Aggregate availability
The Center for Transportation Studies Seventeenth Annual Research Conference, held May 24–25 in St. Paul, featured many presentations of interest to local agencies. This is one of three presentations summarized in this issue of the Exchange.
When it comes to aggregate supplies, Minnesota is a stone’s throw away from trouble.
Reserves are declining rapidly in the Twin Cities metro area largely due to rising demand and new land-use development, said J.D. Lehr of the Aggregate & Ready Mix Association.
The Minnesota Legislature established a program to map aggregate deposits in the 1980s, Lehr said, but because the project has been “consistently underfunded,” the Department of Natural Resources (DNR) has been able to map only 23 of 87 counties.
A 2000 legislative task force predicted that the present resource base will be exhausted by 2029 if policies remain unchanged, Lehr said, with high-quality gravel expected to be gone before other categories. The task force recommended four actions to conserve resources: make the greatest use of recycling as possible, compensate local governments that preserve resources, expand use of multimodal transportation, and educate the public about conservation’s importance.
Government needs to play a role in preserving and planning aggregate resources, Lehr stressed. It also needs to plan access options to existing metro operations and reserves and provide facilities to import aggregates into the Twin Cities by rail or barge. Given the projected depletion, an additional 1 million truck trips would be needed to supply the metro area by 2029.
Dennis Martin of the DNR said we are moving from a time of abundance to one of limited availability and longer hauls to job sites—and higher costs.
With just 23 of 87 counties mapped in detail, only a generalized picture of the natural distribution of aggregates across the state is known, he said. Some areas of the state have very few aggregate resources, while others have an uneven distribution, especially in terms of high-quality aggregates. The middle portion of the state generally contains the potential for aggregate-bearing landforms, but detailed information is not available.
Many factors subtract from these available natural resources, Martin added. Most of the large and high-quality deposits near cities are nearing depletion. Uses such as Superpave and driveways demand higher quality aggregates. Expanding urban areas, protected lands (such as wildlife areas and wetlands), and rural homes are competing for land. Various zoning and permitting issues also affect availability.
—Pamela Snopl, LTAP editor