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`f L n GEOMATRIX b Mr. Don Culbertson Chevron Pipe Line Company 12 January 1995 Page 2 WELL INSTALLATION A total of four new groundwater monitoring wells will be installed, replacing destroyed monitoring wells MW-4, MW-8, MW-11, and MW-12. The proposed locations for the new wells, along with all site soil and groundwater sample locations and analytical data, are "" shown on the site plan (Figure 1, Appendix B). Monitoring wells will be installed in accordance with Geomatrix protocols (Appendix A) using a hollow-stem auger drill rig boo equipped with 8-inch diameter augers. Each boring will be-continuously cored for lithologic control using a 5-foot long core barrel or a 2-foot-long split-spoon drive sampler. Each soil core will be screened for organic vapors using a photoionization detector (PID). To augment existing soil analytical data in the vicinity of the replacement wells (see site plan), soil samples will be collected from selected boreholes and depths as follows: 15 and 18 feet in MW-8 replacement, 15 and 18 feet in MW-11 replacement, and 5, 10, 15, and 18 feet in MW-12 replacement. Additional samples may be collected based on field observations and PID readings. Samples from shallower depths either already exist nearby .. or will be collected during the screening risk assessment fieldwork. Soil samples will be analyzed by a state-certified laboratory for both total purgeable and extractable hydrocarbons as crude oil (EPA Method 8015 modified) and for BTEX (EPA Method 8020). Monitoring wells will be constructed using 2-inch-diameter Schedule 40 flush-threaded PVC casing and 10 feet of factory-slotted PVC well screen with 0.01-inch slots. The wells will be screened between the depths of 5 and 15 feet. A sand filter pack (likely Lonestar #0/30) will be placed in each borehole from the bottom of the well screen to approximately 1 foot above the top of the well screen. A 1-foot bentonite seal will placed r.. above the sand filter pack. A cement-bentonite grout will be placed into the remaining annular space. The monitoring wells will be capped with locking waterproof expansion caps and will be completed above grade with locking steel "stovepipe" well covers set in concrete t• pads protected by traffic bollards. Soil cuttings generated during drilling will be temporarily contained on site in D.O.T.-approved 55-gallon drums. CPL will profile the soil residuals and dispose of the residuals in accordance with local and state regulations. After a minimum of 24 hours following installation, the monitoring wells will be developed using a combination of surging, bailing, and pumping techniques to remove sediment that may have accumulated during drilling, to consolidate the filter pack, and to enhance hydraulic communication between the formation and the well. Development will continue until the field parameters of temperature, specific conductance, and pH have stabilized and AIM the produced water is sufficiently clear. Water produced during development will be .r