AML to mitigate school subsidence

Hanna, Elk Mountain, Medicine Bow (HEM) High School Principal Steve Priest and Hanna Elementary School Principal Jason Greenway provided updates to the Carbon County School District No. 2 (CCSD2) Board of Trustees at their February 19 meeting on issues of subsidence surrounding their respective schools.

Hanna Elementary School and the football field at HEM both sit above Mine No. 4, which was closed and filled with a sand slurry in the 1980s. Over the past 30 years, however, that sand slurry had dissipated as it has moved further into the old mine shafts. Both principals had met with representatives of the Wyoming Department of Environmental Quality’s Abandoned Mine Lands (AML) division about proposed work in the next few years.

According to both Priest and Greenway, investigative work done by AML this past summer had revealed that approximately 25 percent of the original sand slurry remained.

“There’s quite a lot of work to be done,” said Greenway.

The Hanna Elementary School principal informed the Board of Trustees that AML would begin staging equipment in April and May and would start construction the day after school ended. 

“They are going to be tearing up our parking lot, our playground, our fields. Those are all going to be resurfaced. It’s all going to be brand new asphalt on the playground and on the parking lot and they’re going to have to do the sprinkler system,” Greenway said.

When asked by Boardmember Paul Clark if this was the same process that AML went through last year, Priest clarified that AML had done investigative work the year before and would be injecting a new slurry into the voids beneath the elementary school this summer. The following summer, slurry will be injected into the voids beneath the HEM football field.

“The reason they’re not going to do the football field and the track this year is because they know they’re going to tear everything up,” said Priest. “When they tear everything up, they’re going to replace the sprinkler system, level and replace all of the sod after they replace the sprinkler system, and redo the track.”

To prevent the new slurry from moving down further into the mine shafts, retaining walls will be built beneath the Hanna Elementary School and the HEM football field.

“They have to build those walls underneath the ground because there’s such a slope on those mines … they had a sand slurry in there before and there’s only about 20-25 percent of that sand slurry left and that’s why so many of those voids are in there and so big because it’s all run downhill,” Priest said.

As discussion continued, Clark asked why AML had not warned the school district about the voids and diminishing slurry before the Hanna Elementary School was built. CCSD2 Superintendent Jim Copeland answered Clark’s question, stating that he had contacted the State of Wyoming about why the building had been approved following studies of the area. According to Copeland, he had been advised that it was a different company that had done the study and that the State of Wyoming didn’t have control. 

According to Priest, the mitigating of subsidence beneath both Hanna Elementary School and HEM are part of a larger project that AML will be doing in Hanna. A number of residential areas in the town are also at risk of further subsidence and will be addressed as AML continues their project.

The HEM principal informed the Board of Trustees that there will be a discussion of the subsidence in Hanna at the March 10 meeting of the Hanna Town Council. Copeland recommended that representatives for the school district should try to attend the meeting.

The next meeting of the CCSD2 Board of Trustees will be at 4 p.m. on March 16 at Saratoga Middle High School.