An open-pit mine that would supply road-building and other construction-related materials is being proposed for an area off U.S. Highway 17 in southern Beaufort County.

Martin Marietta Materials Inc., the company proposing the mine, said the mine is needed to help keep road-construction costs down. The proposed project has raised concerns among local officials and some environmental advocates about its effects on groundwater wells in the area and the fish and fisheries habitat in Blount’s Creek, a tributary of the Pamlico River.

Martin Marietta Materials has received a permit to dig a 649-acre open-pit aggregate mine that would be about 100 feet deep and operate a rock-crushing operation and associated activities on 1,664 acres site about seven miles east of U.S. 17 on the border of Craven and Beaufort counties.

While the proposed mine will destroy about seven acres of wetlands, its primary effects on the environment will come from pumping some nine million gallons of water a day from the Castle-Hayne Aquifer to drain the mine and the discharge of that water into two tributaries of Blount’s Creek, according to Heather Deck, riverkeeper for the Pamlico-Tar River Foundation.

“It’s going to change the creek,” Deck said in a recent interview.

The project is under review by the U.S. Army Corps of Engineers and the N.C. Department of Environment and Natural Resources.

The deadline for commenting on the project’s effects on wet-

lands is Dec. 31. PTRF plans to ask the U.S. Army Corps of Engineers for a two-week delay of that deadline to allow a more-thorough review of the project, Deck said.

In its application, Martin Marietta Materials proposes to mine marine limestone found in the area. The limestone would be crushed into rocks of various sizes to be used by the N.C. Department of Transportation in road construction and by others in residential and commercial building projects near New Bern and Washington.

The mine would be on land that would be leased from Weyerhaeuser Co. That land is part of a 90,000-acre pine plantation.

The mine would be in operation for about 50 years and be similar to the Clarks Quarry operated by Martin Marietta Materials near New Bern and four other mining operations owned by the company in eastern North Carolina, according to applications filed by Martin Marietta Materials with various state and federal agencies.

In its filings, Martin Marietta Materials said that most of the crushed rocks currently supplied to projects in Beaufort and Craven counties come from the Clarks Quarry, which will run out of its reserves in the coming years.

The company maintains the new quarry is needed because the costs of transporting materials from other existing quarries owned by Martin Marietta Materials are “located further to the South … and would not be able to serve the primary market for the Clarks Quarry site. The cost of transporting the product would greatly increase with these options and would have an adverse impact on the market. … Once Clarks is depleted, there are no other known economically viable aggregate deposits in this part of the state other than the Vanceboro site.”

While it states that “(b)ecause of the type of facility proposed and extensive disturbance required, the wetland and water impacts are unavoidable,” Martin Marietta Materials maintains the alternatives that were considered were determined to be impracticable.

A marine biologist with the N.C. Division of Marine Fisheries believes the fresh water discharged from the mine could adversely affect the fish and seaweed that provides valuable habitat for those fish.

Blount’s Creek and Blount’s Bay, which flow into the Pamlico River, are home to a variety of fish, including important migrating saltwater fish such as striped bass and freshwater fish such as yellow perch, according to fisheries and wildlife officials.

“If high volumes of discharged water enter Blount’s Creek, the discharges could potentially decrease salinity and increase turbidity in that creek,” Kevin Hart, with the DMF regional office in Washington, wrote in a May 17, 2011, letter. “The ecological community in Blount’s Creek could change due to the potential decrease in salinity and increase in turbidity, resulting in a loss of existing (submerged aquatic vegetation) and conditions unsuitable for revegetation.”

PTRF’s Deck is concerned that a one-day fisheries assessment by Martin Marietta Materials was not nearly comprehensive enough to adequately evaluate the project’s effects on fish in the waterway and their habitats.

The project has raised concerns by county officials because of its proximity to some of the county’s drinking-water wells.

The mine will be located about five miles from the county’s drinking-water wells off of N.C. Highway 33 near Chocowinity.

In a letter dated May 11, 2010, Curtis Jett, supervisor of the county’s water department, to DENR’s Land Quality Section wrote that there were “concerns about the dewatering of our wells.”

Wells that supply drinking water to Vanceboro are located about five miles from the proposed mine.

Vanceboro officials contacted by the Daily News said they were not aware of the project but would study it for any affects on that town’s drinking-water supply.