Explosive charge used to create wildlife pond
Rural Princeton farmer Jim Malcolm got off to an explosive start last Saturday in creating a new wildlife pond.
An explosives team, consisting of Phil Miller, Jeff Smith, Cole Smith and Bryan Gilbertson, arrived at the Malcolm farm at about 10 a.m. last Saturday, to create the pond depression for Malcolm, who already had four such ponds.
Within an hour of arriving, Miller and Jeff Smith began running a gas-powered auger to drill nine holes three feet deep in the dark earth to pack explosive materials into. The goal was to explode a hole in the ground about 40 feet in diameter and up to eight feet deep.
The team also laid out longer tubes of explosives in shallow trenches, so that if those tubes exploded as envisioned, they would create channels for water to drain between the new pond hole and an established pond depression nearby.
While Miller and Jeff Smith drilled holes, Cole Smith and Gilbertson emptied containers of ammonium nitrate, presoaked in fuel oil, into three foot long, narrow plastic bags, and also filled bags about five feet long with the same material. Next, the men taped sections of the explosive, TNT, to the bags of ammonium nitrate.
The team dug shallow trenches and laid the longer tubes in those and placed soil over the top in the attempt to direct the explosion downward to make the drainage channels.
The team then strung a network of wires between the charges. Cole Smith unwound a wire from the network of charge wires, out several hundred feet into the field. It would be at that spot that Cole would press buttons on a small device to set off the charges. By then it was close to halfway through the noon hour.
Miller instructed Cole how to do the igniting – press the first button and when the electricity was built up high enough that it lit up an indicator light, then he was to press the second button. That would send electricity down the long wire to set off the charges.
The nearly dozen spectators parked their vehicles about a quarter mile away. Miller then yelled, “Fire in the hole,” several times and Cole Smith pushed the buttons as instructed. When he pushed the second one, a large boom erupted and a black plume of soil rose scores of feet above the ground, followed by the airborne soil falling back to earth.
The blast created a hole about 20-30 feet across and about seven feet deep. Malcolm said he had hoped the hole would have been larger. He later said he also wished the channel between the new hole and the old one had been deeper and wider.
Miller said he had thought that there was enough moisture in the lowland soil there, that the explosion would have been more effective. The drier the soil, the more air pockets that exist in it to absorb the blast energy, leaving not as big a hole in the earth, he explained.
The explosives team had used hand shovels to dig the trench for laying explosives to make the channel, and the relatively dry ground and bottoms of thick plants in the soil made it difficult to dig in. Malcolm even broke something on his tractor scoop trying to dig the trench.
It was common for farmers, many decades ago, to drain large areas so they would no longer be as wet and the farmers could crop the land, Malcolm said. But that was “to the detriment of all wildlife in Minnesota, especially ducks,” Malcolm added.
The lack of rains this year has also been bad for wetlands, said Malcolm, whose first experience with setting off explosives to create wildlife ponds was in the late 1950s.
The explosives team at the Malcolm farm used 150 pounds of explosive material and it isn’t known how many more pounds will be used to finish the job. The second blasting will have to be done after the deer hunting season and if at that point the ground is frozen, the finishing work might have to wait until next spring, Malcolm said.