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M Site Background Information - Fernando ' s Place AGE-NC Project No . 00-0769 Page 4 of 5 limited to near or on the site, therefore a limit of the shallow lateral soil contamination is likely near the former UST area and on the site. The most impacted soil was encountered beneath the former UST locations, the significantly impacted soil is limited to approximately 70 feet bsg, while trace concentrations have been demonstrated at a depth as great as 110 feet bsg. Adsorbed contamination appears to have been spread southwest of the site, well MW-2, at a depth of greater than 30 feet bsg. HYDROCARBON-IMPACTED GROUND WATER The most highly impacted ground water appears to be located near the former UST location on the western portion of the site at wells MW- 1 , MW-5 and MW-2; while at the northeast corner of the site a second UST release location has demonstrated elevated concentration of dissolved hydrocarbons. The dissolved hydrocarbons have been detected in the shallow water table off-site with the greatest frequency are well MW-7, downgradient of the site; with intermittent detections of hydrocarbons at wells MW-6 and MW-8 . The current data indicates the shallow dissolved plume is not present northwest of the site. Vertically, hydrocarbon-impacted ground water was detected in each of the screened intervals of multi-level wells MW-4 through MW-7. While only up-gradient multi-level well MW-9 and cross. gradient multi-level well MW-8 have low to non-detectable concentrations of petroleum hydrocarbon compounds. SITE CONCEPTUAL MODEL Based on the data developed to date, including all soil borings, monitoring wells installed and CPT soundings, AGE has developed an initial site subsurface model for the release, migration and distribution of the varying contaminants in the subsurface as described below: • The subsurface ofthe site contains apoorly stratified upper section, with interbedded sitUclay and thick channel cut sand units. While below 100 feet bsg, the section is well stratified with thick silt/clay units from 90 to 115 feet bsg, from 120 to 135 feet bsg, from 145 to 175 feet bsg and from 200 to 235 feet bsg. The lower section at the site has four major coarse-grained interval of variable thickness, designated HU2 at 120 feet bsg, HU3 at 145 feet bsg, HU5 at 190 feet bsg and the lowest unit as HU6 at 230 feet bsg. The upper section has demonstrated sand units of a varying thickness near 60 to 70 feet bsg. • The predominant ground water flow direction in the upper hydrogeological units has been east to northeast, while lower HUs have exhibited northern flow directions. Advanced GeoEnvironmen[al, Inc.