Guidelines for Backfilling under the Thick Overburden Regulations 405 KAR 16:190, Section 5

1. Kentucky Department for Natural Resources Division of Mine Permits Sept. 6 and 14, Oct. 4 and 18, 2012 Guidelines for Backfilling under the Thick Overburden Regulations405 KAR 16:190, Section 5 Presented by:

2. On July 30, 2012, RAM #156 was signed. The RAM provides guidelines for compliance with the regulatory requirements for backfilling under the Thick Overburden provisions. • This RAM was developed to specifically address the increasing emphasis on backfill for final storage of overburden. The industry has encountered limitations associated with use of excess spoil disposal areas, and were of necessity beginning to compensate within the backfill area. • The RAM is intended only to interpret regulations as they pertain to the issue, and can only be understood in that context. The Cabinet is not here advocating any position regarding the use of backfill and/or excess spoil disposal areas except this: Whatever form of placement is done must comply with the regulations. • The RAM does address a variety of technical issues, most notably structural stability and drainage, but only to the degree that regulatory compliance must be demonstrated. Guidelines for Backfilling under the Thick Overburden Regulations: 405 KAR 16:190, Section 5

3. Regulatory and Technical areas addressed this presentation • Applicability • Configuration • Stability • Drainage • Construction and Certification These issues are made more complex by the diversity of conditions under which these regulations and guidelines must be applied. In general, • the regulations and guidelines are more restrictive for areas with steeper ground slopes, and • these provisions are somewhat more restrictive for a traditional contour cut than for more expansive operations such as cross-ridge mining. Every effort will be made to address this variety of conditions during the course of this presentation Guidelines for Backfilling under the Thick Overburden Regulations: 405 KAR 16:190, Section 5

4. Points to Consider • This regulation provides allowances and limitations for placement of material in the coal extraction area, especially as that placement approaches the extents of the approximate original contour. • This may lead to higher backfill heights, and steeper backfill slopes, creating the risk of worsening slides and erosion in the field. • As engineers, whether in design, production or regulatory oversight, it is our responsibility to understand and use these regulations prudently so as avoid the adverse stability and erosion effects. The potential benefits must be balanced by a higher level of professional responsibility. Guidelines for Backfilling under the Thick Overburden Regulations: 405 KAR 16:190, Section 5

5. Any permit application that proposes to backfill a volume of spoil in the coal extraction area greater than the total volume of material removed from that area, whether for the entire permitted area or some portion thereof, must include a discussion of how the operation will comply with the requirements of 405 KAR 16:190, Section 5. (RAM # 156, p. 1) This is the initial test in making the distinction for applications that will use a backfill plan under the terms of RAM #156. • 405 KAR 16:190, Section 5 limits application of the Section to “only apply where the final thickness is greater than 1.2 of the initial thickness”. As such this regulation does not provide for placement of off-site spoil. While, under certain circumstances, spoil from other sources might be used for backfilling under Section 2 of this regulation, placement of spoil from other sources under “Section 5. Thick Overburden” is not acceptable. (RAM # 156, p. 2) The regulations do not support importation of spoil from others sites for storage under the provisions of 405 KAR 16:190, Section 5. Guidelines for Backfilling under the Thick Overburden Regulations: 405 KAR 16:190, Section 5

6. The statutory criteria for the “Thick Overburden” provisions are found in KRS 350.410. and include; • ….where the volume of overburden is large relative to the thickness of the coal deposit • …where the permittee or operator demonstrates that due to volumetric expansion the amount of overburden … removed in the course of the mining operation is more than sufficient to restore the approximate original contour The regulatory condition, as listed in 405 KAR 16:190, Section 5, is given as; • The provisions of this section apply only where the final thickness is greater than 1.2 of the initial thickness. • Initial thickness is the sum of the overburden thickness and coal thickness prior to removal of coal. Final thickness is the product of the overburden thickness prior to removal of coal, times the bulking factor to be determined for each permit area. . Applicability Guidelines for Backfilling under the Thick Overburden Regulations: 405 KAR 16:190, Section 5

