ROCK SPRINGS -- The subsidence risk remains high due to underground movement in old mine voids in a downtown neighborhood beset by damage from an ill-fated ground-pounding mitigation project in 2007, state officials said Tuesday night.

Wyoming Abandoned Mine Land Division officials unveiled the initial findings from nearly two years of investigative drilling at various locations in the neighborhood known as the Tree Street area.

Geological engineers have been working to better determine exactly what's happening in the numerous, abandoned underground mine shafts and voids scattered across the neighborhood.

Nearly two dozen homes were damaged in the Tree Street area during the controversial reclamation project conducted two years ago that aimed to free up vacant lands in Rock Springs for much-needed housing development.

The subsidence project -- known locally as the "Big Drop" --

involved the use of a pilot technique known as dynamic compaction.

For three weeks beginning in July 2007, cranes pounded the ground with 25-ton and 35-ton weights to collapse the underground mine voids on a tract of land adjacent to the Tree Street neighborhood.

Residents said the shock waves from the ground pounding shook houses, cracked driveways and foundations, accelerated ongoing subsidence and severely damaged most homes in the area.

AML administrator Rick Chancellor told residents during a meeting Tuesday night the detailed investigation revealed there is still movement in the mine voids.

"We think there's evidence of something going on

(underground) ... that may be contributing to something going on on the surface," he said.

Engineers said the investigative drilling will continue through December and then resume in the spring. The data will be used to plot the course and method for future mitigation efforts.

Read more about this story in Thursday's Star-Tribune.

Southwest Wyoming Bureau reporter Jeff Gearino can be reached at 307-875-5359 or at gearino@tribcsp.com.

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