Minnesota's Department of Transportation (MnDOT) has approximately 300 projects a year. It's unrealistic to expect scientific studies to determine specific requirements and designs for each project. We have taken a programmatic approach for ecological enhancement opportunities and/or mitigation requirements. This presentation summarizes several designs that have become 'standards' based on little more than anecdotal evidence of their success.
The partnership between Minnesota's Department of Transportation (MnDOT) and Department of Natural Resources (MnDNR) has led to the development of several design options to include in a project for meeting needs for avoidance, minimization, on-site mitigation, and/or enhancement measures. MnDOT and MnDNR have a high level of cooporation, in which MnDNR area managers identify areas of concern and MnDOT project mangers look to incorporate proposed solutions on their specific projects. If successful, they are incorporated on additional sites the next year. This iterative process has led to many 'experimental projects' becoming incorporated as standard designs into MnDOTs plan sets and provisions.
-Passage Bench (an alteration of riprap for establishment of wildlife trails beneath bridges)
-Aggregate surfacing (riprap modified to be reptile/amphibian friendly at shorelines or under bridges)
-Natural net erosion control blanket (prohibit welded plastic mesh in blanket to prevent small animal entrapment)
-Standardized native seed mix (lowers seed cost and increases availability for species that had depended on prairie ecosystems - particularly butterflies and other pollinators)
-Bridge lighting (turning off unnecessary lighting on bridges during insect hatches and bird migrations (Audubon's 'Lights Out Program')
There are few, if any, citable scientific studies to show the benefits of each of these practices. However there is enough anecdotal evidence to know that these practices are ecologically beneficial and fiscally practical. Maybe more importantly, if not done, following old standard designs would be detrimental. So we do them. Our approach is to do something, rather than nothing. These practices also qualify as mitigation measures for MnDNR permitting, further streamlining timelines in project development. This is our solution to the predicament of not having time and/or money for specific research to develop site specific mitigation.