SUBJECT:Coal Underground Mine Pool Evaluation

Coal Underground Mine Pool Evaluation Guidelines

July 2017

SUBJECT:Coal Underground Mine Pool Evaluation

EFFECTIVE:TBD

PURPOSE:To assist in the evaluation of the potential for development of post-mining mine pool discharges

Introduction

These guidelines are intended to assist in the evaluation of the potential for development of post mining mine pool discharges during the review of underground coal mining permit applications and in already-permitted underground coal mines, in assessing the consequences of such discharges, in the formulation of strategies to address unanticipated mine pool discharges, and in the evaluation of underground mine performance security releases.

Once formed, underground mine pool discharges that adversely impact the hydrologic balance as well as surface water and ground water resources, are extremely difficult to address. Therefore, the goal must be to accurately predict in the permitting process the potential for mine pool discharges, including locations, quantity, and quality, and, most importantly, to formulate actions to prevent such discharges in cases where discharge would result in adverse impact to the hydrologic balance. For mines that are already permitted, it is important to develop a monitoring plan that will serve as an alert when a mine pool begins to form. Addressing mine pool development involves assessment of potential, proper monitoring, evaluation of monitoring results, mine pool discharge handling, and release of performance security.

ASSESSMENT OF POTENTIAL FOR MINE POOL DEVELOPMENT

As part of the Probable Hydrologic Consequences (PHC) discussion required in each underground coal mining permit application, including those for adjacent areas, the applicant is required to include information on coal seam and land surface elevation, portal location, overburden thickness and lithology, and proximity to other underground mines. This information is used to assess the potential for a mine pool discharge. Unless other information is available, potential mine pool discharge sites will be identified as those locations where the highest elevation of the coal to be mined exceeds the land surface elevation. The predicted discharge points or areas will be identified as locations of concern and may require additional evaluation or submittal of additional information. These locations will be required to be shown on a map accompanying the PHC narrative.

MINE POOL MONITORING PLAN

Applications

Approximate mine pool monitoring locations must be stated in the application and shown on the Application/Hydrology Map or other appropriate drawing. The mine pool monitoring plan (“plan”) must state whether quality, quantity, or both will be evaluated at the selected sites. The monitoring frequency must also be stated.

Monitoring will be required within the predicted mine pool discharge areas, based on the map in the PHC narrative. Monitoring sites may include both wells and streams. Existing wells will be used to gauge mine pool development if appropriate.

If appropriate mine pool level monitoring locations do not exist or will not be developed during mining, monitoring wells will be required to be installed. The monitoring areas must be identified in the application and on the Application/Hydrology Map or other appropriate drawing. Proposed designs must also be submitted.

Water level monitoring frequency: The plan must state the water level monitoring frequency. This frequency should increase once water is detected, to determine the rate of mine pool rise and to ensure water is not rising at an unexpectedly fast rate.

Selected streams in the areas of potential discharge, as documented in the PHC, will be required to be monitoring stations if it is likely a discharge will occur.

Mine pools may also impact ground water due chiefly to contamination, but perhaps also due to water level changes. Based on the aquifer descriptions and the water supply inventory in the application or permit, monitoring of selected supplies developed in the mined aquifer will be required, under the assumption that the mine pool would affect supplies in that aquifer.

The timing of well installation and monitoring commencement must be stated. Usually well installation and the beginning of mine pool quality and quantity monitoring will not be required until after mine closure or closure of a portion of a mine where a mine pool could develop. Access issues will be taken into consideration when reviewing monitoring well installation and other monitoring locations.

Mine pool quality monitoring: The plan must state approximately where such monitoring will occur, the parameters to be monitored, the monitoring frequency, and the point in time when such quality monitoring will commence.

Detailed mine pool water treatment plans will usually be required when it is determined that a mine discharge is likely. However, less detailed plans may be required if the expected discharge is far into the future. In such a case, a commitment to submit an Application to Revise a Coal Mining Permit (ARP) with more detailed plans when the need for treatment becomes apparent will be required. The application must contain a contingency treatment plan to address cases where monitoring shows the mine pool to be rising more rapidly than expected.

Existing Permits:

Underground mining permits will be evaluated for appropriate mine pool monitoring plans whenever the permit is renewed or when the mine, or portions of the mine if appropriate, are sealed. At such times, a plan, or revisions to an existing plan, if appropriate, will be required through an ARP.

Detailed or contingency mine pool water treatment plans will usually be required when it is determined through monitoring that a mine discharge is likely.

If the mine is already sealed, DMRM will evaluate the potential for discharge prior to performance security release.

EVALUATION OF MONITORING:

Monitoring results will be evaluated for quality and quantity. If the results indicate that a mine is likely to discharge water of a quality and/or quantity that will likely cause an adverse impact to the hydrologic balance or material damage to the hydrologic balance, remedial action, including a mine pool treatment plan, will be required. The procedures and steps detailed in Procedure Directive Inspection & Enforcement 2009-01,Evaluating Post-mining Discharges apply.

Based on information in the application, normal surface water and ground water elevations at the predicted discharge locations will be compared with monitoring data.

PERFORMANCE SECURITY RELEASE INSPECTIONS

Permit Review by the Division:

If available, information collected in the course of the monitoring discussed above will be evaluated. If this data is not available, information in the existing permit that addresses predicted mine pool discharge locations will be reviewed. In addition, the permit will be reviewed to determine the highest coal elevation and the lowest topography in the shadow and adjacent areas. Test hole data, reports, and cross sections will be consulted. If necessary, cross sections will be constructed.

Based on reports already in the permit, or on the above data, potential discharge locations will be mapped or maps will be reviewed. If necessary, the intersection of the highest coal elevation and the local topography will be mapped.

Field Review:

The areas of potential discharge will be field evaluated. Water samples will be collected from upstream and downstream locations in the main receiving streams and in any tributaries where potential discharge could occur. Water samples will also be taken wherever there is visual evidence of discharge.

Evaluation and Corrective Action:

The water samples will be evaluated for quality and quantity. Evidence of no mine pool discharge, or a determination that the quality and quantity of a mine pool discharge is not causing an adverse impact to the hydrologic balance and material damage, will allow the performance security release process to continue. The length of time since mine closure will be evaluated when determining the presence, absence, or future potential of a mine pool discharge. Reports in the permit addressing expected discharge timelines will be considered.

If discharge is observed or confirmed, remedial action, including a mine pool treatment plan, will be required if water quality is not acceptable. The procedures and steps detailed in Procedure Directive Inspection & Enforcement 2009-01, Evaluating Post-mining Discharges apply.

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