2024 Award Winners and Nominees
Project Name
MnDOT I-35W Stormwater Storage Facility
Description
The MnDOT I-35W Stormwater Storage Facility, completed Spring of 2023, was constructed alongside I-35W on the South side of Minneapolis in the vicinity of 42nd Street. It is an underground water storage facility with a capacity of 4.8 million gallons consisting of six interlocking concrete tanks that are each 46 feet in diameter and 80 feet deep.
The original tunnel system was constructed in the 1960’s to carry stormwater runoff from the highway and the surrounding neighborhoods. As development within the 3,100-acre surface drainage area continued, the volume of water for the storage tunnels to handle increased. Previous heavy storm events on Minnesota’s I-35W in Minneapolis had caused flooding so intense within the existing stormwater tunnels that, in addition to major road closures, manhole lids would be blown off by water pressure. A 2-year storm event would result in the flooding of all I-35W traffic lanes and would take 1 hour to clear, while a 10-year storm event would take 2.5 hours to clear.
As part of a great team effort to mitigate flooding incidents, the Minnesota Department of Transportation contracted Brierley Associates, Barr Engineering and TKDA Team to design a new, underground concrete stormwater storage facility. The Kraemer North America and Nicholson Construction Company Joint Venture then took over the construction phase of the $72 million project through MnDOT’s Construction Manager/General Contractor (CMGC) project delivery process.
The location of the stormwater storage facility presented unique geotechnical/construction challenges, such as: a high groundwater table environment, a variable glacial geology, unbalanced loading on the final structure, the relationship of the new structure on the maintenance of the active service stormwater system, and a tight construction area within a dense residential and business corridor.
Cemstone Products Company is the NRMCA member company that designed and supplied 32,000 yards of highly technical concrete for this project with much of the concrete being placed by Cemstone’s concrete pump trucks. Cemstone’s use of supplementary cementitious materials and specialty admixtures in the concrete was of utmost importance to minimize the environmental footprint and meet the performance-based specifications. Cemstone’s task was to come up with concrete mixtures for a diverse range of applications while meeting the structural performance and constructability needs.
Evidence
Cemstone Products Company, a NRMCA member company, was responsible for designing, testing, and providing concrete mixtures that would help the structure be watertight. The concrete mixtures were designed to minimize cracking by limiting shrinkage. Additionally, a crystalline water-proofing admixture (Penetron Admix SB) was utilized in over 8,400 yards to reduce permeability by permanently self-healing microcracks, pores and capillaries.
Per the performance specification, the concrete mixtures required extensive preliminary testing. The testing included:
• Compressive Strength (ASTM C31) 5000 psi & 7200 psi
• Hardened Air Content (ASTM C457)
• Rapid Chloride Permeability (ASTM C1202) <1500 Coulombs at 56-Days
• Shrinkage (ASTM C457) <0.036%
• Average Residual Strength (ASTM C1399) >150 psi
• Crack Reduction Ratio (ASTM C1579) >85%
• Concrete Abrasion Resistance (ASTM C1138) <1/8”
• Chloride Ion Content (ASTM C1218) <0.10%
• Life Cycle Analysis (Life 365) ≥100-year Service Life
• Thermal Control Plans for Mass Concrete Elements
To lower the Global Warming Potential (GWP) of the concrete mixtures and meet the stringent testing requirements, Cemstone Products Company designed mixes maximizing Supplemental Cementitious Materials (SCM’s). The mix designs below are shown with the specified strength, SCM Percentages, and GWP savings (comparison of mix specific EPD’s to the North Central regional average from the NRMCA Industry Wide LCA Project Report – V 3.2):
• Diaphragm Walls – 5,000 psi, 25% SCM’s, 10.4% reduction in kgCO2e/cy
• Wall Liners & Roof Slabs – 5,000 psi, 39% SCM’s, 10.4% reduction in kgCO2e/cy
• Mass Concrete Base Slabs – 5,000 psi, 39% SCM’s, 11.1% reduction in kgCO2e/cy
In June of 2022 Cemstone was able to switch the cement for this project from an ASTM C150 Type I/II cement to an ASTM C595 Type 1L cement, resulting in additional carbon impact savings. The mix designs using Type 1L cement are shown below:
• Wall Liners & Roof Slabs – 5,000 psi, 39% SCM’s, 17.5% reduction in kgCO2e/cy
• Mass Concrete Base Slabs – 5,000 psi, 39% SCM’s, 17.1% reduction in kgCO2e/cy
• Sloping Fills & Bottom Shaping – 7,200 psi, 35% SCM’s, 21.6% reduction in kgCO2e/cy
Cooperation between MnDOT, Kraemer/Nicholson Joint Venture, and Cemstone Products Company resulted in ZERO compressive strength failures on the project. In total Cemstone Products Company was able to save 915,000 kgCO2e with over 32,000 cubic yards of high-performance concrete supplied and placed.
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