Wetlands and rare mussels could be the best block to the Navy's plans to build a practice airfield in northeastern North Carolina.

The word from representatives of opponents to the Outlying Landing Field, or OLF, came a few days after the Navy said it would delay the release of an environmental impact study until spring, the Virginian Pilot reports.

The study was expected to name the Navy's preferred airfield site from among five - three in Virginia and two in North Carolina.

Wetlands at both North Carolina sites have been underestimated and the necessary permits could be denied, according to a July 21 letter from the U.S. Army Corps of Engineers to the Navy. The letter was released by a firm hired by Camden and Currituck counties to oppose the field.

The Navy has been told "several times" about this deficiency in their environmental study so far, the letter said.

In Gates County, a study in the Chowan River found a mussel listed as endangered in North Carolina — the Lampsilis cariosa, or yellow lampmussel — and five others listed as threatened.

That study was done for Gates County residents who oppose the field.