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Monitoring Well Installation and VET Report-Former Unocal Station#2859,Stockton,CA
<br /> July 30,2001
<br /> MW-11 (720 ppb), MW-12 (19 ppb), MW-13 (1 1 ppb) MW-15 (9 0 ppb), and NP-1 (0 98 ppb) Methyl
<br /> tert-butyl ether(MtBE)was not detected in any wells
<br /> FIELD ACTIVPPIES
<br /> To further evaluate the extent of petroleum hydrocarbons in soil and groundwater on-site and off-site in
<br /> the downgradient direction, groundwater monitoring wells MW-11 through MW-16 were installed at the
<br /> subject site and wells MW-17 through MW-19 were installed northeast of the subject site (Figure 2)
<br /> Fieldwork was performed in accordance with GR's Site Safety Plan#240072 04, dated May 9,2001 GR
<br /> Field Methods and Procedures are included in Appendix A Underground Service Alert was notified prior
<br /> to beginning site activities The wells were installed by Cascade Drilling, Inc. (C57 9717510) under
<br /> SJCPHS-EHD permits #26208, #26209, and #26210, and City of Stockton encroachment permit#66459
<br /> Copies of the permits are included in Appendix B
<br /> The nine groundwater monitoring wells were installed on May 21 through 23, 2001 Wells MW-1 1,
<br /> MW-13, MW-15, and MW-17 were drilled to a depth of 60 feet bgs, and wells MW-12, MW-14, MW-16,
<br /> MW-18, and MW-19 were drilled to depths-of approximately 90 feet bgs using a truck-mounted dnll rig
<br /> equipped with 8-inch-diameter hollow-stern augers A GR geologist observed the drilling activities For
<br /> wells MW-12, MW-14, MW-16, MW-18, and MW-19, soil samples were collected at five-foot intervals
<br /> for description and preparation of a log, and for possible chemical analysis Because wells MW-11,
<br /> MW-13, MW-15, and MW-17 were installed withm 5 feet of wells MW-12, MW-14, MW-16, and
<br /> MW-18, respectively, soil samples were not collected from their well borings Boring logs are included
<br /> m Appendix C Locations of newly installed wells are shown on Figure 2 Copies of the Well Driller's
<br /> Reports are included in Appendix C
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<br /> Soil cuttings generated during dnllmg activities were placed on and covered with plastic Composite
<br /> disposal confirmation sample SP-I(A-D) was collected from the stockpiled soil cuttings (Table 1)
<br /> Stockpile sampling procedures are presented in Appendix A
<br /> Well Installation
<br /> Groundwater monitoring wells MW-11 through MW-19 were constructed using 2-inch diameter Schedule
<br /> 40 polyvinyl chloride (PVC) casing and screen material Wells MW-11, MW-13, MW-15, and MW-17
<br /> are screened from 50 to 60 feet bgs, and wells MW-12, MW-14, MW-16, MW-18, and MW-19 are
<br /> screened from 85 to 90 feet bgs The annular space around the screened interval in each well is packed
<br /> with Lonestar#3 graded sand The sandpack is followed by a seal of bentonite chips,then neat cement to
<br /> approximately 1-foot bgs The top of each well is protected by a vault box, locking well cap, and lock.
<br /> The vault box is installed flush with the ground surface, and is set in concrete
<br /> Well Monitonniz.Development and Sampling
<br /> The newly installed groundwater monitoring wells were developed on May 28 through 30, 2001, by
<br /> Cascade Drilling, Inc (C57 #717510). On June 5 and 6, 2001, all wells (existing and new) were
<br /> monitored and sampled by GR as part of the scheduled 2nd Quarter monitoring and sampling event
<br /> Potentiometric and isoconcentration maps were generated from this data (Figures 2 through 5) Each
<br /> well was checked for the presence of separate phase hydrocarbons (SPHs) No SPHs were observed in
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