7. In order to demonstrate applicability, any application proposing to place a volume of backfill greater than the original, in-situ volume of coal and overburden must include in the application a demonstration of applicability of the Thick Overburden standards. In order to meet these criteria, the operator should provide a demonstration that; The Ht. of OB only * (1+Swell Factor) > 1.2 The Maximum Cut Height Where the Ht. of OB only is the Maximum Cut Height minus the Coal Seam Thickness proposed for removal during mining Documentation may be requested for the assumed Swell Factor (pg 2 of RAM #156) Applicability • Simply put, take your highest projected highwall height, remove the height of all coal to be mined, and apply swell factor. The ratio of swelled material to the cut height must exceed 1.2. • For a 4-ft. coal seam, this translates to a 75-95 ft. HW, depending on swell. Guidelines for Backfilling under the Thick Overburden Regulations: 405 KAR 16:190, Section 5

8. Additional Comments regarding applicability standard and formula • The wording of the regulatory qualification (“is greater than 1.2”) does not allow us to accept rounding on the ratio analysis. The result must exceed 1.2 in order to qualify under Section 5. • We will give some latitude insofar as the assumed swell factor, but once it goes outside the customary range of values we will request documentation. Historically we have seen values ranging from about 20 percent swell (common for shales) to 30 percent swell (typically for sandstones). • It is very important to note that the qualification is only relevant if you wish to backfill under the provisions of Section 5. It is not necessary to invoke Section 5 if you propose to backfill to AOC, regardless of whether you meet the necessary ratio. Applicability Guidelines for Backfilling under the Thick Overburden Regulations: 405 KAR 16:190, Section 5

9. Backfill Configuration Guidelines for Backfilling under the Thick Overburden Regulations: 405 KAR 16:190, Section 5

10. Fundamental to the understanding of the allowances and limitations of Section 5 is a clearer understanding of the ultimate frame of reference for all backfilling and grading operations- Approximate Original Contour (AOC). • KRS 350.010 - 15) "Approximate original contour" means that surface configuration achieved by backfilling and grading of the mined area so that the reclaimed area, including any terracing or access roads, closely resembles the general surface configuration of the land prior to mining and blends into and complements the drainage pattern of the surrounding terrain, with all highwalls and spoil piles eliminated; ….. • Note the key tenets of Approximate Original Contour (AOC) • “Closely resembles” the pre-mining configuration and • “Complements” the drainage pattern • The definition relies on modifiers such as “closely” and “complements”, and thus necessarily involve some area of judgment. The only definitive language involves highwalls and spoil piles, which must be “eliminated”. Guidelines for Backfilling under the Thick Overburden Regulations: 405 KAR 16:190, Section 5

11. As engineers we understand that any design goal must be accompanied by appropriate tolerances. So is the case with AOC. The term itself conveys that it is not a requirement to re-establish the exact original contour, but the statutory qualifications suggest the tolerance from original contour is limited. • Some general principles to consider in assessing AOC; • There is a long term understanding of tolerance below AOC, hinging on the rule of thumb of returning 80% of the AOC volume in a fashion “complementary” to the original terrain. This understanding was developed over the course of several years during the early years of the program. • We have been working on the issues related to material placement above AOC for less than a year, and as such there are not yet clear tolerances or “rules-of-thumb”. • In general, the degree of tolerance is very highly connected to the ground slope of the original configuration, with steeper ground slopes yielding less tolerance from the original contour. • Considerations in assessing AOC, after slope considerations, would include stability, drainage, post-mining land use, and consideration of the pre-mine topography. Vertical and horizontal displacement from the original terrain are contemplated by the regulations, but ultimately the degree of displacement is a combination of all these factors. Guidelines for Backfilling under the Thick Overburden Regulations: 405 KAR 16:190, Section 5 Guidelines for Backfilling under the Thick Overburden Regulations: 405 KAR 16:190, Section 5

