Case History 1: Jay Rd. Erie CO 2009
A large subsidence hole was reported in January 2009 at a residence near the corner of a horse barn. The property owners reported the hole opened up overnight and a fence and gate had been destroyed by the event. The hole measured roughly 25 feet by 25 feet by 15 feet deep and was filled with water. Because of the nature of the opening and the proximity to livestock and human activities, the event was considered a subsidence emergency and was backfilled by the Abandoned Mine Lands program.
Case History 2: Erie, CO 2008
In December of 2008, a report of a large subsidence hole in a field west of Erie was reported. The hole was about 50 feet in diameter and 35 feet deep before being filled with water. The field where the hole appeared was under consideration for annexation by the town for future residential development. A geophysical investigation conducted 3 months prior did not show any evidence of voids in the area. The hole was located outside of the mined area shown on the mine map indicating that the mine map was inaccurate. During the mitigation process, a secondary subsidence pit of smaller dimensions was found directly west of the original hole. Both holes were backfilled by the Abandoned Mine Lands program.
Case History 3: Marshall Area 2007
In May 2007, a consultant reported mine-related subsidence features in a property near Marshall being considered for residential development. Upon investigation, a number of subsidence holes and mine-related features were found on the property. An abandoned building showed significant damage possibly related to the old mine. No records of the mine were found, but several old foundations around the property indicate a mine entry exists west of the site. Due to the unknown mine, lack of records, and the presence of subsidence features, the property owner elected not to pursue development.
Case History 4: Country Club Circle, Colorado Springs, CO- a History of Subsidence
The Country Club Circle area of Colorado Springs has a long history of mine subsidence from multiple mines that were active during the early 1900’s. The mining in the area is very shallow, and there is little bedrock between the mine roof and the ground surface. The area is developed with residential neighborhoods, and residents in the area have been living with subsidence for decades. Starting in 2005, the Abandoned Mine Lands program has been working to try to grout the homes in the area to prevent further damage. The money for this effort was made available by the Office of Surface Mining based on the history of ongoing damage and the age of the residential structures involved. Many of the residents are enrolled in the Mine Subsidence Protection Program. Structures built after 1989 would generally not qualify for assistance and would have to rely on the developer to adequately address potential subsidence hazards.
Case History 5: Colorado School of Mines, Golden, CO- a History of Subsidence
The Colorado School of Mines (CSM) has had ongoing subsidence issues related to the old clay mines west of the main campus for decades. At one point, one of the married student housing units was so badly damaged that it was uninhabitable. In recent years, the school has made the subsidence-prone area into an athletic field; however, ongoing subsidence-related issues are still being reported.
During the construction of the fields in 2004, depressions started occurring. In the spring of 2005 the area reactivated from the snow melt runoff. Several open holes in the field were visible, and the street near the sorority houses was damaged. The structures themselves were not, as they sit on deep piers on the sandstone that was not mined.
A grouting program was implemented to try to stabilize the area in 2005; however, in 2006 additional street damage occurred and several new depressions were found in the field. In 2008, DRMS conducted a geophysical survey to try to establish areas where voids still existed so that a mitigation strategy could be developed to avoid future damage.
Subsidence damage to the CSM married student housing unit circa mid 1990s. Notedisplacement in wall blocks.These units were removed and replaced with an athletic field in the early 2000s. Photo by Dave Noe.
Spring 2005 damage to the road near the sorority houses above the CSM athletic field. This damage was likely initiated by subsidence, then exacerbated by the rupture of a storm water drain. Photo by TC Wait.
Continued road settlement in 2008 prompted geophysical survey efforts to discernremaining subsurface voids. Note subsidence holes visible in the field below. Photo by TC Wait.
Spring 2005 subsidence damage from steeply dipping clay mines to the new CSM athletic field on campus. Two sinkholes are surrounded by red temporary fencing. Block retaining wall is also damaged by subsidence settlement. Pavement cracks in photo at lower left occurs in road above the retaining wall. Photo by TC Wait.
Open subsidence hole in foreground and grouting rig repairing subsidence hole in background during mitigation efforts in late 2005. Photo by TC Wait.