270.21(b)(1)  

Hydrogeologic report for owners and operators of

landfills seeking a variance from the design and operating

requirements under  264.301(b); and

 270.23(b)

Hydrogeologic and/or geologic assessments for owners

and operators of miscellaneous units that are providing

information to address and ensure compliance with the

environmental performance standards of  264.601.

The Regional Administrator can, however, extend the Subpart F requirements to any

corrective actions specified in the permit, including those initiated under  264.101(c).

1.1

Overview of Ground Water Monitoring Programs Under Subpart F

Subpart F outlines a three phase ground water monitoring program for regulated units.

"Detection monitoring," the first phase, involves at least semi annual monitoring of

parameters and/or constituents that provide a reliable indication of the presence of hazardous

constituents in ground water. Detection monitoring is performed at permitted land based

disposal units not believed to be releasing hazardous wastes or constituents into the ground

water. If monitoring indicates a release, analysis of all Appendix IX constituents is required,

and the facility enters "compliance monitoring."

Compliance monitoring, the second phase, requires at least semi annual monitoring for

those constituents detected in ground water during detection monitoring. A facility

performing compliance monitoring also monitors ground water for all constituents on

Appendix IX at least annually, and reports the concentration of any new compound detected

to the Regional Administrator. Detected compounds are then added to the list of analytes

monitored semi annually. The concentrations of all compliance monitoring constituents are

compared to their permitted concentration levels, one of the elements of the facility's

ground water protection standard, to determine whether or not corrective action is required.

If a unit in compliance monitoring contaminates the ground water above the allowable

concentration set forth in the facility's permit, the unit enters "corrective action," the third

phase of ground water monitoring. In corrective action, a facility is required to "remove or

treat in place" ( 264.100(e)) all hazardous constituents that are detected in ground water at

concentrations greater than their respective ground water concentration limits specified in the

facility's permit. The monitoring associated with corrective action tracks the progress of the

clean up and detects any other constituents entering the ground water at concentrations greater

than the allowable concentration limits.

November 1992

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