An alternative to aggregate, bituminous road surfacing

Road 120 in Becker County, Minn., is 26 ft wide and 1.6 miles long, and its average daily traffic (ADT) was 270 in 2004. This section of the road is populated with homes, hobby farms and a large dairy farm. It is also a shortcut for several townships to the nearest blacktop.

This dusty section of road, which had washboard areas and lots of loose aggregate, was becoming very costly to maintain, and the county received many complaints about it from the public. The section was bladed twice weekly at a monthly cost of $1,600. A half-mile section of the road received dust control each year at a cost of $1,973. Annual regraveling cost an additional $3,840.

Yearly, maintenance costs totaled $17,013, or $10,630 per mile.

The county looked at three options to solve these issues. The first option was to complete a base and bituminous project with 5–in. Minnesota Spec. CL-5 base and 2 in. or more of bituminous at an estimated cost of $250,000.

The second option was to complete a 1.6-mile Otta seal project at a present day cost of $71,500 (approximately $44,687.50 per mile). This project consisted of 3–in. Minnesota Spec. CL-5 base material, which would be stabilized with Team Lab’s Base One aggregate base stabilizer to gain additional strength. To finish the project, an Otta seal surface would then be applied.

Finally, the county could maintain the status quo at $17,000 per year, but still have all the public concerns and complaints.

The county selected the second option as a trial project in 2004. This road was a county-aid road funded by local taxes, and the Otta seal method was far less costly than the bituminous, said John Okeson, Becker County’s maintenance superintendent.

“This would give us a good pilot project as we’ve had great success using [the aggregate base stabilizer] in other base stabilization projects,” Okeson said.

The project took four days to complete.

The county added 3-in. of the base material, then added the stabilizing chemical to the base using a pressurized water tanker. On the surface, the county used HFMS-2S high-float emulsion oil and covered it with OS-1 cover material.

“The results have been very promising, even with the large trucks hauling over this section,” Okeson said. “The following year, we chip-sealed the road to give it a smoother finish.”

The project is in its fifth year and has withstood four harsh Minnesota winters. There has been minor transverse cracking, which the county filled with rubber, and minor areas that required hand patching with cold-mix material.

Since this first project in 2004, the county has completed several miles with great success, Okeson said.

“With the continued success of each project, the stabilized base and Otta seal, we’re looking at a life of at least 15 years,” he said. “Public comment has been very positive, with additional requests for their county roads.”

All costs reflect 2008 numbers. Payback versus the regular maintenance is less than five years, with no dust or complaints about washboards.