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Mixed Waste
Waste Management: 

Joint NRC-EPA Siting Guidelines for Disposal of Commercial Mixed Low-Level Radioactive and Hazardous Wastes


The following NRC-EPA siting guidance for low-level mixed-waste (LLMW) disposal was published on March 13, 1987. A joint NRC/EPA memo was published with the guidance.

The Low-Level Radioactive Waste Policy Amendments Act of 1985 (LLRWPAA) required states and compacts to develop siting plans for low-level radioactive waste (LLW) disposal facilities by January l, 1988. These disposal facilities may receive commercial mixed low-level radioactive and hazardous waste. Mixed, low-level radioactive and hazardous waste or more simply, mixed, low-level waste (LLMW) has two components:

  1. radioactively contaminated industrial or research waste such as paper, rags, plastic bags, or water-treatment residues. Its categorization does not depend the level of radioactivity it contains. (See the regulatory definition in the Low-Level Radioactive Waste Policy Amendments Act of 1985 (LLRWPAA) It is waste that does not meet the criteria for any of three other categories of radioactive waste:
  2. hazardous waste that falls into either of the following classes under the Resource Conservation and Recovery Act (RCRA):
    • listed hazardous wastes (Subpart D of 40 CFR Part 261)
    • characteristic hazardous wastes (Subpart C of 40 CFR Part 261).

To assist in applying that definition, NRC and EPA developed joint guidance entitled Guidance on the Definition and Identification of Commercial Mixed Low-Level Radioactive and Hazardous waste and Answers to Anticipated Questions.

NRC has promulgated LLW regulations and EPA has promulgated hazardous waste regulations that pertain to the siting requirements for disposal facilities for LLMW. This document provides combined NRC-EPA siting guidelines to facilitate development of siting plans for disposal facilities that may receive LLMW.

Combined NRC-EPA Siting Guidelines

NRC Requirements

Site suitability requirements for land disposal of LLW are provided in 10 CFR Section 61.50.

These requirements constitute minimum technical requirements for geologic, hydrologic, and demographic characteristics of LLW disposal sites. Several of these requirements identify favorable site characteristics for near-surface disposal facilities for LLW. The majority of the site suitability requirements, however, identify potentially adverse site characteristics that must not be present at LLW disposal sites.

The site suitability requirements in 10 CFR Part 61 are intended to function collectively with the requirements for facility design and operation, site closure, waste classification and segregation, waste form and packaging, and institutional controls to assure isolation of LLW for the duration of the radiological hazard. The NRC technical position entitled Site Suitability, Selection, and Characterization (NUREG-0902) provides detailed guidance on implementing the site suitability requirements in 10 CFR Part 61.

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EPA Requirements

EPA has also promulgated certain minimum location standards for hazardous waste treatment, storage, and disposal facilities. These standards are provided in 40 CFR Section 264.18.

These regulations include other location considerations and applicable provisions of other federal statutes. For example, Subpart F of 40 CFR Part 264 requires ground-water monitoring programs capable of detecting contamination from land disposal units. While not a siting criterion per se, this requirement can preclude siting in locations that cannot be adequately monitored or characterized.

A further description of location-related standards and applicable provisions of other federal statutes can be found in the Permit Writers' Guidance Manual for Hazardous Waste- Land Storage and Disposal Facilities: Phase Criteria for Location Acceptability and Existing Applicable Regulations (Final Draft - February 1985) This guidance manual describes five criteria for determining location acceptability:

The first four criteria have a basis in the regulations and are fully described in the manual. The fifth criterion, vulnerable hydrogeology, is defined in the RCRA interpretive guidance manual, Criteria for Identifying Areas of Vulnerable Hydrogeology under the Resource Conservation and Recovery Act--Statutory Interpretive Guidance July 1986, Interim Final [EPA 530-SW-86-022/PB-86-224953]

However, since HSWA also added other requirements in addition to location standards to prevent or mitigate ground-water contamination, EPA recognizes that vulnerable hydrogeology must be considered in conjunction with design and operating practices. Vulnerability should not be the sole determining factor in RCRA siting decisions. Rather, this criterion provides a trigger for more detailed evaluation of sites that are identified as having potentially vulnerable hydrogeology. The extent of necessary site review and evaluation is related directly to the extent to which a location "fails" or "passes" the vulnerability criterion. Sites that are determined to be extremely vulnerable will require much closer examination than sites that are deemed non-vulnerable. The results of this more detailed review may then provide a basis for eventual permit conditions or modifications in design or operating practices.

