|FHWA > HfL > Projects > Minnesota Demonstration Project > Project Details|
Minnesota Demonstration Project: Reconstruction of Trunk Highway 36 in North St. Paul
The highway within the project limits is a busy commercial and light industrial corridor with a 2005 average annual daily traffic (AADT) of about 43,450, with 2.9 percent heavy commercial vehicles. Within the project limits, the existing highway had three at-grade signalized intersections and three at-grade nonsignalized intersections with significant congestion and numerous safety issues. The general project location is indicated in figure 1. Figure 2 shows the project limits.
Figure 1 . General project location. (Source: Google Maps)
Figure 2 . Project limits. (Source: Google Maps)
Pedestrian traffic was a concern because North St. Paul High School is located on the north side of the highway and a bicycle-pedestrian trail (Gateway Trail) runs parallel to the south side of the highway. The Gateway Trail is the most heavily used Minnesota Department of Natural Resources trail in the State.
In fact, this project was born of concern for high school students crossing the busy four-lane highway twice a day, on their way to school in the morning and returning home in the afternoon. Safety concerns coupled with the need to alleviate congestion for motorists traveling through six interchanges on this portion of the highway expanded the project from the need for a safe pedestrian crossing to a complete reconstruction.
Limited funds for this project focused designers on coming up with ways to save construction time and costs while maintaining a high level of safety and delivering a quality product. These challenges were an ideal match for the HfL goals and led to the use of innovation to make this project a reality.
When design was 50 percent complete, designers conducted a constructability review meeting and asked qualified contractors for input on how fast they could build the project and what maintenance of traffic would be the most beneficial. Given the sheer volume of earthwork, the most effective way to ensure safety was to keep all traffic away from the many trucks and earth-moving equipment. Completely eliminating traffic from TH 36 was determined to be the best-case scenario from a safety standpoint, one that would allow the contractor unrestricted access to all parts of the projects and expedite construction.
Public involvement was sought in the early stages of planning to help engineers decide whether to use a full roadway closure, which would disrupt traffic for an estimated 5 months, or stay with traditional staged construction techniques lasting up to 19 months. The result of a preconstruction telemarketing survey conducted for Mn/DOT by a private marketing firm concluded that among the local residents, commuters, and businesses, about 50 percent were in favor of a full road closure and 50 percent were opposed.
Considering the absence of strong public opinion and the anticipated cost and time savings of using the full closure, Mn/DOT took the opportunity to apply this innovative technique as a cornerstone to minimizing motorist impact on the TH 36 project.
TH 36 was converted to a four-lane freeway by removing the three at-grade signalized intersections at McKnight Road, First Street, and Margaret Street and the three at-grade nonsignalized intersections at Second Street, Third Street, and Charles Street. Figure 3 shows the project plan. The project includes the following newly built features:
The milestones in the construction schedule activities are as follows:
Figure 3 . TH 36 project plan. (Source: Mn/DOT)
Grading operations were guided by machine control technology based on GPS instead of traditional construction staking carried out by surveyors. Bulldozers, scrapers, road graders, and other excavation equipment were equipped with GPS technology (GPS instrumentation indicated by arrows in figure 4) to enable operators to monitor in real time where fill needed to be placed and cuts made. This eliminated the need for surveyors to install (and reinstall) embankment layout and elevation stakes. Only minimal staking was required.
Figure 4 . Bulldozer equipped with GPS receivers for grade control.
The complete reconstruction of TH 36 required cuts and fills in excess of 20 feet on the mainline. The project included about 750,000 cubic yards (573,416 cubic meters) of excavation, 500,000 cubic yards (382,277 cubic meters) of embankment, and 75,000 tons (68,038 metric tons) of HMA. Steel sheet piling was used to shore excavations during construction (figure 5) for areas of TH 36 that were lowered below the existing grade.
Figure 5 . Shoring being placed along TH 36.
A major component of the project was the construction of the McKnight Road diamond-type interchange over TH 36. Separate bridges were built for the northbound and southbound lanes of McKnight Road to match alignment of the rest of McKnight Road. Figure 6 shows the early stages of construction for the two bridges. Precast bridge elements (other than the bridge beams) were not used because the interchange was not on the project’s critical path and bridgework could continue after the full closure was over.
Figure 6 . McKnight Road bridges under construction.
Standard precast box culvert sections were placed to form the Gateway Trail tunnel under Margaret Street (figure 7). Before construction, the trail crossed Margaret Street at grade. The new tunnel will increase safety for trail users. Likewise, the pedestrian bridge shown under construction in figure 8 will make it safer to cross TH 36.
Figure 7 . Gateway Trail box culvert tunnel at Margaret Street.
Figure 8 . Pedestrian bridge under construction.
During peak a.m. and p.m. periods, traffic was encouraged to take marked detour routes around the full closure. Eastbound traffic was routed onto northbound TH 61 to eastbound Interstate 694 and back to TH 36 for a 6.7 mi detour. Westbound traffic on TH 36 outside the I-694 loop was routed onto southbound I-694 to westbound I-94 and then to northbound I-35 to rejoin TH 36 for a 17.7 mi detour.
Full closure was the chief innovation on this project used to promote safety, speed construction, and eliminate congestion through the work zone. Innovative contracting methods were also employed to help shorten project time, including LID and lane rental to promote on-time completion and A+B bidding to speed contract time. These and other innovations, such as using a lightweight deflectometer and intelligent compaction to ensure quality and ITS, are discussed in the following sections.
