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Geon ica(Technks lite. Page 2 Wel?lnstallation Report City of Escalon Project No. 750.2 January 30,2001 monitoring wells and one deep, discretely screened monitoring well. Ms Duncan approved the work plan on July 7, 2000. The work was performed during the week of October 16, 2000. 2.0 SCOPE OF INVESTIGATION 2.1 Soil Boring Installation Water Table Wells In an effort to define the lateral extent of gasoline range petroleum hydrocarbons beneath �. the site, GTI installed two monitoring wells, MW-4 and MW-5, to 78 and 75 feet below grade, respectively. The well borings were drilled using an 8-inch outside diameter, continuous flight, hollow stem auger owned and operated by V&W Drilling (C57# 720904). �* Soil boring permits were secured as necessary and the local regulatory agency was notified 48 hours prior to commencing work. The subsurface was cleared of underground utilities by notifying Underground Service Alert. Extensive problems were encountered while drilling MW-4 with heaving sands. On two occasions the center bit became wedged inside the augers due to fine grained sands, which flowed into the hollow stem auger latching mechanism and could not be removed. The augers had to be pulled from the hole so a pressure washer could be used to remove the sand from around the bit. A combination of bentonite and barite were mixed and added to the inside of the augers to hold the sand out. The well was successfully installed after losing 4- .Or almost a full day dealing with the heaving sands. MW-5 was installed as planned. �. Deeper Well In an effort to define the vertical extent of the plume, GTI proposed to install one deep, discretely screened well to approximately 100 feet below grade. The boring was to be 1-0 drilled using a mud rotary drill rig to combat heaving sands. The following procedure was used to drill the deep borehole. A set of 10-inch hollow stern 4.0 augers was drilled down to a depth of 50 feet. The augers served to provide a return conduit for the drilling mud and to isolate the drilling mud from the heavy contamination in shallow soil. A 6-inch diameter rotary bit was then lowered down the inside of the augers and drilling progressed. The drilling mud was a mix of bentonite gel with a small amount of polymer added to aid in reducing loss of drilling mud to the formation. The mead was pumped down the inside of the drill rods and up the borehole. A portable mud pit was placed around the I0-inch augers to catch the mud and cuttings as they came out of the hole. +-r The drilling mud was continually reused during the drilling process. The mud rotary rig is owned and operated by V&W Drilling (C57# 720904). y,, Clay was encountered at a depth of 95 feet bgs so drilling continued to determine if the clay was only a thin lens and a well could be set below it. Drilling continued to a depth of 115 feet bgs. The geology was still plastic clay so drilling was discontinued. After conversations with Ray Kablanow of GTI and Lori Duncan of SJC PHS/EHD, it was tom,, decided to drill a new borehole and set a well on top of the clay with a total depth of 90-feet. +..