RI 9653 REPORT OF INVESTIGATIONS/2000

Economics of Safety at Surface Mine Spoil Piles

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES

Public Health Service

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health
Report of Investigations 9653

Economics of Safety at Surface Mine Spoil Piles

Thomas W. Camm

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES

Public Health Service

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Spokane Research Laboratory

Spokane, WA

July 2000
International Standard Serial Number

ISSN 1066-5552
CONTENTS

Page

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Introduction ................................................................................... 2

Background ................................................................................... 2

Overview of dump-site injuries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Costs of injury . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Considerations for choosing a dumping method ....................................................... 4

Cost modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Cost categories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Cost analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

ILLUSTRATIONS

1. Edge-dumping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2. Short-dumping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

3. Cracks near berm of spoil pile can create hazards for trucks dumping material near edge ..................... 4

TABLES

1. Direct and indirect cost categories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2. Costs per injury by severity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

3. Breakdown of labor expenses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

4. Operating costs for surface mines calculated using various cost models .................................. 6

5. Estimated dozer production capacities ............................................................ 7

6. Estimated dozer operating costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT

h hour mt/h metric ton per hour

Lm3 loose cubic meter st short ton

m meter $ dollar

mt metric ton % percent

mt/d metric ton per day
ECONOMICS OF SAFETY AT SURFACE MINE SPOIL PILES

By Thomas W. Camm1

ABSTRACT

This study was done to evaluate the costs of various dumping operations at waste and spoil piles. It has

been theorized that accidents associated with dumping operations might be reduced by short-dumping rather

than edge-dumping, but many operators have been reluctant to use short-dumping because they believe it is

not as cost effective as edge-dumping. To evaluate this perception, researchers at the Spokane Research

Laboratory of the National Institute for Occupational Safety and Health reviewed the costs of various dumping

methods at waste and spoil piles. The study found that overall cost differences between the two methods were

not significant in most cases. However, while overall cost differences between the two methods appear small,

capital costs could be more significant when short-dumping if numerous dump sites are used concurrently.

The choice of which method to use should be based on considerations of the safety of dozer and truck

operators.

1

Mining engineer, Spokane Research Laboratory, National Institute for Occupational Safety and Health, Spokane, WA.
2

Figure 1.—Edge-dumping. Figure 2.—Short-dumping.

INTRODUCTION

Powered haulage is a major contributor to fatalities at all

mining operations and is one of the top five sources of injuries

at surface mines. This study is one task in a larger project to

investigate ways to reduce hazards from surface mine haulage

equipment being conducted at the Spokane Research Laboratory

(SRL) of the National Institute for Occupational Safety and

Health. As part of the project, a cost modeling approach was

undertaken to study the economic effects of injury prevention

as a useful tool for promoting public health. 

BACKGROUND

Typically, when mine haulage trucks dump waste rock or

overburden at a spoil pile, the trucks are backed up to a berm at

the edge of the pile and the material is dumped over the edge

(edge-dumping, also called end-dumping or berm-dumping)

(figure 1). An alternative used less frequently is to dump the

material back from the edge of the spoil pile and push the

material over the edge with a dozer (short-dumping, also

referred to as plug-dumping, back-dumping, or butt-dumping)

(figure 2).

The main consideration in the edge-dumping method is

reduction in the amount of dozer work required. Often, a

rubber-tired dozer is of sufficient size to maintain the berm

adequately. At smaller operations where haulage distances are

short, a rubber-tired dozer can sometimes split time between

maintaining the spoil pile and performing cleanup duties at the

shovel. This split duty is less likely if the mine is shortdumping because of the added time required for the dozer to be

at the spoil pile.

Initially, it was thought there would be a time savings in

truck cycle time at a dump site if short-dumping was used

instead of edge-dumping. However, site visits and discussions

with engineers at various mines indicated that there was little

difference in cycle times because in most instances, the

dumping phase was a small segment of a truck’s cycle time. 

OVERVIEW OF DUMP-SITE INJURIES

The potential for dump-site injuries exists at any mine.

