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Facility and PBR Units Closure Work Plan r 1848 and 1856 Field Ave., Stockton, California Prior to Tyco's removal of the secondary containment systems,the schedule for facility closure requires that .. Earth Tech sample the native soil under the plastic liner.Further schedule information is presented in Section 6.Initially,a subcontractor using a jackhammer or other heavy equipment will be used to remove the concrete ` in an area covering a few square feet. The concrete and underlying sand will be removed from this area.The underlying plastic will be cleaned,cut to allow sampling,and the plastic edges elevated to prevent sand from getting under the plastic.Then,Earth Tech will collect confirmation samples from the first native soil beneath each of the three tanks.One sample from beneath each tank will be analyzed for pH(by EPA Method 9040B) and copper EPA Method 6010B), the two analytes previously detected at elevated levels in the area. The analyses will be performed by a state-certified laboratory.Analytical results will allow Tyco to determine if further action is necessary in this area. r. Earth Tech also intends to collect three samples from areas of the site with no chemical usage history to determine natural pH levels in site soil,potentially for comparison to the pH analysis results for the samples ■, collected under the these tanks. ` If the confirmation samples determine that a release from the secondary containment system has occurred, Tyco will evaluate the appropriate remedial options. If a minor release is found, we anticipate that soil excavation will be the remedial options selected. We anticipate excavation will continue until residual soil meets the cleanup goals presented in Section 4. If such an excavation is necessary,Tyco will solicit County input regarding such an action prior to performing any excavation,disposal and confirmation sampling. Once the Tyco demolition contractor mobilizes to the site,on approximately September 10,Earth Tech will r observe the Tyco-coordinated removal of the concrete, sand and plastic liner which form the containment system for the former chemical storage tanks adjacent to 1848 Field Avenue.The removal will be documented, .. including with photographs,to show that there is an integrated sand/plastic layer extending beneath all three tanks.The excavated sand material will be temporarily stored on-site,as in bermed drum storage areas south of ` the former chemical storage tanks. The excavated sand material will also be sampled prior to disposal, to determine the most appropriate disposal method for this material.All excavated material will be disposed in accordance will all applicable requirements. LJWOW690991GenemAFie1d WPiFiefd Ave WPAug03 rev2.dx 7 August 1003