Best Strip Mining Technique: 5 Methods Compared

There is no single best strip mining technique. The terrain and the coal seam decide. Open-pit and area methods suit flat ground, contour mining suits coal that outcrops along a hillside, and mountaintop removal is a legal exception that needs its own permit findings. In 2024, US open-pit surface mines produced 134.7 million short tons and contour mines 132.3 million, together 87% of the 305.8 million short tons that came from surface coal mines (EIA, Annual Coal Report, Table 3.1). A short ton is 2,000 pounds.

This page compares the five methods side by side, using EIA tonnage and productivity by method, then sets out the federal reclamation rules every US coal strip mine must meet, how the bond is released, and a stripping-ratio calculator for a quick cost check. It is written for consultants and mine planners who need to decide which method to study first and what the permit will demand. Strip mining here means surface mining where the soil and rock above a flat-lying seam (the overburden) are removed to expose it.

Which strip mining technique fits which site

Match the method to three things: how steep the ground is, how thick the seam is, and how deep the overburden lies. The table ranks the methods by 2024 US output, the only metric used to order them. Output says which method is used most. It does not say which is best for your site.

Source: EIA, Annual Coal Report 2024 (November 2025), Tables 3.1 and 22.1. The “other” column counts mines that use auger, highwall or punch methods and mines that produce under 50,000 short tons, so treat its productivity as a rough guide only. The categories come from operator survey responses (Form EIA-7A), so they follow how each mine reports itself.

The five methods ranked by US output

Each entry below gives what the method is, where it is used, its 2024 numbers and its strengths and limits. The overburden is the rock and soil above the coal. The highwall is the steep face left standing at the edge of a cut. Spoil is the broken overburden that is dug out and put somewhere else.

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US surface coal output by mining method

Million short tons, 2024

1. Open-pit surface mining: best for very thick seams on level ground

Open-pit surface mines produced 134.7 million short tons in 2024, and Wyoming alone supplied 111.4 million of that. The method works where one or more thick seams lie under moderate cover. About 79% of 2024 surface coal (242.4 of 305.8 million short tons) came from seams thicker than 120 inches, or 10 feet (EIA). Thick seams spread the cost of stripping over many tons.

Best for: large, thick, flat-lying seams. Strengths: the highest output per employee hour of any method, 15.20 short tons in 2024, and an average sales price of $22.06 per short ton, the lowest of the methods for which EIA publishes a price. Limits: as the pit deepens the waste per ton rises. A 2007 National Research Council report expected stripping ratios in the Powder River and Rocky Mountain basins to exceed an economic limit as surface mining proceeds there.

2. Contour mining: best for coal that outcrops on a slope

Contour mines recover coal in steep, hilly or mountainous terrain. A wedge of overburden is removed along the outcrop, forming a bench at the level of the coal. After mining, the overburden goes back on the bench so the hill returns to its natural slope, as the Kentucky Geological Survey describes it. Contour strip mines produced 132.3 million short tons in 2024 at 9.65 short tons per employee hour.

Best for: seams that wrap around a hill. Strengths: the cut follows the seam, and the spoil can be returned to the bench behind it. Limits: a highwall remains until backfilling is finished, and steep reclaimed slopes need erosion control. A caution on the data: most 2024 contour tonnage was reported in Wyoming (78.9 million), North Dakota (21.2 million) and Montana (13.9 million), so the label reflects how each mine reports its layout, not only the slope.

3. Area mining: best for level ground with regular parallel cuts

Area mines remove shallow coal over a broad area of fairly flat land. Large draglines (cranes with a bucket on a long boom) lift the overburden, and the rock goes back into the pit left by the previous cut, so the pit moves across the land and reclamation follows close behind. In the Midwest, where the ground and seams are generally flat, area strip mining places the broken overburden directly into the space where coal has been removed.

US area mines produced 20.8 million short tons in 2024, led by Texas (8.9 million) and Montana (6.0 million), at 5.79 short tons per employee hour. EIA gives an average sales price of $41.32 per short ton for area-mined coal. Best for: flat, shallow, wide deposits. Strengths: short haul for spoil and quick backfill. Limits: it needs flat ground and cover that a dragline can lift.

4. Auger and highwall mining: best as an add-on, not a stand-alone method

Auger mines work from surface-mine benches before they are covered up. Coal in the side of the hill that contour mining cannot reach is drilled out with an auger (a large screw drill), according to the Kentucky Geological Survey. EIA does not report auger mining on its own line. It groups auger, highwall and punch mines with mines under 50,000 short tons as “other”, which produced 15.9 million short tons in 2024.

Best for: extending a bench where a deeper cut would not pay. Strengths: adds coal without moving more overburden. Limits: it depends on a bench and highwall that rules require to be backfilled once the work is done, so it has to be planned together with the main cut.