Whether dump sites are temporary materials stockpiles or

semipermanent or permanent spoil piles, mobile mining

equipment is used extensively in elevated areas near dumping

points (May 1990). Dumping over an edge is considered the

most efficient means of handling material at many sites. For

this reason, dumping over an edge is widely practiced.

However, injury data suggest that the practice of end-dumping

has a significant degree of risk associated with it. Krowczyk

(1995) noted that between 1991 and 1994, the operation of a

haulage truck accounted for 26 fatalities, which was 27.7% of

the total number of fatalities at surface mines. A sizeable

proportion of these fatalities related to a truck’s rolling off a

bench, highwall, or roadway. May noted also that from 1983 to

1987, haulage trucks were implicated in 80% of all dumping

point injuries, resulting in seven fatalities and 61 lost-workday

injuries.
3

As a follow-up to the work done by May, NIOSH researchers examined haulage truck dump-site injuries using Mine

Safety and Health Administration (MSHA) accident data. A

subset of injury data for the period 1988 through 1997 was

identified for coal and metal/nonmetal mines. The set included

370 lost-time injuries and fatalities involving haulage trucks

working at a dump site. Narratives were analyzed for each

injury, and a coding scheme was developed that included the

activity, result, and factors contributing to the injury. An

outline of the key findings involving injuries to personnel is

given below.2

Of the 370 haulage truck incidents, 26 resulted in fatalities,

and 5 resulted in permanent disabilities. Thirty-three were

2

This injury section is adapted from an unpublished report entitled “Haulage Truck Dump Site Safety: An Examination of Reported Injuries,” by Fred

Turin and William Wiehagan, industrial engineers at the Pittsburgh Research

Laboratory, prepared in conjunction with the study presented here.

classified as lost-day and restricted-activity injuries. Threehundred and six injuries were classified as days away from

work only.

! Incident type: Trucks falling over edge = 3; truck rollovers

on same level = 93; truck bounced or shaken = 78; collisions

= 12; trucks hung up on edge = 10; contact with power line

= 3; unknown/other = 23.

! Mine category: 133 bituminous coal, 180 stone, 66 metal,

46 sand and gravel, 17 nonmetal, and 8 anthracite coal.

! Truck activity: 179 dumping but not moving, 156 backing

up, 32 moving forward, 3 unknown or other.

! Effect on operator: 200 thrown into object, 80 jarred or

tossed about, 52 thrown from cab, 16 suffered musculoskeletal injury, 8 struck by object, 8 burned, 4 drowned,

2 electrocuted.

COSTS OF INJURY

Workplace injuries in the United States were estimated by

Miller and Galbraith (1995) to cost $140 billion annually

(December 1990 dollars). Fatal injuries were only 0.1% of the

total number of cases, but were 20.5% of total costs. Also of

note, nonfatal, compensable lost-work accidents were 20.9% of

the cases and 73.8% of the total costs. In 1992, workplace

injuries (fatal plus nonfatal) in the United States cost $145.37

billion (Leigh et al. 1997). 

Employer costs are only part of the total. Leigh et al. (1997)

described direct costs as including actual dollars spent on

providing health care, property damage, police and fire services,

and insurance administration expenses. Indirect costs to the

worker included lost earnings, lost home production, and lost

fringe benefits. Indirect costs to employers included costs

associated with retraining and restaffing, coworker costs of lost

or lowered productivity, and time delays. While direct costs

canbe substantial, they only represent about 34% of total costs,

with indirect costs contributing 66% of the total (Leigh et al.

1996). Table 1 is a summary of direct and indirect cost

categories.

A fatal injury has an average cost of $2.57 million and a

nonfatal compensable injury $46,400 (Miller and Galbraith

1995; Miller 1997). Viscusi (1996) estimates the cost of a

fatality at $5 million. The costs based on Miller and Galbraith

(1995) are listed by category in table 2. A large proportion of

the cost of fatality is quality of life at $1.9 million. Quality of

life is calculated based on estimates of the wage premiums paid

to compensate workers for taking risky jobs. The average used

by Miller and Galbraith was $24 in after-tax wage compensation per a 1-in-100,000 chance of being killed on the job

during the year. The quality-of-life estimated cost of $1.9

million was computed by subtracting the values in the other cost

categories (medical, wages, fringe benefits, and household

work) from the wage compensation per fatality. 

