25th International Conference on Ground Control in Mining 

284 

ABSTRACT 

 Bowie Resources maintains one of the most pro-active ground 

control programs in the U.S. mining industry today. Its guiding 

philosophy is that everyone in the organization, from the miners at 

the face all the way through the top management, are involved in 

ground control. Some of the unique elements of the Bowie ground 

control program include: 

• Roof bolt operators log the stratigraphy of test holes in nearly 

every cut. These “lith-graphs” are used by section foremen 

to determine the need for additional roof support, and they 

are entered into the geologic data base for use in geologic 

modeling and mapping. 

• Underground core drilling is conducted to obtain data for 

CMRR and stability maps. 

• Weekly “Quality” meetings, involving mine management 

and technical staff, are held to ensure that ground control 

information is integrated into production operations. 

 The paper will describe the program in detail, discussing the 

involvement of roof bolters, section foremen, surveyors, technical 

staff, and production managers. It will also show how the program 

has contributed to the mine planning process. Case histories of 

successful ground control interventions will be discussed. 

INTRODUCTION 

 Bowie Resources operates the Bowie No. 2 longwall mine, 

located near Paonia, CO. The mine employs approximately 160 

people and produced 4.1 million tons of clean coal in 2005. 

 Mining has been conducted on the Bowie property for many 

years. The Bowie No. 1 Mine (formerly the Orchard Valley Mine) 

was a room-and-pillar mine that was active in the Upper B seam 

during the 1980’s and early 1990’s. The Bowie No. 2 Mine opened 

in 1996 and initially worked the D seam. Bowie first employed 

longwall mining at the No. 2 Mine in 1999. D seam mining was 

completed in 2005, and the longwall was relocated to the No. 3 

portal in the Upper B seam, approximately 300 ft below the D seam 

(figure 1). A typical stratigraphic column is shown in figure 2. 

 The Bowie property has presented a number of ground control 

challenges. The depth of cover increases rapidly, from 0 at the 

outcrop to more than 2,000 ft. Access to the coal can be difficult 

due to an extensive burn zone at the outcrop. Five major faults 

were encountered in the Bowie No. 2 Mine alone. Igneous sills 

have penetrated parts of the reserve, coking the coal in place and 

rendering it difficult to impossible to mine. The immediate roof 

varies widely, from competent sandstone in some places to very 

weak mudstone in others. Seam splits and riders also cause local 

roof problems. Extensive slump faults, caused when the soft 

sediments slumped shortly after deposition, have been a problem in 

the Upper B Seam mine in some areas. 

GEOLOGY, GROUND CONTROL, AND MINE PLANNING AT 

BOWIE RESOURCES, PAONIA, CO 

Collin Stewart, Manager of Technical Services 

Greg Hunt, Sr. Geologist 

Bowie Resources 

Paonia, CO, USA

Christopher Mark, Chief, Rock Mechanics Section 

NIOSH-Pittsburgh Research Laboratory 

Pittsburgh, PA, USA 

B1 Longwall Panel

B2 Longwall Panel

B3 Longwall Panel

North Mains

East Mains

West

Mains

Portals

Figure 1. Bowie No. 2 Mine, Upper B Seam workings, first 

longwall district. 
25th International Conference on Ground Control in Mining 

285 

 In response to these challenges, Bowie Resources has put in 

place an innovative ground control program. Some elements of the 

program, such as surface drilling and underground mapping, are 

widely practiced throughout the industry. Others, such as the 

routine “lith-graphs” made by the roof bolt operators when they 

drill test holes, are unique to Bowie. What makes the program 

effective, however, is the day-to-day involvement of the mine’s 

personnel in ground control, from the mine manager to the 

production crews. This involvement is maintained through regular, 

structured, two-way communication between Bowie’s geologic 

staff and its operating personnel. 

