Landslides along Natchez Bluff in Natchez, Miss., have been a problem for centuries. However, by tackling one section of the bluff at a time, great strides have been made in restoring the erosion-damaged area and preventing further erosion. A 1000-foot section of the bluff was stabilized by an innovative retaining wall project built by Hayward Baker Inc. of Atlanta.

Natchez Mayor Larry L. Brown made an appeal to the National Resource Conservation Services (NRCS) for emergency assistance in the late 90s. Hayward Baker was eventually awarded a three-phase contract to stabilize and restore much of the bluff that had slid away.

"This was an unbelievable project, and probably the most exciting project I ever worked on in my entire career," said John Wolosick, vice president of Hayward Baker Inc. "A 74-foot high retaining wall is as high as an 8-story building!"

A combination of soil nailing, shotcrete and a Keystone retaining wall stabilized a 74-foot bluff and restored the front yards of several historic houses. The project began with the stabilizing of Learned Mill Road, which ran from the top to the bottom of the bluff.

Phase 1 included the site investigation and establishing of a temporary access road for the residents at the bottom of the bluff. Using a 1985 study of the area conducted by the U.S. Army Corps of Engineers, Hayward Baker began its geotechnical investigation of the site.

"The original concept was a challenge from the beginning," Wolosick said. "The [total] wall that we have there is 74 feet high. When you go out and look at fhat landslide it's mind-boggling to figure out how you would fix something like that. We thought we were going to have to bring in cranes and reach across from the back yards of these houses and suspend drills in the air. We didn't know how we would do it. The Corps of Engineers, in their assessment of the problem in 1985, suggested that they backfill a big slope all the way across Learned Mill Road and put the road in a tunnel. They estimated that cost would have been $20 million.

"This was only a 1000-foot long section of the bluff, so to spend $20 million [on that section] would have never been done. We did our fix in 1997 for only $5 million. They've already spent $20 million, and will spend $20 million more, but that will fix miles of bluff."

Several of the houses on Clifton are in the National Register of Historic Places: antebellum, four-story mansions, some of which have been turned into bed-and-breakfasts.

Phase 2 involved the construction of two lower retaining walls along Learned Mill Road, which had been eroded by 4 to 6 feet in places. At the lowest level, the design/build team constructed a 990-feet long wall, 32 feet in height.

"We stabilized Learned Mill Road using a technique called soldier piles and tiebacks, where we put steel beams in the ground, put wooden boards between those beams and drilled cables into the earth to hold those up," Wolosick said.

Phase 3 involved extending the eroded front yards of homeowners along the bluffs. "There used to be a road called Clifton Avenue that ran along the bluff, but it slid off [due to erosion]," Wolosick said. " When we were first called and went out to look at it, there was concrete pavement hanging out into the air because the bluff had slid away and taken the whole roadway with it."

Keystone standard units were used to build the 32-foot retaining wall, which was backfilled with lightweight aggregate "This was an unbelievable project, and probably the most exciting project I ever worked on in my entire career," said Wolosick. "A 74-foot high retaining wall is as high as an 8-story building!"

Several of the houses on Clifton are in the National Register of Historic Places: antebellum, four-story mansions, some of which have been turned into bed-and-breakfasts. "The folks who live along that street were accessing their houses from the rear alleys since they lost their front driveways," Wolosick said.

Hayward Baker used a technique called soil nailing to solve the problem. "You drill and grout steel bars into the ground to shore it up and then spray shotcrete over the face of the soil to keep it from eroding anymore," Wolosick said. "In addition, we also built a wall out into the air and we actually added land back to Natchez that had slid away. We built a mechanically stabilized embankment wall by using Keystone retaining wall.

The remaining area was stabilized with geogrid soil reinforcement and filled with lightweight aggregates. "We backfilled that wall with lightweight aggregates in order to keep from adding a lot of weight [that would] further destabilize the bluff," Wolosick said. "There was a shelf left on the bluff while we were stabilizing it, then we came back on that shelf and built this 32-foot high Keystone wall."

Wolosick said the real breakthrough in the project design was when the team decided to take land away and then give it back in the form of a new wall. "Nobody had ever thought about digging some of the good dirt out, which is what we had to do. We actually dug 15 feet further back from the edge of the bluff. What that allowed us to do was to get our equipment in there on the ground instead of hanging it from cranes. So we could work on the ground, and that saved probably 50 percent of the project cost right there. We dug within a few feet of the front porches of these houses."