Arkansas Highway and Transportation Department engineers have gone back to the drawing board in their quest to improve access to Interstate 430 from Cantrell Road in west Little Rock.
Out is the slip ramp they envisioned being built into the side of the hill down to I-430 north for traffic going west on Cantrell, also called Arkansas 10, after bids came in too high twice last year. In for now is a flyover that will take traffic over the interstate and allow it to merge from the outside northbound lane.
"We've taken bids on that job a couple of times where you're cutting into the mountain to have a slip ramp," Scott Bennett, the department director, said at a meeting of the Arkansas Highway Commission last week. "But we're actually looking at another alternative that we believe is cheaper that would go over 430 and swing back to the outside lanes northbound."
The latest proposal would have traffic traveling west on Cantrell Road and exiting Cantrell at the same location motorists do now to go south on I-430. The new ramp would begin at the southbound loop and carry traffic over the southbound lanes of I-430 and onto the northbound lanes, according to Danny Straessle, a department spokesman.
Reducing congestion at the interchange has proved vexing for engineers, who have been studying the corridor for more than five years. About 55,000 vehicles daily enter and exit the western end of the interchange, according to the latest department data.
That's about 5,000 more vehicles per day than five years ago when the department began studying of the corridor andinterchange. Driven by development west of I-430 that includes homes, businesses and other "traffic generators," the traffic is projected to increase to 76,000 vehicles daily within 20 years.
Department engineers thought they had developed a partial fix for the interchange: adding the slip ramp from Cantrell west to I-430 north.
The ramp would eliminate a movement in the interchange that requires westbound motorists now to turn left against eastbound traffic to access I-430 north at a traffic signal. Eliminating the movement would have moderated the congestion while the engineers worked on other areas of the interchange and corridor.
It also was conceived as a separate project, Straessle said, that needed to be completed before the department worked on what was envisioned as the next phase: converting the interchange into a continuous flow interchange, a design that removes left turns from the main interchange.
For westbound traffic, drivers wanting to turn left onto Rodney Parham would make that turn several hundred feet before the intersection. That traffic, controlled by a light, would move into a segregated lane, with another traffic light at North Rodney Parham where the turn would be executed.
Putting in the slip ramp proved too costly, however. Twice the department invited companies to bid on the project -- in October and again in December -- and twice they came in at more than $22 million. The department doesn't discloses its engineering estimates for the cost of the project, but the agency estimate for the project in the 2013-2016 statewide transportation improvement program was $11 million.
Putting in that ramp wasn't going to be easy. The project design called for the ramp to go down the side of a large hill from Cantrell to the interstate. Several residential properties are in and around the hill in a small neighborhood called the Johnswood addition, which includes the former home of the late poet and essayist John Gould Fletcher, one of the state's most eminent literary figures.
Because of the rocky terrain, explosives would be needed to help remove an estimated 55,000 cubic yards of material from the hillside as part of the project. That is equal to about 4,000 dump-truck loads, according to one engineer's estimate.
Special provisions for the project restricted any blasting "deemed necessary" by state engineers to between 8 and 10 p.m. on the section fronting I-430. Further, traffic on the interstate couldn't be stopped for intervals not exceeding 15 minutes "in order that the [blasting] activities can progress without endangering the traveling public," according to the project provision document. "Between closure periods the roadway must be opened for a sufficient time to allow re-establishment of the normal flow of traffic."
Another special provision for the project requires that the contractor limit lane closures to one lane with a maximum work area of 1¼ miles.
And no lane closure was permitted unless "active work will begin immediately," according to the provision. "In addition, when gainful work is not being accomplished in an area where a lane has been previously closed, steps shall be taken to return traffic to normal conditions -- that is, all lanes open to traffic in each direction within 1 hour after construction operations have ceased."
The penalty for a violation was steep.
"Failure to comply with this requirement will result in a lane use charge of $34,000 per hour for I-430 Northbound until work begins in the closed lane or the lane closure is removed," the proposal document states. "A lane closure will not be considered to be removed until all advance warning devices specific to the lane closure have been removed or revised. In assessing this lane use charge any portion of an hour will be counted as a full hour."
State engineers say the $34,000 represents the road-user cost during peak travel times and is based on a formula that cannot be changed.
With the new proposed ramp, the department is almost starting over, Straessle said. The project will require another public hearing and environmental review.
The project also puts into question the continuous flow intersection. At last week's commission meeting, Bennett said for the intersection of Cantrell and North Rodney Parham Road, engineers also were studying using a bridge to carry Cantrell traffic over the intersection.
"It's almost building an interchange because you'll have a bridge on Highway 10 that goes over Rodney Parham," he said. "And then from Rodney Parham, you would come under and there would have to be a connection to get you back to Highway 10."
For now, though, the designs remain in flux.
"Things are going to have to change," Straessle said. "What those changes will look like, we don't know yet."
In the draft statewide transportation improvement program, which covers 2016-2020, the department has programmed major widening for the Cantrell corridor between Pleasant Valley Drive on the east and Pleasant Ridge Road on the west. The estimated cost is $58.3 million.
Bennett said the department hopes to take the widening further west as part of the overall project for which the funding is unavailable now.
"It is basically additional capacity of either six to eight lanes all the way down to Taylor Loop," he said.
The department has applied for discretionary money under the Transportation Investment Generating Economic Recovery competitive grant program administered by the U.S. Department of Transportation. No individual grant can exceed $100 million, but if the department receives any money, it will be in the range of $10 million to $15 million, Bennett said.
Commission member Tom Schueck of Little Rock is confident that commuters will see improvement in the next few years. The project is scheduled to be awarded a contract in 2019.
"We're going to try to do this in the next five years," he said. "Traffic will get better through that area."
Metro on 04/25/2016