Improvements to Interstate 29 and Interstate 229 in southwest Sioux Falls, South Dakota, will add capacity to meet increasing demands and improve the safety of the roadway by reducing congestion.

"We are doing this project due to the growth of Sioux Falls," says Greg Aalberg, Engineering Supervisor with the South Dakota Department of Transportation. "We needed to increase capacity for traffic and enhance the safety aspects of the roadway for drivers."

The U.S. Census Bureau estimates the population of Sioux Falls has grown from 153,888 in 2010 to 171,544 in 2015. The South Dakota Dashboard, an online community information service, reports that during that same period, South Dakota's population grew at a rate of 5.4 percent, faster than the nation in general, which had a rate of 4.1 percent.

Forbes magazine considered Sioux Falls one of the best small places for business and careers in 2016, ranking it at number 20 in job growth and number 30 in the cost of doing business. The publication estimates 2 percent job growth and calls the city the cultural center of South Dakota, with its festivals, fair and party in the park. Forbes also says the city is a hub for retail trade, health care and financial services. 

About 45,000 vehicles use I-29 and I-229 daily. The volume is expected to increase to 65,000 by 2040.

"It's the busiest intersection in South Dakota as far as interstate goes," says Ryan Gulbranson with T&R Contracting of Sioux Falls, the general contractor. 

Working a Tight Schedule

T&R Contracting was the successful bidder to complete the $33.8 million job, which includes grading, concrete paving, bridge replacements, lighting and signage. In addition to the congestion, the pavement had reached its expected life and needed to be replaced, Aalberg reports.

About 1 mile of the project is on I-229 and 3 miles are on I-29. When the work is complete, there will be three lanes of traffic in each direction on I-29. Work began in February 2016 and is scheduled for completion in August 2017, with the majority of the work being completed in 2016.

"Dealing with the mass amounts of traffic, getting trucks in and out with materials, was one of the more challenging aspects," Gulbranson recalls. "It was a really tight timeframe for building two bridges and all that paving in one construction season. We're proud we were able to complete the work and open all lanes to traffic a couple days ahead of time with no accidents to employees." 

Aalberg agrees, saying, "it has been a challenging project to build and to maintain traffic while keeping workers and drivers safe." while keeping workers and drivers safe."   

Replacing the Pavement 

The department widening a section of the I-29 the northbound lanes, in 2015, to make two temporary lanes and a shoulder in order to maintain two lanes of traffic during the current project. In 2016, T&R removed all of the concrete and replaced it with new pavement. The company crushed the old concrete and mixed it into the roadway embankment, to make a strong roadway base and to process it into a gravel cushion product, a granular material that the concrete was placed on. Excess material was saved for future projects.

T&R used a string-less method to fine grade and pave the roads, using GPS technology. The method saves time and allows deployment of crews to other aspects of work.

"It is a time-saving process," Aalberg says. "I think it's cost effective not only to the contractor but to the department. You don't have a crew out there setting pins and string lines and checking it. You also reduce some errors. You eliminate the potential for irregularities in the string line when you are using a string-less operation."

The bridges are classified as continuous composite girder bridges and range from 303 feet long to 316 feet long and were built using steel girders, with concrete abutments and footings and steel piling and pier columns.

"The structures will look nice and be more aesthetically pleasing," Aalberg indicates.       

A New Type of Concrete Surfacing

In 2017, work will focus on bridge rehabilitation on I-29 at Exit 73. T&R will replace the pavement at all bridge ends and apply a two-coat bridge deck polymer high-friction chip seal to the deck. The contractor will complete the work at each bridge, one half at a time, reducing I-29 to one lane while the work is being accomplished. 

Also subcontractor crews will apply a Next Generation Concrete Surfacing (NCGS) texture to the concrete placed in 2016. T&R hired an entity familiar with the NCGS grinding process. 

"NCGS is a surface planning process," Aalberg explains. "They grind for smoothness first, and after they have achieved that, they make the final pass and cut the longitudinal grooves in. It's done after the concrete has received design strength."

The American Concrete Pavement Association reports that the texture was introduced about 20 to 30 years ago. It indicates the texture's properties are predictable and are the most quiet, nonporous textures yet developed. The process uses conventional grinding equipment and blades, using a different head configuration and a two-pass process. 

This will be the first time this surface texturing and grooving has been applied in South Dakota. It has been used in other locations with success with a goal to make the pavement smoother and quieter. There are many residences to the west and north of the interchange.

"The biggest thing left is the NGCS grinding and clean up," Aalberg says. "Early indications are that the process is providing both a smooth surface and a quiet surface, which is shat we want. We wanted to try the NCGS surface texture to mitigate as much noise as we could. The most outstanding thing is how quiet the pavement is where we have completed the NCGS. It is amazingly quiet. When you transition from an existing longitudinally timed surface onto this, there is a significant and noticeable difference in the level of sound."