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Stantec Well Destruction Work Plan Stockton Charter Way Commingled Plume August 12, 2011 approximately twelve feet (ft) above mean sea level on flat terrain. The area surrounding the Site is of mixed residential and commercial use. Former ARCO Service Station No. 2168 is currently comprised of an active car wash facility; no underground storage tanks (USTs) or fuel dispensers are present on the property. Chevron Facility#9-2033 is currently comprised of a station building, four fuel dispensers on two islands, and three USTs. Former Colombo/Toscana Bakery (Sara Lee) is currently comprised of a warehouse building; no USTs or fuel dispensers are present on the property. The ARCO- branded service station [former Texaco (Shell)) is currently comprised of a station building, a car wash, four fuel dispenser islands, and four USTs. This station is currently anticipated to be redeveloped during the summer of 2011. Site history and previous investigations are summarized in Appendix B. Table 1 summarizes the soil boring and well construction details. 2.0 PROPOSED SCOPE OF WORK 2.1 Basis of Proposing an Alternative Well Destruction Methodology SJCEHD offered the following requirements for destroying CMT wells in an email dated July 7, 2011. 1 Install a low pressure (7 grain/foot) wire-line explosive cord down the center of the CMT casing from top of upper most screened interval to full depth of the well's original construction depth. 2 Fill all chambers of the CMT well with a thin mix (94 pounds of Portland Type IIN cement110 gallon potable water mix). 3 Detonate the cord. 4 Drill out/core out the entire depth of the well with same size diameter as originally installed. 5 Finish off the upper most five ft of the drilled out well to best match surrounding conditions. A California-license drilling contractor and OSHA-approved well destruction provided SJCEHD assurance that the requirements above would not endanger subsurface utilities and underground storage tanks. Stantec and the responsible parties (RPs) of the Site believes that the offered well destruction requirements are unacceptable based on the following and that a more appropriate methodology will be implemented for destroying wells SMW-18-80 and SMW- 18-120 as approved by SJCEHD. 1. Stantec and RPs believe that the removal of the entire well contents is unnecessary for the purpose of preventing potential vertical migration of petroleum hydrocarbons. Based on the Site Conceptual Model dated January 14, 2011, "The presence of water in the fine-grained materials, as noted on many of the boring logs, indicates that the Stockton Charter Way Commingled Plume Well Destruction Work Plan.doc 2