Area Of Expertise:
Transportation Engineering
022 (2) image overlay
022 (2) image overlay
Area Of Experience:
County

County Highway 22

Late in 2013, Richland County, North Dakota hired Interstate Engineering to provide professional engineering services for work on County Highway 22. The project was an overlay, mine and blend, and curve reconstruction project on 4.5 miles of the road, stretching from the junction of State Highway 127 heading west.

Thanks to the large amount of agriculture in the area, this roadway services one of the larger elevator cooperatives in the area where trucks transfer their agricultural goods.
The roadway was bituminous pavement until 2005 when Richland County placed six inches of aggregate over the top. At the time, the bituminous surface was beyond the point of an overlay being effective. In 2013, it was time to relook at the road and the options available to accommodate the truck traffic.

Funding for the project came from HB1358. This funding allowed County Highway 22 to become a federal aid road and increased the legal weight limit from 80,000 pounds to 105,000 pounds.
The design for the best use of this roadway was as follows:
1. Add two inches of aggregate base material over the existing roadway
2. Blend the material with the existing aggregate and bitumen
3. Treat the top six inches with Base One stabilizer
4. Add a five-inch bituminous surface.
5. Federal aid required two intersections be converted into curves.

The initial design included two 55 mph curves. This met opposition from local landowners. In order to secure the appropriate amount of right-of-way, the team offered three alternatives to the County and landowners (35 mph, 45 mph, and 55 mph curves). After extensive debate, the groups agreed on the 45 mph curve alternative. Interstate Engineering secured the right of way.
The plans and specifications were completed, and the project was let on May 7, 2014. Central Specialties, Inc. (CSI) out of Alexandria, Minnesota, was the low bidder. The County hired Interstate Engineering to perform the construction engineering.

Construction began in late May with the construction of the two curves. Borrow material came from the obliterated sections of the existing road and some off-site borrow. Due to the wet, late spring and high water table in the region, the project did not start out as one would anticipate. The borrow material was at 30% moisture, with the optimum being around 14%. Water was pumping out of the ground as the dozers and excavators moved the material. It was decided that the contractor would bring the curves up to plan grade to bridge the water table, and let the weight of the material push the ground water down and away from the new curves. Once the curves were built to grade, the contractor spent the entire month of July digging up the roadway, disking and plowing the material to dry it out. In early August, after numerous failing density tests, the curves met specifications, and the next phase of the project could begin.

During the design phase, it was assumed that the existing typical section included four inches of aggregate base below the existing bituminous surfacing. Once the reclaiming process was started, it was determined that the existing base was clay (not four inches of the aggregate base as believed). The reclaiming machine was burning through teeth, as they were not cooling off in the clay. It was decided by IE, CSI, and the County to suspend blending operations as more problems could occur due to the silt clay layer under the bituminous. The Contractor spent one week hauling in aggregate base material across the 4.5 miles. Base One material was then added to the aggregate base and relayed.

Paving started in late September and finished two weeks later. CSI paved the five inches in three different lifts and used three different paving crews.

Shoulder work and clean-up was finished by the end of October. The project is not complete as there are some permanent pavement markings to be placed at the railroad crossings.
Despite the setbacks and challenges, the County was happy with the result and Interstate Engineering continues to work with them on numerous projects.