GEOLOGIC DATA COLLECTION 

 Ground control begins with geologic information. At Bowie, 

the geologic data base is considered a living entity, that grows and 

changes as new information is collected. One important goal is to 

develop a geologic model that facilitates predictions about 

conditions in advance of mining. The model provides insight into 

sandstone channel trends in the roof and floor, seam splits and 

partings, and fault trends. 

Figure 2. Generalized stratigraphic column for the Bowie Mine (after Robeck, 2005). 
25th International Conference on Ground Control in Mining 

286 

 Geologic information is gathered at several scales, beginning 

with pre-mining surface core drilling and geophysics. 

Underground core drilling has been used to fill many of the gaps 

between surface holes. Finally, roof lith-graphs and underground 

mapping provide detailed documentation of the near-seam geology. 

Surface Drilling and Geophysics 

 In planning a surface drilling program, Bowie faces many of 

the same challenges as most Rocky Mountain coal mines. The 

steep terrain, great depths, permitting issues, and drillsite 

reclamation requirements all make exploration drilling an 

expensive proposition. To maximize the return from each hole, 

Bowie begins an exploration program with a few widely-spaced 

holes. The results from this “first-order” drilling then dictate where 

additional holes will go. 

 Coal quality is of course a key parameter that is obtained from 

each hole. Seam correlation is also crucial, and can be quite 

complex. For example, recent interpretations have shown that the 

old Orchard Valley Mine was located in the Upper B seam, not the 

Upper D as was previously thought. 

 Stratigraphic columns obtained from surface drilling are the 

first look at the roof and seam conditions that will be encountered 

during mining. However, many features in the immediate roof 

occur on far smaller scales than are likely to be picked up from 

surface holes. Faults are also very difficult to locate. 

 Bowie has made some use of geophysical techniques to 

supplement surface drilling. A magnetometer survey was 

employed to help identify the burn zone to aid in locating the 

portals for the Upper B Seam Mine. Currently, a seismic survey is 

being conducted to locate faults in future areas of the Upper B 

Seam lease. 

Underground Core Drilling 

 During the past few years Bowie has made very effective use 

of underground drilling to supplement surface core drilling. 

Portions of the B seam reserve below the existing D-seam workings 

were proved out by a program of 70 holes drilled from the D seam 

down into the lower seam. The drilling was done with a “Hagby” 

wireline drill rig that enabled the entire 300 ft interval to be cored. 

 One reason for the intensive drilling program was the presence 

of igneous sills that were thought to have ruined large areas of the 

Upper B and Lower B seams for mining. The drilling showed that 

the sills were not nearly as extensive as had been believed. As a 

result, a completely new mine plan was developed to target the 

available reserves. 

Figure 3. "Stability Map" generated from CMRR and underground mapping data. 
25th International Conference on Ground Control in Mining 

287 

 Currently, underground horizontal core drilling is being 

conducted within the Upper B seam using the “Hagby” drill. This 

horizontal core drilling successfully located the “Mains Fault” that 

had been previously encountered in the D seam. That knowledge 

helped locate the B seam mains, provided design information for 

the fault crossing in the B East Mains and maximized the reserve 

block for the first sets of longwall panels in the Upper B Seam 

Mine. 

Underground Geologic and Conditions Mapping 

 One to two times per week, depending on mine productivity, 

detailed face, rib and conditions mapping is conducted in each 

continuous miner section and along the longwall face. The results 

of this mapping is summarized on the various Autocad geologic 

map layers for the B seam workings. 

 On a more informal basis, “conditions” mapping is conducted 

along current and future longewall gateroad entries. This mapping 

concentrates on the current conditions of ribs, roof, floor heave and 

water. This information also is entered on AutoCad map layers for 

the Upper B seam. 