Medical and emergency services costs are based on data

from the government’s annual reports on total workers’

compensation medical payments. Wages and fringe benefits

losses for fatalities were computed at a 4% discount rate. For

Table 1.—Direct and indirect cost categories (adapted

 from Leigh et al. 1996).

Direct costs Indirect costs

Medical Lost earnings

Administrative: Lost fringe benefits

Workers’ compensation Lost home production

Private insurance Workplace training, restaffing,

 distribution

Medicaid Time delays

Medicare Injuries to innocent third parties

Welfare

Indemnity administrative:

Workers’ compensation

Private insurance

Social Security

Property damage

Police and fire service

Injuries to innocent third parties
4

 Figure 3.—Cracks near berm of spoil pile can create hazards for

trucks dumping material near edge.

Table 2.—Costs per injury by severity, December 1990 dollars (adapted 

from Miller and Galbraith 1995)

Cost category Fatal Nonfatal compensable

Medical/emergency services . . . . . . . . . . 13,000 6,300

Wages/fringe benefits ............... 520,000 15,000

Household work disruption ........... 110,000 2,500

Work disruption . . . . . . . . . . . . . . . . . . . . 9,900 2,500

Legal and administrative . . . . . . . . . . . . . 18,000 2,100

Subtotal . . . . . . . . . . . . . . . . . . . . . . . . 670,900 28,400

Quality of life . . . . . . . . . . . . . . . . . . . . . . 1,900,000 18,000

Total . . . . . . . . . . . . . . . . . . . . . . . . . . . 2,570,900 46,400

costs of injuries, workers’ compensation data were used.

Household work loss was estimated on the basis of $0.214 in

lost household production for each dollar of wage loss. This

took into account reduced wages from workers’ compensation,

sick leave, and lost fringe benefits. Workplace disruption and

employer productivity loss costs included supervisor’s time

spent in dealing with the incident. In addition, a fatal injury

costs 4 months of productivity (wages plus fringe benefits) due

to recruitment, retraining, and lost special skills. A compensable lost-time work injury cost 1 month of productivity.

Legal and administrative costs were computed using multipliers

for health insurance, life and disability insurance, workers’

compensation, auto liability insurance, auto property damage

insurance, and sick leave. These costs are summarized in

table 2 (Miller and Galbraith 1995:December 1990 dollars).

CONSIDERATIONS FOR CHOOSING A DUMPING METHOD

Edge-dumping is favored by mine operators because it is the

simplest method—just back a truck up to a berm and dump.

Most of the material falls over the edge, so there is a minimal

amount of dozer work required to maintain the berm.

Consequently, the effective life of the dozer is longer because

the dozer is used less.

With edge-dumping, the material is basically in place and

only needs to be sculpted to maintain the berm. This requires

that only 20% to 50% of the material needs to be moved by the

dozer, and this for only a very short distance. This situation

contrasts with short-dumping, where 100% of the material must

be moved by dozer. Because material is dumped back from the

edge, it must be moved a greater distance than edge-dumped

material. Thus, short-dumping requires more material to be

moved over a greater distance than does edge-dumping. 

There are, however, circumstances where short-dumping is

preferred. In three situations in particular, short-dumping is

strongly advisable for safety reasons. The first is when the

spoil pile has been loaded out. This occurs when material has

been removed from the lower part of the slope of the spoil pile,

causing a steep wall that exceeds the natural angle of repose of

the material. The main danger in this situation is that the added

weight of a loaded truck at the upper edge of the pile could

cause the wall to collapse. If the truck falls over the edge, the

driver is likely to be injured, and any machine or worker at the

bottom may be buried by collapsing material. 

The second situation is when there are cracks in the edge of

the pile. The presence of cracks increases the likelihood that

the edge will collapse if any weight is added. Figure 3 shows
5

an edge with cracks. It is best to use a dozer to push more

material over the edge to stabilize the spoil pile before any other

equipment is allowed near the edge.

