A fundamental precept of SMCRA is that the adverse hydrologic consequences from mining will be prevented or mitigated through proper planning prior to initiating a coal mining operation. This principle is applied throughout the permitting process. While each individual Regulatory Authority (RA) defines its own minimum requirements for permit approval, all permits contain:
Baseline information describes site-specific conditions prior to mining and is the foundation on which permitting is based. The applicant must collect sufficient baseline data to adequately describe the quality and quantity of both ground water and surface water. This includes information to characterize seasonal variation, ground-water recharge and flow direction, surface-water peak and low-flow rates, sediment yield, and water chemistry. An understanding of the geology of the permit and adjacent area and the quality of the overburden helps to establish baseline information needs and requirements.
Prior to the collection of any baseline overburden or hydrologic data, a thorough understanding of the geology of the permit and adjacent areas is essential. The nature and spatial distribution of stratigraphic units is important. For example, the location of the coal bed relative to any regional or local aquifers is important in choosing baseline and monitoring locations. Similarly, the areal extent and continuity of the coal seam is important.
In some areas overburden may possess chemical and physical properties that can adversely affect water quality and re-vegetation. Premining evaluation of overburden provides important information that may indicate the potential for adverse impacts to the hydrologic balance. The principle objective of overburden analysis is to delineate the spatial occurrence of potentially acid or toxic material. Once identified, this material can be given special handling during mining and reclamation. In addition, strata that possess neutralization potential, and strata that may serve as a topsoil substitute or supplement should also be identified.
Baseline overburden data should include chemical analyses of each stratum from the surface down to the strata underlying the lowest coal seam to be mined, or to any potentially impacted aquifer beneath the lowest seam. A full-suite analysis would commonly include all major cations and anions, trace elements and heavy metals. Overburden parameters that are related to potential water-quality impacts are listed. Once the overburden chemistry has been adequately determined, only those parameters that are of environmental concern need to be monitored. A discussion of overburden sampling and analytical techniques is available.
Baseline hydrologic information is needed to describe the hydrologic balance of the permit and adjacent areas prior to mining. Before any new data are collected at the site, a search and evaluation of known data sources should be conducted. A comprehensive discussion of the types of geohydrologic information needed in permit applications and a description of 11 geohydrologic case studies is provided by Richards, (1985 and 1987.) Richards, D.B., 1985, Ground Water Information Manual: Coal Mine Permit Applications-Vol 1, 275 pp. Richards, D.B., editor, 1987, Ground Water Information Manual: Coal Mine Permit Applications-Vol 2, 396 pp.
At a minimum, ground-water information should include the location and ownership of existing wells and springs, approximate rates of usage or discharge, a measure of total dissolved solids, Ph, total iron, and total manganese, and depth to water for each water-bearing stratum, including the coal seam, and any potentially impacted strata below the coal seam. Additional information may be required depending upon the complexity of the hydrogeologic system and the particular concerns of the RA.
The hydrologic balance of the ground-water flow regime involves the relationship between the recharge rate, the change in quantity of water stored, and the rate of discharge and withdrawal from the system. Information needed to define baseline ground-water quantity includes aquifer hydraulic characteristics, flow directions, and seasonal water levels.
Defining baseline ground-water quality requires sampling frequently enough that seasonal changes can be detected. Water-quality samples must be collected, handled and analyzed in accordance with prescribed QA/QC procedures to ensure the integrity of the data. Clesceri, C. S., editors, 1989, Standard Methods for the Examination of Water and Wastewater, 17th edition. To further ensure the quality of the data, the wells should be properly completed to ensure that the water in the well is representative of the aquifer being sampled and not a composite of numerous strata. Water quality analyses should include determinations for major cations and anions so that the integrity of the data can be verified. In addition, analyses should include those chemical constituents identified in the overburden strata which may have a deleterious effect on water use. Identification of other constituents that may be of local importance is best accomplished by seasonal full-suite analyses for each baseline monitoring site.
Minimum baseline surface-water information includes an inventory of surface-water bodies, such as streams, lakes, and impoundments located in the permit and adjacent areas. The inventory should include the name, location, ownership, and a description for each water body identified. It should also show the location of points of discharge into or withdrawal from any of the water bodies, the names of water users, and the quantities of water used by each. In addition, all registered rights to any of this water should be listed.
