Question:A frac sand mine recently blasted 140 holes in a day. What might they be doing?

Hi @engineerjaykumar, thanks for offering a thought toward this question. "Frac" sand is a kind of sand used for "hydrofracking," the extraction of gas from shale rocks below ground. It is a different kind of sand than that used in cement.

I'd usually agree with you @liz, but I found some more research on the site, and in this case there's a mix of limestone, quartz, and other materials present. They're going after the quartz/silica veins for frac sand mining but they're still producing the granite and limestone for gravel and cement use.

Thank you for finding this out @Joe! Very helpful.

My limited understanding: looking for “veins” is done with a digger not by blasting. One seeks sand close to the surface where it’s easier to dig. It’s too expensive to have to go deep. Blasting is usually done to “loosen” ground and structure up to make collecting easier.

Many companies do "bore" holes before they start mining. One requirement in the state of WI is that those bore holes be sealed so that contaminants do not get into the ground water below. If the company has indeed accomplished borings, the DNR must be notified in order to check out whether or not those holes have appropriately been sealed off. Water contamination is serious and can impact the drinking water of many. In some cases, companies have actually asked that land owners sign "gag order" agreements with the requirement that land owners not report such violations which makes it even more serious. I recommend that the DNR be contacted or the Land Conservation Agent in your county be notified.

This is likely a contracted blasting service where the blasting company drills a "grid" of 5.5-6.5" bore holes (comparable to well water casings) ~75' - 90' deep, and ~20' - 25' apart. These bore holes are then cast with ~ 125 - 250 pounds of ammonium nitrate/diesel fuel oil (ANFO) slurry charge. Each bore hole charge is electronically time controlled to blast independently (millisecond differentials) across the established mine site grid pattern. The old blasting system used 80% nitroglycerin with blasting caps/fuses. The intended purpose is to break apart rock layers located above the frac sand material.

We experienced 25 such events in 2019 alone at the Schlumberger/WI Proppants Hixton mine site. These events create challenging air and water quality conditions on a regular basis, not to mention structural integrity issues.

My response in the thread:

From this article, I learned: As of January 2019, the quarry was producing gravel, limestone, and sand. Fracking was mentioned as a future venture with a potential 700 tons of product as well. Any expansions or changes in program such as these would have required an entirely separate set of permits and new conversations. The pit is estimated to have at least another 15 years of material production within it. There are 5 to 6 years’ worth of sand and gravel within the pit and 15 years’ worth of limestone. A layer of silica exists below the other material, but no contract to harvest it was in place. When the lifetime of the quarry has expired, reclamation of the land, per a plan filed with Polk County, is supposed to occur.

As of June 2019, they were mining at deeper levels for silica sand, possibly without necessary permits for the new mining for the new material. I found another article provided by a group called St. Croix River Communities Against Frac Sand Mining: The new permit allows mining to approximately 80 feet below the surface. They are permitted to place temporary concrete and hot mix plants on the site. The only controls on the mine’s activities is a 6-foot buffer zone along their property lines, an annual submission of water samples to the Board, and a requirement that new equipment shall be converted to white noise backup alarms. Under prior owners, blasts caused a couple of wells to collapse at homes along Ridge Road. The owners were never compensated for the cost of new wells.

As of January 2020, according to this article, the township put a moratorium on new permits while they do more research. This halted an attempted expansion beyond the current 80 acres that would have included 200 new acres.

I'm not able to figure out from East Farmington township's meeting notes whether new permits were issued after January 2020. I'm also going to check records for Polk County.

This article has some very suspect information shared by the mine operator. The mine sits atop a bluff that's a half mile from the St. Croix River, and there are wells and crops next to the property line, so water monitoring should be a big concern here.

“They talk about water quality,” said Torgerson, “We’re internally drained. No water can go off the site. We are highly regulated by the DNR. The permit we had to get is called the Industrial Sands Permit. … The DNR goes through a process to make sure we meet all the criteria. Flocculants have to be approved. There’s one chemical we use to wash silica sand. It’s the same flocculent that was used in building the bridge over the St. Croix River because it was a safe flocculent. They approved it.”

The quote is suspect. Unless the mine has been lined with clay or with plastic, internal drainage implies that the storm water and the wastewater ponds will be drained into the aquifer and/or ground water which continues to drain until it reaches the River. All water travels. All pits leak if not immediately they do later given expansion and contraction particularly during the winter months and when "freeze/thaw" occurs. Pollution knows no boundaries in the frac sand industry! Water (storm water and wastewater) travels, flocculants travel. fugitive dust travels. If mines are drained internally it doesn't prevent them from being "clogged". "Waste" is really heavy industrial waste or sludge and should be deposited in a landfill specifically designed for that purpose. Monitoring wells must be critically placed around mines but even then when there are warnings, it might be too late to stop the interior drainage and mitigate the problem.