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Stantec <br /> ADDENDUM TO JULY 8,2010 WORK PLAN FOR MONITORING WELL DESTRUCTION AND REPLACEMENT AND ADDITIONAL <br /> PATH FORWARD <br /> Former Thrifty No. 172/ConocoPhillips No.5449 <br /> Seotember 23,2010 <br /> 1.1.8 Monitoring Well Development/Sampling <br /> Prior to development of the wells, the bentonite seal and neat cement grout will be allowed to <br /> cure for a period of at least 48 hours. The newly installed monitoring wells will be developed by <br /> surging the well over the length of the screen interval and by purging approximately 10 casing <br /> volumes of water. The groundwater monitoring wells will be sampled at least 72 hours after <br /> development. The wells will be sampled using three casing volume purging procedures and <br /> analyzed for the presence of TPPH, BTEX, 1,2-DCA, DIPE, EDB, ETBE, ethanol, MTBE, <br /> TAME, and TBA by EPA Method 8260. <br /> 1.1.9 Well Surveying <br /> Following installation and well recovery activities, the new and pre-existing groundwater <br /> monitoring wells (including the revised tops of casings for restored wells MW-3, MW-7, and MW- <br /> 12R) will be surveyed by a licensed surveyor to the NAD 83(1986) datum for geographical <br /> location, and to the NAVD 88 datum for elevation. At least two existing unaltered offsite wells <br /> (i.e. MW-5, MW-6, or MW-9) will be tied in to this survey. <br /> 1.1.10 Soil and Water Disposal <br /> Cuttings, well casing, and water generated during drilling operations and well development will <br /> temporarily be stored on-site in California Department of Transportation (DOT)-approved 55- <br /> gallon steel drums pending characterization and disposal. The drums will be removed and <br /> transported by a licensed disposal contractor to an appropriate treatment or disposal facility. <br /> Soil cuttings and rinsate/purge water drums will be temporarily stored on-site for approximately <br /> 2 to 4 weeks. Copies of the disposal manifests will be included in the report or submitted under <br /> separate cover. The well boxes will be disposed of as construction waste. <br /> If you should have any questions concerning the information provided in this work plan please <br /> contact either of the undersigned at (916) 861-0400. <br /> Sincerely, <br /> Stantec Consulting Corpora ion <br /> Laura Shook <br /> Geologic Associate NAL <br /> o eo, <br /> � eaaaar N <br /> CL wo.HG <br /> Diane Barclay, C.H.G. CFTFIM <br /> Principal Geologist P GEOLOGIST <br /> 9TF OF C AO�cc <br /> ATTACHMENTS <br /> Figure 1 Site Location Map <br /> Figure 2 Site Plan <br />