The third circumstance where edge-dumping should be

avoided is when the berm along the edge is too low. To avoid

having the truck go through the berm and over the edge when

dumping, the berm should be at least the height of the axle of

the largest piece of equipment dumping at the berm. The main

function of the dozer during edge-dumping is to ensure that the

berm is adequately maintained.

COST MODELING

There are several approaches available for cost modeling,

and which one is chosen depends primarily on the level of

detailed information available, the precision required for costs,

and the amount of time and personnel available to perform a

cost analysis. The general approach for prefeasibility studies is

to use generalized cost equations with limited design variables.

These equations are most commonly a geometric regression

equation in the form y = axb

, where y is the cost, a and b are

constants, and x is the design variable (tons per day, for

example). This type of approach is most useful for calculating

the overall cost of a mine in a short amount of time with limited

engineering design required (Camm 1991; O’Hara and

Suboleski 1992; Schumacher 1997). 

A more detailed approach involves a specific engineering

design that itemizes the particular requirements of each unit

process in the mine. This includes estimating specific labor

requirements, types of supplies and their consumption amounts

per day (or per ton), and equipment (type, size, number of each)

and its utilization. Using all these detailed items and amounts,

a more specific (and accurate) cost estimate is calculated. Case

studies of actual mining operations with characteristics similar

to the mine being evaluated can provide guidance in developing

engineering designs (Camm 1995; Gentry and O’Neil 1984). 

A cost-modeling approach to studying the economic effects

of injury prevention provides a useful tool for promoting public

health. It puts the cost of safety, and perhaps more importantly,

the cost (and consequences) of minimizing or ignoring safety,

into terms that will get the attention of decision makers. While

the concept of worker safety is readily agreed upon by most

people, in practice it often is sublimated to perceived economic

expediencies. By demonstrating that injury prevention not only

makes good social and public relations sense, but is also good

economic sense, there is increased likelihood that new

approaches to injury prevention will be embraced with more

enthusiasm.

COST CATEGORIES

The cost of operating a dozer at a dump site is the main

variable to consider when comparing edge-dumping and shortdumping. These costs can be divided into two broad categories,

labor and equipment. 

Labor costs depend on numerous factors: geographic

location, availability of experienced workers, commodity being

mined, size of the mine, unionized or nonunionized labor, use

or nonuse of contractors, and size of the corporation operating

the mine. Hourly wages paid to an equipment operator are

usually considered a direct operating cost (Gentry and O’Neil

1984; Humphreys 1991).

Added to the direct costs of wages is the wage (or labor)

burden. This factor includes insurance, Social Security taxes

(FICA), unemployment tax, and other expenses that are based

on hourly wages. Table 3 provides a summary of the typical

items included in labor calculations. The wage burden can add

from 25% to 58% to labor costs at surface coal mines in the

western United States (Schumacher 1998).

Indirect labor costs include maintenance, supervision,

support services, administration, and overhead.

Equipment costs can be broadly divided into two categories,

operating cost and capital cost (Camm 1994b; Gentry and

O’Neil 1984; Humphreys 1991; Schumacher 1996). Operating

costs include what is consumed or used during actual operation

of equipment. Replacement and repair of parts during normal

operation of equipment, diesel fuel, lubrication, tires, and

maintenance labor costs are all included in equipment operating

costs. These costs are expressed in dollars per hour of

equipment operation, dollars per ton of ore mined, or dollars per

day.
6

Table 3.—Breakdown of labor expenses (adapted from Schumacher 1998; Pruitt 1998)

Federal:

Social Security (FICA) . . . . . . . . . . . . . . . . . . . . . . . . . 6.2% of wages less than $68,400

Medicare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.45% of all wages

Unemployment tax (FUTA) . . . . . . . . . . . . . . . . . . . . . 6.2% of wages less than $7,000

0.8% of wages less than $7,0001

Black lung insurance .......................... $500 lump sum annually

State (varies by state. Wyoming is used as an example below.):

