Stormwater runoff is a major source of water pollution, which results in impaired recreational water use and increased cost of water treatment. As development intensifies and extreme weather conditions continue, contaminated surface water drainage and flooding have become major concerns.
In response, federal and state government entities have drafted model stormwater management guidelines for developing community ordinances on runoff protection. Based on the extent and nature of development, many local jurisdictions have implemented best practices for limiting the total coverage of impervious surfaces on residential and commercial properties.
Otter Tail County in west-central Minnesota is home to more than one-thousand lakes. Recognizing the adverse effects of uncontrolled development, the county imposed a Shoreland Management Ordinance to minimize overland runoff of polluted water entering its pristine lakes and streams. The rules limit total impervious surface coverage to 25% of a property area.
A county homeowner in the City of Richville recently contracted Skjeret's Decorative Concrete to install a concrete driveway. The lakefront property’s impervious surface—grandfathered in at a 30% limit—was already approaching nearly 29% of the lot area. After the forms and base were placed for the driveway, the county put a halt to the project because it would raise the impervious surface coverage above 30%.
The owner is a disabled military veteran who required a fully paved driveway up to his home. After being denied a variance to exceed the impervious limit, he wanted to use pervious concrete. The county misunderstood the request and approved the limited use of pervious pavers in the tire paths of the proposed driveway. Because the county considers pavers as 50% pervious, this would put the property’s impervious coverage at 30.1%. This was not the complete driveway the disabled homeowner needed.
In search of a highly permeable pavement solution, Skjeret's Decorative Concrete reached out to Aggregate Industries for assistance. After reviewing the project details, the specialists at Aggregate Industries recommended the use of Hydromedia® pervious concrete to pave the entire driveway and keep the impervious coverage below the 30%. Designed to achieve the right balance between fluidity and viscosity, this next-generation drainage technology enables the ultra-rapid evacuation of stormwater through its void structure and directly into the soil.
Because the county had no prior experience with Hydromedia® pervious concrete, they required detailed project and product information before approving a fully paved driveway. In response, Aggregate Industries engineered a pavement design and submitted a report on concrete and drain-base thickness. The methodology included subgrade conditions per the U.S. Department of Agriculture, precipitation frequency based on National Oceanic and Atmospheric Association data, and extreme flood event criteria in the Minnesota Stormwater Manual. After reviewing the report and meeting with Aggregate Industries, the county gave the green light to move forward in paving the entire driveway.
To optimize a custom-designed Hydromedia® mix for the project, Aggregate Industries’ quality control laboratories conducted local material assessments and ran trial batches a week before the scheduled pour of the homeowner’s driveway. Since this was the contactor’s first job with pervious concrete, a 3 cubic yard test slab was poured to give the work crew a better feel for how the mix works in real-world conditions and to provide them with some practice time in placing, finishing, and curing the pavement. As a final step in the preconstruction process, the owner and contractor were provided with post-installation best-practice instructions to achieve a long service life of the pervious driveway pavement.
On the day of the pour, the Aggregate Industries’ team was on site to ensure the project went smoothly by providing instant feedback on the mix and its placement, as well as to answer any questions from the homeowner and the county’s Assistant Director of Land and Resource Management.
This City of Richville project—the first pervious concrete driveway in Otter Tail County—is an outstanding example of an innovative and sustainable approach to stormwater management. The homeowner is thrilled to have a fully paved, 16-cubic-yard concrete driveway to help with his disability, and the County has a better understanding of how this highly permeable rainwater management system can reduce the risk of flooding and mitigate water pollution. This solution is not only an important development for other residents but also for the county when planning future public works projects.
The successful installation of the new Hydromedia® driveway also provided Skjeret's Decorative Concrete with a strong competitive advantage as they are now the only local professionals with experience placing this advanced technology. Word quickly spread and Skjeret's Decorative Concrete was placing a new Hydromedia® pervious concrete walkway within weeks of the driveway project.