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Project 113-26-04, 05, Page 8 November 17, 1995 groundwater existed in these sandy soils at about 6.5' BGS Gasoline contamination was apparent within these soils at most of the investigation locations A similar sand layer was encountered at MW-8 from about 9-10 feet BGS Below this sandy layer and down to about 19 feet depth were mainly layers of clay, (CL), or silt, (ML), colored light yellowish brown to brown with some mottling. These layers were up to a few feet thick- Very fine grained sand could be seen in these layers at about 1070 of total composition. The clays and silts were stiff to crumbly with wet spots or patches and small capillaries which contained free water At about 19-20 feet BGS there was a sandy layer very much lake that which existed between 5 and 7 feet BGS This sand layer was mostly very fine to medium grained, light yellowish brown in color, and was saturated At MW-6 there were one to three foot thick, saturated layers of light yellowish brown sandy clay and sandy silt between about 20 and 25 feet depth which were sealed from the borehole with bentonite prior to well installation to 15 feet BGS Groundwater Monitoring Well Installation, Soil Boring Abandonment Upon termination of drilling, the wells were installed through the augers to total drilled or backfilled depth (15 or 20' BGS) MW-6 was backfilled from 25 feet BGS up to 15 feet depth with bentonite chips FIush threaded, two or six inch I D schedule 40 PVC casing (0-5 feet BGS) and well screen (5-15' or 5-20' BGS of machine slotted 0 02") were inserted through the augers to total depth SRI #8 washed sand was poured through the augers, around the casing up to 4 feet depth BGS, or about one foot above the perforated interval About 1 foot of medium bentonite chaps were placed above the sand, then hydrated with tap water. Portland cement grout filled the remainder of the well annulus up to original grade A surveying and water level measurement notch or mark was made at the top of casing Locking well caps and flush mount, water tight, traffic rated well covers comprised the surface completions Hand augered soil borings were backfilled from total depth to original grade with cement grout and/or concrete The grout seal placement was inspected by the permitting agency's representative. Groundwater Sampling On September 20, 1995 the four new wells were developed Development was accomplished by mild surging and pumping of groundwater A plastic submersible pump was lowered into the well to the bottom, then raised and lowered over the screened interval whale pumping from various levels The surging was intended to loosen and suspend residual soil within the well and draw residual fines from the sand pack into the well Groundwater was pumped at about 15 gallons per minute (gpm) until about 45 gallons had been removed from each of MW-5, 6, and 7 Fifty five gallons was pumped from MW-8 At each well the water was noted to be clear . or clearing The groundwater was pumped into labeled drums Parker Environmental Services, 190 East 7th Street, Pittsburg, CA 94565-2317 Phone (510) 439-1024 Fax (510) 439-2566