After six years, a 72 mi. (116 km) portion of U.S. Highway 12 in northern South Dakota will be completed to create a four-lane expressway. The final year’s work, a 2.8 mi. (4.5 km) stretch through Rush Lake, will be completed by mid-October.
Work on the $60-million project consisted of urban reconstruction as well as additional rural lanes to change the pre-existing two lane road into a four-lane divided highway, except through Rush Lake, which is undivided.
Working on a waterway requires that certain natural resource stipulations be met, creating more of a challenge for the contractor, which is why this portion of the project through the lake was left until last.
“The DENR [South Dakota Board of Water and Natural Resources] has created a plan that severely limits the water exposure,” said Craig Mizera, project engineer with SD/DOT. The plan requires that only a 500-ft. (152 m) section of the bank can be exposed at one time to prevent erosion.
The process begins by pushing the riprap from a 500-ft. section of the existing bank into the water to form a base. Gravel is then placed until the gravel is above the water.
“It makes it difficult but it is working well,” Mizera said. “We try to confine the times when we are working close to the water when the wind is not out of the south [which is the side of the highway where the additional two lanes are being added]. Then we put drainage fabric over the gravel as soon as possible to prevent washout.”
He added, “So as we build a section, we cover it with drainage fabric, add riprap and then we move onto another section.”
The lake is between 2 and 8 ft. (.6 and 2.4 m) deep; the deeper water and the waves it creates is a challenge.
“We need the riprap placed in a timely manner and make sure the equipment is lined up so it is where it needs to be,” said Shaw Loiseau of Loiseau Construction, the general contractor of Flandreau, SD. “The wind is more of a factor than the water. If the wind is out of the south hitting the shore, we can’t haul material. So we try to work on the top adding subsoil.”
Loiseau explained, “We get two feet of fill on and then we start on another 500-foot section until that section also has two feet of fill, and then we continue filling on that 1,000-foot section.”
He added that they continue in this process so they can work on longer sections to make the process more efficient. This 4-in. (10.2 cm) granular material is used until the roadbed is up to sub grade.
When working in water like this, Loiseau said they usually use clay. “This is the first time we’ve used pit run,” he said. “I would rather use clay because it doesn’t soak up the water as quickly, but there isn’t a lot of clay in this area.”
Approximately 550,000 tons (498,952 t) of material will be hauled by the time this 2.8 mile section of the project is complete, 10 ft. (3 m) is fill, 10 in. (25.4 cm) is gravel, and asphalt will create the 40-ft. (12.2 m) wide surface, Mizera said.
Approximately 15 trucks, side and belly dumps, haul the fill from a site approximately 5 mi. (8 km) away, making it possible to haul approximately 7,500 cu. tons each day, a process that took approximately three and a half months, Loiseau added. Graders, dozers, a power sprayer to place water to help with compaction, and a 42-in. roller to pack the fill, are all part of the process.
Four pipe extensions also were extended under the roadway through the water to allow water flow and an equal water level to equalize the pressure on both sides of the road, Loiseau added. A box culvert on the west end of the project also was extended to help equalize the water pressure.
The six year project, which began in 2000, was divided into four phases and 13 projects.
“This section [going through Rush Lake] is the last segment of those projects, Loiseau said. “A good thing about the project is there is no traffic to deal with; we’re just adding another set of lanes, and we could finish the work before winter so no temporary surfacing was needed.”
Prime contractor, Upper Plains Contracting of Aberdeen, incorporated a new method of inserting dowels with a dowel bar inserter, rather than with dowel baskets.
“This technique is new to South Dakota and this is possibly the first time it has been used in the state,” said Nathan Reede of Upper Plains Contracting.
“Typically dowel baskets are used and the dowels are placed on grade. But we brought in dowel bar insertion, using a Gunner and Zimmerman 1500 and a Gomaco 2800 to insert the dowels into the mix for vertical and horizontal placement. We’ve viewed the process and the methodology on other concrete paving operations and with the miles of dowels needed on this project we decided this was a great opportunity to do this.”
The process is computerized and sets the dowels at 20-ft. (6.1 m) joint spacing, which is required in South Dakota, and automatically drops the bars using a four-prong fork.
The machine vibrates and places the bars in a vertical and horizontal area that is 24-ft. (7.3 m) across and 26-ft. (7.9 m) wide. The machine then pulls itself out and finishes off the pavement before moving on to the next location, Reede explained. “We used this on about 40 miles on the Eastern Dakota Expressway and it enhanced production.”
The machines are costly, but Upper Plains Contracting does a lot of highway work, requiring a huge amount of dowel insertion, Reede said, so the machines are beneficial even though transporting them requires seven or eight semis.
For the dowels to stay in the proper place and not sink to the bottom, a well graded concrete mix is needed.
“We adopted the use of the Air Force constructability chart to try to find gradation for better workability,” Reede said. “It is like making a cake and inserting plums, you want a well composite grade of different rock sizes so the dowels stay in the right location. It took us four to five months with multiple presentations and multiple mix design runs to get acceptance.”
For the mix designs, Upper Plains Construction worked with Jeff Senst in the regional SD/DOT office to get the whole process put into place.
“We flew in representatives from Gomaco and put together some testing and verify how we would do it,” Reede said.
To come up with the proper mixes, “We ran about 10 different mix designs of varying strengths, before coming up with the proper well-mixed design,” Reede said. “It is a hell of a learning experience for a contractor.”
On the first day on the job, they paved approximately 500 ft. and stopped to cut three or four portions apart and show the dowel placement and the process.
“It is not always easy trying to pioneer something new,” Reede said. “In some testing labs by Belfourche, SD, the inspector said this is one of best operations he’s seen. It can definitely do the job and stand up to the methodology of placing baskets. I feel like we did something right.”
Upper Plains Contracting is now using the process on Highway 85, using the Gunner and Zimmerman 1500, from Spearfish, SD, to Belfourche in western South Dakota, and in Sioux Falls, SD, on the eastern edge.
“The process is running on both sides of the state,” Reede said. CEG