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' Job No. 4780200 Page 6 <br /> ' 4.0 CONCLUSIONS AND RECOMMENDATIONS <br /> Based on our site observations, laboratory reports, and our professional opinion, <br /> E2C concludes that soils at the subject site have been adversely impacted by <br /> the former presence of gasoline and USTs. Elevated levels of TPHg and BTEX <br /> t were reported from boring B2 which was installed in the former vicinity of a <br /> 2,000-gallon gasoline UST. The high concentrations of TPHg and BTEX were <br /> ' reported from soil samples collected from 15 and 20 feet bgs. The laboratory <br /> reported that TPHg and VOCs (including BTEX) were not present in detectable <br /> ' levels from soil samples collected from the 5 and 10 foot bgs in B2 or from any <br /> of the other soil borings installed on-site (including the stockpile sample). <br /> ' While drilling B2, we noted that the soil cuttings from an approximate horizon <br /> ' of 12 to 23 feet bgs were very wet (See Section 3. 1), while in-situ soil samples <br /> collected from 10 and 15 feet bgs were only damp to moist. The two most <br /> likely explanations for this wet zone are that it is a small perched aquifer or, <br /> more likely, water which has seeped into soils at this horizon from the runoff <br /> water observed in the open excavation next to the boring. Possible <br /> environmental significance of this wet zone is that, if it is a perched aquifer, it <br /> ' represents a zone of lesser resistance which would allow for a greater <br /> dispersion of contamination. Or, if the wet zone is the result of water seeping <br /> ' into the area from the excavation and the water in the excavation is <br /> contaminated (which is likelygiven its proximity to 82), the water is serving as <br /> ' a means of transportation of contamination which would not normally be <br /> present. It is the recommendation of E2C that this water be pumped from the <br /> ' excavation and further drainage of water into the excavation be prevented. It <br /> should be noted here that in the likelihood that the water indeed is the result <br /> ' of a perched aquifer, water will seep into the excavation soon after the removal <br /> of the existing water. <br /> 1 <br /> TPHg was reported from B2 at concentrations of approximately 687 and 693 <br /> ppm. A concentration of 100 ppm total petroleum hydrocarbons in soil is <br /> ' EC, Inc. January 29, 1993 <br />