The South Carolina Department of Transportation announced its preferred route for the southern leg of Interstate 73 in Columbia on Tuesday - between the towns of Marion and Mullins.

While representatives of the state's conservation community said the route was largely acceptable, they expressed disappointment that the route did not follow the existing right of way of U.S. Highway 501 and the road would cross a State Heritage Trust Preserve on the Little Pee Dee River.

As planned, the southern leg would run from Interstate 95 in the Dillon/Latta area to the Conway/Myrtle Beach area. The preferred route runs along a few existing rural corridors, including State Route 917.

If built, the new interstate would intersect with the Conway Bypass, which runs between U.S. 501 and U.S. Highway 17 in North Myrtle Beach. The northern leg would run from near Rockingham, N.C., to I-95.

As originally conceived in 1991, I-73 would have run from Sault Ste. Marie, Mich., to Georgetown or Charleston. Since that time, little has been built. Residents of Michigan and Ohio have expressed lukewarm support for or outright opposition to the road, and routes through both of those states now appear unlikely. The interstate is still in the planning stages in Virginia but has seen some construction in both West Virginia and North Carolina, where approximately 35 miles have been completed. Heated opposition to I-73 from South Carolina conservation groups and residents of Georgetown, McClellanville and Charleston led the South Carolina Department of Transportation to pick the more northerly route for the Southern Project. The South Carolina projects combined would cost an estimated $2 billion and carry 60,000 cars along 90 miles of road.

The "Northern Project" for I-73 is in the middle of a three-year environmental review stage and the DOT has not yet indicated a preferred route.

According to I-73 Project Manager Mitchell Metts, the DOT worked hard to arrive at a route that minimized the negative effects on residents, including 1,708 acres of farmland and 384 acres of wetlands.

"The route has the least effect overall on wetlands of any of the alternatives," he said.

While groups including the Coastal Conservation League, the Southern Environmental Law Center and Wildlife Action agreed that the wetlands impact was minimized, there was disappointment that it might be built through a Heritage Trust Preserve and that a less-environmentally harmful use of the U.S. 501 corridor was not used between the towns of Rains and Aynor.

"If we had our druthers, we'd have liked to have seen the development and widening of an existing corridor," said Bunny Beeson, president of the 14,000 member Wildlife Action group. "Instead, we're cutting up the county and the state in a place that's already among the worst in the nation for sprawl."

Metts said that the DOT had considered utilizing the 501 corridor, but found that limiting access to its many local drivers and purchasing right of way would be prohibitively disruptive and expensive on a project that still has little money.

Given the state and federal government's already limited funding for highways, Metts said that the DOT is likely to explore public-private partnerships that would make I-73 a toll road. Typically, he said, that the federal government puts in 80 to 90 percent of an interstate budget and expects a state to fund the rest. "But it would be tough for us to match even if we got that money," he said.

Reach Chris Dixon at (843) 745-5855 or cdixon@postandcourier.com.