Surface Proton Magnetic Resonance Sounding System Evaluation

A recently developed, nonintrusive, surface geophysical technique known as surface proton magnetic resonance sounding (MRS) can delineate the spatial distribution of aquifer-system units (aquifers and confining units) and provide information about aquifer effective porosity and permeability. This technique may provide a cost benefit over traditional methods of obtaining these data, such as drilling, coring, sediment lab analysis, well and pump installation, and aquifer and tracer testing. However, the MRS method is still in development and has yet to be validated by comparing these data to values estimated from data collected at the same sites, same dates, and equivalent depth horizons using traditional well or borehole testing and analysis methods. The U.S. Environmental Protection Agency (USEPA) is interested in evaluating the accuracy of MRS data to determine if the technique can produce results comparable to traditional, but more intrusive, techniques typically used to characterize the hydrologic framework of contaminated shallow aquifer systems.

Objectives

Evaluate the adequacy of MRS technology to delineate aquifer and confining units and estimate aquifer free-water content (effective porosity) and permeability by comparing data collected from surface geophysical surveys at Ash Meadows National Wildlife Refuge (NWR), Nevada, to borehole-lithologic and aquifer-hydraulic data from selected sites along survey transects.

Strategy and Approach

MRS and Transient Domain Electromagnetic (TDEM) surface geophysical techniques will be applied at Ash Meadows National Wildlife Refuge to determine the depth to ground water, delineate aquifer units and confining zones, and estimate effective porosity and permeability values at selected depths below land surface. These tasks will be completed by 1) performing MRS and TDEM surveys along previously surveyed transects, 2) drilling two boreholes to collect lithologic cuttings and core samples at selected sites along surface geophysical survey transects, 3) performing borehole geophysical logging, 4) installing small-diameter casing and performing slug tests, and 5) comparing results of MRS and TDEM surveys to data collected from boreholes and test wells.

Relevance and Benefits

This study will help to assess a relatively new and innovative technique that may be used as an alternative and non-intrusive method to estimate hydraulic properties and delineate aquifer systems. The proposed study is in accordance with several components of the Nevada Water Science Center Science Plan, the USGS Water Resources Discipline Western Region Science Plan, and the Environmental and Natural Resources mission goal of the USGS Strategic Plan for FY 2000-2005.