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Ground Water Monitoring Requirements for Hazardous Waste Treatment, Storage and Disposal Facilities

The groundwater monitoring requirements for hazardous waste treatment, storage and disposal facilities (TSDFs) are just one aspect of the Resource Conservation and Recovery Act (RCRA) hazardous waste management strategy for protecting human health and the environment from accidental releases of hazardous constituents. While land disposal restrictions and unit specific standards seek to reduce the toxicity of waste and prevent releases, respectively, the groundwater monitoring requirements represent the last line of defense by ensuring that any releases are detected and remediated in a timely manner.

TSDFs that manage hazardous waste in landfills, surface impoundments, land treatment units and some waste piles (referred to as “regulated units” in the regulations) are required to implement a groundwater monitoring program to detect the release of hazardous constituents to the underlying groundwater. The regulations for permitted facilities are found at 40 CFR part 264, subpart F – Releases from Solid Waste Management Units, and the interim status regulations for facilities in operation before these rules came into effect are found at 40 CFR part 265, subpart F – Groundwater Monitoring.

The requirements for permitted and interim status TSDFs differ significantly. The major differences being:

  • Interim status waste piles are not subject to the groundwater monitoring requirements.
  • There are no corrective action requirements under the interim status set of regulations.

Even with these differences, the overall goal of these requirements is the same: protect the groundwater in the uppermost aquifer from contamination by the hazardous constituents managed at the TSDF.

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Permitted Facilities

For permitted TSDFs, a groundwater monitoring program consists of three phases: detection monitoring (40 CFR §264.98), compliance monitoring (40 CFR §264.99), and corrective action (40 CFR §264.100). The phases are sequential with a facility able to move back and forth between phases as certain criteria are met. The regulations establish performance standards that require each facility’s groundwater monitoring program to have a sufficient number of wells installed at the appropriate locations. The regulations also require groundwater monitoring wells to be located at depths that can yield representative samples of background conditions and water quality at the point of compliance in the uppermost aquifer (defined as the geological formation nearest the natural surface that is capable of yielding significant quantities of groundwater to wells or springs).

To meet these standards, each facility must design, install and operate a groundwater monitoring program based on the site’s specific geology and hydrology. The program must also address the type of waste management unit and the characteristics of the waste being managed. The monitoring wells must be appropriately designed and installed, as well as have consistent sampling and analytical procedures in place to ensure accurate and representative samples are taken.

The specific sampling requirements and procedures (including frequency of sampling) are specified in the facility’s hazardous waste permit. Typically, these requirements are included in a sampling and analysis plan. All data collected as part of a facility’s groundwater monitoring program must be maintained in the facility’s operating record.

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Detection Monitoring

Detection monitoring is phase one of the groundwater monitoring program. Under this phase, facilities are monitoring to detect and characterize any releases of hazardous constituents into the uppermost aquifer. Samples are taken from the monitoring wells and analyzed for specific indicator parameters and any other waste constituents or reaction products that indicate that a release might have occurred. The EPA Regional Administrator designates in the facility’s permit the specific constituents and parameters to be monitored and establishes the frequency of sampling. At a minimum, four samples must be taken from each well semi-annually.

Samples taken from the point of compliance (i.e., the wells down-gradient of the waste management unit) are compared to the background samples taken from the up-gradient well(s). These samples are analyzed to determine if a statistically significant increase (SSI) in the levels of any of the monitored constituents has occurred. When analyzing the samples, facility owner/operators may use one of the following five methods:

  • Parametric analysis of variance.
  • Nonparametric analysis of variance based on ranks.
  • Tolerance or prediction interval procedure.
  • A control chart approach.
  • Another statistical test method approved by the EPA Regional Administrator.

Unless the owner/operator can demonstrate that detected SSI is due to a sampling, analysis or statistical analysis error or natural variation in the groundwater chemistry, the facility must switch to a compliance monitoring program. If unable to make this demonstration, the owner/operators must:

  • Notify the EPA Regional Administrator of the SSI within seven days.
  • Immediately sample all wells for 40 CFR part 264 Appendix IX constituents.
  • Determine which 40 CFR part 264 Appendix IX constituents are present and at what levels.
  • Submit a permit modification application within 90 days to begin a compliance monitoring program.
  • Submit an engineering feasibility plan for a corrective action program within 180 days.