By combining the above technical requirements, standards and guidance of both agencies, NRC and EPA have formulated the eleven guidelines listed below. The use of terms in the guidelines is consistent with their regulatory definitions in 10 CFR Part 61 and 40 CFR Parts 260 and 264. The combined set of location guidelines is intended by the agencies to apply only as guidance to states and compacts developing siting plans for LLW disposal facilities that may receive LLMW. They do not displace existing standards and guidance.

  1. Primary emphasis in disposal site suitability should be given to isolation of wastes and to disposal site features that ensure that the long-term performance objectives of 10 CFR Part 61, Subpart C are met.

  2. The disposal site shall be capable of being characterized, modeled, analyzed, and monitored. At a minimum, site characterization must be able to
    1. delineate ground-water flow paths
    2. estimate ground-water flow velocities
    3. determine geotechnical properties sufficiently to support facility design. At a minimum for site ground-water monitoring, disposal site operators must be able to
      1. assess the rate and direction of ground-water flow in the uppermost aquifer
      2. determine background ground-water quality
      3. promptly detect ground-water contamination.
  3. The disposal site must be generally well-drained (with respect to surface water) and free of areas of flooding or frequent ponding.

  4. The disposal site shall not be in the 100-year floodplain.

  5. The site must be located so that upstream drainage areas are minimized to decrease the amount of runoff that could erode or inundate waste disposal units.

  6. Disposal sites may not be located on lands specified in 10 CFR Section 61.50(a)(5), including wetlands (Clean Water Act) and coastal high hazard areas (Coastal Zone Management Act). Location of facilities on the following lands must be consistent with requirements of applicable federal statutes:
    1. archeological and historic places (National Historic Places Act)
    2. endangered or threatened habitats (Endangered Species Act)
    3. national parks
    4. monuments and scenic rivers (Wild and Scenic Rivers Act)
    5. wilderness areas (Wilderness Protection Act)
    6. wildlife refuges (National Wildlife Refuge System Administration Act).
  7. The disposal site should provide a stable foundation for engineered containment structures.

  8. Disposal sites must not be located in areas where:
    1. tectonic processes such as faulting, folding, seismic activity, or vulcanism may occur with such frequency and extent to affect significantly the ability of the disposal facility to satisfy the performance objectives specified in Subpart C of 10 CFR Part 61, or may preclude defensible modeling and prediction of long-term impacts in particular, sites must be located more than 200 feet from a fault that has been active during the Holocene Epoch
    2. surface geologic processes such as mass wasting, erosion, slumping, landsliding, or weathering occur with such frequency and extent to affect significantly the ability of the disposal facility to meet the performance objectives in Subpart C of 10 CFR Part 61, or may preclude defensible modeling and predicting of long-term impacts
    3. natural resources exist that, if exploited, would result in failure to meet the performance objectives in Subpart C of 10 CFR Part 61
    4. projected population growth and future developments within the region or state where the facility is to be located are likely to affect the ability of the disposal facility to meet the performance objectives in Subpart C of 10 CFR Part 61
    5. nearby facilities or activities could adversely impact the disposal facility's ability to satisfy the performance objectives in Subpart C of 10 CFR Part 61 or could significantly
  9. The hydrogeologic unit beneath the site shall not discharge ground water to the land surface within the disposal site boundaries.

  10. The water table must be sufficiently below the disposal facility to prevent ground water intrusion into the waste, with the exception outlined under 10 CFR Section 61.50(a)(7).

In general, areas with highly vulnerable hydrogeology deserve special attention in the siting process. Hydrogeology is considered vulnerable when ground-water travel time along any 100-foot flow path from the edge of the engineered containment structure is less than approximately 100 years Criteria for Identifying Areas of Vulnerable Hydrogeology Under RCRA--Statutory Interpretive Guidance, July 1986, Interim Final (EPA 530-SW-86-002/PB-86-224953). Disposal sites located in areas of vulnerable hydrogeology may require extensive, site-specific investigations which could lead to and provide bases for restrictions or modifications to design or operating practices. However, a finding that a site is located in an area of vulnerable hydrogeology alone, based on the EPA criteria, is not considered sufficient to prohibit siting under RCRA.

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