5. Mountaintop removal: best only where a permit finds a post-mining use

Under 30 CFR 785.14, mountaintop removal mining takes out an entire seam or seams running through the upper fraction of a mountain, ridge or hill, removes substantially all of the overburden off the bench and leaves a level plateau or gently rolling contour with no highwalls. The Kentucky Geological Survey notes that the removed material is used to fill in valleys next to the mine. In 2024 the method produced 2.05 million short tons, from West Virginia (1.90 million) and Virginia (0.15 million), at 3.10 short tons per employee hour.

Best for: ridgetops with several thick seams near the top, where the planned end use needs level land. Strengths: it removes the whole seam through the upper ridge in one operation (30 CFR 785.14). Limits: the law lets a regulator waive the return to approximate original contour for this method, but only after written findings (see the rules below). Its output is under 1% of US surface coal.

Strip mining vs open pit mining: what is the difference

The two overlap, so sources use the words loosely. In coal reporting, EIA lists open pit as its own surface method. The National Research Council describes contour, area strip and open-pit mining as surface methods that differ principally in how the spoil is loaded, hauled and stored. In a strip mine the spoil from each new cut fills the previous cut, so the pit migrates. In an open pit the hole stays and the waste is hauled to dumps or backfilled later.

In metal mining the usual surface method is the open pit, and stripping describes the waste you remove. The stripping ratio is the amount of waste you move per unit of ore, and it controls how deep an open pit can go. Our guide on the environmental effects of open-pit mining covers the impact side.

Strip methods are not limited to coal. Florida phosphate ore (the matrix) usually lies under 15 to 50 feet of sandy or clayey overburden, which electric draglines remove, according to a University of Florida extension bulletin. The Florida Department of Environmental Protection lists 28 phosphate mines covering more than 450,000 acres, 11 of them active, and 10 mines that are fully reclaimed and released from reclamation obligations. For a different commodity, see our note on strip-mine tips and coordinates for diamonds.

▶ A short claymation on surface (strip) mining: pros, cons and the fix. · 4:37

Where US surface coal comes from

Surface mines supplied 305.8 of the 512.5 million short tons of US coal in 2024, or 59.7% (EIA). Output is concentrated. Wyoming produced 190.7 million short tons from surface mines, 62% of the national surface total, and the Powder River Basin 204.9 million. The chart shows the largest surface-producing states in 2023 and 2024. Wyoming’s surface output fell 19.6% from 2023, from 237.3 to 190.7 million short tons (EIA).

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Surface coal output in the largest producing states

Million short tons, surface mines only

Productivity and price by method

Output per employee hour varies by a factor of seven between methods. Open pit leads at 15.20 short tons. At the other end, the grouped “other” mines reach 2.16. All surface mines together averaged 8.94 short tons per employee hour, against 3.24 at underground mines. The average sales price of surface-mined coal was $29.61 per short ton, against $85.88 for underground coal. EIA also publishes price by coal rank, and the gap is wide: bituminous coal averaged $86.72 per short ton in 2024. Prices therefore reflect rank and region as well as method, so do not read a method’s average price as a reason to choose it.

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Output per employee hour by mining method

Short tons per employee hour, 2024

SMCRA rules that apply to every US coal strip mine

The Surface Mining Control and Reclamation Act of 1977 (SMCRA) is the federal law for US coal mining. Before it, there was no regulatory oversight of coal operators or of what happened to mines after mining stopped, according to the Office of Surface Mining Reclamation and Enforcement (OSMRE). SMCRA covers coal. Metal mines on US public land follow the Bureau of Land Management’s 43 CFR 3809 surface-management rules, which come from the Federal Land Policy and Management Act, and state law. The core coal requirements are in 30 U.S.C. 1265 and the OSMRE rules under it.

Sources: the statutes and rules named in the right-hand column, as published by Cornell Law School’s Legal Information Institute.

Reclamation step by step

The National Research Council lists the unit operations of a surface coal mine in order: topsoil removal and storage, drilling and blasting the overburden, loading and hauling the spoil, drilling and blasting the coal, loading and hauling the coal, backfilling with spoil and grading, spreading topsoil, establishing vegetation and then releasing the area for other purposes. Methods differ in the middle of that list. The first and last steps are the same for all of them. The flow below shows the reclamation half.

Infographic

Reclamation in 6 steps

1. 1Strip and store topsoilRemove topsoil as a separate layer before digging, and keep it apart from spoil.
2. 2Remove overburden and coalMethod-specific: draglines, shovels or trucks move the cover, then the coal is loaded out.
3. 3Backfill and gradeReturn spoil to approximate original contour, with no highwalls and safe slopes.
4. 4Replace topsoilSpread the stored topsoil over the graded area in time to avoid its deterioration.
5. 5Revegetate and control erosionPlant the approved cover and keep sediment out of runoff.
6. 6Release the bond in stages60% after grading; the rest after vegetation and the responsibility period.

Reclamation bonds, liability and the abandoned mine fee

The bond is released in stages. Under 30 U.S.C. 1269 and 30 CFR 800.40, the first release is 60% of the bond once the operator finishes backfilling, regrading and drainage control. The next release follows once revegetation is established, and the regulator keeps enough bond to pay a third party to redo the planting if needed. The final part is released only after the period of operator responsibility ends and all permit requirements are met.

