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' T&T Trucking Subsurface Investigation Results and Site Conceptual Model Page 4-8 TPH-d Only groundwater samples collected from CPT-5 were analyzed for TPH-d due to its proximity to the former diesel UST Low TPH-d concentrations were detected in the samples from 85-ft bgs (120 µg/L) and 110-ft bgs (180 µg/L) as shown In Figure 4-6 ' TPH-g TPH-g concentrations were detected in only two groundwater samples, one sample from CPT-1 at 108-ft bgs (1,000 µg/L) and the other from CPT-2 at 70-ft bgs (110 n/L), as shown on Figure 4-6 Other Fuel Oxygenates Of the 22 groundwater samples collected tert-butanol was the only oxygenate (other than MtBE) detected A concentration of 25 µg/L was detected in a sample from ' CPT-1 at a depth of 108-ft bgs However, the laboratory flagged this result as being biased high due to the conversion of MtBE to tert-butanol during the analysis ' 44 g Conceptual H dro eolo is Model P Y g ' The Site Conceptual Model (SCM) is a comprehensive but sunphfied view of the current information available concerning the hydrogeology of the Site and, for regional context, the ' surrounding area The conceptual model combines factual information about the hydrology, geology, contaminants, and a working hypothesis on groundwater flows, contaminant fate and transport, potential exposure pathways, and potential receptors that may be impacted The SCM for the T &T Trucking Site is graphically represented in the cross-sections shown on Figures 4-7, 4-8 and 4-9 These cross sections show the conceptual hydrogeology and extent of ' petroleum hydrocarbon contamination of the Site Using data from previous and current Site investigations and quarterly groundwater monitoring events the current SCM represents two-dimensional illustrations of Site lithology,water table fluctuation movement, and current ' interpretation of lateral and vertical extent of one or more petroleum hydrocarbon or related oxygenates (primarily MtBE) The model sections show actual well locations and relationships between well construction, hthology, and the range of water level movement Additional data may modify the SCM and the model will be continuously updated until new data doesn't change the model parameters The hthologic column is divided into three hydrologic zones vadose, smear, and saturated The hthology is described in detail in Section 4 1 The vadose zone is the hthological interval between the capillary fringe or smear zone and saturated zone and the land surface The vadose zone is ' characterized by dry or moist conditions The smear zone is the interval between the historic high and low water levels where contaminants can absorb and desorb to soil particles or remain in interstitial pore spaces during water level fluctuations The saturated zone is characterized by the ' pore spaces in the soil are filled with water at a pressure greater than atmospheric However, there can be low permeability layers within the saturated zone that impede the migration of groundwater and dissolved contaminants Migration of groundwater through these low permeable layers can be ' through root casts or fractures as interpreted on Figures 4-7, 4-8 and 4-9 • Y\23000\23954 11 trucking\CY I Summary Report\FIN Al, I&'I I rucking DOC