ARCHIVED REPORTS_XR0002835 - Laserfiche WebLink

Home Browse Search

I' In August 1998, ATC advanced three additional soil borings, which were completed as groundwater monitoring wells designated MW-1 through MW-3 The monitoring wells were completed to a depth of approximately 28 ft bgs and were located in the vicinity of the former UST's Analytical data from the soil and groundwater samples contained detectable concentrations of petroleum hydrocarbons In April and June 2000, ATC advanced seven additional soil borings at the site, three of which were completed as groundwater monitoring wells The borings were designated SB- 8, SB-9, SB-10, SB-12, and the monitoring wells MW-4 through MW-6 A soil sample collected from the boring for monitoring well MW-4 contained detectable concentrations of TPHg and TPHd Soil samples from SB-8 through SB-10, SB-12 and monitoring wells ' MW-5 and MW-6 did not contain detectable concentrations of TPHg, TPHd, BTEX, or oxygenate fuel additives Groundwater grab samples from borings SB-8 through SB-10 did not contain detectable concentrations of TPHg, TPHd, BTEX, or oxygenates fuel additives, however the groundwater sample collected from SB-12 did contain trace amounts of toluene In June and July 2000, groundwater samples were collected from monitoring wells MW-1 through MW-6 The groundwater samples collected from MW-2, MW-3 and MW-4 contained concentrations of TPHd, and MW-2 and MW-4 also contained xylene and TPHg (ATC, 2002) conducted quarterly groundwater monitoring at the site from August 1998 through ATC q y g g June 2002 Groundwater samples were analyzed for TPHg, TPHd, and BTEX In June 2004 Haley and Aldrich, Inc conducted a soil and groundwater investigation at the site The purpose of this investigation was to delineate the vertical and horizontal extent of petroleum hydrocarbon impact to soil and groundwater in the vicinity of the former tank excavation area During the investigation a total of 20 soil samples and seven groundwater hydropunch samples were collected Soil samples were analyzed for TPHd and TPHg Groundwater samples were analyzed for TPHd and TPHg In addition one of the borings was converted to monitoring well MW-7 The findings of this investigation are reported in the Report on Soil and Groundwater Investigation (Haley and Aldrich, 2004) 1.1.3 Site Geology In general, sod encountered in shallow borings advanced at the site consists predominantly of clay and silt to a depth of approximately 10 to 15 ft bgs Silty sand and sand are encountered below the stltJclay layer to the maximum depths explored (generally approximately 30 to 35 ft bgs) One boring, SB-12, was advanced to a depth of 51 5 ft bgs, and a sandy clay lens was encountered at a depth of 41 to 46 5 ft bgs with a layer of sand beneath the clay 1..1.4 Site Hydrogeology Historically, depth to groundwater has ranged from 4 87 to 13 84 ft below casing and groundwater had flowed towards the south with some variation toward the southeast and southwest, with an average hydraulic gradient ranging from 0 0002 to 0 001 ft/ft During HAM this quarterly monitoring event groundwater was encountered at depths ranging from 7 22 to ' ALDRICH 2