Construction of an offset single point interchange, a first of its kind for the state of Minnesota, recently hit the halfway point of a 15-month construction schedule. Located just north of St. Paul, the new interchange will replace an existing and more traditional diamond interchange.
The $20 million interchange links Rice Street, a minor arterial, to TH 36, both busy commuter routes for the northern and eastern suburbs and townships of the Twin Cities.
Rice Street runs north from downtown St. Paul through several suburban cities and is an important reliever to I 35E traffic just to the east. TH 36 is an east/west commuter highway connecting the St. Paul/Minneapolis region to the state of Wisconsin 25 mi. (40 km) to the east.
Ramsey County, the operating authority of Rice Street, awarded the low bid to Lunda Construction. With headquarters in Black River Falls, Wis., Lunda is a nationally known bridge builder.
Lunda brought in Arnt Construction of Hugo, Minn., to excavate the site. C.W. Houle, Shoreview, Minn., is laying the sewer pipe for the interchange and Hardrives Incorporation from Rogers, Minn., is placing the asphalt for the new street.
Main construction features to this project include a new bridge on Rice Street crossing TH 36, two flyover ramps, a 32,000 sq. ft. (3,023 sq m) infiltration basin, more than 1,000 ft. (305 m) of retaining wall along Rice Street and County Road B and a 11,250 sq. ft. (3,431 sq m) wood noise attenuator wall.
On the way to building the interchange, construction workers and equipment will excavate an estimated 169,000 cu. yds. (129,000 cu m) of common excavation and 22,000 cu. yds. (16,830 cu m) of muck excavation.
Eventually, 4,400 cu. yds. (3,360 cu m) of structural concrete will be poured and 38,000 tons (34,500 t) of bituminous mixture and 522,000 lbs. (234,900 kg) of reinforcement bar placed. Pipe quantities include 8,500 linear ft. (2,930 m) of sewer pipe and 3,600 linear ft. (1,097 m) of water main.
For many years, a growing ADT and narrow road width and bridge deck on Rice Street plagued this section for morning and evening commuters and caused traffic slow downs and back-ups.
According to Ramsey County documents, the current ADT of 20,000 for Rice Street is expected to grow to 27,200 in 20 years.
Meanwhile, the project became more urgent when St. Jude Medical, a medical device company headquartered near the interchange, expanded its campus with an additional 600 employees, according to local media reports.
Transcending the rising ADT counts and lack of capacity, however, was the fact that the deteriorating old bridge hit its 75th anniversary, no longer met current geometric standards was and deemed structurally deficient by the Minnesota Department of Transportation (MnDOT) according to Ramsey County documents.
Joel Hanson, the city administrator for Little Canada, a neighboring suburb, added that “concrete chunks have been known to fall off the bridge and land on TH 36 below.”
When the bridge became eligible for federal bridge replacement funds, MnDOT made its replacement a priority.
Besides the narrow road width on Rice Street, and poor pedestrian and bicycle accommodations, “the spacing of the south ramp terminal intersection of the interchange and the Rice Street intersection at County Road B caused additional traffic operational issues,” said Beth Engum, construction project engineer with the design firm of Kimley-Horn & Associates headquartered in Raleigh, N.C., with a local office in St. Paul.
When the bridge and interchange are completed this November, daily commuters will see less congestion and a faster drive time on Rice Street, Ramsey County officials said.
Running between County Road B and County Road B2 and stretching the length of .5 mi. (8 km), Rice Street will be widened from two to four traffic lanes with turn lanes at each of the four intersections through this section of road.
The original bridge only carried two through lanes of traffic and narrow, 5 ft. (1.5 m) sidewalks on each side. At 116 ft. (35 m) wide, the new pre-cast concrete girder bridge will be nearly twice the original width. It will carry two through lanes of traffic in each direction, a northbound right turn lane, dual northbound left turn lanes, 8 ft. (2.4 m) sidewalks and wide shoulders that will also serve as bike lanes.
Instead of a low rising concrete parapet and metal railings, the new bridge concrete parapet will be topped with a 4 ft. high (1.2 m) dark brown/bronze decorative wrought iron fencing accented by architectural concrete pilasters.
What will really stand out though, to daily motorists and commuters driving through the new interchange will be the much different looking geometrics to this busy highway crossing.
Unlike the more traditional diamond interchange, where entrance and exit ramps are stationed at each end of the bridge deck, the offset single point interchange will move all ramps to one end of the bridge.
The tight spacing of the signal lights between County Road B, a minor east and west arterial carrying an ADT of 5,000 and TH 36 with an ADT of 83,000 and running parallel to County Road B made this new interchange the most advantageous for commuters, according to Ramsey County documents.
Currently, two signal lights control traffic on Rice Street and TH 36 ramp traffic at each end of the short bridge deck, just 400 ft. (122 m) apart. Exacerbating this tight spacing is a third signal light to manage intersecting traffic at the County Road B crossing located just another 200 ft. (61 m) further south of the bridge deck.