Rock Testing and Coal Mine Roof Rating (CMRR) 

 Geotechnical data is collected from all core drilling conducted 

at Bowie. First, core is logged to show lithologic contacts, 

fractures, and RQD. Point load tests (PLT) are conducted on the 

first 10-12 ft above the coal in every hole. To facilitate testing, 

Bowie purchased its own Point Load Tester, together with a tile 

saw to prepare samples. Both diametral and axial PLT are 

conducted. The axial test is used to estimate the rock’s unconfined 

compressive strength (UCS, in psi), while the diametral tests 

evaluate the strength parallel to bedding. The axial test values are 

converted to UCS using a site-specific formula developed from past 

Bowie testing. In general, Bowie has found that the PLT provides 

consistent results with stronger rocks and coal, but is less reliable 

with weak mudstones. 

 The PLT and RQD values are used to determine the CMRR for 

the bolted roof horizon at each drillhole location. Once the input 

data has been collected, the NIOSH CMRR program is used to 

calculate the CMRR values (Mark and Molinda, 2005). The 

CMRR values are then saved in the Autocad B seam CMRR 

contour map. As additional values are entered, the CMRR contours 

are updated. 

 The CMRR map for the Upper B seam has developed in three 

stages. The initial hand-drawn contours were based on surface 

drillholes alone. These were later adjusted with data from the 

Hagby holes drilled from the D seam. Underground data, from 

both roof bolter lith-graphs and mapping, is now being used to 

refine the contours. The result is a detailed view of the immediate 

roof that is highly valuable to roof support selection as well as to 

the development of a geologic model for the Upper B seam. The 

CMRR map also serves as the foundation for a “stability map,” 

with the strongest roof contoured in green and the weakest in red 

(figure 3). 

Roof Bolter Lith-graphs 

 Perhaps the most unique element of the ground control 

program at Bowie is the collection of the roof bolter lith-graphs. 

Lith-graphs are actually stratigraphic logs that are created by roof 

bolters while they drill 10-18 ft test holes. Figure 4 shows the form 

that the bolters use to collect the data. The bolters try to identify 

four different rock types (sandstone, siltstone, shale, and coal) from 

the degree of difficulty of drilling and the appearance of the 

cuttings. Cuttings are most easily obtained when an auger drill is 

used for the test hole in place of the usual dust hog bit. Because the 

vacuum cannot be used with the auger steel, the roof bolter must 

wear a dust mask when drilling these holes. 

 The roof bolters also note fractures (drill jumps) and the 

presence of groundwater on the logs. The number of bits per hole, 

or holes per bit is noted. The primary support pattern (bolt type, 

length, and spacing) is also recorded. 

 After the roof bolters collect them, the lith-graphs are brought 

outside and filed in a reference book by the office staff. A staff 

geologist then enters the lith-graphs into a data base and uses them 

to refine the stratigraphic cross-sections that were previously 

generated from surface and underground drilling (figure 5). The 

lith-graphs are also used to refine the CMRR contour map. 

 Lith-graphs typically recorded once during every shift in every 

entry that is being developed. Over time Bowie has found that this 

frequency of data collection provides a sufficient density of 

geologic information with minimal interruption to the production 

process. 

BRL Roof Bolter Data

Section: ________________________ Shift: _____________ Data: ___________ 

Entry: _______________________________ X-Cut ________________________ 

Survey Station No: _________________________________________________ 

Ft. Indy X-Cut Center: ______________ or Ft. Inby Survey Station: ________ 

Bolt Type: __________________________________ Bolt Length: __________ 

Bolt Spacing: ______________________________________________________

Monster Mats: ____ Heavy Mesh: ___ Mesh: ____ Other: ________________ 

Bits This Hole or Holes per Bit in this area: ______________

Figure 4. Form used by roof bolt operators to collect 

lith-graph data. 
25th International Conference on Ground Control in Mining 

288 

 One obvious advantage of the lith-graph program is that it 

makes a wealth of information available for geologic modeling, 

mine planning, and decisions about support selection. The crosssections are particularly valuable for the design of secondary 

support. Less obvious, but perhaps equally valuable, is that the 

lith-graphs help focus the attention of the production crew on 

ground control. As one roof bolt operator put it, “there is no 

second guessing about what the top is doing.” Bowie’s roof bolters 

report that they discuss their observations with the section foreman 

at least once per day. Based on the information they provide, the 

foremen may adjust the cut length or the amount and spacing of 

primary roof support. 

