7. Technical and Regulatory Challenges and Solutions

Although BCRs can remove metals or other constituents of concern from MIW, in many instances their performance has not been perceived as consistently repeatable from site to site. This perceived lack of consistency can be overcome through careful planning, engineering, and design. Proper attention must therefore be paid to the site-specific technical aspects of a project and regulatory requirements to determine the potential applicability of BCRs.

7.1 Technical Challenges

MIW is generally a result of uncontrolled releases of constituents of concern from historical operations over large or remote areas. Because of changes in regulations, releases from new mines are not as common or extensive as releases from historical mining operations. Table 7-1 presents some of the typical technical issues that can be encountered and references to specific sections within this document that address these issues.

Table 7-1. Technical challenges and relevant guidance

Table 7-1. Technical challenges and guidance for these challenges
Technical Challenges	Referenced Sections
Site Locale and Space
Discharge sites for MIW, particularly for abandoned mines, can often be in isolated areas of steep, rough terrain that are difficult to access and may not have electricity. Space for the placement of a BCR can often be a challenge in narrow valleys, steep hillsides, or when additional private land may be required but not available for use.	Section 2.6: Evaluate Site Environment and BCR Size Section 4.2.2: Design for Site Conditions Section 5.2.1: Physical Settings
Site Locale—Elevation and Climate
Higher elevation and colder climates can reduce year round performance due to lowered microbial activity, however insulating BCRs can help compensate. In areas with intense rainfall events or large spring flows, equalization basins may be required for storage of larger volume flows and diversion of clean water around treatment system.	Section 2.1: Characterize Influent Section 2.6: Evaluate Site Environment and BCR Size Section 4.2.3: Temperature Effects Section 4.2.4: Flow variability Section 5.2.2.5: Cover Installation Section 6.1: System Start-up Section 6.2.2.2: Water Chemistry and Quality Parameters
Site Locale—Neighboring Land Use
A vital aspect of site locale that should be considered is the proximity and compatibility to neighboring land uses, principally residential areas, where local acceptance is important. The aesthetic properties, in addition to odor and safety issues for humans and wildlife, should be recognized and managed.	Section 2.9: Public and Tribal Concerns and Acceptance Section 4.2.2: Design for Site Conditions Section 4.5: Site Control Design Section 6.2.1: Monitoring the Physical Condition of the System
Hydrogen Sulfide Gas—Odor and Toxicity
Hydrogen sulfide gas is produced in BCRs in varying levels. The designer must ensure that surrounding residences or work places are not exposed to toxic levels of hydrogen sulfide gas. Low levels of hydrogen sulfide gas emissions may be below the toxicity level but can still result in nuisance odors (rotten egg smell) to surrounding properties.	Section 2: Determining the Applicability of a Biochemical Reactor Section 2.3: Evaluate Treatment Effectiveness for Contaminants of Concern Section 2.9: Public and Tribal Concerns and Acceptance Section 4.2.2: Design for Site Conditions Section 5.2.2.5: Cover Installation Section 6.2.1: Monitoring the Physical Condition of the System
Aesthetic Issues
Often the appearance of the BCR and pre- and posttreatment cells concerns surrounding land users. Some BCRs are designed to look like wetlands areas and some are designed with plastic covers. Consider public acceptance of the site's appearance when building BCRs in populated areas.	Section 2.9: Public and Tribal Concerns and Acceptance Section 4.5: Site Control Design
Accessibility, Trespassing, and Safety
The accessibility of the site can influence the likelihood of trespassing and public safety. The designer must carefully consider the use of open ponds in residential areas that may attract children or curious adults. Open ponds that are lined with plastic liner can attract animals as well and may create trapping and drowning hazards for animals and humans. Designs can be modified to limit access and prevent trapping hazards for humans and animals.	Section 2: Determining the Applicability of a Biochemical Reactor Section 2.9: Public and Tribal Concerns and Acceptance Section 4.5: Site Control Design Section 5.2.1.1: Siting the BCR System Section 5.2.4: BCR Systems Site Construction Restoration Section 6.2.1: Monitoring the Physical Condition of the System
Mine Influenced Water Quality
The size of a BCR is a function of metal loadingMass of something per time entering a volume (volumetric loading rate) or flowing into an area (areal loading rate). rate, which includes factors such as flow, metals concentration and required retention time. A higher metal loading rate requires a larger system and more retention time, which can be a challenge when adequate space is not available. The MIW quality can necessitate a pretreatment or posttreatment step(s).	Section 2.1: Characterize Influent Section 2.2: Define Treatment Goals Section 2.3: Evaluate Treatment Effectiveness for Contaminants of Concern Section 2.5: Determine Pre- and Posttreatment Requirements Section 4.2.1: Influent Chemistry Concerns Section 4.4.2.4: Overflow Structures and Loading Control
Substrate Issues
Local availability and cost of substrateEither (a) a chemical which reacts or (b) a solid surface or (c) an electron donor. can be a challenge to the siting and construction, as well as the effectiveness, of BCR treatment. Substrate type can also affect the amount of operation and maintenance including removal, replacement, and disposal–either on site or off site.	Section 2.7: Evaluate Substrate Section 2.8: Evaluate Cost Section 3.1: Selecting BCR Substrate Section 5.2.2.4: Substrate Installation Section 7.2: Legislative and Regulatory Challenges
Maintenance
BCRs requiring regular chemical input or a power source will require more frequent operations and maintenance activities than passive BCRs. A key aspect of a successful BCR is to plan adequately for expected maintenance issues and identify who will be responsible for maintaining the system in perpetuity.	Section 6.3: Maintenance Section 6.5: Contents of an Operation and Maintenance Plan
Troubleshooting
The long-term success of a BCR depends on identifying and resolving issues preventing effective treatment of MIW. The two primary categories of troubleshooting problems with a BCR include chemical trends and physical trends.	Section 4.4.4: Bed Clogging Section 4.4.5: Short Circuiting Section 6.2.1: Monitoring the Physical Condition of the System Section 6.3.2: Troubleshooting

