A sinking feeling

State investigates possible subsidences
Photo by Eleanor Guerrero A crew inserts a steel rod to measure ground changes over time for MT DOT.

 If you’re seeing a lot of orange vests around Red Lodge, the State Department of Environmental Quality (DEQ) wants you to know it is in response to two home owners about sinking ground concerns. Bill Snoddy, DEQ Abandoned Mine Reclamation Specialist in the Remediation Division, contacted CCN on Thursday, Jan. 23, to explain to the public why they are here and what they are doing in Red Lodge. “We received some calls from concerned property owners about possible subsidence. We are checking the area right now between 16th and 17th from Hauser to Hagen.” So far, he said, no definitive correlation has been found linked to the history of mining there.

Workers are inserting steel pipes in the corners of these areas with an aluminum cap. They will come quarterly to survey the points and monitor any ground elevation changes. They will also conduct a detailed survey of the district. “We haven’t confirmed anything, yet,” said Snoddy. Colorado Geological Survey defines subsidence as: “…the sinking or settling of the ground surface.  It can occur by a number of methods.  Ground subsidence can result from the settlement of native low density soils, or the caving in of natural or man-made underground voids.” It further explains, “In Colorado, the types of subsidence of greatest concern are settlement related to collapsing soils, sinkholes in karst (water dissolved rock) areas, and the ground subsidence over abandoned mine workings.” Snoddy said that there are a large number of things that can create what appears to be subsidence, although he knew the town contained underground mine tunnels.

“They are deep, though, about 300 feet down,” he said. Snoddy said signs of subsidence include cracks in foundations, “breaking pipes, and in the older homes there might be cobble and grout foundations cracking.” He said manmade events that can cause subsidence include drilling and excavations, “ev

en the replacement of the water pipes on Broadway could cause some damage. It can show up as cracks in foundations.” Natural events can also occur with the shifting and settling of ground. This is especially true in Montana from movement of water in winter due to sequences of frost and thawing. This winter has already seen more of its share of extreme high and low temperatures. Snoddy said he was aware that mine related subsidence occurred in Bearcreek. A few years ago, the state conducted a repair of land near Highway 308 by Bearcreek hill.

“There’s still a little in the area,” he said. Mine related subsidence was found in a past geological study (Spectrum, 1989) of the area “east of Red Lodge and Bearcreek.”

In 2011, the DEQ commissioned a subsidence study performed by DOWL, HKM, an engineering consulting firm, regarding the same Red Lodge district currently being investigated. The study is available online. Snoddy discussed the new Red Lodge project. “Later this summer, we’ll be drilling coal seams to see if there are any broken rocks-that points to subsidence.” He will also look at a few other areas around town. Snoddy added, “The DEQ commissioned DOWL to do inspections on both houses of interest. The results are interesting and while the possibility of subsidence is noted there is no definite correlation with historic mining activities. The drilling that is planned for later this year will focus on the stability of the ground beneath these homes and at other locations in Red Lodge and any relationship of ground conditions to subsidence. I will certainly keep you informed of the program plans as they are finalized.” Should subsidence be occurring, Snoddy wants people to know the state is on it. “…to get ahead of anything. I

t’s very common in coal states such as Virginia, West Virginia, Pennsylvania, Ohio and North Dakota, in the towns.” Snoddy said residents can contact him regarding any possible subsidence in their area at: (406) 841-6070 or bsnoddy@mt.gov.