Unemployment insurance . . . . . . . . . . . . . . . . . . . . . . 0.30-8.80% of wages less than $12,500

Workers compensation . . . . . . . . . . . . . . . . . . . . . . . . $0.91 per $100 of all wages

Other misc. (Federal, state, or local) . . . . . . . . . . . . . . Varies

Company (dollars per month, varies by company):

Medical insurance . . . . . . . . . . . . . . . . . . . . . . . . . . . . $300

Dental insurance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (included in medical)

Vision insurance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (included in medical)

Disability insurance . . . . . . . . . . . . . . . . . . . . . . . . . . . $50

Life insurance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . $20

Black lung insurance . . . . . . . . . . . . . . . . . . . . . . . . . . $20

Auto liability insurance . . . . . . . . . . . . . . . . . . . . . . . . . $20

Excess liability insurance . . . . . . . . . . . . . . . . . . . . . . . $20

Total insurance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . $430

Company retirement contribution . . . . . . . . . . . . . . . . . . . 0-10% of all wages

Other miscellaneous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Varies

Paid leave (typical range, days per year):

Holidays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-12

Vacation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-25 (depending on length of service)

Sick leave . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0-10

Total leave . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20-47

 TOTAL BURDEN (for surface coal, western United States) 25-58%, average 40% nonunion, 43%

union.

 1

Tax rate is 6.2%; a credit up to 5.4% can be taken for state unemployment taxes paid. If the full

5.4% state credit is taken, the effective Federal rate is 0.8%.

COST ANALYSIS

Overall operating costs typical for surface mines are

summarized in table 4. These are direct mine operating costs

and do not include administrative, infrastructure, corporate

overhead, or mineral processing costs. Depending on the cost

estimation system used and the tonnage of material moved, total

operating mining costs for a surface operation can vary from

$0.96 to $1.46 per ton of material moved. Costs are adjusted to

1998 dollars using Mining Cost Service indexes (Schumacher

1999).

The choice of which earthmoving machine to use at a dump

site will depend on the amount of material that must be moved.

The most common dozer sizes found at operating mines are

Caterpillar’s D10 or D11 (or an equivalent machine). At sites

with less capacity requirements and where the dozer is used to

clean up away from the dump as well as to maintain the dump

site, rubber-tired dozers are often used. Using data from the

Caterpillar Performance Handbook (Caterpillar 1996) the

capacities of D10, D11, and 834D dozers over distances of 15

and 30 m are summarized in table 5. 

Table 4.—Operating costs for surface mines calculated using

various cost models, dollars per metric ton of material

 moved (all costs adjusted to 1998 dollars)

Cost model Ore production, mt/d

10,000 20,000 40,000

Camm (1991) . . . . . . . . . . . . . 1.43 1.29 1.17

Camm (1994a) . . . . . . . . . . . . 1.46 1.30 1.16

Schumacher (1997) . . . . . . . . . 1.21 1.12 0.96

 NOTE: All costs based on a stripping ratio of 2:1. Details of cost

equations appear in appendix.
7

In many cases, a mine will be able to switch to shortdumping using existing equipment. For example, if a mine used

a D11 dozer and produced 40,000 mt/d of waste, then it could

meet the requirements for edge-dumping (table 5). Assuming

that short-dumping would require 15 m of dozing distance, the

D11 is still adequate to meet the needs of the mine. Table 6

indicates that operating costs for a dozing distance of 15 to

30 m would increase by $0.011/mt of waste material moved on

the spoil pile. Based on a typical direct mine operating cost of

$1.10/mt of material moved by edge-dumping, short-dumping

would increase costs by $0.01/mt, an increase of 0.9%. A

constant labor wage for the dozer operator of $19.49/h is used

in table 6. The wage burden would add 40% ($7.80/h), for a

total labor cost of $27.29/h. Equipment costs are compared

for three common dozer sizes: a large rubber-tired dozer

(equivalent to a Caterpillar model 834B) and two track-type

dozers (equivalent to Caterpillar models D10 and D11). 