7.2 Legislative and Regulatory Challenges

Often, there are many permitting issues that must be addressed when constructing treatment systems, from land disturbance and erosion and stormwater control issues to discharge permits for active mining operations. BCRs have applicability across the country at abandoned and active mining sites; however, local, tribal, and state and federal regulations may differ for each site. Federal requirements are discussed on the National Pollutant Discharge Elimination System (NPDES) web site mining page (USEPA 2012). All required permitting agencies should be consulted throughout the process to ensure that appropriate regulatory processes are being followed. Note that the following discussion does not include all of the existing regulatory programs in every state.

Most of the early BCRs were used on abandoned or inactive sites. In these cases, the receiving streams were often devoid of aquatic life. The goal of treatment was to improve water quality in the stream so that it could once again support an aquatic community. As a result, the key issue was usually increasing the pH and reducing the metal toxicity of the discharge. No strict numeric standards were imposed. A well-designed passive treatment system will increase pH and remove metals, but may not be able to continually meet strict numeric limits. Pennsylvania still allows passive systems, including BCRs, to be used at abandoned sites without permit restrictions. These are considered to be more like a best management practice, rather than a permitted facility. The West Fork BCR system (see Appendix B.7) in Missouri is operated under an NPDES permit. Regulatory challenges at this site are discussed in Gusek et al. (1998).

As the technology has matured, there are a growing number of applications where the goal is to meet NPDES discharge standards. Although BCRs can generally meet pH limits, meeting very low chronic toxicity standards can be problematic. However, the biotic ligandA chemical which interacts with a metal to bind that metal into a complex. model, which accounts for reductions in toxicity when metals are complexed with organic carbon typically found in BCR effluent, may be worth examination in the context of BCR permitting. In addition, the initial water from the BCR can contain high levels of organic carbon and nutrients. These parameters may require some form of management or treatment prior to discharges as described in Section 2.5 and Section 4.3.5.

7.3 Disposition of Residual Materials

As with all residual materials, the designation of waste must consider if the material still has economic value. In many cases residual materials from BCRs can include high concentrations of metals that may prove to be economically recoverable (Gusek and Clarke-Whistler 2005; Gusek, Wildeman, and Conroy 2006). Use care in appropriately evaluating and managing any residual material removed from a BCR. In the federal code, 40 CFRCode of Federal Regulations 261.24 lists the maximum concentration of contaminants for the characteristic of toxicity from the toxicity characteristic leaching procedure (TCLP) test that would define a substrate as hazardous waste or not. Nevertheless an in-depth review of all materials removed from the system routinely or at the end of its service life should be done to establish proper disposition (see Section 2.5.3 and Section 6.3.1).

7.4 Wetlands (CTW and Mitigation)

One of the most pressing challenges in some areas is how to address wetlands present at a site. Differences exist between United States Army Corp of Engineers (USACE) districts as to the applicability of §404 of the Clean Water Act (CWA) to wetlands that were created by mine drainage. In order to create treatment systems for MIW, occasionally, poor quality wetlands created by the MIW must be removed. Consult with the local USACE district and other agencies at the planning stage to determine regulatory requirements regarding any wetlands that may be present and any mitigation (in-kind, out-of-kind, on-site, or off-site) that may need to be performed. Additionally, tribal, state, and local agencies should also be consulted about wetland permitting and mitigation issues. For additional guidance, see Chapters 7 and 8 of ITRC's WLTD-2 document (ITRC 2005).

Mayer Ranch Wetlands Mitigation

At the Mayer Ranch Superfund site, mitigation of the volunteer cattail wetlands that sprung up after the mine water began to discharge in 1979 was not required. In theory, the clean polishing pond at the end of the treatment system could replace (in terms of mitigation credits) the contaminated volunteer wetlands that were destroyed during construction of the treatment system.

Publication Date: November 2013

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