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S E C 0 R
<br /> Ms. Devra Lewis
<br /> April 15, 2004
<br /> Page 4
<br /> In 2001, additional assessment activities were conducted by T&R in the vicinity of the Site within Area
<br /> 3. Results are included in T&R's report entitled Subsurface Investigation for Area 3, dated August
<br /> 17, 2001.
<br /> In September 2001, a total of 11 Cone Penetrometer Test (CPT) borings (DP-1 through DP-11)were
<br /> drilled to investigate the following: (1) subsurface lithology, (2) the presence of separate phase
<br /> hydrocarbons (SPH), (3) the lateral extent of petroleum hydrocarbon-impacted groundwater east,
<br /> south, and west of the Site, and (4) to investigate potential off-site sources upgradient (north-
<br /> northwest) of the Site. Surficial soil samples were also collected from depths up to 5 feet below
<br /> ground surface(bgs) to evaluate whether the presence of residual concentrations of metals present a
<br /> threat to groundwater quality. Results are presented in Clayton's report entitled Further
<br /> Characterization at the West Weber Avenue and North Lincoln Street Site, Parcel 2A, dated
<br /> December 18, 2001.
<br /> In May 2002, Clayton initiated quarterly monitoring activities, installed eight additional CPT soil
<br /> borings (DP-12 through DP-19), and collected grab samples to delineate soil and groundwater
<br /> impacts previously identified in the vicinity of borings DP-1 through DP-6. In July 2002, Clayton also
<br /> oversaw the performance of a soil gas survey involving the installation of 111 Gore-Sorber®modules
<br /> to investigate the areas of greater petroleum hydrocarbon impact. Results are summarized in
<br /> Clayton's Site Delineation Report, dated August 6, 2002.
<br /> In December 2002, a 5-day dual-phase extraction (DPE) feasibility test was performed at the Site,
<br /> following the installation of seven DPE wells (DPE-1 though DPE-7). SPH were reportedly present in
<br /> wells DPE-1, DPE-3, DPE-4, DPE-6, and DPE-7 prior to the initiation of testing. DPE tests were
<br /> performed utilizing well 2AMW-14 for approximately 45 hours; simultaneously on wells DPE-4 and
<br /> DPE-6 for approximately 28 hours; and simultaneously on wells DPE-1, DPE-3, and DPE-7 for
<br /> approximately 26 hours. Results of DPE feasibility testing indicated the following: (1) a significant
<br /> reduction in the SPH thickness in six of the wells (2AMW-14, DPE-1, DPE-3, DPE-4, DPE-6, and
<br /> DPE-7), which reported SPH prior to testing; (2) a calculated radius of influence of 31 feet west of
<br /> well 2AMW-14, and lower estimated radii of influence to the south and east due to the presence of
<br /> low permeability clays and lower induced vacuum readings in wells DPE-3, DPE-4, and DPE-7; and
<br /> (3) the removal of an estimated 196.38 pounds of total petroleum hydrocarbons as gasoline (TPHg)
<br /> from soil and groundwater, 97.02 pounds of total petroleum hydrocarbons as diesel (TPHd) from
<br /> groundwater, and 9.57 pounds of total petroleum hydrocarbons as motor oil (TPHo) from
<br /> groundwater. Results are summarized in SECOR's report entitled Well Installation and DPE
<br /> Feasibility Report, dated January 24, 2003.
<br /> An additiohal DPE test was performed at the Site from March 3 through 7, 2003, using a 25-hp liquid
<br /> ring vacuum pump connected to a thermal oxidizer unit for abatement of the extracted soil vapor prior
<br /> to discharge to the atmosphere. DPE tests were performed separately on wells DPE-4 and 2AMW-
<br /> 14 simultaneously for approximately 21.5 hours, and wells DPE-4, DPE-6, and 2AMW-14
<br /> simultaneously for approximately 72.5 hours. The DPE unit ran for a total of approximately 97 hours
<br /> during the test. Groundwater and soil vapor were removed simultaneously from the respective test
<br /> wells by applying a high vacuum to a drop tube that was lowered into the water table within each test
<br /> well. Results of DPE feasibility testing indicated the following: (1) a significant reduction in SPH
<br /> thickness in wells 2AMW-14, DPE-1, DPE-4, and DPE-6; (2) an effective radius of influence of at
<br /> least 36 feet to the west of 2AMW-14, and (3) the removal of an estimated 212.3 pounds (34.2
<br /> gallons) of TPHg from soil vapor, and approximately 0.29 pounds (0.05 gallons) of TPHg, 17.56
<br /> pounds (2.46 gallons) of TPHd, and 8.29 pounds (1.13 gallons) of TPHo from groundwater. Results
<br /> Stockton Parcel 2A:Work Plan for Pipeline Abandonment,Removal,and Soil Excavation and SVE Well Install
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