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' Geolo ical Technics InO Page 4 g g ' Sinclair Trucking Report-Subsurface Investigation Project No.321.2 September 27,1995 Geological Technics Inc. concludes from the information gathered during this preliminary subsurface investigation that a release of petroleum hydrocarbons has occurred and is presently impacting the soil and groundwater environments of this ' property. The preliminary data suggest that the plume has not been defined to the northwest and to the northeast in the suspected historical down gradient direction. ' Geological Technics Inc. recommends that the lateral and vertical extent of impacted soil and groundwater be defined and remedial alternatives be evaluated. Our proposed approach to this problem is outlined below. ' • Hold a meeting with Jay and Verna Sinclair, Ron Rowe, Don Light, and Ray Kablanow to discuss cost effective options and approaches and to develop a ' schedule of tasks to be performed. Items to be discussed would include the following, plus other concerns or alternatives. ' • To move forward towards site characterization Geological Technics Inc. recommends that the magnitude and lateral extent of the plume be evaluated using cost effective reconnaissance techniques i.e. a passive soil gas survey. The boundaries of the plume identified with the reconnaissance techniques would then be confirmed using conventional soil and groundwater sampling methods ' i.e. soil borings and groundwater monitoring wells/Hydropunch. The locations and methods of plume delineation confirmation testing would be proposed in a site characterization work plan. ' We recommend that Sinclair Trucking seek pre-approval from the USTCFP for conducting the passive soil gas survey and preparing the site characterization ' workplan. Once the soil gas survey has been completed and the results written in a report with conclusions, and the work plan has been prepared and approved by the County, Sinclair Trucking could solicit bids using the work plan as the ' bidding documents' scope of work. In this manner unit cost can be evaluated line item by line item and additional work could be performed using th,ese unit costs by obtaining cost pre-approval from the USTCFP. • Once the site's plume has been fully characterized then remedial options could be evaluated which may include but not limited to intrinsic attenuation, excavation, ' groundwater pump and treat, and/or air sparging and soil vapor extraction. The nature of the site may require that an approach utilizing combined technologies be employed to mitigate this site. Goals of site remediation would be to remove ' the source of petroleum contamination to the groundwater, containment of the groundwater plume, mitigation of the groundwater plume to protect