Flexibility Key in Adapting to I-90 Project Delays

Border States is responsible for all QC measures and has a certified lab technician conducting tests, as well a certified field technician monitoring pavement placement by taking density readings and core samples.

When the $14.6 million project is complete, the contractor will have placed approximately 160,000 tons of HMA that was produced at its nearby portable Beta parallel-flow, 400-tph asphalt plant. Reclaimed asphalt pavement (RAP) was not allowed in the project mix designs, with original trial mixtures consisting of 15 percent ¾-inch aggregate, 20 percent 9/16-inch chips, 46 percent manufactured sand and 19 percent quarried sand.

HMA placement

Border States used a Blaw-Knox PF-3200 paver to place the three HMA lifts required for the main travel lanes of the I-90 project. All three 2-inch thick mats were constructed with the DOT’s HVT mix design. Mix was transferred from the plant and deposited in windrows in front the paving crew, which used a Barber Greene material pick-up device to convey the HMA back into the hopper. Initial breakdown and density was achieved with an Ingersoll-Rand DD-130 vibratory roller, with a Dynapac 3116 roller used for shoulder work. A rubber-tire roller was also used during the placement of the base and intermediate courses.

Border States’ QC measures call for sample testing every 1,000 tons of HMA produced and then taking two core samples for every 1,000 tons placed. The density requirement for the project’s HVT mix was set at 92 percent.

Flexible Pavement Smoothness guidelines for the project were monitored by the DOT using a profiler to measure and analyze the International Roughness Index (IRI) of the final roadway surface of only the main travel lanes. Smoothness was evaluated on a lot basis, with a lot defined as a single paved lane 12-feet wide and one-tenth of a mile long.

If Border States maintains an IRI smoothness specification of fewer than 45 inches of surface deviations (1/4-inch) for every mile, the contractor can pick up another $125 incentive per tested lot (one-tenth of a mile). Incentives decrease as total length of deviations increase, and disincentives are levied if surface deviations exceed 75 inches per lane mile. If there are more than 100 inches if deviated surface, Border States is required to grind those surfaces.

In September, Lynn Anderson, general superintendent of paving for Border States, says work on the eastbound lanes had been completed and bridge work on the westbound lanes was underway.

“We experienced some significantly delays at the start of this project (due largely to the weather), and we know we’ll lose a large portion of the original completion bonus as a result of the delays, but we’re moving forward and expect to complete the westbound portion next spring,” Anderson says. “It’s been an interesting project (only the third DOT rubblization reconstruction in South Dakota, according to Anderson) and when we’re finished, I know we’ll have a very good road that meets the travel needs of that part of the state for a long time to come.”