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22 February 1999 AGE-NC Project No. 98-0534 Page 2of3 from beneath the ends of each UST and soil samples were also collected from the center portion of the 20,000-gallon USTs. Three soil samples were collected from beneath the fuel dispenser. A total of fourteen soil samples were collected from the product line trench, approximately one soil sample for every twenty linear feet of product line. In addition, eighteen soil samples were collected from the stockpiled soil. • During the removal of the USTs and fueling system approximate 450 cubic yards of soil were removed from the two adjacent excavations. This soil was stockpiled on the site. At your request the following impacted-soil treatment methods are presented and compared: Natural Attenuation-Aeration, On-Site Enhanced Bio-Remediation or On-Site Thermal Treatment: • The Navy Drive site has adequate space for ex-situ soil treatment. However, it is not possible to pile and treat the soils without causing an economic hardship to the site operator by reducing the space available for lease or rental on the site. • The cost for preparation of the soils for treatment, re-sampling and reporting would be equal to or greater than direct soil disposal. Off-site Thermal Treatment: • According to representatives of Granite Construction and Environmental, and in line with AGE's experience thermal treatment will require transportation of the soil to an off-site locality would be required. Disposal or resale of the treated soil will then require additional transportation of the soil. The costs for soil transportation and treatment would be greater than simple offsite disposal. Even with current prices for fill-material, the additional soil transportation costs for treatment would be greater than for other soil disposal/treatment options. Asphalt Re-Constitution • According to representatives of George Reed Construction, Teichert Construction, and Granite Construction & Environmental, and consistent with AGE's experience treating or `re-using' soil with a high silt and clay content, such as that excavated from the site, is not practicable as such soil can not be used for finish or saleable asphalt. Therefore the impacted soil on the site can not be easily treated in a cost effective manner utilizing this remedial method. Only sand with a very low percentage of fines (silt and clay) can be used for production of construction-grade asphalt.