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• • Page 2 of 3 <br /> with the neat grout making 'sand slurry'. once all of the sand is mixed with the <br /> cement grout and the casing is out, the hole can be topped off to -5' bgs with <br /> more neat cement grout. the last five feet to surface can be the fully hydrated <br /> bentonite chips. If you choose this way ensure your driller uses 'slip' caps on <br /> the bottom of the PVC casings before installed. <br /> One other way is that the bore hole must be reamed out again with the 6.25" <br /> hollow stem augers and neat grout introduced down them from the surface <br /> after total depth of original borehole is reached. Cement grout to --5' bgs once <br /> the augers have been filled and removed. then the borehole can be topped <br /> with adequately hydrated bentonite chips to the surface. <br /> let me know which of the two above you plan on performing. <br /> From: John Cooper [mailto:jcooper@gercorp.com] <br /> Sent: Tuesday, October 14, 2008 8:38 AM <br /> To: Mike Infurna [EH] <br /> Cc: Fisher, Victor; 'Jeff Hawkins' <br /> Subject: Lima Ranch boring abandonment <br /> Mr. Infurna; <br /> The drilling program for the Lima Ranch investigation has been modified because of the hardness of <br /> the subsurface material encountered, and the slow flow of water into the direct push exploratory <br /> borings. We will be using a hollow stem auger drill rig with a 6-1/4 inch auger to advance the <br /> remaining 5 exploratory boring on Wednesday. We will advance the boreholes into shallow <br /> groundwater(the boring will probably be advanced to a depth of 30 feet or so). The driller will place <br /> a 2-inch diameter temporary well casing in the borehole and backfill around the well screen with <br /> Monterey sand to above the water table, pulling the auger above the sand pack as he places it. We <br /> will bail water from the well screen to collect the reconnaissance groundwater samples. <br /> Once the sample has been collected, the driller will pull the temporary well, leaving the sand pack in <br /> place. The driller will then pull the auger and abandon the borehole. He will place about 3 feet of <br /> bentonite chips above the sand pack material, and hydrate the chips. Above that he will place <br /> cement grout (cement and water) to a depth of about 5 feet below grade. He will then place 4 to 4- <br /> 1/2 feet of bentonite chips above the grout and hydrate the chips. He will top off the borehole with <br /> native soil. <br /> Attached please find a sketch of how we plan to construct the temporary well and abandon the <br /> borehole. Please let me know if the abandonment procedure meets the County's approval. <br /> Respectfully submitted, <br /> John Cooper <br /> John Cooper <br /> 10/14/2008 <br />