Peroxide phase in the core/source area would still be initiated immediately as <br /> approved in the County's July 30, 2010 letter. <br /> 704.PRI.03 I Response to 7-30-10 County letter <br />