12. Configuration Component of Thick Overburden Regulations: KRS 350.410 “…the permittee or operator shall after restoring the approximate contour, backfill, grade, and compact (where advisable) the excess overburden and other spoil and waste materials to attain the lowest grade but not more than the angle of repose, and to cover all acid-forming and other toxic materials, in order to achieve an ecologically sound land use compatible with the surrounding region and that the overburden or spoil shall be shaped and graded in such a way as to prevent slides, erosion, and water pollution and shall be revegetated in accordance with the requirements of this chapter”. The regulatory requirement for backfill are itemized under Section 5, and include; • Transport, backfill, and grade all spoil and wastes, not required to achieve the approximate original contour of the permit area, to the lowest practicable grade, to achieve a static factor of safety of 1.3 …. • Transport, backfill and grade excess spoil and wastes only within the permit area and dispose of those materials in accordance with 405 KAR 16:130. • Transport, backfill, and grade excess spoil and wastes to maintain the hydrologic balance, …. and to provide long-term stability by preventing slides, erosion and water pollution. • Transport, backfill, grade, and revegetate wastes and excess spoil to achieve an ecologically sound land use approved by the cabinet as compatible with the prevailing land uses in unmined areas surrounding the permit area. Guidelines for Backfilling under the Thick Overburden Regulations: 405 KAR 16:190, Section 5

13. Eliminate all spoil piles. The final configuration shall conform to the AOC standards, be compatible with the surround terrain and land use, and shall not dramatically alter the general configuration of the land.( RAM #156, p. 4) • The backfilled material must be placed in an “ecologically sound land use compatible with the surrounding region” and “shall be shaped and graded in such a way as to prevent slides, erosion, and water pollution” (as per KRS 350.410). Guidelines for Backfilling under the Thick Overburden Regulations: 405 KAR 16:190, Section 5 Guidelines for Backfilling under the Thick Overburden Regulations: 405 KAR 16:190, Section 5

14. RAM #156 addresses a specific component of the backfilling and grading regulations. If a proposed spoil disposal area toes out on an area not proposed for coal extraction, the disposal area may be permitted under specifications for excess spoil disposal included in 405 16:130. This would include: • 1. A hollow fill toeing about below coal level; • 2. Disposal areas toeing out on an existing mine bench or pre-existing bench, where the existing bench is not associated with the proposed permit and no further extraction proposed; or • 3. Areas at or above the permitted coal seam for which no extraction is proposed. • Fill areas that toe out on non-coal extraction areas may be extended onto the backfill area, in accordance with the “Fill Placement Optimization Process” as described in RAM #145, and material may be placed on existing and proposed fill decks in accordance with that procedure and 405 16:130. This RAM does not apply to spoil placed in excess spoil disposal areas. (RAM #156, p. 3) Guidelines for Backfilling under the Thick Overburden Regulations: 405 KAR 16:190, Section 5

15. The final configuration shall not significantly increase the peak elevations of the permitting area, though some increases are to be expected. In general such increases shall be limited to twenty (20) percent of the cut depth. Proposals for increases (above AOC) greater than 20 percent will be evaluated on a case by case basis, under the supervision of the Director’s Office. Generally this provision is more relevant to contour mining, as area or crop-to-crop cuts can more commonly exceed this limitation while still meeting the compatibility criteria. (RAM #156, p. 4) Guidelines for Backfilling under the Thick Overburden Regulations: 405 KAR 16:190, Section 5

16. Stability Guidelines for Backfilling under the Thick Overburden Regulations: 405 KAR 16:190, Section 5

17. • The backfilled material can never be placed steeper than the ANGLE OF REPOSE, and the backfill material must be placed to achieve a static safety factor of at least one and three-tenths (1.3). (RAM #156, p. 2) Because the angle of repose in essence represents placement of the material at a safety factor of 1.0, the requirement for a F.S. of 1.3 will always govern the design, unless additional controls or modification of the backfill material is proposed. Any such additional controls will be routed to the Directors Office for review and guidance. Guidelines for Backfilling under the Thick Overburden Regulations: 405 KAR 16:190, Section 5

