Minnesota Department of Transportation (MnDOT) researchers conducted a review of literature and case studies to develop a report to guide local road engineers in considering permeable pavement for specific low-volume road sites.
MnDOT ‘Local Road Research Board (LLRB)’ Technical Summary titled, “Guidance on Permeable Pavements in Cold Climates” (pictured left) pertains to the LRRB-produced Report 2015-30, “Permeable Pavements in Cold Climates: State of the Art and Cold Climate Case Studies”: Stormwater runoff carries pollutants from roadway surfaces to the surrounding environment and sometimes directly into waterways. Permeable pavements may be able to reduce such runoff and improve water quality. Porous asphalt, pervious concrete, and permeable interlocking concrete pavers allow water to in filtrate through the pavement structure to be stored temporarily and then filtered into the underlying subgrade.
Although they are too porous to durably support high-volume/high-load roadways, porous pavements have been used successfully for parking lots and low-volume roads like neighborhood streets in some areas of the country. Little research had been done on permeable pavement performance in cold climates for Minnesota.
The goal of this project was to create a guide for local road engineers to use in deciding where and how to install permeable pavements and how to maintain them. This study aimed to summarize the research and practice of permeable pavements in areas of North America with cold climates like those in Minnesota.
Researchers began by conducting an extensive literature search that identified and summarized 170 documents on permeable pavement use and performance. They also identified and summarized case studies, including test cells at MnROAD and in four Minnesota cities or water districts, as well as in parking areas in Denver, Colorado; at the University of New Hampshire; and in Ontario, Canada. Researchers then worked closely with a Technical Advisory Panel composed of state and local road engineers and industry representatives to develop a simple, Web-based tool for initially deciding where a permeable pavement might be feasible and a final report that would function as a guide to decision-makers.
For the full Technical Summary and the results on: Materials and Construction; Hydrologic Design and Hydraulic Performance; Water Quality; Maintenance; and Knowledge Gaps, please click on the image(s) above, or go to the 2-page PDF of the technical summary: http://www.dot.state.mn.us/research/TS/2015/201530TS.pdf.
The MnDOT FINAL REPORT #2015-30 titled, “Permeable Pavements in Cold Climates: State of the Art and Cold Climate Case Studies” is an extensive review of full-depth permeable pavements including porous asphalt, pervious concrete, and permeable interlocking concrete pavers (PICP). Also included is a brief section on articulated concrete blocks/mats. The main topics, divided into chapters, include:
- Structural and mix design
- Hydrologic design
- Hydraulic performance (i.e. infiltration capacity)
- Maintenance needs/frequency/actions
- Impact of permeable pavement on water quality
- Results of a highway shoulder feasibility study, knowledge gaps
- Several cold climate case studies from the United States and Canada
While progress has recently been made with the relatively new permeable pavement technology, researchers have also identified many unresolved issues that are not well understood. These include:
- A methodology to measure subgrade infiltration rates
- Filling data gaps related to structural integrity, construction, and related issues associated with permeable pavements
- Determining what maintenance activities are most effective on various pavement types and how frequently specific maintenance actions should be performed
- A better understanding of the processes involved in the observed reduction of contaminant concentrations in stormwater flowing through permeable pavements
- A better understanding of the performance of permeable pavements over a time frame that better corresponds with a life-span of 20 years.
For the PDF of the MnDOT FINAL 375-page REPORT #2015-30, titled “Permeable Pavements in Cold Climates: State of the Art and Cold Climate Case Studies” please click on the image of the cover above, or go to: http://www.dot.state.mn.us/research/TS/2015/201530.pdf.
While not all case studies showed positive experiences, most installations performed well in managing stormwater and water quality. No follow-up research projects have been planned, but this report identified knowledge gaps that can be explored further. Long-term evaluation of existing installations and of the MnROAD cells should be undertaken to monitor performance and deterioration of the pavement structures over periods of decades.