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hydrocarbons (TPH-D,TPH-K, TPH-MO)by EPA Method 3510/8015, and benzene,toluene, ethylbenzene, and xylenes (BTEX)by EPA Method 602. BOREHOLE ABANDONMENT On November 25, 1992, at the conclusion of the drilling and sampling activities,the temporary well casing and screen was removed from each borehole and the borings were backfilled to the surface with a cement grout containing about 5%powdered bentonite. The grout was pumped into the bottom of each borehole to prevent the possibility of bridging. The upper few inches of each borehole were backfilled with 3/4-inch gravel to match the surface of the facility. Borehole abandonment was witnessed by a representative of SJCPHSD. GROUNDWATER MONITORING WELL PROCEDURES Drilling and Monitoring Well Installation On November 24, 1992, a groundwater monitoring well (MW-1)was constructed in boring B-1 to a total depth of 20 feet(Figure 4). A diagram showing well construction details is provided on the well log for MW-1 contained in Appendix A. The 8-inch diameter borehole for the well was drilled using PG&E's Mobile B-80 truck-mounted,hollow-stem auger drill rig and the well was completed with 2-inch diameter, flush-threaded, Schedule 40 PVC casing and screen with 0.01-inch slots. The well was screened from 7%Z to 20 feet and the bottom of the well screen was fitted with a threaded end plug. The sandpack consisted of Lonestar No. 2/16 sand and was tremied through the augers from the total depth of the borehole to a depth of 6'/z feet. A 2-ft seal of hydrated bentonite clay was placed on the sandpack and the remaining annular space was filled to the surface with cement grout containing about 5%powdered bentonite. The well was finished with a traffic-rated, security box and the wellhead was equipped with a expandable, water-tight, locking cap. A representative of the SJCPHSD was present at the site to observe the placement of the cement grout seal and the construction of the traffic box. The top of casing elevation of the well was surveyed to the benchmark located on the Middle River bridge (Geodetic Survey Hub No. W474 at 22.98 ft above MSL) in order to establish an elevation control point for depth to water measurements. Well Development and Sampling Monitoring well MW-1 was developed on January 14, 1993 using a vented surge block, bailer, and a pump. Prior to well development, the depth to water was measured in the well using a Solinst electronic immersion probe(accurate to 0.01 ft) and the groundwater was checked for the presence of free product using a clear bailer. Approximately 30 gallons of water(i.e., about 15 well volumes)were removed from the well during the development process and the final discharged water was free of suspended sand and coarse silt. A sample of the groundwater was collected in a disposable bailer and carefully decanted into two 40-m1 VOA vials with caps equipped with Teflon septums and two 1-liter amber bottles with Teflon- cca/08/23/93/9449arpt.doc/mkn4 54