WORK PLANS_CASE 2 FILE 2 - Laserfiche WebLink

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Mr. Ron Rowe C A M B R I A June 19,2000 Soil Borings: Approximately six soil borings will be advanced at the locations shown on Figure 1 using hydraulic-push methodology (Geoprobe). The borings will be advanced to a depth of approximately 45 feet, if subsurface conditions allow. Continuous cores will be made in each boring and sediments encountered will be logged in the field. If a competent aquitard is encountered, such as a low permeability clay greater than 3 feet in thickness, the boring will be terminated. After each boring is completed, it will be grouted from the bottom to near the surface using a tremie pipe. Soil Sampling: Selected soil samples will be submitted for chemical analysis based on field observations of staining and odor, stratigraphic considerations, and field screening results using a photo-ionization detector(PID). In particular, attempts will be made to collect a soil sample from the capillary fringe. The depth to capillary fringe will be estimated based on depth-to-water measurements made in the onsite monitoring wells prior to drilling. Groundwater Sampling: Grab groundwater samples will be collected from a few feet below the top of the water table,encountered in each boring. Monitoring Well Construction: Based on the results of the soil boring. phase of assessment, groundwater monitoring well locations will be selected with the concurrence of the SJCPHS. The wells will be constructed of 2-inch-diameter schedule-40 PVC and the well head will be sealed and locked beneath a traffic-rated vault. Depth to groundwater, as measured in the three existing monitoring wells, has ranged from approximately 15 to 20 fbg. In addition, silty to gravelly sands were encountered in borings for the onsite wells at a depth of approximately 26 feet. In an effort to ensure adequate well penetration into the sandy stratum encountered previously, to keep the top of the wells screens above the highest observed water levels onsite,and to keep the maximum length of well screen to 20 feet, we propose an approximate well screen interval of 15 to 35 fbg. Actual well screen intervals may be modified based on field observations. Cambria will be prepared to install a variety of slot sizes and screened intervals, as required by site conditions. Chemical Analysis: The soil and groundwater.samples will be analyzed as follows: TPHg by EPA Method 8015; • BTEX and MTBE by EPA Methods 8020; and • Samples with reported concentrations of MTBE will be re-analyzed using EPA Method 8260. • Grab groundwater samples and water samples from the new and existing monitoring wells will be analyzed using EPA Method 8260, full scan. If any analytes are detected, the quarterly monitoring program for the site will be adjusted to include analysis for those compounds. 3