HARPERS FERRY – Adding safety measures to protect motorists from falling rocks and boulders along U.S. 340 below Loudoun Heights will be the focus of a West Virginia Division of Highways public meeting on Thursday, Feb. 6 in Harpers Ferry.
Highway officials plan to present the results of a geological stability survey of three “priority slopes” over U.S. 340 between Chestnut Hill Road and Harpers Ferry Road. Safety measures that might be used would also be part of the presentation during the public information meeting.
After examining the stability of rocky cliffs above U.S. 340 in January 2018, a Pennsylvania geological engineering firm recommended about $14 million in “slope remediation” safety measures for that highly traveled half-mile stretch of highway.
The stability study also prompted state highway officials to shore up a deteriorating embankment next to Chestnut Hill Road at U.S. 340.
Meanwhile, several possible long-term safety measures were recommended in the 70-page report prepared by HDR Engineering Inc. based in Pittsburgh. Those measures include possible combinations of rock bolting, blasting, berms and barriers to protect motorists from tumbling rocks and boulders.
Different barriers or metal mesh were suggested in different combinations for certain geological conditions—from overhanging ledges to saplings growing out of crevices—found along the three slopes studied. Removing, trimming or bolting loose rocks were also recommended.
Installing any of the recommended safety measures would require temporarily closing the roadway, the report states.
State highway officials are aware of several instances when rocks ranging from six inches to three feet in diameter have tumbled onto the highway, according to the rockfall report. “A majority of failures that occur along U.S. 340 are rockfalls of minor volume and impact.
“However, large rockfall events have occurred in the past and will pose a risk in the future.”
Most rockfalls along the highway appear to occur during rapid freezing and thawing cycles in winter and spring, the report states.
Groundwater regularly seeps from different areas of the slopes and cliffs. “The potential for dislodging blocks from freeze-thaw action is high in this area.”
HDR Engineering called its 2018 findings a “preliminary assessment.” Any long-term safety system to prevent rocks from falling into the highway would be years away, state highway officials have said.
The highway agency set a budget of $830,000 to conduct the rockfall survey and prepare possible engineering designs for a system that would protect motorists from falling rocks along the highway.
U.S. 340 is considered a major traffic corridor into and from West Virginia. Traffic counts conducted three years ago found more than 30,000 vehicle trips are made daily on that 45 mph section of the highway, about half of the volume of traffic then flowing on Interstate 81 at Martinsburg, state highway officials have said.