Laserfiche WebLink
' Californitegional Water Quality Coreol Board <br /> Central Valley Region <br /> Karl E. Longley,ScD,P.E.,Chair <br /> Linda S.Adams _ Arnold <br /> 5'ecreraryjo, Sacramento Main Office —, <br /> la wronmen/al 11020 Sun Center Drive 4200,Rancho Cordova.Calif ��9 h4��4 Schwarxenegger <br /> �� 1/I <br /> Phone(916)464-3291 •FAX 916 464-4845 L`�- J L� " O Governor <br /> Praleelion ( ) <br /> hup://www.waterboards.ca.gov/centralvalie% <br /> OCT 1 5 2007 <br /> 4 October 2007 <br /> ENVIRONMENT HEALTH <br /> Mr. Mark Inglis Mr. Jay A% MfT/SERVICES <br /> Chevron Environmental Management Company Stone Brothers Management Company <br /> 6001 Bollinger Canyon Road 1024 W. Robinhood Dr. <br /> San Ramon, CA 94583 Stockton, CA 95207 <br /> WORK PLAN REVIEW, CLEANUP AND ABATEMENT ORDER (CAO) NO. 5-00-0707, <br /> FORMER UNOCAL STATION #5098 AT 5606 PACIFIC AVENUE, AND FORMER <br /> MONTGOMERY WARDS AUTO SERVICE AT 5400 PACIFIC AVENUE, STOCKTON, <br /> SAN JOAQUIN COUNTY <br /> I reviewed the Work Plan for Replacement of Decommissioned Monitoring Well MW-15 <br /> (Workplan), received electronically on GeoTracker from ENSR, Chevron's consultant, on <br /> 10 September 2007. ENSR submitted the Workplan in response to my request for an <br /> upgradient replacement well for MW-15. <br /> In February 2007, 1 was informed by Robert L'Heureux, ENSR that monitoring well MW-15 <br /> would be destroyed as a result of a City of Stockton street widening project on the northwest <br /> corner of Robinhood Drive and Pacific Avenue in Stockton. My 16 February 2007 letter <br /> approved the 15 February 2007 Workplan to decommission MW-15. On 21 February 2007, 1 <br /> observed a portion of the well decommissioning, which included over-drilling the well casing <br /> down to 69 feet below ground surface (bgs), prior to grouting. When asked onsite by Robert <br /> L'Heureux, with ENSR, if a replacement well was necessary, I responded yes and requested a <br /> workplan for the new well. <br /> A new monitoring well, MW-15R (Enclosed Figure 2) will be installed approximately 115 feet <br /> south of former MW-15 and nearer to the corner, due to construction of a new building. The <br /> Workplan states that the boring for MW-15R will be constructed by air knife from surface to <br /> 8 feet bgs; then by 6.5-inch diameter Hollow Stem Auger (HSA) drilling from 8 to 40 feet bgs; <br /> followed by installation of a 2-inch diameter poly vinyl chloride cased well, screened from 25 to <br /> 40 feet bgs. <br /> Comments: <br /> 1) The Workplan does not include an explanation why the new well will be screened from <br /> 25 feet to 40 feet bgs, which is 29 feet shallower than the well it replaces. Please <br /> provide the rationale for completing the well at a shallower depth in a revised Workplan. <br /> Note that MW-15's depth to groundwater over the last three years varied from 32 to 37 <br /> feet bgs. An alternative screened interval might be from 28 to 43 feet bgs, depending <br /> on the actual site lithology. <br /> California Environmental Proteclion Agency <br /> ped Recycled Paper <br />