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North Dakota State Public Service Commission

Jurisdiction: Abandoned Mine Lands

2002 Completed Projects Archive

2002 Maintenance (Sinkhole Filling) AML Project Summary

Project Type: Surface backfilling of dangerous sinkholes
Primary Locations: Twelve sites near the cities of Noonan, Wilton, New Salem, Dickinson, Beulah and Haynes, North Dakota
Project Dates: October 30 to November 26, 2002
General Contractor: Onsite Improvements, Inc., of Dickinson, ND
Project Cost: $35,428.50

The 2002 Maintenance (Sinkhole Filling) Project was conducted to repair approximately 100 dangerous sinkholes at twelve sites in western North Dakota. These sinkholes were caused by collapse of abandoned underground coal mines. The standard requirements for sinkhole filling under this contract were as follows.

1. Remove and stockpile topsoil or suitable plant growth material from around/within sinkhole.
2. Excavate the sinkhole (as directed) with a backhoe or excavator.
3. Backfill the sinkhole with approved fill material, compaction with loader or excavator required between lifts.
4. Grade area to blend with adjacent topography and re-establish drainage.
5. Respread topsoil over disturbed areas and finish-grade.
6. Seed (broadcast spreader allowed) disturbed areas with required mixture.
7. Drag the seeded areas with a spike-tooth harrow or equivalent.

The required seed mixture for native grassland areas consisted of the following varieties and rates:

This AML Project reduced the likelihood of death or injuries to property owners and the public and of property damage by eliminating some deep and dangerous sinkholes. However, there are many more sinkholes that need to be repaired and new sinkholes are reported each year. Hundreds of collapsing abandoned underground mines are located in Western North Dakota. Sinkhole filling projects such as this one have been conducted annually in North Dakota and will likely continue for the foreseeable future. Photos:

• Wilton1 (65kb pdf)
• Wilton2 (63kb pdf)
• Noonan (47kb pdf)
• Dickinson1 (71kb pdf)
• Dickinson2 (57kb pdf)
• Beulah1 (69kb pdf)
• Beulah2 (57kb pdf)
• Haynes (75kb pdf)

Beulah/Zap Phase VI AML Project Summary

Project Type: Underground, Pressurized Grout Remote Backfilling
Primary Location: Along U.S. Highway 200 in Sections 12 and 13, T144N, 88W, approximately one mile north of Beulah, ND
Project Dates: July 25 to October 1, 2002
General Contractor: Earth Energy and Water Systems, New Salem, ND
Material Testing Contractor: Geoserv, Inc., Bismarck, ND
Project Cost: $262,539.55

More than fifty coal mines have been located within 20 miles of Beulah and Zap, making it one of the most heavily mined areas in the state. The Knife River Coal Mining Company's Underground Mine, encompassing an area of nearly 2000 acres immediately north and east of Beulah, was one of these. It operated between 1915 and 1953 and produced over ten million tons of lignite coal.

More than fifteen abandoned mine land reclamation projects have been conducted at or near Beulah since 1980 at a total cost of over five million dollars. Many hazardous underground mine collapse features, or sinkholes, have occurred near Beulah and Zap. These sinkholes usually collapse suddenly and some have been more than thirty feet in diameter and depth. They can be extremely hazardous, especially when they occur near homes, buildings or roads.

The 2002 Beulah/Zap Phase VI AML Project was the sixth in a continuing series of pressurized grout remote backfilling projects designed to address all remaining high-priority undermined sites near Beulah and Zap. In pressurized grout remote backfilling, grout is pumped under pressure through drilled holes into mined cavities to fill them and reduce the likelihood of collapse. Grout used in this project was composed of cement, flyash, sand, water, and superplasticizer. Grout injection generally continued until subsurface void areas were filled to refusal or until injection pressures indicated that surface lifting was likely.

The 2002 Beulah/Zap Phase VI AML Project was conducted along U.S. Highway 200, north of Beulah. A total of 3800 cubic yards (475 truckloads) of grout were injected into mined workings beneath the right-of-way of Highway 200. Geoserv, Inc. conducted material testing of the grout and collected samples at fifty cubic yard intervals throughout the project. Samples were allowed to cure and were lab tested for compressive strength. The compressive strength requirement for this project was 150 PSI after 28 days. All samples exceeded this requirement.

This AML reclamation project reduced the likelihood of death or injuries to the public and of property damage potentially resulting from underground mine collapse. However, due to budgetary constraints, work has been conducted in phases at the Beulah/Zap Sites. More work is needed to reduce the hazards of underground mine collapse at these sites. Plans are already underway for a seventh phase to this project to be conducted in 2003.