That period of responsibility is set in 30 CFR 816.116. In areas with more than 26.0 inches of average annual precipitation it runs for at least five full years. In areas with 26.0 inches or less, it runs for at least ten full years.

Operators also pay into the Abandoned Mine Land (AML) fund. The fee is charged on each ton of coal produced, and under 30 U.S.C. 1232 it is set per ton for surface and underground coal. OSMRE reports that the fund had collected $14.233 billion, including interest, as of 30 September 2025, and that fee collection authority now runs through 30 September 2034.

▶ The 7 environmental impacts of mining, explained in clay. · 2:31

Stripping ratio: will the overburden pay for itself

The stripping ratio compares the overburden you must move with the coal you recover. In this calculator it is bank cubic yards (bcy) of overburden per short ton of coal. Bank volume means the rock measured in place, before blasting swells it. One acre-foot is 43,560 cubic feet, or 1,613 cubic yards. Multiply the overburden thickness in feet by 1,613 to get bank cubic yards per acre, and divide by the tons of recoverable coal on the same acre.

The breakeven ratio is the highest ratio at which the coal still covers its other costs. A mine faces that limit as a pit deepens, because each extra foot of cover adds waste without adding coal. The numbers entered below are examples, not benchmarks. Use your own thickness, density, unit costs and the day’s price.

Screening a surface mining site from satellite images

Choosing a method starts with the ground: slope, seam outcrop, water courses and access. Farmonaut’s satellite-based mineral detection service screens an area of interest from space, from a KML, KMZ or polygon file, before ground crews go in. Reports take 5 to 20 business days depending on the size of the area and the mineral. It is an early-stage exploration screen. It does not design a pit, set a stripping ratio or replace the permit work described above. The hero image at the top of this page is a Sentinel-2 composite of the Powder River Basin coal district near Wright, Wyoming.

▶ What Farmonaut Mining Pro is and how a licence boundary becomes a satellite-based screening report. · 4:56

Related reading on this site: Machine to Separate Gold From Sand: 6 Types Compared.

Frequently asked questions

What is the best strip mining technique?

It depends on the ground and the seam. Open pit and area mining fit flat ground, contour mining fits seams that outcrop on slopes, and auger and highwall mining extend a bench. In 2024, open pit and contour mines produced 87% of US surface coal (EIA).

What is the difference between area and contour strip mining?

Area mining takes shallow coal over a broad, fairly flat area in parallel cuts, with draglines placing the spoil in the previous cut. Contour mining follows a seam around a hillside, cutting a bench at the coal level and returning the overburden to the bench afterwards.

What is the difference between strip mining and open pit mining?

In a strip mine the spoil from each new cut fills the one before, so the pit moves across the land. In an open pit the waste may be hauled to dumps or backfilled later, so the pit can stay open longer. EIA reports both as surface coal methods.

Is mountaintop removal the same as strip mining?

It is a form of surface mining. Under 30 CFR 785.14 it removes the seams in the upper part of a ridge and leaves a plateau or gently rolling land with no highwalls. It produced 2.05 million short tons in 2024, under 1% of US surface coal.

What does SMCRA require after strip mining?

Backfill and grade to approximate original contour, eliminate highwalls and spoil piles, replace the topsoil, re-establish vegetation and meet the approved post-mining land use. Special rules apply to mountaintop removal.

How much is a reclamation bond for a coal strip mine?

The amount must be enough to complete the reclamation plan if the regulator had to do the work, and under 30 U.S.C. 1259 never less than $10,000 for the permit. The regulator sets the actual amount for each permit.

How long does the reclamation responsibility period last?

At least five full years where average annual precipitation is above 26.0 inches, and at least ten full years at 26.0 inches or less (30 CFR 816.116).

How much US coal comes from surface mines?

Surface mines produced 305.8 million of the 512.5 million short tons mined in 2024, or 59.7% (EIA, Annual Coal Report 2024).

What is a stripping ratio?

It is the overburden you must remove for each unit of coal or ore recovered. In this guide it is bank cubic yards of overburden per short ton of coal. When the ratio passes the breakeven value, the next cut no longer pays.

Does SMCRA apply to metal mines?

No. SMCRA covers coal. Metal mines on US public land follow BLM’s 43 CFR 3809 rules, and states add their own permits and reclamation bonds. Confirm the rules with the regulator for your site.

Who issues the permit and sets the bond?

The rules name the regulatory authority for the site, and that authority sets the bond amount for each permit (30 U.S.C. 1259). Ask it for the current application forms. For mineral titles in other countries, see our guide to mining cadastre portals by country.

Can satellite images help with a surface mine?

Satellite images show land cover, disturbed ground and water over time, so they are useful for a first look at a site. Farmonaut’s service is an early-stage mineral screening product and does not certify reclamation or replace a regulator’s inspection.