Groundwater Monitoring Programs

groundwater monitoring

Because of the importance and fragility of underground aquifers, managers of hazardous waste treatment, storage and disposal facilities (TSDFs) must periodically monitor groundwater quality at and around the site. In fact, the Resource Conservation and Recovery Act (RCRA) makes groundwater monitoring mandatory in order to prevent the migration of hazardous substances in groundwater which can endanger human health and damage the environment. According to the U.S. Environmental Protection Agency (EPA), groundwater monitoring regulations are the last line of defense by ensuring that the release of pollutants can be quickly detected and remediated before substantial harm can occur.

The following is a brief summary of the RCRA’s groundwater monitoring requirements:

  • A groundwater monitoring program at TSDFs is required under 40 CFR part 264, subpart F – Releases from Solid Waste Management Units

  • A groundwater monitoring program consists of three components: detection monitoring; compliance monitoring; and corrective action.

  • Each facility’s groundwater monitoring program is required to have a sufficient number of groundwater monitoring wells installed at appropriate locations and depth intervals and sampled at appropriate time intervals.
  • At a minimum, well locations include upgradient (to establish background conditions) and downgradient (for the detection of contaminants), and may also include sidegradient wells. Monitoring wells may be nested (two or more adjacent wells drilled to different depths) if multiple aquifer systems exist beneath a site.
  • Well locations and design specifications are based on depth to groundwater, aquifer and aquitard characteristics, and direction(s) of groundwater flow.

  • Chemical analyses for groundwater samples collected from the wells are included in the facility’s permit, and chemical analytical parameters are based on materials treated, stored, or disposed on site.

  • Analytical results are reduced to determine if a statistically significant increase (SSI) in indicator parameters or contaminant concentrations exists.
  • All data collected in the groundwater monitoring program must be submitted to the appropriate regulatory agency (federal, state, and/or local).
  • Reports typically include a summary of the facility’s monitoring program, calculated groundwater flow directions within the various aquifers beneath the site, groundwater sampling methods, chemical analytical results, conclutions about groundwater quality conditions, and recommendations for future work.
  • If an existing SSI cannot be attributed to a sampling error, the facility must segue to a compliance program which may result in the facility’s being required to take corrective action to ameliorate the increase in hazardous substances.


For more information about groundwater monitoring at your facility, please call the professionals at HSA Golden at 1.407.649.5475, or email us at