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� 3 <br /> S E C O R <br /> Ms. Vicky McCartney <br /> September 15, 2003 <br /> Page 7 <br /> from the City of Stockton, Public Works Department (CSPWD) prior to the <br /> commencement of drilling activities. <br /> • OS Wells. Eight-inch diameter soil borings for the 10 proposed OS wells (OS-1 <br /> through OS-10) will be drilled using hollow stem auger drilling equipment. Upon <br /> .completion of drilling, a 1.25-inch diameter, Schedule 80 PVC groundwater <br /> monitoring well equipped with a 3-foot long OS diffuser tip will be installed in <br /> each borehole. Each OS well will be completed at a depth of 30 feet bgs. Based <br /> on historical site groundwater monitoring-data, depth to groundwater within the <br /> OS wells is anticipated between approximately 3,2 to�___14 feet bgs— Field <br /> procedures for the installation of the groundwater monitoring and OS wells are <br /> provided in Attachment 1. <br /> • Groundwater Monitoring Wells. Eight-inch diameter soil borings for the two <br /> proposed wells will also be drilled using hollow stem auger drilling equipment. <br /> Upon completion of drilling, a 2-inch diameter, Schedule 40 groundwater <br /> monitoring well casing will be installed in each boring. Each of the wells will be <br /> constructed with approximately 20 feet of well screen, extending from <br /> approximately 10 feet to 30 feet bgs.As stated above, depth to groundwater <br /> ` within the wells is anticipated between approximately 12 and14 feet bgs:-'_Field <br /> �J procedures for the installation of the groundwater monitoring wells are provided <br /> in Attachment 1. <br /> • Soil Selection and Analysis. Soil samples will be collected for lithological <br /> description and possible laboratory analysis at 5joot.int aIs from each of the <br /> borings for the OS and groundwater monitoring wells'. Soil samples showing �. p/✓ <br /> positive readings on a photo-ionization detector (PID) and/or at least 3 soil �f <br /> samples will be sent under chain-of-custody procedures to a California state- <br /> certified laboratory, and analyzed for the presence of TPHg, BTEX, and MtBE by� v��v+� <br /> EPA Method 82606 (Single Run). J0 <br /> • Monitoring and OS Well DevelopmentfSampling/Analysis. After installation, Sp <br /> the newly installed OS and monitoring wells will be developed by SECOR by �JYh .p3 <br /> rigorously surging the well over the length of the screen interval and by purging <br /> approximately 10 casing volumes of water. Initial groundwater samples will be <br /> collected from groundwater monitoring wells MW-11 and MW-12 as part of the <br /> next scheduled quarterly groundwater monitoring and sampling event. Wells <br /> MW-11 and MW-12 will be added to the quarterly monitoring and sampling <br /> program for the site. Groundwater samples from the newly installed OS and <br /> monitoring wells will be analyzed for the presence of TPHg, BTEX, and fuel <br /> oxygenates (MtBE, TAME, DIPE, EtBE, TBA, ethanol) and lead scavengers 1,2-<---- <br /> DCA and EDB by EPA Method 82608 (Single Run). Field procedures for <br /> groundwater monitoring well development and sampling are included in ` <br /> Attachment 1. <br /> • Well Surveying and Hydraulic Gradient Evaluation. Upon completion of well <br /> construction, the groundwater monitoring and OS wells will be surveyed by a <br /> licensed surveyor to a local benchmark relative to mean sea level. Using the <br /> 1AConocoPh111ips\Tosco Marketing1111931Repots\Revised RAP&wP.doc <br />