6C (6) - Laserfiche WebLink

Home Browse Search

Ivy Tower Phase II February 27, 2012 Page 3 of 7 PROPOSED SCOPE OF SERVICES Ground Penetrating Radar Survey Prior to the initiation of any Phase II Environmental Site Assessment activities, Wightman Petrie proposes to conduct an extensive Ground Penetrating Radar Survey of the subject site for the purpose of identifying the potential presence of features such as previously abandoned and /or removed underground storage tank systems, cisterns and tunnels, as well as the presence of possible fill materials from prior demolition activities. Key areas of initial GPR Survey will be along the south side of Building 113 where the location of a former UST is thought to exist, as well as the cleared lot to the south of the entry drive from S. Lafayette Blvd. We would also propose the use of GPR for the basement area of Building 84, as confirmation that there were no buried features such as cisterns (approximately 32,000 gallons based upon identification at other locations on the Studebaker property). However, we understand that the thickness of the existing concrete flooring within the basement may have some bearing on the ability to perform such survey with any accuracy. Ground Penetrating Radar (GPR) offers the means to detect buried objects that are not otherwise detectable. In addition to the ability to locate metal objects (i.e., underground storage tanks, drums), GPR is able to detect non - metallic objects. The system sends radar pulses into the surface, receives, and processes the reflected energy. Through advanced processing technology, the system calibrates the di- electric constant of the surrounding material. When the signal is reflected from the material having a different di- electric constant, the signal is displayed on the screen as an anomaly. Depth can also be determined by processing the sampling interval and determining the size and comparing relative data to other objects detected. Characteristics of underlying soils effect the penetration of the radar through the ground. Sands and gravel offer the greatest depth penetration and clearest resolution. Whereas, dense saturated clays offer limited penetration of the radar signal. For purposes of this proposal, Wightman Petrie has assumed a depth limitation for the GPR of approximately 8 feet below land surface. Areas of the suspect former UST system location(s) will be scanned by GPR and delineated using varying interval grid patterns. Multiple scans in a north -south and east -west direction will be performed utilizing the GPR, looking for anomalies. Any identified anomalies (i.e., disturbed subsurface soils) will be marked on the surface using paint, as appropriate for utility locators and for soil boring locations by Wightman Petrie. Soil Sampling via Geoprobe Methodology Using Geoprobe methodologies (small track mounted hydraulically driven sampling probe) soil samples will be collected from a total of seven (7) locations. Boring locations will be determined based upon the results of historical document review and field data gathered from the completion of the Ground Penetrating Radar. In general, Wightman Petrie would propose to install at least three (3) soil borings within the cleared area to the south of Building 113 as a location for which the potential migration of contaminants may occur. Wightman Petrie would also propose the installation of a minimum of two (2) soil boring along the southern wall of Building 113 (area of likely historical UST system), depending upon the findings of the GPR survey. One (1) of the remaining proposed soil borings would be installed along the southern walls of Building 112 and Building 84. The final soil boring, as proposed would be located within the small grassy area to the west of Building 112, nearest United Drive and the former Industrial Fuels and Resources facility. For each of the Geoprobe boring locations, discrete soil samples will be collected at 5 -foot intervals throughout the soil profile until saturated soil conditions are encountered (assumed to be approximately 25 feet below land surface). Each soil sample interval will be screened for the presence of volatile organics by placing a portion of the soil sample into a plastic bag, allowing time for equilibration, and insertion of a photoionization detector (PID) probe to observe a reading of "total VOCs" in parts per million