 Another advantage is that the lith-graphs give the roof bolters 

themselves ownership in the ground control program. After all, 

they are ultimately the ones whose efforts protect everyone in the 

mine from roof falls. The roof bolters know that their logs are 

being used because they get feedback from the mine’s technical 

staff. One experienced roof bolt operator commented that “there is 

much more focus on ground control at Bowie then at other mines I 

have worked at.” 

 Of course, the lith-graphs must be of good quality if they are to 

be useful. The best lith-graphs are collected by well trained, 

experienced roof bolt operators. Unfortunately, roof bolting is a 

difficult job at Bowie, as it is at most mines, so turnover can be 

high. At Bowie, in a typical year, 4-5 of the 30 or so roof bolt 

operators will move to other positions. Each new operator must be 

trained to take the lith-graphs, preferably by a mine geologist. 

Stability Map 

 Bowie has adopted the stability mapping program developed 

by Dr. Keith Heasley and his graduate students at the West Virginia 

University (Heasley et al., 2006). The information described above 

plus model runs from the LaModel program (Heasley, 1997) and 

overburden depths is combined with the results to produce a 

stability map of current and projected conditions. 

 In the case of development mining, the stability maps are used 

to highlight possible difficult areas in advance, so the crews can be 

prepared for changing conditions. With respect to the longwall, 

stability maps are used to design supplemental tailgate support, to 

design supplemental headgate support, and to project face mining 

conditions. 

 The stability map projections are also used to determine runof-mine coal quality and zones where out-of-seam dilution will 

significantly increase the ash. These projections are used in budget 

plans and operational plans for the coal preparation plant. 

 The stability map projections are also used in the mine 

scheduling and budgeting processes to estimate zones of lower 

productivities and higher roof support costs. 

MANAGEMENT AND COMMUNICATION 

 The success of Bowie’s ground control program depends on 

two-way communication between the geologic staff and the 

operations people. The geologists know that they must acquire 

credibility by making predictions that are useful. To do this, they 

need to understand the needs of the production side. 

 The Manager of Technical Services has a key role in the 

communication process. With extensive experience in production, 

mine planning, and ground control, he has a unique understanding 

of how geology can impact the mine. Often, it is his job to ensure 

that information is flowing smoothly and is being understood by all. 

 To facilitate direct communication between all parties, Bowie 

conducts weekly “Quality Meetings.” These are attended by the 

Mine Manager, the Technical Services Manager, the Development 

Production Coordinator, the Longwall Manager, the Mine Engineer, 

the Surface Operations Superintendent, the Customer RelationsShipping Manager and the geologists. As mentioned above, prior 

to the meeting, a geologist goes underground to map the faces in 

the development sections and on the longwall and prepares face 

maps of existing conditions. The attendees discuss the experience 

of the past week, and the stability map projections and the geologic 

forecast for the upcoming week regarding conditions, productivity 

Figure 5. Geologic cross-section generated from core drilling (surface and underground) and lith-graph data. Abbreviations: 

STS=Siltstone; MS=Mudstone; SS=Sandstone; Sndy STS=Sandy Siltstone; BU4=Upper B Seam, 4th Bench (Rider Coal). Height above roof line (ft)

62 61 60 58 57 56 55 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36

0

2

4

6

8

10

12

0

2

4

6

8

10

12

Crosscut number

STS

MS

MS

BU4

SS

Sndy STS

STS
25th International Conference on Ground Control in Mining 

289 

and quality. The updated colored stability map and the relevant 

cross sections are prominently displayed during the meeting. 

 At one recent meeting, one of the development sections was 

encountering a rider seam, while the longwall was dealing with 

slump faulting on the face. The geologists were able to predict how 

much longer these features would be present, and what forms they 

were likely to take. The discussion focused on control techniques, 

particularly the proper mining horizon for each face. 

