WORK PLANS - Laserfiche WebLink

Home Browse Search

quarterly monitoring on September 1, 2002 monitoring wells MW-1, MW-2, MW-5D, MW-8D, MW-8S, MW-9D, MW-9S had positive analysis for TPHg and 1,2-dca. Monitoring well MW-7D had a positive analysis for 1,2-DCA. Quarterly monitoring of this site has a history of large variation in groundwater elevation between quarters. This variation is much greater than what is considered normal for the Stockton area. SCOPE OF WORK Item 1. Install five CPT's to a depth of 100' to 135' with soil and groundwater sampling (assumed at four samples of groundwater and four soil samples per CPT). Item 2. Drill two eight-inch soil bores with depth determined by the CPT results (assumed to be between 100 and 135 feet below the surface). The two deep monitoring wells, MW#1D and MW#10D, will have a one-inch PVC casing that is to be installed at the bottom of the soil bore with five feet of screen. MW#10S, a shallow monitoring well with a one-inch PVC case, is to be installed with the bottom of the casing sixty feet below the surface. This shallow monitoring well will have twenty feet of screen. A typical groundwater surface is forty to fifty feet below the surface (See drawing of monitoring wells attached). CPT Locations and Restrictions All the proposed CPT's are located within the tire shop area or under the canopy of the fuel island. The floor in both the tire shop and the canopy area consist of 8" to 10" concrete slab without reinforcing. The tire shop has a restricted roof structure height of +/- 16'. The canopy has a restricted height of about 20' (See layout of CPT's attached). CPT Sampling Procedure The standard CPT soil sampling and water sampling procedure will be used with the sample extracted at depths determined during the Cone Penetrometer run. Soil Boring Location and Restrictions The proposed location of soil bore for MW#10S & MW1OD is thirty to forty feet west of the existing monitoring wells, MW#9S & MW#9D. This location may be modified slightly to fit the building conditions. This location is limited by a sixteen-foot height restriction on a drill rig. MW#1 is a shallow well under the canopy and proposed MW#1D is to determine the vertical extent of the plume at the same location. Sampling of Soil Boring Existing soil borings have shown contamination starting at twenty-five below the surface. It is proposed that sampling begin at twenty feet below the surface. Samples will be extracted with a split spoon sampler at five foot intervals to the bottom of the soil boring. Soil Sample Transportation and Analysis Soil samples will be extracted with a metal liner that will be covered at the ends with a Teflon sheet and secured with a standard plastic cap. The cap will be secured with duct tape and the samples stored on ice for transport under a chain of custody to a state-certified laboratory. The samples will be analyzed by EPA methods 8015, 8020, and 8260 oxygenates (incl. 1,2-DCA EDB) 2