|
S E C 0
<br /> ' Cleanup Plan
<br /> • October 27, 2003
<br /> ' Page 4
<br /> 2.6 Previous Investigations and Remedial Actions
<br /> ' Between December 1983, and September 2003, 54 monitoring wells, 13 remediation wells, and
<br /> three piezometers were installed at the site. During this same period, 13 wells (T-2, MW-2, MW-10,
<br /> MW-11, MW-14A, MW-16, MW-20, TW-4, MW-21, MW-53A, MW-57A, MW-58A, and MW-59A) have
<br /> ' been destroyed; Well MW-9 can not be located following demolition and rough grading of the former
<br /> the Keylock facility. In an attempt to locate MW-9, soil was excavated to approximately 5 ft bgs in
<br /> excavation areas 1, 2, and 3, as shown on Figures 2 and 7. Fifty four of the existing wells were
<br /> constructed to monitor the shallow water-bearing zones (Upper A-zone and A-zone) to depths of 15
<br /> to 30 feet bgs. The remaining six wells (MW-12B, MW-13B, MW-22B, MW-23B, MW-5013, and MW-
<br /> 64B) are used to monitor the B-zone, installed to depths ranging between 55 to 65 feet bgs. A profile
<br /> ' of monitoring well screen intervals is included as Figure 6.
<br /> Previous remedial actions have included dual extraction (DE), limited soil excavation, and ISO-
<br /> GEN TM pilot testing.
<br /> Historical soil concentration maps and 2Q03 groundwater elevation and concentrations maps are
<br /> ' provided as Attachments C and D, respectively.
<br /> The following is a brief chronology of past work performed at the facility.
<br /> '• In December of 1983, Groundwater Technology, Inc. (GTI) installed groundwater monitoring
<br /> wells MW-1 through MW-7 in the vicinity of the above-ground tanks and pump islands (PEG,
<br /> 1995).
<br /> ' E In November of 1984, GTI installed wells T-1 through T-3 in the area of an underground
<br /> diesel storage tank (PEG, 1995).
<br /> ' 0 In October of 1988, EA Engineering, Science, and Technology (EA) installed groundwater
<br /> monitoring wells MW-8 through MW-11 on the periphery of the property boundaries (PEG,
<br /> 1995).
<br /> ■ During November of 1988, EA advanced shallow exploratory soil borings B-1 through B-9
<br /> along the northern property boundary (PEG, 1995).
<br /> ' a During January through April of 1988, EA conducted a soil vapor survey in the impoundment
<br /> area (PEG, 1995).
<br /> ' 0 In May of 1989, Dames and Moore (D&M) installed monitoring wells (MW-12 and MW-13) to
<br /> a depth of approximately 60 feet bgs. The wells were screened from 48 to 50 feet bgs in a
<br /> presumed lower water bearing zone (PEG, 1995).
<br /> ' 0 In May of 1990, EA prepared a Problem Assessment Report (PAR) and Work Plan (PEG,
<br /> 1995). The PAR, included a '/2 mile radius well search, fate and transport modeling, and
<br /> summary of previous site work.
<br /> ■ In July of 1993, Geraghty and Miller, Inc. (Geraghty) installed five extraction wells (MW-14
<br /> through MW-16, MW-18 and MW-19) and three groundwater monitoring wells (MW-17, MW-
<br /> ' I:\Chevron\1001621\REPORTS\2003\2003-Cleanup Plan\Cleanup Plan.doc
<br />
|