At its Annual Meeting, April 9-12, 2016, in Bonita Springs, Fla., the National Corrugated Steel Pipe Association (NCSPA) presented its Project of the Year and Hall of Fame awards, highlighting a range of applications of corrugated steel pipe and structural plate. Following are winning projects in five contest categories — Department of Transportation, Rehabilitation, Structural Plate, Retention/Detention, and Hall of Fame.
Department of Transportation
Truenorth Steel: Pembina County Structural Plate Pipe Extension (U.S. and Canadian border station crossing) — The North Dakota Department of Transportation has been busy with this crossing over the years. They continue to utilize the versatility of corrugated steel pipe by extending this structural plate pipe at the border crossing station. The initial installation was performed in 1968, the first extension was completed in 1996, followed by another extension in 2013. As traffic continues to increase, another expansion is slated for this year’s construction season. This crossing also has a paved invert to provide additional service life.
Naastad Construction noted that the new plate sections (12 gauge, 6-inch by 2-inch corrugation) fit well together with the existing plate. Also, proper backfilling was completed to provide the structural support needed.
Lane Enterprises, Inc.: Poe Paddy Tunnel Reline (Bald Eagle State Forest, Pa.) — Structural plate arch (10 gauge, 6-inch by 2-inch corrugation) was used as a tunnel reline material to address safety concerns associated with falling rock fragments on a popular hiking/biking trail. In addition, the old tunnel — blast constructed around 1880 to an internal height of approximately 20 feet — had become a hibernation locale to an Eastern Small-footed bat population deemed an endangered species.
The reline design included preservation of 5 to 7 feet of space below the existing tunnel ceiling to serve as a hibernation cave for the bat species. Flowable fill reline encasement extended a minimum of 1 foot above the arch to serve as a floor for the cave, with several depressions to allow water to pool into small ponds 3 to 6 inches deep for humidity control. Bat-friendly gates installed in the headwalls at each end of the tunnel above the reline allow the bats ingress and egress for the hibernation season, as well as access for hibernacula surveys.
The 307-foot curvilinear reline (radius of curvature around 745 feet) required 10 horizontal elbows.
Big R Bridge: Audubon Hollow (Houston) — This project showcases several benefits of using flexible buried structures:
- Site adaptability — The Galleria district of Houston is a well-developed urban center. The project consisted of developing unused space and required a specific-sized structure and orientation to conform to site constraints.
- Foundation design — Foundation soils were poor. Because a flexible structure was being used, higher bearing pressures could be provided. This made the corrugated steel structure an economical alternative to precast concrete and bridge structures that were being considered.
- Sustainability — The structure included welded-wire, mechanically stabilized earth (MSE) headwalls and wing walls. Steel consists of approximately 90 percent recycled content. The structure and MSE walls were backfilled and faced with recycled concrete. This resulted in a recycled content of around 95 percent or higher for the entire project. This level of reuse of materials is just not possible with any other type of material. With the exception of the backfill, the entire structure and headwall system was shipped on a single truck. Any other type of structure would have required multiple trucks, resulting in additional pollution, traffic disruption, unloading time, and other hassles and inefficiencies.
- Aesthetics — The Galleria district is known as a high-end retail and arts area of Houston and aesthetics were an important factor in the project. The eye-appealing arch shape, layout flexibility, and strength of the MSE wire headwall system and uniform coloring and gradation of the recycled concrete facing material in the walls provided exactly the look the architect wanted.
- Staged construction — Site access needed to be maintained throughout the project. The nature of the selected structure easily accommodated a staged-construction approach where the structure was partially constructed and immediately put in service to maintain access. The remainder of the structure was built as grading was completed.
Contech Engineered Solutions LLC: U.S. Bank Stadium (Minneapolis) — U.S. Bank Stadium is a fixed-roof stadium being constructed in downtown Minneapolis as the new home of the Minnesota Vikings football team. The stadium is the anchor of substantial redevelopment in the City of Minneapolis.
Architect HKS and the Minnesota Sports Facilities Authority are targeting LEED certification for the stadium. Contributing to LEED certification are an innovative roof system that will help with both heat prevention and heat retention, energy efficiency, public transportation, and stormwater management. However, since the stadium is being built downtown, there is limited footprint for a stormwater storage system. Engineers chose to store the stormwater in an underground retention system that would provide the required storage in a limited and constrained footprint.
The retention system is made from 1,600 feet of 144-inch-diameter perforated Aluminized Type 2 corrugated metal pipe. The system not only stores the water, it releases it slowly over time into the surrounding soil via the perforations in the pipe. This reduces the amount of runoff leaving the site, recharges the groundwater supply, and eliminates the need to pipe the water into the city’s sewer system.
Also used was 400 feet of 48-inch-diameter DuroMaxx steel reinforced polyethylene. DuroMaxx was used because it can be made watertight, which was needed since the pipe was located behind a retaining wall.
Hall of Fame
Metal Culverts, Inc.: Multi-plate arch (Union County, Iowa) — In 1941, Union County, Iowa was poised to start a grading project that included a multi-plate arch as well as more than 1,000 feet of culverts on a farm-to-market road. The county contracted out the excavation and culvert installation for less than $7,000 but decided to assemble the arched multi-plate themselves. Measuring 15 feet by 7 feet, 8-3/8 inches by 30 feet, 4 inches in length, the multi-plate arch was constructed in 13 days. This structure was designed to drain 640 acres in a rolling countryside in Spaulding Township. The total assembled cost was $674.14, with $566.15 of that being materials only. The day labor costs were $66.00; equipment costs totaled $41.99.
Over the years, the county has added concrete footing and headwalls but little else has been done besides several inspections over 75 years. The latest inspection report listed the multi-plate in good condition. There are thousands of structural plates and riveted galvanized corrugated metal pipe in this condition and of this vintage throughout the Midwest. What is unique to this project is the intact bridge record dating back to 1941. This is a prime example of galvanized material performing as expected and living up to its design.
Information provided by the National Corrugated Steel Pipe Association (ncspa.org). The NCSPA seeks to promote sound public policy relating to the use of corrugated steel drainage structures in private and public construction. It collects and distributes technical information and assists public and private agencies in the formulation of specifications and designs to encourage greater knowledge of corrugated steel pipe’s benefits and uses.