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24 October 2008 <br /> AGE-NC Project No. 95-0106 <br /> Page 2 of 2 <br /> • Installation of dedicated temporary vapor points at proposed soil vapor boring locations;and <br /> • Advancement of each temporary vapor point to a depth of 3.5 feet below surface grade(bsg), (� <br /> instead of the originally proposed depth of 5 feet bsg. Depth to water at the site is shallow, <br /> generally ranging between approximately 5 feet and 7 feet below the tops of the monitoring <br /> well casings. C. <br /> k. <br /> Proposed temporary soil vapor points will be single-completed utilizing 3/4-inch diameter schedule <br /> 40 polyvinylchloride (PVC) 0.010-inch slotted screen and blank casing. Each vapor point will be <br /> completed with a 0.5-foot length of screen attached to blank casing extending to near surface. After <br /> installation,a filter pack material consisting of pre-washed#2/12 sand will be added over the screen <br /> interval to approximately 0.5-feet above the screen interval. Remaining annular space will be sealed <br /> with Volclay bentonite from surface grade to approximately 2.5-feet bsg. Additionally, a PVC cap <br /> with '/4-inch diameter polyethylene tubing will be attached to the surface end of the temporary vapor <br /> point in order to collect vapor samples. Proposed temporary vapor point construction diagram is <br /> illustrated in Figure 3. Field procedures for vapor sample collection are described in the Soil Vapor <br /> Survey Work Plan, dated 25 April 2007. <br /> After collection of soil vapor samples, dedicated temporary vapor points will be removed from the , <br /> soil-vapor borings, and borings will be abandoned by backfilling with portland cement from total <br /> depth to surface grade. <br /> Please contact our office at (209)467-1006 if you have any questions or comments. <br /> Sincerely, <br /> Advanced GeoEnviron mental, Inc. Q°��CO, <br /> L <�,a <br /> � I* No. 7473 *� <br /> Rebecca E. Nata William R. Little <br /> Staff Scientist Senior Project Geologist <br /> California Professional Geologist 74o% <br /> cc: Mr. Weldon Church <br /> Advanced GeoEnvironmental,Inc. <br />