• Beulah/Zap Phase VI Photo 1 (73kb pdf)
• Beulah/Zap Phase VI Photo 2 (47kb pdf)
• Beulah/Zap Phase VI Photo 3 (55kb pdf)
• Beulah/Zap Phase VI Photo 4 (69kb pdf)

Haynes Phase IV

The Haynes AML Site is comprised of 850 acres of surface and underground mines located in Adams County, Sections 5, 6, 7, 8, 9, 15, 16, 21, and 22, T129N, R94W, approximately two miles north of Haynes, North Dakota. The area was mined in the mid 1920's through the late 1960's.

The Haynes AML site was characterized by a series of sink holes, vertical openings, highwalls, and adjoining spoil piles. The mines contained numerous areas of subsidence resulting from underground mining of lignite coal. The highwalls in places approached vertical elevation drops in excess of 90 feet. These mines constituted a dangerous situation to hunters and landowners that used the area. Snow cover during fall and winter presented an inherent danger on and around the vertical openings, sinkholes, highwalls and spoil piles.

The Haynes Phase 4 project site is within Section 8 and 9, T129N, R94W in Adams County. The project entailed the elimination of 1550 feet of dangerous highwall left at the old surface coal mine. Reclamation work on this site started on August 12, 2002. Project Manager and Engineer for the project was Mark Knell. The contractor, Wilson Construction Inc., moved approximately 250,000 cubic yards of soil material to eliminate the hazardous highwalls from a 55-acre area. The contractor utilized a fleet of construction equipment, which included scrapers, dozers, motorgader and excavator. An approximate 30-acre subsidence area was also reclaimed. The sink holes were filled and over 6000 feet of level terraces were constructed to control water and prevent erosional problems.

Topsoil material was salvaged prior to spoil dirt work operations then respread following completion of the dirt work. On October 3, 2002 the dirt work at the Haynes Phase 4 project was completed. The project area was fertilized, seeded and mulched October 17-28, 2002. Larry Reisenauer inspected the project. The project was completed for $273,552.92. Trees will be planted on the site next spring. The following photographs show a small portion of the reclamation area:

• Haynes Phase IV Photo 1 (251kb pdf)
• Haynes Phase IV Photo 2 (240kb pdf)
• Haynes Phase IV Photo 3 (221kb pdf)

Lehigh Road Phase VII AML Project Summary

Project Type: Underground, pressurized grout injection Location: E ½ of Section 7, W ½ of Section 8, W ½ of Section 17 and NE ¼ of Section 18, T139N, R95W in Stark County,approx. 2.5 miles Southeast of Dickinson, North Dakota
Grout Placement: Under roads and ditches of Lehigh Road, Lehigh Drive and a private residence
Project Dates: July 31, 2002 to October 16, 2002
General Contractor: Thiem Drilling, Inc., Williston, ND
Drilling Contractor: S & S Drilling, Williston, ND
Material Testing: Geoserv Inc., Bismarck, ND
Asphalt Patching: Northern Improvement Company, Dickinson, ND
Project Cost: $278,778.35

At least seven, and possibly more underground mines, and several large surface mines make up what was once a prominent mining district around the old town site of Lehigh, North Dakota. Approximately 2.4 million tons of lignite coal was removed by underground extraction methods in this area encompassing approximately 1,100 acres.

Much of the coal was used for the production of charcoal briquettes at the nearby Royal Oak (formerly Husky) plant located in the NW ¼ of Section 17. A large portion of the coal was also used as home heating fuel, and also sold as fuel to the Dickinson Power Plant and the Dickinson Pressed Brick Company. Mining underground for coal began in this area in 1890 and continued until around 1949.

Depth below surface to the underground workings varies between 30 feet and 130 feet depending upon topographic location, although most workings average around 65 feet below surface. Most of the coal extraction was from the 10-13 foot thick Lehigh Bed, although a limited amount of extraction from the shallower (4 feet thick) Dickinson bed was also reported.

Over the years, the underground mines have begun a deterioration and collapsing process, which results in large and dangerous sinkholes on surface. Pressurized grouting is a reclamation procedure in which holes that are drilled from surface intercept the abandoned underground workings and a grout mixture is pumped into the mine to fill void spaces left by the underground rooms and tunnels.

Over the last 7 years, a total of 36,600 cubic yards (the gravimetric equivalent of over 64,000 tons) of grout were injected into abandoned mine workings under Lehigh Road, Lehigh Drive and several other township and private roads in the area. The Lehigh Road Phase VII project was a continuation of grout injection projects in this area in which 4,632 cubic yards of grout were injected under the above-mentioned roads and under a private residence. Over the past 20 years, at least 12 instances of sinkholes opening up on roadways and within ditches in this area have been documented. The goal of these underground grouting projects is to minimize the possibility of additional sinkhole development within roadways and to make the area as safe as possible for the driving public and local residents.

Additionally, four areas of previously collapsed road areas from sinkhole development were repaired and asphalted by a local contractor.