INTERPRETATION OF AIRBORNE ELECTROMAGNETIC AND MAGNETIC DATA IN THE 600 AREA

GD, CUMMINS

Hanford Site (Wash.)

关键词: Magnetic Surveys;    Magnetic Fields;    Helicopters;    Geologic Structures;    Floods;   

DOI  :  10.2172/1000064
RP-ID  :  SGW-47839 Rev 0
RP-ID  :  DE-AC06-08RL14788
RP-ID  :  1000064

美国|英语

来源: UNT Digital Library

【 摘 要 】

As part of the 200-PO-1 Phase I geophysical surveys, Fugro Airborne Surveys was contracted to collect airborne electromagnetic (EM) and magnetic surveys of the Hanford Site 600 Area. Two helicopter survey systems were used with the HeliGEOTEM{reg_sign} time domain portion flown between June 19th and June 20th, 2008, and the RESOLVE{reg_sign} frequency domain portion was flown from June 29th to July 1st, 2008. Magnetic data were acquired contemporaneously with the electromagnetic surveys using a total-field cesium vapor magnetometer. Approximately 925 line kilometers (km) were flown using the HeliGEOTEM{reg_sign} II system and 412 line kilometers were flown using the RESOLVE{reg_sign} system. The HeliGEOTEM system has an effective penetration of roughly 250 meters into the ground and the RESOLVE system has an effective penetration of roughly 60 meters. Acquisition parameters and preliminary results are provided in SGW-39674, Airborne Electromagnetic Survey Report, 200-PO-1 Groundwater Operable Unit, 600 Area, Hanford Site. Airborne data are interpreted in this report in an attempt to identify areas of likely preferential groundwater flow within the aquifer system based on the presence of paleochannels or fault zones. The premise for the interpretation is that coarser-grained intervals have filled in scour channels created by episodic catastrophic flood events during the late Pleistocene. The interpretation strategy used the magnetic field anomaly data and existing bedrock maps to identify likely fault or lineament zones. Combined analysis of the magnetic, 60-Hz noise monitor, and flight-altitude (radar) data were used to identify zones where EM response is more likely due to cultural interference and or bedrock structures. Cross-sectional and map view presentations of the EM data were used to identify more electrically resistive zones that likely correlate with coarser-grained intervals. The resulting interpretation identifies one major northwest-southeast trending preferential flowpath with several minor units running along a similar trend. This presumed path of preferential flow is compared with the tritium concentration levels observed for the 600 Area. Analysis of the magnetic field data shows the location of potential bedrock faults and lineaments which may influence the horizontal and vertical flow of water. Faults lying within, or in the vicinity of preferential groundwater flow paths may allow flow into or out of the otherwise confined basalt layers.