For comparative purposes, the costs in table 6 are given for

surface mines having a stripping ratio of 2:1 and average dozing

distances of 15 m for edge-dumping and 30 m for shortdumping. Capital costs for minerals extraction at a surface

mine (excluding infrastructure and minerals processing) are

$24 million, $53 million, and $94 million for production

capacities of 10,000, 20,000 and 40,000 mt/d of ore,

respectively, in 1998 dollars (Schumacher 1996). The appendix

contains details of individual cost calculations. 

Depreciation schedules are set by the Internal Revenue

Service at a fixed rate over 7 years for mobile mining equipment

(Internal Revenue Service 1998). Whether the equipment is

used constantly or for only a few hours a day, depreciation is

the same for tax purposes.

Estimated capital costs for dozers are $584,000 for a 834B

(rubber-tired), $790,000 for a D10, and $1,216,000 for a D11

(both the D10 and the D11 are track-type machines)

(Schumacher 1996). Unit costs are estimated based on

published sources and represent typical costs. 

Equipment purchase costs and operating costs (table 6) can

vary markedly from mine to mine, depending on geographic

location and the corresponding availability of experienced

labor; size of mine; use of union or nonunion labor; size,

type, and age of equipment; and effectiveness of equipment

maintenance program. Because of this variability, costs used

here should be considered only as illustrative of the modeling

process. Any actual mine is going to have specific labor wages,

labor burdens, and equipment costs unique to its operation.

As an example, a mine that extracts 20,000 mt of ore per day

and has a stripping ratio of 2:1 will produce 40,000 mt of waste

per day. Using edge-dumping and assuming only 20% of the

material needed to be moved, a dozer should be able to move an

average of 8,000 mt/d for a distance of 15 m. All three of the

dozers in table 5 could handle this requirement. If the mine

used short-dumping, all 40,000 mt of waste per day would need

to be moved an average distance of 30 m. Based on the

information in table 5, a D11 would probably be necessary.

Actual operating costs per ton moved would decrease because

of the increased efficiency of a D11. However, because more

material is being moved, operating costs per day would increase

by $624/d (8,000 mt/d × $0.047/mt = $376/d versus 40,000 mt/d

× $0.025/mt = $1,000/d). 

Based on a mining cost of $1.10/mt of material moved and

60,000 mt of ore and waste mined per day, the estimated daily

operating cost is $66,000/d. The $624/d is slightly less

Table 5.—Estimated dozer production capacities

 Dozer model Av. dozing distance, m 1

Lm3/h Material moved, mt/h 2 Daily capacity, mt/d

D10 . . . . . . . . . . . . . . 15 2,600 3,640 49,500

30 1,500 2,100 28,500

D11 . . . . . . . . . . . . . . 15 4,000 5,600 76,100

30 2,200 3,080 41,800

834D . . . . . . . . . . . . . 15 1,100 1,540 20,900

30 650 910 12,300

 1

Lm3 = Loose cubic meters. This term refers to material that has been excavated and therefore is less dense than its

equivalent volume in the ground. 

 2

Based on 1.4 Lm3/h, 85% equipment availability, two 8-h shifts per day. (Source: Caterpillar 1996)

Table 6.—Estimated operating dozer costs

 Dozer model Av. dozing distance, m Operating cost, $/h Material moved, mt/h Operating costs, $/mt 

D10 . . . . . . . . . . . . . . . 15 $62.24 3,460 $0.017

30 62.24 2,100 0.030

D11 . . . . . . . . . . . . . . . 15 78.27 5,600 0.014

30 78.27 3,080 0.025

834D . . . . . . . . . . . . . . 15 71.68 1,540 0.047

30 71.68 910 0.079

NOTE: All costs in 1998 dollars. Based on Schumacher 1996.
8

 than a 1% increase in daily mine operating costs. The increase

in capital costs for a D11 over an 834D is $632,000

($1,216,000 to $584,000). The estimated capital cost for a

20,000-mt/d surface mine is $52 million, which is an increase

of 1.2%. 

If nonroutine costs were included, such as for repairing a

truck that has fallen over an edge, for loss of use of that truck,

and for the use of equipment needed to free a truck after it has

been stuck, then the cost difference between the two methods

would be reduced further.

