U.S. Department of Labor Mine Safety and Health Administration 

1100 Wilson Boulevard 

Arlington, Virginia 22209-3939 

EFFECTIVE DATE: 02/16/2012 EXPIRATION DATE: 03/31/2014 

PROCEDURE INSTRUCTION LETTER NO. 112-V-02 

FROM: 

SUBJECT: 

Scope 

KEVIN G. STRICKLIN 

Administrator for 

Coal Mine Safety and H al~,g 

7 

/ (;1 

LINDA F. ZEILER .d.~~)' *~~P<- /?-

Director of Technicaf Support 

Pillar Recovery Design, Technologies, and Procedures in Roof 

Control Plan Reviews 

This Procedure Instructional Letter (PIL) applies to personnel from Coal Mine Safety 

and Health and Technical Support. 

Purpose 

The purpose of this PIL is to establish guidance for Mine Safety and Health 

Administration (MSHA) personnel to use in assessing the quality and potential safety 

risk associated with roof control plans. This includes evaluating the pillar design, mining 

technologies, and mining procedures for pillar recovery (retreat mining). 

Instructions Pertaining to Retreat Mining Pillar Design 

Title 30 Code of Federal Regulations Section 75.203(a) states that "The method of 

mining shall not expose any person to hazards caused by .... faulty pillar recovery 

methods. Pillar dimensions shall be compatible with effective control of the roof, face 

and ribs and coal or rock bursts." To comply with this standard, the retreat mining 

submittal should include an engineering design and supporting analysis. The analysis 

method is at the discretion of the mine operator. Pillar recovery plans submitted to 

MSHA for approval should include: 

You can now file your MSHA forms online at www.MSHA.gov. It's easy, it's fast, and it saves you money! 
2 

o A brief description of the pillar desi~n analysis method used including design 

software version (release number). 

o The listing or identification of pillar stability factors or safety factors for the 

analysis method used. 

o A pillar design that meets or· exceeds the generally accepted, or recommended 

design criteria, for the analysis method used or meets mine-specific design 

criteria that is supported by sufficient documentation and mining history. 

MSHA personnel should pay particular attention, including examining inputs and other 

factors used to support the proposal, when pillar recovery plans are submitted that 

propose pillar recovery under any of the following conditions: 2 

• Pillar recovery at depths exceeding 2000 feet may not be appropriate due to the 

heightened risk of bursts at such unusual and extremely deep cover. In most 

cases, when an entire pillar is over 2000 feet deep, careful analysis may 

determine that the pillar should be a "Leave Pillar" that should not be retreat 

mined. When any portion of a pillar is less than 2,000 feet deep (i.e., any portion 

of pillar is outside the 2000 ft depth of cover contour}, and the pillar is judged to 

have a stability factor or safety factor that meets design criteria, then in many 

cases it may be technically sound to allow the pillar to be recovered by retreat 

mining following an approved roof control plan. 

• At depths exceeding 1000 feet, the practice of pillar splitting may be particularly 

problematic, due the extremely high stresses and burst-prone conditions existing 

in the core of pillars adjacent to the gob. Plans including such a proposal should 

be carefully examined. 

• At depths exceeding 1000 feet, properly designed barrier pillars are particularly 

important to effective control of the ground. The purpose of the barrier pillars is 

to isolate each new panel from previously mined ones. The retreat mining plan 

submittal should contain: 

o A brief description of the barrier design analysis used, and 

o The barrier pillar stability factor or safety factor for the analysis method 

used, and a statement indicating that the design meets the generally 

accepted or recommended design criteria for the analysis method used. 

1 For analyses using NIOSH Analysis of Retreat Mining Pillar Stability (ARMPS) and Analysis of Multiple Seam Stability (AMSS), 

ARMPS version 6.0.29 and AMSS version 2.0.26 or later are to be used. For further information see: PIL 111-V-01 Technical 

Support Assistance in Reviewing Roof Control Plans, PIB P09-03 General Guidelines for the Use of Numerical Modeling to 

Evaluate Ground Control Aspects of Proposed Coal Mining plans, PIB P10-23 Re-Issue of POS-08- Precautions for the Use of the 

Analysis of Retreat Mining Pillar Stability {ARMPS) Computer Program. 2 Room and Pillar Retreat Mining Plans at overburden depths of 1000 feet or greater should be forwarded to Technical Support 

for review {Procedure Instruction Letter No. 11-V-1) 
3 

Instructions Pertaining to Roof Control Technologies 

MSHA personnel should pay special attention to the following roof control technologies 

when evaluating roof control plans or amendments for coal mine room and pillar retreat 

mining: 

Whether the plan leaves an engineered final stump rather than extracting the 

entire pillar. The final stump that is not to be mined should be clearly marked on 

the pillar rib and/or mine roof. 

