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S E C 0 R
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<br /> J
<br /> Ms Victoria McCartney
<br /> March 24, 2005
<br /> Page 3
<br /> In February 1995, Alisto conducted a pump test to determine aquifer properties beneath the
<br /> site Pumping occurred from well MW-1, generating approximately 1 5 feet of drawdown at
<br /> an extraction rate of 6 gallons per minute (gpm) Alisto concluded that the rapid recovery
<br /> may be due to the sand unit encountered in the lower portion of well MW-1, and may not be
<br /> representative of the material in the saturated zone (Alisto, 1995) Revised calculations of
<br /> hydrogeologic parameters were submitted in October 1995 Resulting hydraulic
<br /> conductivity (K) values for wells MW-1, MW-2, and MW-5 ranging from 2 25x10 to
<br /> 8 68x10 centimeters per second (cm/s) were within the lower range of expected K values
<br /> associated with the soil types encountered beneath the site (1 to 1x10 cm/s, Freeze and
<br /> Cherry, 1979), which consisted of silt and silty sand underlain by fine to medium sand
<br /> (Alisto, 1995)
<br /> Between December 10 and 22, 1998, Gettler-Ryan Incorporated (GR) supervised the
<br /> removal of two 10,000-gallon USTs and one 8,000-gallon single-walled UST, dispensers,
<br /> and associated product dispenser piping Laboratory analysis of soil samples collected
<br /> from the UST excavation indicated maximum concentrations of TPHg at 31 ppm (3W),
<br /> benzene at 0 27 ppm (3W), and methyl tertiary butyl ether (MtBE) at 80 ppm (3E)
<br /> Laboratory analysis of soil samples collected from the beneath the dispensers and product
<br /> piping detected maximum concentrations of TPHg at 1,600 ppm (D1) and MtBE at 1 8 ppm
<br /> (D3) Additionally, approximately 15,000 gallons of water was removed from the excavation
<br /> during the installation of the new USTs Laboratory analysis of a grab groundwater sample
<br /> indicated maximum concentrations of TPHg, benzene, and MtBE at 17,000 micrograms per
<br /> liter (µg/Q, 1,500 ttg/L, and 120,000 µg/L, respectively Well MW-1 was destroyed to allow
<br /> the enlargement of the existing UST excavation for the installation of the new USTs (GR,
<br /> 1999)
<br /> On October 7 and 8, 1999, Cambria Environmental Technology, Incorporated (Cambria)
<br /> conducted a Cone Penetration Testing (CPT) investigation by advancing six borings (CB-1
<br /> through CB-6) for soil and groundwater sampling, and two borings (CB-2E and CB-4E) for
<br /> electric soil logging Water samples were collected using a hydropunch at depths of 16 and
<br /> 29 feet bgs in borings CB-1, CB-2, and CB-4 through CB-6 Water samples were collected
<br /> at depths of 16 and 29 feet bgs in boring CB-3 Laboratory analysis of soil samples
<br /> collected from the soil borings detected maximum concentrations of gasoline range
<br /> organics (GRO) at 27 milligrams per kilogram (mg/kg, CB-3-13 5), MtBE at 27 mg/kg (CB-3-
<br /> 13 5), and tertiary amyl methyl ether (TAME) at 0 058 mg/kg (CB-3-13 5) Benzene,
<br /> toluene, ethylbenzene and total xylenes (BTEX) were not detected above laboratory
<br /> detection limits Laboratory analysis of groundwater samples collected from the soil borings
<br /> confirmed maximum concentrations of GRO at 87,000 µg/L (CB-4-16HP), benzene at 1,300
<br /> ug/L (CB-4-16HP), MtBE at 38,000 µg/L (CB-1-16HP), and TAME at 160 µg/L (CB-1-16HP)
<br /> (Cambria, 1999)
<br /> Also in late 1999, Cambria conducted a sensitive receptor survey Based on a review of
<br /> United States Geological Survey (USGS) topographic maps and recent area maps, an
<br /> unnamed levy-restricted slough was identified 2,000 feet south of the site, and a man-made
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