Inel Cold Test Pit Demonstration Of Improvements In Information Derived From Non-Intrusive Geophysical Methods Over Buried Waste Sites

A high density, multiple sensor geophysical survey was conducted at the Idaho National Engineering Laboratory<br>(INEL), a Department of Energy test facility, at its Cold Simulated Waste Demonstration Pit (CTP). The CTP site<br>was specifically prepared for testing and evaluation of remediation technologies, including geophysical surveys.<br>The INEL has been involved in the testing and development of nuclear power production since the early 1950’s. A<br>variety of waste products from nuclear processes on and off-site have been disposed of, primarily at the<br>Radioactive Waste Management Complex (RWMC). Included are waste products from the Rocky Flats Plant<br>(RFP) in Colorado. The simulated waste forms constructed for the CTP were formulated from 1971 to 1973<br>records of waste shipments from RFP, and deposited in a similar fashion as described in the records.<br>The objectives of the geophysical demonstration were to reduce risk, and improve the technologies that help to<br>meet DOE’s cleanup goals by providing a foundation for further advancing the use of geophysical methods for the<br>detection of buried waste. In this demonstration, the use of high density, multiple sensor data sets, advanced data<br>processing techniques, and the testing of an innovative time domain electromagnetic instrument were conducted.<br>Other instrumentation used included frequency domain electromagnetic conductivity profiling, total field<br>magnetics and vertical magnetic gradient, time domain electromagnetic profiling, and ground penetrating radar.<br>The geophysical field survey was conducted over a 15 day period on a grid over the CTP of about 300 feet by 140<br>feet. For most geophysical measurements a 2.5 foot grid was used.<br>The TDEM metal detector and the in-phase component of the FDEM conductivity surveys provided good<br>resolution of the CTP boundaries, berms and contents. The results over the CTP provide good illustrations of the<br>influence of the local geologic setting to sensor behavior. The GPR data was ineffective in providing any<br>information about the contents of the CTP. EM conductivity and magnetic data were influenced by variations in<br>thickness of surface sediments and basalt bedrock. These factors provide evidence of the necessity of using<br>multiple sensors for buried waste delineation. A combined interpretation using all available data was successful in<br>defining the CTP.<br>In addition, methods were developed to display the locations of the identified targets in a 3-D which can be<br>manipulated in real-time on a graphics workstation. Forward models were developed for the EM61 and used to<br>evaluate the resulting data.