Geophysical Mapping of Freshwater-Saltwater Interfaces: Examples from the Coastal Plain Aquifer System of

North Carolina

Lewis LandNew Mexico Bureau of Geology and Mineral

Resources

Central Coastal Plain Capacity Use Area (CCPCUA)

• Encompasses 15 counties in eastern North Carolina, within which ground water use will be regulated to protect long-term productivity of aquifers beneath the coastal plain.

• 100,000 GPD threshold for permitting ground water withdrawals from Cretaceous and Tertiary aquifers.

Summary

• A TDEM sounding used alone does not provide the same degree of vertical resolution as a borehole record.

• However, a much higher effective level of precision can be attained when TDEM soundings are integrated with existing borehole data, effectively increasing the density of subsurface information by several hundred percent.

Summary

• Electromagnetic soundings provide an efficient, inexpensive, and semi-quantitative method for evaluating ground water resources in coastal aquifers, on both local and regional scales.