More than 50 years ago residents of Rock Springs were shocked to learn that many of their houses, schools, and churches were in danger. The coal mines built underneath the town were beginning to collapse due to neglect and some environmental factors. It’s called subsidence and it’s happening in older mining towns all over the West. Wyoming Public Radio’s Amanda Le Claire has more on how the city is dealing with the problem now.
Ambient driving noise
WAYNE JOHNSON: “Where that park is across there were 2 or 3 houses that were you might say totally demolished and moved out.”
AMANDA LE CLAIRE: I’m driving down a street in Rock Springs with Wayne Johnson, a retired engineer and a man who’s lived in his entire life here in Southwest Wyoming. Back in the 70s and 80s Johnson ran a company that created the first official report about a problem which shook up local residents and changed the way mining communities all over the world thought about infrastructure.
Ambient noise still underneath. Wayne continues driving…
JOHNSON: “Years ago, when they started having problems you could actually look down this street and you could see it…like waves would go up and down. And the high spots would be over coal left in the mine and the low spots would be where it subsided.”
LE CLAIRE: The problem began in earnest only a few decades after coal mining initially began in Rock Springs. Subsidence was first reported in 1909 at the State Hospital. The damage was minor, but enough to crack the hospital’s water main and cause excavators to discover that the ground underneath the hospital was sinking- and fast. Over the next few decades, sinkholes opened up in the area that’s now the historic district of the city; one in front of the old Opera House, another at the Southside Catholic Church. But the height of the subsidence problem really began in the late 60s, more than 40 years after the last coal mine closed in Rock Springs. In January of 1968 residents living on D Street woke to find large crevices underneath their homes had opened up overnight. The problem escalated so quickly that within months some residents were forced to abandon their homes for good. Johnson pulls out a few archival photographs of the area.
JOHNSON: This guy’s name was John Marushak and his house was right in here. Now he kind of maintained his house but he was in the basement every day and you could see part of a jack where he would jack it up every day to keep his house level.”
LE CLAIRE: State efforts to deal with subsidence began in the mid-70s. That’s when JaNell Hunter came in. She’s currently the local liaison for the Abandoned Mine Land Division, also known as the AML.
JANELL HUNTER: “We started having homes falling in, streets falling in, utilities failing. Bureau of Mines came in and started doing a test program where they injected a slurry, sand slurry, into the mine workings and that was done in the downtown Rock Springs area and several other outlying residential areas.”
LE CLAIRE: That initial testing with sand slurry wasn’t exactly successful. Hunter says that due to the way coal was mined in Rock Springs- where shafts were built on an angle instead of horizontally- the water in the slurry separated and did not support the ground above the empty mine shaft. According to Hunter, a number of different techniques were tried over the years. But by far the most successful has been the use of a cement-based slurry called grout. Since then no major problems have been reported near those areas first affected by subsidence. But as more than 60% of Rock Springs is believed to be undermined, the process of filling in all the potential problem areas is ongoing. Hunter says nowadays state government is more proactive. Instead of waiting for a sinkhole to open up or a building to show signs of damage, the AML regularly fills empty shafts with grout before subsidence begins. Rob Gerrard is the project manager for the engineering firm JFC. He and his crew are busy this summer filling in an area on the west end of the city.
Ambient sound of construction
ROB GERRARD: “This is a crucial area in Rock Springs. We are supporting the water tanks and also the water lines that feed the tanks and these tanks here feed the majority of the town water. We’ve encountered some large voids under it and we’re just trying to be proactive and to support these tanks and make sure nothing happens to them.”
LE CLAIRE: Crews are also filling in vital areas near Interstate 80 and other major thoroughfares. Hunter says that while the problem of subsidence is no longer an immediate concern for most residents, the AML expects to continue working in Rock Springs for years to come. On a positive note, she says, that’s led to significant progress in mining technology.
HUNTER: “Most of the drilling and grouting technology that is utilized worldwide a great portion of it has developed here in Rock Springs as we’ve had to go through these residential areas. It’s a difficult thing to set up a drill rig in the middle of a residential area and drill a hole and pump grout into when the person is living right there next to the drill rig. So we’ve developed a lot of techniques to make it as pleasant as possible if I can use that word.”
LE CLAIRE: Hunter adds that while most of the abandoned mines in the area have been documented, new sinkholes occasionally surprise the agency. She asks local residents to contact authorities right away if they find one on their property.
For Wyoming Public Radio, I’m Amanda Le Claire in Rock Springs.