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2 WELL COMPLETION Monitoring well installation permits, were obtained from San Joaquin Department of Environmental Health before drilling was initiated. Drilling was completed by Woodward Drilling, Inc. of Rio Vista, California using a CME-75 drill rig. Hollow stem augers were used to advance each borehole. Down hole drilling equipment was steam cleaned between each boring. Soil samples were collected using a standard split-spoon technique (SPT) sampler. The split spoon sampler was washed with water before each sample was collected. During drilling, sample recovery percentage and blow counts for each sample were recorded on the boring logs. Soil samples were logged using the Unified Soil Classification System (USCS) based on: type, color, grain size, stiffness, moisture content, and plasticity when appropriate. Detailed well boring logs are provided in Appendix A. r ' 4 The first well boring MW-11 was completed on April 10, 2006. The boring was s advanced to 46.5 feet below ground surface (bgs) using 8 inch outer diameter hollow kstem augers. 1.5 foot soil samples were collected as the auger advanced in 5 foot intervals and logged for grain size, color, hardness, moisture content and plasticity where appropriate. Soils were described using the Unified Soil Classification System (USCS). Encountered geology was as follows: sand was encountered from surface to r 7.5 feet bgs;from 7.5 to 13.75 feet bgs sandy silt was encountered; from 13.75 to 23 feet bgs silty sand was encountered; from 23 to 45 feet bgs sandy silt was encountered;from 45 to 46.5 feet bgs sand was encountered. Semi confined ground water conditions were s observed with first ground water encountered at 26 feet bgs and the static water level r E inside the boring was measured at 21.2 feet bgs 20 hours after the boring was € completed. A monitoring well was constructed on April 11, 2006. The 8 inch test boring was reamed using a 12 inch outer diameter hollow stem augers with a wooden plug placed in the lead bit, the 12 inch boring could not be advanced beyond 39 feet bgs [ as the bottom of the well had been filled with slough material from the over drill. The monitoring well (MW-11) was constructed using 4 inch diameter Schedule 40 PVC f casing, screen consisted of 4 inch diameter Schedule 40 PVC, 0.020 inch machine slotted screen. Bottom of casing was set at 38.5 feet bgs with 15 feet of screened interval from 38 to 23 feet bgs. The filter pack consisted of RMC #3 natural beach sand, filter pack was placed from 39 to 19 feet bgs. The well seal consisted HoleplugTM bentonite chips from 19 to 14 feet bgs, followed by Basalite TM type II cement from 14 feet to 0.8 feet bgs. Well protection features were constructed and consisted of a lockable above grade steel casing and four steel bollards. Chit of Riverbank Wastewater Treatment Plant Monitoring Well Installation May 2006 DE Project No.:109-06 7 Rev.0