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'. GPolr icalTeclucicslnc Page Groundwater Monitoring Report Project No.425.2 October 19,2004 1.2 Groundwater Sampling Procedure ' On July 23, 2004, Del-Tech Geotechnical Support (Del-Tech) personnel arrived on-site, opened the wells, and measured the depth to water with an electrically actuated sounding tape. The water level reading was recorded to an accuracy of 0.01 foot. ' Stagnant water in the well casing was purged using a Honda® centrifugal pump or a Waterra® pump with dedicated tubing as recorded in the field logs (Appendix Q. The rate ' of well purging was monitored. The wells were purged of at least three casing volumes or until the groundwater parameters (temperature, conductivity, and pH) had stabilized (Appendix C) indicating that water representative of actual aquifer conditions was entering ' the well. Groundwater parameter stabilization was characterized by three successive readings within 10%. ' Before a sample was collected, the well's water level was allowed to recharge to at least 80% of its initial level. MW-4, MW-5, MW-7, and MW-8 exhibited very poor recharge. Heavy sheen was noted in MW-2. All the water removed from the monitoring wells and not used as ' a sample was placed in a properly labeled 55 gallon DOT (Department of Transportation 17- H) approved container and temporarily stored on-site. A 1-foot stainless steel bailer and stainless steel wire line or a Waterra®pump with dedicated tubing was used to collect each sample. Extreme care was exercised while collecting samples to prevent agitation of the water contained in the bailer. Water samples were transferred from the bailer into 40-m1 VOA vials preserved with hydrochloric acid using a bottom- emptying device that minimizes sample aeration during transfer of the sample. All samples ' were checked for headspace bubbles, labeled, inserted into foam holders and placed into a cooled ice chest for transport to the Iaboratory. The sampling technician wore disposable gloves while collecting all samples. A chain of custody document, listing all samples collected and their intended analyses, accompanied the samples from field to the laboratory, thereby providing a means to track the ' movement and insure the integrity of the samples. 1.3 Laboratory Analyses ' Theoundwater collected on Jul 23, 2004 were delivered to Sherwood Labs �' samples P Y Corporation (California ELAP# 1400), of Hilmar, California, for analysis. The samples were ' analyzed using the following methods: • BTEX—EPA method 8020/8015(m) ' • TPH-Gasoline—EPA method 8020I8015(m) • MTBE—EPA method 8020/8015(m) o Positive results confirmed by EPA method 8260