The offset single point interchange design moves all highway ramps to the north side of the bridge at a signalized intersection and eliminates the signal light located on the south side of the bridge to allow for more efficient traffic flow on Rice Street, Engum said.
The design, though, came at a cost. To make room for the additional space required to bring highway entrances and exits to a common area and to widen the bridge and road approaching it, four properties along this busy commuter and commercial route had to be acquired according to Ramsey County documents.
Preliminary construction on the project began in June, 2010 to move utilities out of the way. It ramped up in earnest, though, the following month when Lunda crews arrived with Arnt Construction to begin excavation work for the wider road, ramps, bridge and the storm sewer and infiltration pond system.
A peak work force of nearly five dozen workers will complete the project. And dozens of pieces of heavy equipment including Cat, Liebherr, Volvo and Samsung, American and Link- Belt cranes, dozers, vibratory rollers, excavators, wheeled loaders, Peterbilt dump trucks and crawler cranes will eventually move in for the heavy field work.
Construction is on schedule despite heavy rainfall in the fall and an unusually cold and snowy winter, said Jesten Sterry, project engineer of Lunda.
“The weather has been challenging, especially last fall when we had the heavy rain fall and this winter with the cold weather and abundance of snow. Though it has slowed production a little it has not jeopardized the overall schedule,” Sterry noted.
Bridge crews have been working through the winter despite the challenges mainly “continuing construction on the sub-structures of all the bridges,” Sterry said.
When Lunda crews hit the site last July, Lunda moved in an American 7260 100 ton (90.9 t) and a Link-Belt LS138H 75 ton (68 t) crane to start construction on the first phase of the Rice Street bridge and the piers for the two flyover ramp bridges.
Within nine weeks, Lunda had the first phase of the new bridge completed and moved traffic to it last October and began preparations for the demolition of the existing bridge.
Bringing the existing bridge down was another challenge for Lunda workers not only for a heavy and early snowfall that set the demolition back by one week but also because of the design of the structure, Sterry said.
For Sterry, it was an interesting demolition because the existing bridge “was a rigid, concrete frame structure designed to freely rotate about the footings.”
“So, as we started taking the deck off we had to monitor it as the structure weakened to make sure that the collapse didn’t happen to abruptly, or it didn’t collapse in such a way to put our personnel or equipment in danger.”
With TH 36 safely buttoned up at the bridge site and traffic routed up and over the entrance and exit ramps, bridge crews began demolition on the Friday night of the third weekend in November and put traffic back on it in time for the Monday morning rush hour.
Construction crews again recently closed off the highway so they could set the pre-cast concrete girder beams for the second half of the new bridge and the two flyover ramps. Crews placed a total of 34 pre-cast concrete girders for the three structures over the last two weekends in February of this year, Sterry said.
As in most road or highway rebuilding projects, equipment and workers are building this bridge and interchange under traffic conditions and is another, ongoing challenge for this project, Sterry remarked.
Space is tight. Workers and equipment have very little elbow room on the construction site. Up and down the work zone along Rice Street, dozens of workers and heavy construction equipment dug for storm sewer and water main placement, peeled asphalt from the road surface, graded the road base and placed asphalt while sharing space with over 20,000 motorists each day.
At the same time, cranes, backhoes and dozers shared tight space along the highway and on a narrow piece of center median to begin pier and bridge work and sewer pipe installation within feet of four, fast moving highway traffic lanes and 83,000 vehicles per day.
“The complexity of the traffic control and phasing to limit the impact of traffic disturbance was largely the responsibility of the contractor,” Sterry remarked and continues to be one of the more challenging aspects to this project.
Despite working under traffic conditions, digging in and around numerous underground utilities including several high pressure gas lines, underground electric and telephone lines, Arnt crews also made good time removing topsoil and digging for new sewer and the infiltration basin said Nick Arnt, vice president of Arnt Construction.
“We had to install storm sewer while flagging large volumes of traffic around the work zones and the telephone lines were in a duct that had to be lowered and relocated because of the placement of the new storm sewer,” Arnt explained.
And, heavy rainfall last fall also challenged Arnt crews.
“Controlling storm water runoff while constructing three large ponds was difficult each time we experienced large rainfalls because we didn’t want to degrade their infiltration capacity,” Arnt said.
Arnt crews relied on nearly a dozen pieces of Cat equipment including a Cat 143 blade, three Cat backhoes, four dozers and a loader help dig and move soil.
According to Justin Klabo with the SEH design firm located in Vadnais Heights, Minn., the infiltration basin was designed to meet local Watershed District, State and Federal Clean Water Act requirements.
“The site selected for the infiltration basin consisted of coarse sands and gravel with high infiltration capacity,” Klabo explained. “The drainage area to the infiltration basin consists of portions of TH 36, Rice Street, and residential and commercial properties along the Rice Street corridor.”
“The infiltration basin was designed to infiltrate the 100-year runoff volume from these contributing drainage areas.”
With the pre-cast concrete girders now in place on the new bridge and the two flyover ramps, Lunda crews are right on schedule and are expected to have the interchange and bridge completed by this fall. CEG
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