By LeAnn R. Ralph
EAU CLAIRE — After the frac sand mines are closed in 50 years, what will be left?
A five-year study in Chippewa County will be assessing the topsoil in frac sand mines to determine what the best end use would be for reclamation of the sand mines, said Dan Masterpole of the Chippewa County Land Conservation Department on The West Side on Wisconsin Public Radio March 3.
Chippewa County currently has 5,200 acres permitted for ten different industrial sand mines and has 73 sand and gravel operations under permit.
According to state regulations, topsoil must be stockpiled from mining operations and saved for reclamation.
State regulations also require mining companies to have reclamation plans that declare an end use for the reclamation before the mining operation begins and require native vegetation to be restored as much as possible.
In addition, state regulations require that reclamation be completed in stages while the site is being actively mined and not all at once at the end of the mining operation.
When topsoil is stockpiled, it suffers a breakdown of organic matter and loses some of its nutrients, said Holly Dolliver, an associate professor of geology and soil science at UW-River Falls.
Chippewa County Land Conservation and UW-River Falls are collaborating on the five-year mine reclamation study.
The soil in areas where frac sand mining takes place in Chippewa County is “thin” upland soil, Dolliver noted.
Benchmarking and evaluating the topsoil before mining begins is an important part of the study and will include the physical characteristics of the soil, such as texture and depth, as well as a measurement of nutrients, such as carbon, nitrogen and phosphorus, along with measurements of micro-organisms in the soil, Dolliver said.
Evaluating reclamation would be difficult without benchmark data for the topsoil, she said.
Studies in Canada have found that topsoil loses 30 percent of its carbon when it is stockpiled, Dolliver noted.
Areas where frac sand mining occurs only have about four inches of topsoil, Masterpole said.
Topsoil develops over hundreds or thousands of years, and when the topsoil is disrupted and put into stockpiles, it will change, Dolliver said.
The goal of the study will be to scientifically evaluate reclamation, she said.
The challenges of reclamation are what can the soil grow, how can the soil be stabilized, what are limits of the soil and what is the potential of the soil, Masterpole said.
The Chippewa County reclamation study will involve test plots where the mining overburden will be put down first, then the subsoil and then the topsoil, Dolliver said.
The study will determine whether the topsoil will need nutrient management, such as the addition of lime and manure and in what amounts, to create optimal growing conditions, she said.
Two companies, Superior Silica Sand and Mathy Construction, are sponsoring test plots for the Chippewa County reclamation study, Masterpole said.
“We are hoping this will be the beginning of a long-term program,” he said.
At the end of five years, the study hopes to have five test plots, Masterpole noted.
Over the past five years, the public has played an important role in how the sand mines have been permitted in West Central Wisconsin, he said.
It is important for the public to continue to be engaged, to attend public hearings, to provide suggestions, to ask questions and to follow the work of the reclamation study, Masterpole said.
A stakeholders group that includes mining company officials, university staff and interested citizens has been formed, he said.
The stakeholders group will meet one time each year to review and discuss the results of the reclamation study. UW-River Falls and Chippewa County Land Conservation also will post study results on their websites, Masterpole said.