SUMMARY

There were 370 lost-time accidents involving haulage trucks

at mine dump sites between 1988 and 1997. One-hundred

thirty-seven involved trucks falling over an edge. According to

Miller (1997), the direct cost of a fatality to an employer is

$9,900 and the cost of a lost workday injury is $1,600. Direct

employer costs of fatalities or injuries are a small proportion of

total costs. According to Miller and Galbraith (1995), the total

cost of a fatality can be $2,590,900 and the cost of a nonfatal

work injury $46,400.

Edge-dumping is the most common method for dumping

waste at mine spoil piles. Short-dumping is usually employed

when there is a safety concern about edge-dumping. The added

cost of short-dumping can be quite variable depending on the

circumstances. In test calculations, short-dumping added about

1% to both mine operating and capital costs. The largest cost

difference was seen when a rubber-tired dozer was initially used

for both edge-dumping at the spoil pile and for other duties,

such as shovel clean-up, and it became necessary to switch to

short-dumping, which required a larger track-type dozer to be

used at the spoil pile full-time. 

ACKNOWLEDGMENTS

The author would like to thank Fred Turin and William

Wiehagen (industrial engineers, PRL) for providing information on haulage truck injuries at dump sites and their

participation in field visits to several mining operations. The

following personnel were also kind enough to provide mine

tours or information on their operations: Aaron Grinager,

Michael Lock, and Doug White (Glenrock Coal Co., Glenrock,

WY); Jeff Whipple and Pat James (Bridger Coal Co., Rock

Springs, WY); Dave McCarthy (Black Butte Coal Co., Port of

Rocks, WY); and William Pruitt (Kiewit Mining Group,

Omaha, NE).

REFERENCES

Camm, T. W. Simplified Cost Models for Prefeasibility Mineral

Evaluations. U.S. Bur Mines Inform. Cir. 9298, 1991, 35 pp.

___. Engineering Analysis Cost Models for the East Mojave National Scenic

Area, California. U.S. Bur. Mines OFR 6-94, January 1994a, 45 pp.

___. Simplified Cost Models for Prefeasibility Mineral Evaluations. Mining

Engineering, v. 46, no. 6, June 1994b, pp. 559-562.

___. The Relationship Between Engineering Design and Cost Estimation in

Cut-and-Fill Mine Stopes. Ph. D. dissertation, Univ. of Idaho, Moscow, ID,

1995, 240 pp.

Caterpillar, Inc. (Peoria, IL.) Caterpillar Performance Handbook, 27th ed.,

1996, 942 pp.

Gentry, D. W. and T. J. O’Neil. Mine Investment Analysis. SME., Littleton,

CO, 1984, 502 pp.

Humphreys, K. K., ed. Jelen’s Cost and Optimization Engineering, 3rd ed.

McGraw-Hill, 1991, 631 pp.

Internal Revenue Service. How To Depreciate Property. Publi. 946, 1998,

104 pp.

Krowczyk, C. Haulage Fatalities at Surface Coal Mines, 1991-1994. Mine

Safety and Health Administration, Office of Injury and Employment

Information, Denver, CO. 1995.

Leigh, J. P., S. Markowitz, M. Fahs, J. Bernstein, L. Mishel, C. Shin, and

P. Landrigan. Costs of Occupational Injuries and Illnesses in 1992: Final

NIOSH Report for Cooperative Agreement with E.R.C., Inc. U60/CCU902886.

NIOSH, 1996, 98 pp.

Leigh, J. P., S. B. Markowitz, M. Fahs, C. Shin, and P. J. Landrigan.

Occupational Injury and Illness in the United States. Archives of Internal

Medicine, v. 157, July 28, 1997, pp. 1557-1568.

May, J. P. Analysis of Dump-Point Accidents Involving Mobile Mining

Equipment. U. S. Bur. Mines Inform. Cir. 9250, 1990, 19 pp.

Miller, T. R. Estimating the Costs of Injury to U.S. Employers. Journal of

Safety Research., v. 28, no. 1, 1997, pp. 1-13.