ROOF SUPPORT 

 Decisions about roof support in the development sections are 

made daily at the Bowie Mine. While a set of guidelines has 

emerged over time, the rapidly changing conditions preclude rigid 

standards. The primary decision maker is the Production 

Coordinator, but every member of the ground control team 

contributes. 

 The roof bolting cycle at Bowie includes bolting and meshing 

the roof, meshing the rib on the operator side of the entry, and 

bolting the rib on the other side. Normally a dual-boom roof 

bolting machine, with a three-man crew, is employed in each threeentry development section. Roof bolting is typically the production 

bottleneck, however, so an extra bolting machine is usually 

assigned to whichever section is on the “critical path.” 

 Four different primary supports are employed, depending on 

the ground conditions. In normal conditions, six ft, no. 6, fully 

grouted, non-tensioned needed rebar bolts are employed. Where 

conditions demand them, three other types of bolts may be installed; 

• Eight ft, no. 6, fully grouted, non-tensioned rebar; 

• Eight ft, 0.804 inch diameter, fully grouted, non-tensioned 

rebar, and; 

• Seven ft, 0.75 in diameter, resin-assisted mechanical anchor, 

with four-ft of resin grout. 

 One universal rule is that two ft of solid anchorage is required 

for primary supports. Where rider coal, soft drilling, or many slips 

are encountered in the anchorage horizon, then longer bolts or 

supplemental support will be installed. Extra support is always 

installed in the intersections, and in the headgate because later 

access is difficult. If the roof seems likely to fall in before it can be 

bolted, the section foreman and the continuous miner operator may 

also decide to reduce the cut depth and narrow the headings (other 

than the belt heading). 

 Cable trusses have traditionally been the preferred 

supplemental support when difficult conditions are encountered 

during development, based primarily on their ease of installation. 

However, cable bolts are increasingly used as supplemental support 

in “softer” ground conditions where cable truss performance has 

been problematic. Bowie’s philosophy is that “it is easier to put 

support in early then wait for things to get bad.” When possible, 

supplemental support will be installed on the downshift to 

minimize impacts on production. 

 Decisions concerning secondary supports in the tailgate and 

elsewhere are normally made by the engineering staff. The typical 

tailgate support for “good” ground conditions consists of one row 

of 24-inch Burrell TM Cans on 11 ft centers, with a row of 12 ft 

cable bolts on five-ft centers. The cable bolts are installed in a 

“baseball stitch” pattern, with alternating bolts each 2.5 ft off the 

entry centerline. Cable trusses are also often installed, on 5-ft 

centers. Where the roof bolter lith-graphs show that weak roof 

conditions are anticipated, a second row of Cans is installed, and 

the Can spacing may be decreased to 8 ft. The cable bolt density 

also is increased to four per row, on 4- to 5-ft centers, with Monster 

Mats. Cable bolt lengths are varied from 12-ft to 18-ft depending 

on the conditions. 

Case History – Southwest Longwall Mining District 

 Adherence to the methods and procedures described above 

allowed BRL to successfully recover over 2 million tons of 

longwall coal from the B2 and B3 longwall panels in the southwest 

mining district. Figure 1 illustrates the layout of the development 

and longwall panels in this district. Details of the stability mapping 

developed for this area are presented in more detail in Heasley et al. 

(2006). The stability map of the mining district is shown on 

figure 3. 

 The initial core drilling for the area, conducted from the 

overlying D-seam workings using the Hagby drill, indicated 

generally good mining conditions for the southwest mining district. 

However, development mining experience indicated possible 

gateroad stability problems due to slump faulting (figure 6) and 

splitting off of a thin rider seam across the mining district. CMRR 

values, updated continuously with the lith-graph data, showed 

consistently low values (CMRR<40) for the inby halves of the B1 

and B2 longwall panels. 

