The South Carolina Department of Health and Environmental Control last week certified a permit sought by Spectrum GEO. North Carolina has approved permits for both Spectrum and GX Technology.
The companies plan to use air guns to send sound waves through the water to survey. Conservation groups worry the guns could hurt endangered right whales and sea turtles.
While state waters extend 3 miles offshore, the testing will be done in federal waters farther off the coast. However, each state was allowed to review whether the testing is consistent with state coastal programs.
Several other companies also want permits to conduct surveys.