Closing TH 36 is an innovative concept that Mn/DOT had not attempted before on a major urban freeway. Of paramount importance was to keep the duration of the full closure to the absolute minimum while allowing enough time to get the eastbound lanes open and a substantial portion of the earthwork and bridgework finished. The full closure allowed the contractor maximum mobility during grading, which increased the efficiency of hauling and placing materials. When it came time to pave the eastbound lanes of TH 36 with HMA, the full closure allowed for uninterrupted paving, fewer cold joints, and more uniform HMA compaction. After the full closure ended, the eastbound lanes were opened to one lane of traffic in each direction (figure 9).
Figure 9. Eastbound lanes carrying head-to-head traffic. (Source: TERRA)
The alternative to full closure was to reconstruct the corridor under traffic and manage traffic in stages using three bypasses (during various stages) from one end of the project to the other. This option would have intensified the complexity of the traffic management plan and increased the amount of total project construction to include building and removing the bypass lanes.
The University of Minnesota multiple task study2 used this opportunity to document and evaluate the benefits of full closure on a major highway. The aim of the study was to develop a simulation model to analyze the traffic impact and benefits of completely removing live traffic from the work zone. Researchers developed a microsimulation network based on the geometry of the surrounding roadways and regional travel demand data collected during the project and from the Mn/DOT traffic database. The results were not available when this report was published, but it is anticipated that modeling this real-world example will assist in future decisionmaking on the appropriate closure type (partial or full closure) for highway construction.
Intelligent compaction (IC) rollers and lightweight deflectometers (LWD) were used on this project to improve the quality of grading operations. The IC rollers are equipped with sensors that allowed the operator to easily self-monitor the compaction of the material beneath the roller in real time through an onboard compaction monitoring display screen (figure 10). This helped optimize compaction operations and made it possible for the operator to easily identify soft spots in the compacted embankment. The operator could then apply additional compaction effort to soft areas in the fill as needed.
Figure 10. Intelligent compaction roller (left) equipped with compaction display (right).
IC rollers were also beneficial in preventing overcompaction of the pavement layers, which could result in crushing the aggregates and weakening the finished pavement. Compaction was verified with the LWD (figure 11). This was the first time Mn/DOT used IC and LWD as acceptance testing in lieu of test rolling and sand cone density checks. Traditional methods of quality acceptance were used to verify compaction with test rolling and sand cone density testing.
Figure 11 . Technicians check the embankment compaction with an LWD.
Iowa State University3 researchers collected field data during construction to help Mn/DOT further develop its IC specifications. This study considered the data from this and other projects to examine the relationships among IC-measured compaction values, test rolling rut measurements, in situ point measurements, and LWD measurements.
Locked Incentive Date
Mn/DOT took a new approach to the LID specification in this contract. On past projects, incentives often were paid even though deadlines were extended because of delays caused by the owner, bad weather, change orders, or late material deliveries. The new approach gave the contractor two options. The first option provided the contractor with a lump sum incentive, but did not allow time extensions and claims. The second option allowed contract extensions, but no incentives. The contractor chose to receive the lump sum incentive.
LID is new for Mn/DOT and provided a no-excuse bonus as an incentive for the contractor to complete the project early. The LID specification had the full closure targeted for 145 days, but with the help of good weather the contractor used only 122 days, allowing the eastbound lanes to be opened sooner than anticipated. As a result, the contractor earned the maximum incentive bonus of $650,000 ($350,000 plus $75,000 for each five days, not to exceed $650,000).
Cost-Plus-Time (A+B) Contract Bidding
Mn/DOT selected A+B contract bidding to reduce the amount of contract time. This contracting procedure selects the low bidder based on a monetary combination of the contract bid items (A) and the time (B) needed to complete the critical portion of the project. The cost of time in this case is a function of a road user cost ($15,000) for each day the contractor needed to keep the full closure in operation. The allowable time was 145 to 210 days, giving each bidding contractor the flexibility to balance time with cost. This method favors contractors that explore innovative construction methods to reduce cost and motivates the contractor through incentives to minimize the delivery time.
Six contractors submitted bids ranging from $27.6 million to $32.7 million and from 145 to 195 days for the full closure. The winning bid was for $30.7 million and 145 days to complete the full closure.
A lane rental fixed fee of $15,000 a day was charged to the contractor as a disincentive in case the lanes on TH 36 needed to be closed outside of the scheduled full closure’s beginning and end dates. The lane rental fee is the same as the road user cost in A+B bidding. In essence, the total amount of road user cost is a “lane rental working fund” in which any money not used to rent the lanes during full closure becomes an incentive given to the contractor and overruns are disincentives charged to the contractor.
A good example of lane rental is when all four lanes of TH 36 were open after the full closure and final cleanup work was needed. This type of work was allowed during offpeak times and, since every hour counted against the bottom line, the contractor had the incentive to coordinate work and get in and out quickly with full use of the closure. This not only gets work done quickly and keeps closures to a minimum, but it also discourages idle lane closures during which the public perceives inconvenience for no reason.
Intelligent Transportation System
ITS was implemented to monitor traffic on the alternate routes. The system included cameras placed on the detour routes to monitor traffic flow. This information was linked to Mn/DOT’s Regional Transportation Management Center, which allowed Mn/DOT to adjust signal timing and other traffic management systems in real time. An additional feature of the ITS was providing travel-time systems on the alternate routes, which helped motorists decide which route to take.
2 University of Minnesota. December 2008. TH 36 Full Closure Construction: Evaluation of Traffic Operations Alternatives, Task 5 Deliverable: Development of Traffic Simulation Model.
3 White, D.J., P. Vennapusa, J. Zhang, H. Gieselman, and M. Morris. July 2009. Implementation of Intelligent Compaction Performance-Based Specifications in Minnesota. Earthworks Engineering Research Center, Department of Civil, Construction and Environmental Engineering, Iowa State University.