18. The principal stability requirements of KRS 350.410 and Section 5 of 16:190 are as follows; • The material cannot be stacked at steeper than the angle of repose, and the backfill material must have a safety factor of no less than 1.3. From page 2 of RAM 156: The final backfill slope will not exceed 26.6 degrees (1v:2h or fifty (50) percent) unless the applicant providessite specific sampling and testing of the backfill material. The sampling must accurately reflect the material to be used in backfilling the site, with standard engineering testing to determine relevant engineering characteristics such as cohesion, friction angle, and/or angle of repose. Theaccompanying plan of operation shall clearly delineatethe details of each element of the backfill plan, including segregation/use of specific materials, source of underdrain material, placement and compaction standards, etc. Guidelines for Backfilling under the Thick Overburden Regulations: 405 KAR 16:190, Section 5

19. Testing Objectives, Standards, and Recommended Methods Testing Objectives To secure sufficient, site specific data sufficient to verify the finding of the stability analysis for the proposed backfill. Typically this will involve developing numbers for the material’s friction angle, cohesion, and unit weight. In extreme cases porosity, permeability, and in-situ phreatic levels might need be evaluated in assessing steep slope backfill areas. Test Methods • Angle of Repose – Direct measurement of the angle of repose can be utilized to determinate the effective friction angle of the material. More information on this relationship is available upon request, and will likely be discussed later in this seminar. • Traditional Bag samples, where existing, with undrained tri-axial testing may be accepted with suitable justification of the sample’s suitability to the material to be placed. The RAM designates “site specific sampling and testing of the backfill material” where backfill slopes exceed 26.6 degrees. While we hesitate to set a fixed, maximum distance, the closer the sampling the better and directly on-site is preferable. In cases where existing activity provides access and information from adjacent operations some latitude will be considered. Guidelines for Backfilling under the Thick Overburden Regulations: 405 KAR 16:190, Section 5

20. Drainage Guidelines for Backfilling under the Thick Overburden Regulations: 405 KAR 16:190, Section 5

21. The final backfill configuration may not have level areas (decks). All backfill must have positive drainage. (RAM #156, p.3)3 At present we are considering 5 percent or greater as positive drainage, though approval of such slopes is dependent on the height and steepness of the backfill. • Terraces in the backfill shall be limited to a width of twenty (20) feet. For steep slope areas (>20 degrees) this includes permanent roads in the backfill unless specifically approved by the cabinet as necessary for stability, erosion control, or roads included in the approved postmining land use plan. (RAM #156, p.3) Guidelines for Backfilling under the Thick Overburden Regulations: 405 KAR 16:190, Section 5

22. Backfill must be placed behind the undisturbed natural barrier (as per 405 KAR 16:010 Section 4). If there is no natural barrier in place, the backfill material shall be placed only on the solid portion of the bench. • (RAM #156, p.3) • The plan shall specifically address drainage from above, across, and below the terraces, including the slope of the terrace and the frequency and type of any down-drains (to prevent erosion from concentrated flow). Where terraces cross natural drains, the plan shall include provisions to prevent erosion from the natural drain, including features such as energy dissipaters and enhanced erosion protection. (RAM #156, p.3) • Where necessary, the applicant will provide suitable sub-surface drainage (e.g. underdrains, French drains, etc) to ensure proper drainage of backfill materials. Where the Thick Overburden provision are used, if no underdrain or sub-surface drainage system is proposed the application should contain a justification as to why such a system is not necessary. (RAM #156, p.4) Guidelines for Backfilling under the Thick Overburden Regulations: 405 KAR 16:190, Section 5

23. All highwalls must be eliminated. If utilizing a fresh water diversion above the mine area, it must be permitted above the highwall in solid ground.(RAM #156, p.4) • For contour operations the proposed backfill configuration shall not allow placement of backfill material higher than the top of the associated highwall in such as way as route drainage towards the highwall or create a water impoundment or conveyance. (RAM #156, p.3) Guidelines for Backfilling under the Thick Overburden Regulations: 405 KAR 16:190, Section 5

24. Construction and Certification Guidelines for Backfilling under the Thick Overburden Regulations: 405 KAR 16:190, Section 5

