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SECOR
<br /> Ms. Vicky McCartney
<br /> March 29, 2004
<br /> Page 3
<br /> concentrations of TPHg at 2,100 ppm (TD-2), toluene at 3.5 ppm (TD-3), ethylbenzene at 18 ppm
<br /> (TD-3), and total xylenes at 110 ppm (TD-3). TPHd, total petroleum hydrocarbons as oil (TPHo), and
<br /> benzene were not detected above laboratory detection limits. Laboratory analysis of soil samples
<br /> from borings THP-1 and THP-2 detected maximum concentrations of TPHd at 1 ppm (THP1 S-10)
<br /> and benzene at 0.03 ppm (THP@S-15). TPHg, TPHo, toluene, ethylbenzene, and total xylenes
<br /> were not detected above laboratory detection limits. Laboratory analysis of groundwater samples
<br /> from borings THP-1 and THP-2 detected maximum concentrations of TPHg at 6,900 ppb (THP2W-
<br /> 21), TPHd at 840 ppb (THP2W-21), benzene at 1,900 ppb (THP2W-21), and total xylenes at 77 ppb
<br /> (THP2W-21). TPHo, benzene toluene, ethylbenzene, and halogenated volatile organic compounds
<br /> (HVOC's) were not detected above laboratory detection limits (EMCON, 1994).
<br /> In February 1995, Alisto conducted baildown testing to determine aquifer properties beneath the site.
<br /> Pumping occurred from well MW-1, generating approximately 1.5 feet of drawdown at an extraction
<br /> rate of 6 gallons per minute (gpm). Alisto concluded that the rapid recovery may be due to the sand
<br /> unit encountered in the lower portion of well MW-1, and may not be representative of the material in
<br /> the saturated zone (Alisto, 1995). Revised calculations of hydrogeologic parameters were submitted
<br /> in October 1995. Resulting hydraulic conductivity (K) values for wells MW-1, MW-2, and MW-5
<br /> (2.25x10-" to 8.68x105 centimeters per second [cm/s]) were within the lower range of expected K
<br /> values associated with the soil types encountered beneath the site (1 to 1x10-5 cm/s, Freeze and
<br /> Cherry, 1979), which consist of silt and silty sand underlain by fine to medium sand (Alisto, 1995).
<br /> • Between December 10 and 22, 1998, Gettler-Ryan Incorporated (GR) supervised the removal of two
<br /> 10,000 gallon USTs and one 8,000 gallon single-walled UST, dispensers, and associated product
<br /> piping. Laboratory analysis of soil samples collected from the UST excavation reported maximum,
<br /> concentrations of TPHg at 31 ppm (3W), benzene at 0.27 ppm (3W), and methyl tertiary butyl ether
<br /> (MtBE) at 80 ppm (3E). Laboratory analysis of soil samples collected from the beneath the
<br /> dispensers and product piping detected maximum concentrations of TPHg at 1,600 ppm (D1) and
<br /> MtBE at 1.8 ppm (D3). Additionally, approximately 15,000 gallons of water Y/9%moved from the
<br /> excavation during the installation of the new USTs. Laboratory analysis of a grab groundwater
<br /> sample reported maximum concentrations of TPHg, benzene, and MtBE at 17,000 micrograms per
<br /> liter (Itg/L), 1,500 �ig/L, and 120,000 Ag/L, respectively. Groundwater monitoring well MW-1 was
<br /> destroyed to allow the enlargement of the existing UST excavation for the installation of the new
<br /> USTs (GR, 1999).
<br /> On October 7 and 8, 1999, Cambria Environmental Technology, Incorporated (Cambria) conducted
<br /> CPT by advancing six borings (CB-1 through CB-6) for soil and groundwater sampling and two
<br /> borings (CB-2E and CB-4E) for electric soil logging. Soil samples were collected every five feet to
<br /> approximately 20 feet bgs. Water samples were collected using a hydropunch at depths of 16 and
<br /> 29 feet bgs 1 borings CB-1, CB-2, and CB-4 through CB-6. Water samples were collected at depths
<br /> Y" nq of 16 and feet bgs in boring CB-3. Laboratory analysis of soil samples detected maximum
<br /> q-,k concentrate ns of gasoline range organics (GRO) at 27 milligrams per kilogram (mg/kg) (CB-3-13.5),
<br /> MtBE at 2� mg/kg (CB-3-13.5), and TAME at 0.058 mg/kg (CB-3-13.5). Benzene, toluene,
<br /> ethylbenzene, and total xylenes (BTEX) were not detected. aljove laboratory detection limits.
<br /> Laboratory analysis of groundwater samples collected from the soil borings detected maximum
<br /> concentrations of gasoline range organics (GRO) at 87,000 pg/!_ (CB-4-16HP), benzene at 1,300
<br /> µg/L (CB-4-16HP), MtBE at 38,000 µg/l_ (CB-1-16HP), and TAME at 160 Ag/L (CB-i-16HP)
<br /> (Cambria, 1999).
<br /> 1:1ConocoPhi11ips\111931Work PlansllRAP&Off-site Asmt WP Addendum v 2.doc SECOR International Incorporated
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