Note: This project won a National Recognition Award in the American Council of Engineering Companies (ACEC) 2023 Engineering Excellence Awards (EEA) competition.
Braun Intertec was contracted by Inland Development Partners and Opus Development Corporation to be the environmental and geotechnical consultant on a redevelopment project in the City of Maple Grove Minnesota. The development project was in jeopardy after a previously unknown waste containing a dangerous combination of pH, lead, and trichloroethylene was found at the dump site. The challenge with addressing this waste was that no one involved could identify the waste or its origin, and there was not an established methodology for treating these three conditions simultaneously.
Braun Intertec was hired as a consultant to propose a solution to clean up and prepare the property that had been home to a 70-year-old privately-owned and unpermitted dump. Braun Intertec also helped secure grant funding for the project, which had a three-year shelf life before expiring. Due to the environmental complexities of the project, the development did not immediately move forward. As a result, the grant monies, which were in jeopardy of expiring, would have to be returned to the grant agencies. Braun Intertec assisted with the planning and permitting with the City of Maple Grove and the MPCA that allowed the Response Action Plan (RAP) to be implemented in a time frame prior to an expiration of the grant funds.
The Response Action Plan
The response action plan by Braun Intertec involved excavating the unpermitted dump and off-site landfilling the wastes. The excavation was challenging due to the depth of the buried wastes, reaching 25 feet. During the process, they discovered a large vein of an unidentifiable viscous, black substance emitting a strong odor, estimated to be from the 1950s or 1960s.
To address this, Braun Intertec paused the response action to evaluate and characterize the substance. Laboratory tests revealed hazardous properties with a low pH, lead, and trichloroethylene, which posed a unique challenge as treating the uncommon combination of substances did not have an established treatment method.
Working along Ursus, Braun Intertec developed a unique method to treat the hazardous waste using a chemical process. By mixing the material with magnesium oxide, the team was able to stabilize the lead, while also increasing the pH to a non-hazardous level. The resulting exothermic reaction drove off the trichloroethylene, a volatile organic compound, into the atmosphere. Once volatilized, the sunlight then breaks this substance down into its basic components: carbon dioxide and water.
The on-site treatment approach required a deep understanding of the Environmental Protection Agency’s (EPA) area of contamination (AOC) policy that is not well-known or used. By leveraging this approach, Braun Intertec avoided invoking land disposal restrictions under Federal EPA rules, resulting in significant cost savings.
Braun Intertec played a crucial role in coordinating with the Minnesota Pollution Control Agency (MPCA) and grant agencies. They facilitated understanding of the waste’s nature, the on-site treatment approach, and the need for additional grant funds to cover remedial implementation costs. The MPCA imposed new restrictions, including sampling for volatile organic compounds and designing a vapor mitigation system. Braun Intertec designed an active sub-slab venting system, included in the grant funds request and approval.
Pioneering Sustainable Solutions
Overall, Braun Intertec had a unique approach to the investigation and remediation of the Arbor Lakes Corporate Center. They developed a response action plan (RAP) to remove the waste and prepare it for redevelopment; secured grant funding for the remediation costs; identified little-known EPA policies to manage on-site waste; and ultimately developed a novel process that treated the waste on-site, allowing the project to continue and saved developers more than $2 million in waste disposal.
Once remediation and the installation of a vapor mitigation system were complete, the project site received a certificate of completion from the Minnesota Pollution Control Agency. This certificate documents that all previous environmental problems are resolved for this property.
In addition to the value this adds to the engineering field and remediation projects broadly, the redevelopment project in Maple Grove has brought numerous benefits such as job creation, increased tax revenue, and significantly reduced carbon emissions by avoiding the transporting of over 5,000 tons of waste over long distances.