Miller, T. R. and M. Galbraith. Estimating the Costs of Occupational Injury

in the United States. Accident Analysis and Prevention, v. 27, no. 6, 1995,

pp. 741-747.

O’Hara, T. A. and S. C. Suboleski. Costs and Estimation. In SME Mining

Engineering Handbook, ed. by H. L. Hartman. SME, Littleton, CO, 1992,

pp. 405-424.

Pruitt, W. Kiewit Mining Group, Inc., personal communication, Omaha,

NE, 1998. 

Schumacher, O. L., ed. Mining Cost Service. Western Mine Engineer.

Spokane, WA, 1999, 1998, 1997, 1996.

Viscusi, W. K. The Dangers of Unbounded Commitments To Regulate

Risk. In Risks, Costs, and Lives Saved: Getting Better Results from

Regulation, ed. by R. W. Hahn. Oxford Univ. Press, New York, 1996,

pp. 135-166.
9

APPENDIX—MINE OPERATING AND CAPITAL COSTS

Cost indexes

All costs are updated to 1998 dollars using Mining Cost Service

indexes for surface mines (Schumacher 1999).

Year Cost index

1989 90.4

1991 97.7

1996 105.7

1998 106.9

Camm 1991:

5.14(X)-0.148, where X = short tons of material mined (ore +

waste) for a 2:1 stripping ratio and production of 11,023,

22,046, and 44,092 st (10,000, 20,000, and 40,000 mt) of ore

per day.

1989 dollars:

10,000 5.14(11,023 × 3)-0.148 = $1.10/st material 

20,000 5.14(22,046 × 3)-0.148 = $0.99/st material 

40,000 5.14(44,092 × 3)-0.148 = $0.90/st material 

Updated to 1998 dollars and converted to dollars per metric ton

(dollars per short ton ÷ 0.9072):

10,000 1.10 × (106.9/90.4)/0.9072 = $1.43/mt material

20,000 0.99 × (106.9/90.4)/0.9072 = $1.29/mt material

40,000 0.90 × (106.9/90.4)/0.9072 = $1.17/mt material

Camm 1994a

[6.725(X)-0.165](SR+1)0.835, where X = short tons of ore and

SR = stripping ratio for a 2:1 stripping ratio and production of

11,023, 22,046, and 44,092 st (10,000, 20,000, and 40,000 mt)

of ore per day.

1991 dollars:

10,000 [6.725(11,023)-0.165](2+1)0.835 = $3.62/st ore,

 3.62/(SR+1) = $1.21/st material

20,000 [6.725(22,046)-0.165](2+1)0.835 = $3.23/st ore,

 3.23/(SR+1) = $1.08/st material

40,000 [6.725(44,092)-0.165](2+1)0.835 = $2.88/st ore,

 2.88/(SR+1) = $0.96/st material

Updated to 1998 dollars and converted to dollars per metric ton:

10,000 1.21 × (106.9/97.7)/0.9072 = $1.46/mt material

20,000 1.08 × (106.9/97.7)/0.9072 = $1.30/mt material

40,000 0.96 × (106.9/97.7)/0.9072 = $1.16/mt material

Schumacher (1997)

For a 2:1 stripping ratio and production of 10,000, 20,000, and

40,000 mt of ore per day.

1996 dollars:

10,000 $3.63/mt ore, 3.63/(SR+1) = $1.21/mt material

20,000 $3.36/mt ore, 3.36/(SR+1) = $1.12/mt material

40,000 $2.88/mt ore, 2.88/(SR+1) = $0.96/mt material

Updated to 1998 dollars:

10,000 1.21 × (106.9/105.7) = $1.22/mt material 

20,000 1.12 × (106.9/105.7) = $1.13/mt material 

30,000 0.96 × (106.9/105.7) = $0.97/mt material 
DHHS (NIOSH) Publication No. 2000-129

2000

To receive other information about occupational safety and health problems, call

1-800-35-NIOSH (1-800-356-4674), or

visit the NIOSH Home Page on the World Wide Web at

http://www.cdc.gov/niosh