25. Any backfill configuration proposed under the Thick Overburden guidelines shall be designed and certified by a qualified, registered, professional engineer in conformance with professional standards established to assure the stability, drainage, and configuration necessary for the intended use of the site. (RAM #156, p. 4) • A Certificate of Design (SMP-31-A) will be required for backfill plans developed under RAM # 156. The form can be utilized by describing the area(s) under the “Facility Type”. • The plan of operation shall clearly delineate the details of each element of the backfill planning, including segregation/use of specific materials, source of underdrain material, placement and compaction standards, etc., and shall further specify certification stages appropriate to that plan. The application must clearly describe those areas of the operation where material is to be backfilled under the Thick Overburden provisions, clearly defining those areas on the Mining and Reclamation Plan Map and providing appropriate drawings, specifications, design analysis, and certification under “Backfilling and Grading Plan” section of the application form (MPA-03).(RAM #156, p. 4) • There must be a narrative, typically following the applicability test, summarizing the aspects of the Section 5 plan and itemizing special handling procedures. The areas affected should be noted on the MRP, and the various drawings, cross sections, must take the required Thick Overburden specifications into consideration. Guidelines for Backfilling under the Thick Overburden Regulations: 405 KAR 16:190, Section 5

26. If no special handling procedures are proposed, backfilling and grading will be placed in accordance with the approved plan and no construction certification will be required. The application should so clearly state as much. • Ifthe plan does include special handling procedures such as • material segregation, • material augmentation, • alternate compaction standards, • underdrains/French drains, • drainage baffles, • grouted ditches, • or other practices as proposed by the applicant, • a construction certification will be required attesting that the backfilling specifications have been followed in the field, and that the material has been placed in accordance with the approved design. • Failure to follow the approved plan may result in a violation requiring the permittee to re-work or re-place backfilling materials. Guidelines for Backfilling under the Thick Overburden Regulations: 405 KAR 16:190, Section 5

27. The construction certification for permitted features constructed as singular events, such as underdrain placement, will be submitted to the appropriate Regional Office within fourteen (14) days of completion of construction. These certifications should include, at a minimum, (1) a description of the feature, the location, and the reference as designated in the approved permit, with as-built drawings as appropriate (2) color photographs of the constructed feature and copies of any verification testing or measurements made in the field to ensure compliance with the permitted plan, and (3) the engineer’s certification that the feature was constructed in accordance with the plans provided in the approved permit application. Guidelines for Backfilling under the Thick Overburden Regulations: 405 KAR 16:190, Section 5

28. For operations that take place over an extended time frame (such as backfill operations requiring material segregation or compaction standards), an engineering certification detailing construction progress to-date will be filed quarterly. This quarterly construction certification should be filed within fourteen days of achieving of the end of each quarter, and should provide, at a minimum, • (1) cross-sections showing the approved and constructed grade, with the cross- section locations taken from the design sections, • (2) the nature of special handling or placement of the spoil, referenced in the permitted requirements. • (3) any verification testing or measurement made in the field to ensure compliance with the permitted plan, and • (4) an engineer’s certification that the backfill was placed in accordance withthe plan as described in the approved permit application. • For those instances when material testing was the basis for the design evaluation and the designated material was used in construction, no verification testing should be needed. If a substitute material is used in construction verification testing should be performed prior to placement and the permit revised to show suitability with the design. Guidelines for Backfilling under the Thick Overburden Regulations: 405 KAR 16:190, Section 5

29. A final certification, attesting that the construction is complete for the • area under consideration, should be included with the final progress • certification. The final construction certification should attest that all • operations were performed in accordance with the approved plan, but • needs only to include cross-sections and documentation for those areas • that had not previously been addressed in a progress certification. • The intent of this is to allow for the final quarterly certification to be noted as the final certification. There is no intention to replicate previously submitted and accepted certification materials. Guidelines for Backfilling under the Thick Overburden Regulations: 405 KAR 16:190, Section 5 Guidelines for Backfilling under the Thick Overburden Regulations: 405 KAR 16:190, Section 5

30. Questions? Guidelines for Backfilling under the Thick Overburden Regulations: 405 KAR 16:190, Section 5