For room and pillar retreat mining sections, whether supplemental roof bolts that 

are longer and stronger than the mine's primary roof bolting system are to be 

installed on advance, particularly in intersections. 

Whether the plan calls for mechanized Mobile Roof Support (MRS units), rather 

than traditional wood timbers, for the roof-to-floor standing support for the mining 

of cuts or lifts into the pillar. 

Instructions Pertaining to Pillar Recovery Procedures 

MSHA personnel evaluating roof control plans for coal mine room and pillar retreat 

mining should pay particular attention to the following pillar recovery procedures: 

- Whether the mining plan for pillar recovery describes a cut and support sequence 

that maximizes ground stability and safety and takes into consideration the 

following: 

o Whether the mine site ground conditions warrant limiting access to just 

one roadway into the intersection when the last lifts for a pillar are taken. 

o Whether the mine site ground conditions warrant having supplemental 

support installed in the entry and/or crosscut in addition to being installed 

in the intersections. 

- Whether the plan describes safe work locations for miners while coal is being 

mined or loaded. 

- Whether the plan incorporates best practices for using MRS units identified in 

Program Information Bulletin P11-30 titled: Reissue of P05-19- Use of Mobile 

Roof Supports (MRS) Units for Retreat Mining. (P11-30 includes information on 

MRS operation and operator positioning.) 
4 

Instructions Pertaining to Communication with the Mine Operator 

When roof control plans for room and pillar retreat mining are being reviewed for 

approval, MSHA personnel should discuss the following items with the mine operator so 

that the mine operator can develop a suitable roof control plan: 

Pre-shift and on-shift examinations should include a thorough assessment of 

geologic conditions, and hazards should be reported and dangered off, or 

appropriately supported. Examinations should include areas outby the pillar line 

to anticipate geologic conditions prior to pillar recovery. Roof fall accident 

studies reveal that in more than one-third of the fatal incidents, poor conditions 

were observed in the area before the fatality occurred, but no action was taken. 

Conducting a geologic assessment of the entire panel before retreat mining 

begins is a prudent practice. The assessment should identify major roof 

fractures, which can then be marked, mapped, and supported. It is good practice 

to plan to skip lifts or not recover pillars in order to leave coal as support to avoid 

such adverse features. 

Test holes are useful to determine if there is roof separation and they can be 

monitored during retreat mining to see if conditions worsen. 

The pressures and loading rates of MRS units can provide information on roof 

stability. Mine-specific trigger points indicating unusually high loads or loading 

rates can be identified and procedures developed to respond to loading. 

Where retreat mining is proposed and the depth of cover exceeds 1,000 feet, 

mine operators should identify areas of high burst likelihood in advance of 

mining. The assessments should identify significantly elevated burst likelihood 

based on the depth of cover, the geological conditions, the potential for multiple 

seam interactions, and recent ground control experience. The assessments 

should be guided by an experienced ground control professional and should be 

conducted as mining conditions/experience warrant, but at least on an annual 

basis. 

Background 

Many new technologies and procedures have been identified with recent mining 

research3

. This PIL provides guidance in applying the new pillar design, mining 

technologies, and mining procedures to retreat mining pillar recovery. 

3 NIOSH, February 2010, Research Report on Coal Pillar Recovery under Deep Cover, available at 

http://www .cdc.gov In iosh/ mining/pubs/ pu brefe renee/ outputid34 70. htm 
5 

Authority 

The Federal Mine Safety and Health Act of 1977 

Filing Instructions 

This PIL should be filed behind the tab marked "Procedure Instruction Letters" in the 

binder for Program Policy Handbooks and Procedure Instruction Letters. 

Issuing Office and Contact Persons 

Coal Mine Safety and Health, Division of Safety 

Christopher Mark, (412) 386-6522 

E-mail: mark.christopher@dol.gov 

Technical Support, Pittsburgh Safety and Health Technology Center 

Michael Gauna, (304) 547-2311 

E-mail: gauna.michael@dol.gov 

Distribution 

MSHA Coal Program Policy Manual Holders