 Based on this data, significant additional supplemental support 

was installed in the first third of the B1 tailgate. This support 

consisted of: 

• 12-ft cable bolts, 4 per row, with heavy duty roof mats, 5-ft 

maximum row spacing 

• 24-in Burrell TM cans, 2 per row, maximum 8-ft skin-to-skin 

spacing 

 Mining progressed with minimal tailgate problems as a result 

of this extra supplemental support. However, problems were 

encountered along the longwall face due to the slump faults and 

along the headgate due to the rider seam splitting off into the roof. 

Figure 6. Photograph of a slump feature encountered in the 

Upper B Seam gate entry development. 
25th International Conference on Ground Control in Mining 

290 

 Both issues negatively impacted longwall productivity and coal 

quality in the B1 panel. The slumps caused mid-face falls of the 

roof ahead of the longwall shields and increased floor heave in the 

headgate belt line. The rider seam contributed of mid-face falls and 

increased roof sag in the headgate belt line. Longwall operations 

were interrupted while the belt line was partially removed for 500 ft 

and the floor was re-graded. 

 In preparation for mining the B2 panel, the weekly quality 

meetings focused on reviewing past mining experience and 

predicting future ground responses to longwall mining. The 

Stability Mapping software and procedure presented by Heasley et 

al. (2006) was implemented, and cross-panel radar imaging was 

performed to better define possible problems areas along the face. 

Other preparation included installing pumpable cribs between 

existing supports in the tailgate, rebolting approximately 2,500 ft of 

the belt line with 18-ft post tensioned cable bolts and heavy duty 

roof mats, and installing transfer lines and holding tanks for 

polyeurathane grout on the longwall face. 

 Experience on the B2 longwall panel showed that these 

mitigation measures were adequate to allow continued, safe mining 

of the B2 longwall panel. The cross-panel imaging and the CMRRbased stability mapping successfully predicted the areas of difficult 

mining conditions. Based on the B2 panel experience, the future 

tailgate for the B3 panel was divided into stability zones and 

supplemental support type and density were defined and tailored to 

the conditions. 

CONCLUSIONS 

 Bowie Resources maintains a pro-active ground control 

program that has evolved in response to varying and difficult 

mining conditions. Its guiding philosophy is that everyone in the 

organization, from the miners at the face through upper 

management, are involved in ground control. As a result of this 

commitment to our pro-active ground control program, Bowie 

Resources will be able to recover over 2 million tons of developed 

reserves that otherwise would have been lost to poor ground 

conditions. Our ground control program allows us to continually 

match the roof support to the conditions on development as well as 

for longwall tailgate support. It identifies areas that need extra 

attention before they interrupt longwall production. 

Specific lessons include: 

• In our conditions, cross-panel radar imaging has been 

successful in projecting zones of slumping and weaker roof in 

the B2 longwall panel. 

• Roof bolter operators are a key source of data on changing 

roof conditions. Use of a lith-graph system allows this 

experience and information to be captured for use in 

subsequent analyses. The data is particularly important for 

CMRR analyses and stability analyses. 

• Weekly quality meetings attended by senior operations, 

engineering, geology and surface personnel are an important 

tool in determining developing trends and problems in ground 

control and as-shipped coal quality. 

REFERENCES 

Mark, C. and Molinda, G.M. (2005). The Coal Mine Roof Rating 

(CMRR)—A Decade of Experience. International Journal of Coal 

Geology 64, pp. 85-103. 

Heasley, K.A. (1997). A New Laminated Overburden Model for 

Coal Mine Design. NIOSH IC 9446, pp. 60-73. 

Heasely, K.A., Petrovich, M., Stone, R. and Stewart, C. (2006). 

Mine Stability Mapping. Proceedings, 25th International 

Conference on Ground Control in Mining, Aug. 1-3, (IN PRESS). 

Robeck, RD (2005). The Effects of Fault-Induced Stress 

Anisotropy on Fracturing, Folding, and Sill Emplacement: Insights 

from the Bowie Coal Mines, Southern Piceance Basin, Western 

Colorado. MS Thesis, Brigham Young University, 62 pp