The number of surface-water sites needed to characterize the permit area depends on the complexity of the drainage system and the nature of existing information. As a minimum a site should be located at each location where a steam enters or leaves the permit area. Discharge and water quality should be evaluated at each site.
To define surface-water quantity, baseline data should be adequate to describe seasonal variations in streamflow. Flow characteristics for perennial and intermittent streams may be defined by
To characterize surface-water quality baseline information should include, at a minimum, discharge and measurements of total suspended solids, total dissolved solids, Ph, total iron, and total manganese. If the geologic and overburden samples indicate the presence of acid-or toxic-forming materials, then sulfate, acidity and alkalinity information should also be considered. Surface-water quality analyses should include major ions and selected full-suite analyses for the identification of chemical constituents critical to water use. The length of record and frequency of sampling for all the baseline information should be sufficient to demonstrate seasonal variability of sampled parameters. Additional information may be necessary depending on the complexity of the hydrologic system and the concerns of the RA, especially regarding potential impacts on flooding and streamflow alteration. Surface-water quality samples must be collected, handled and analyzed in accordance with prescribed QA/QC procedures.
Applicants must identify potentially adverse impacts of the operation through the PHC process which builds on baseline hydrologic conditions. Minimum regulatory requirements for inclusion in the PHC are:
Whether adverse impacts may occur to the hydrologic balance of the area;
Whether acid-forming or toxic-forming materials are present that could contaminate surface water or ground water.
Whether the proposed operation may result in contamination, diminution or interruption of water uses; and
Whether the proposed operation may result in additional contributions of suspended solids to streamflow or runoff outside the permit area.
In addition to the PHC, an application must include a reclamation plan for the proposed mining operation. In the hydrologic reclamation plan (HRP), the applicant describes the manner in which the operation will control drainage, avoid acid or toxic drainage, and prevent to the extent technologically possible additional contributions of suspended solids to streamflow. It includes a description of preventive and remedial measures to deal with all hydrologic impacts identified in the PHC process.
Once a PHC determination has been made by the applicant, the RA must assess the cumulative hydrologic impacts (CHIA) of all existing and anticipated mining in the surrounding area to determine whether the proposed mining operation will prevent material damage to the hydrologic balance outside the permit area.
The PHC, as provided by the applicant, is a prediction of the hydrologic consequences within the permit and adjacent areas resulting solely from the proposed operation. The RA must ensure that the PHC is complete and accurate prior to approving the permit.
The CHIA, on the other hand, is an assessment of the incremental hydrologic impacts of the proposed operation in combination with the impacts of all other existing and anticipated mining within a defined cumulative impact area. The written finding by the RA that the proposed operation is designed to prevent off-site material damage to the hydrologic balance is based on the CHIA.
The link between the PHC and CHIA articulated by Congress in section 507(b)(11) of SMCRA is based entirely on hydrologic data. Congress required the "collection of sufficient data" so that the RA could develop the CHIA but directed that the data would not be required from the applicant until "hydrologic information on the general area" was available from appropriate Federal or State agencies. Congress also directed that the permit application incorporate this hydrologic information before it could be approved. The language of this section clearly distinguishes between the responsibilities of the applicant, which are to provide data for the mine site and surrounding areas as the basis for the PHC, from the responsibility of the RA which is to utilize these and other hydrologic data to assess cumulative impacts of all anticipated mining in the area.
Monitoring of selected parameters during mining provides a record of hydrologic changes. The record also serves as feedback to ensure that the operation is proceeding according to the approved mine plan. The selected parameters and monitoring frequency are designed to track the water quality and quantity concerns in the area of the operation--specifically the suitability of the water for current and postmining uses.
There are two key findings related to the hydrologic information developed in the permit process which support the RA's decision to permit a surface coal mining operation:
The permitting decision is based on a planned approach to solving problems which may themselves be ill-defined. The decision-making process then relies on the ability of the permit applicant and the RA to define the key elements of the hydrologic system that may be affected, how they might be affected, and what corrective actions are needed to mitigate anticipated adverse impacts. The accuracy and precision of hydrologic information needed to support the decision will be determined by the degree of risk to hydrologic resources.
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