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Compliance Monitoring

The purpose of a compliance monitoring program is to ascertain whether the constituents released to the uppermost aquifer are exceeding acceptable concentration levels and threatening human health and the environment. The first step in this process is establishing a groundwater protection standard (GWPS). As stated above, a facility must submit a permit modification application to switch from detection monitoring to compliance monitoring when an SSI is detected. As part of this modified permit, the EPA Regional Administrator specifies the GWPS for the facility. The GWPS establishes:

  • The list of hazardous constituents for which to monitor (from Part 261, Appendix VIII).
  • The concentration limits for each of the listed constituents based either on background levels, Clean Water Act Maximum Contaminant Levels (MCLs), or alternate concentration levels (ACLs) determined by the EPA Regional Administrator.
  • The point of compliance, which is the vertical surface at which the facility must monitor the uppermost aquifer to determine if the GWPS is being exceeded.
  • The compliance period during which the GWPS applies and compliance monitoring must be continued.

During compliance monitoring, samples are taken at each well located at the point of compliance (four samples from each well) and compared to the GWPS. The frequency of sampling is determined by the EPA Regional Administrator and specified in the modified facility permit. At a minimum, samples must be taken at least semi-annually. The facility must also analyze samples for part 264 Appendix IX constituents at least annually. If any new constituents are found to have an SSI then they must also be added to the GWPS list of constituents.

If the level of any of the constituents exceed the GWPS, the owner/operators must notify the EPA Regional Administrator in writing within seven days. The owner/operators also must submit a permit modification application to establish a corrective action program. Compliance monitoring must be continued during this period.

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Corrective Action

Once an exceedance of the GWPS has been detected, the facility must take action to bring the constituent concentration levels back into compliance with the GWPS. To achieve this, the owner/operator must either remove the hazardous constituents or treat them in place. The EPA Regional Administrator will approve the facility’s selected corrective action method and specify the time frame in which it must take place. Any hazardous constituents that have migrated beyond the point of compliance must also be remediated. The facility must continue corrective action until the GWPS has not been exceeded for three consecutive years. At which point, the facility may return to compliance monitoring.

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Interim Status Facilities

The interim status groundwater monitoring requirements apply only to facilities with hazardous waste landfills, surface impoundments or land treatment units in operation prior to the hazardous waste rules’ effective date. An interim status facility subject to the groundwater monitoring requirements must design and implement a groundwater monitoring system capable of representing the background groundwater quality and detecting any hazardous constituents that migrate from the hazardous waste management units.

This system must consist of at least one up-gradient and three down-gradient monitoring wells that can collect representative samples for analysis. If an SSI in any constituent is detected and confirmed during sampling, the owner/operators must submit written notification to the EPA Regional Administrator in writing within seven days. The owner/operators must then continue to monitor the groundwater quality. While the interim status regulations do not contain corrective action provisions, the EPA Regional Administrator may order cleanup under RCRA §3008(h) or §7003 authority, or when the facility permit is issued.

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Groundwater Monitoring Resources

Handbook of Groundwater Protection and Cleanup Policies for Resource Conservation and Recovery Act (RCRA) Corrective Action - Designed to help TSDF owners/operators find and understand EPA’s policies concerning groundwater protection and cleanup.

RCRA Training Module: Introduction to Groundwater Monitoring - Provides an introduction to the groundwater requirements for TSDFs.

RCRA Orientation Manual: Chapter 5. Regulations Governing Treatment, Storage and Disposal Facilities - Provides introductory information on the groundwater monitoring requirements for hazardous waste TSDFs.

RCRA Online – Search letters, memoranda, publications and questions and answers issued by EPA's Office of Resource Conservation and Recovery (ORCR). These documents represent EPA Headquarters interpretations of the RCRA regulations governing the management of solid and hazardous waste.

RCRA Frequently Asked Questions Database - Search over 1,000 frequently asked questions, or submit your own question or comment on a variety of RCRA issues and topics.

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