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Work Plan For Monitoring Well Installation — Former Chevron Service Station #9-5775, Lodi, CA
<br />Anril7 9000
<br />TAME of 161 and 274 ppb, respectively. Well MW -2 was nondetect for TPHg, benzene, toluene,
<br />ethylbenzene, and xylenes (BTEX), MtBE, ETBE, and TAME. Ethanol, tert-butyl alcohol (TBA), or
<br />di -isopropyl ether (DIPE) were not detected in any of the wells. Groundwater flow direction was to the
<br />east at a gradient of approximately 0.007 ft/ft. Depth -to -water ranged from 56.45 to 57.15 feet below top
<br />of casing (btoc). Historically, groundwater in the immediate vicinity of the Chevron station has ranged
<br />from 56.33 to 69.35 feet btoc.
<br />On March 1, 2000, newly installed wells MW -5 though MW -9 and EX -1 were developed and sampled.
<br />Wells MW -5, MW -6, and EX -1 had detectable concentrations of TPHg at 150, 170, and 51,000 ppb,
<br />respectively. Benzene was detected in wells MW -5, MW -6, MW -7, and EX -1 at concentrations of 67,
<br />140, 0.72, and 39,000 ppb, respectively. MtBE by EPA Method 8260 was detected in wells MW -5
<br />(250 ppb), MW -6 (520 ppb), MW -8 (3.1 ppb), MW -9 (78 ppb), and EX -1 (720,000 ppb). ETBE was
<br />detected in wells MW -5 (22 ppb), MW -6 (56 ppb), MW -9 (6.8 ppb), and EX -1 (18,000 ppb). TAME was
<br />detected in wells MW -6 (6.8 ppb) and EX -1 (6,000 ppb). TBA and DIPE were not detected in any of the
<br />wells. Depth -to -water in all wells, including MW -1 through MW -4, ranged from 52.96 to 55.56 feet btoc,
<br />and groundwater flow direction was to the southeast at a gradient of approximately 0.005 ft/ft.
<br />SCOPE OF WORK
<br />To further evaluate the lateral and vertical extent of the dissolved hydrocarbons in the subsurface
<br />groundwater beneath and to the south and northeast of the site, GR proposes to drill and install three
<br />additional off-site and three additional on-site groundwater monitoring wells (Figures 3). Field Methods
<br />and Procedures are included in Appendix A. To complete the specified work, GR proposes the following
<br />six tasks:
<br />Task 1. Pre -field Activities
<br />GR will update the site safety plan and obtain the necessary well installation permits from
<br />SJCPHS for all wells, and encroachment permits from the City of Lodi Department of Public
<br />Works and the California Department of Transportation for the well on the south side of West
<br />Kettleman Lane adjacent to well MW -8. An access agreement will be obtained from the property
<br />owners south of West Kettleman Lane for the installation of two wells located approximately 100
<br />feet south of well MW -9. USA will be notified at least 48 hours prior to initiating work. A
<br />private utility line locator will be contracted to clear all boring locations.
<br />Task 2. Well Installation
<br />GR will drill and install three off-site and three on-site groundwater monitoring wells at the
<br />locations shown on Figures 3. Drilling and well construction will be performed by a licensed
<br />California well driller. A GR geologist will monitor the drilling activities. A log will be prepared
<br />of each boring except were a well is installed within 5 feet of an existing well. In those cases,
<br />only the deepest well will be sampled and logged. In the cases where a deeper well is installed
<br />within 5 feet of an existing well, such as the proposed wells next to wells MW -5 and MW -8, only
<br />the interval the extends below the depth of the existing well will be sampled and logged.
<br />346408.09
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