[Code of Federal Regulations]

[Title 40, Volume 24]

[Revised as of July 1, 2006]

From the U.S. Government Printing Office via GPO Access

[CITE: 40CFR258.51]



[Page 415-416]

 

                   TITLE 40--PROTECTION OF ENVIRONMENT

 

         CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)

 

PART 258_CRITERIA FOR MUNICIPAL SOLID WASTE LANDFILLS--Table of Contents

 

         Subpart E_Ground-Water Monitoring and Corrective Action

 

Sec.  258.51  Ground-water monitoring systems.



    (a) A ground-water monitoring system must be installed that consists 

of a sufficient number of wells, installed at appropriate locations and 

depths, to yield ground-water samples from the uppermost aquifer (as 

defined in Sec.  258.2) that:

    (1) Represent the quality of background ground water that has not 

been affected by leakage from a unit. A determination of background 

quality may include sampling of wells that are not hydraulically 

upgradient of the waste management area where:

    (i) Hydrogeologic conditions do not allow the owner or operator to 

determine what wells are hydraulically upgradient; or

    (ii) Sampling at other wells will provide an indication of 

background ground-water quality that is as representative or more 

representative than that provided by the upgradient wells; and

    (2) Represent the quality of ground water passing the relevant point 

of compliance specified by Director of an approved State under Sec.  

258.40(d) or at the waste management unit boundary in unapproved States. 

The down gradient monitoring system must be installed at the relevant 

point of compliance specified by the Director of an approved State under 

Sec.  258.40(d) or at the waste management unit boundary in unapproved 

States that ensures detection of ground-water contamination in the 

uppermost aquifer. When physical obstacles preclude installation of 

ground-water monitoring wells at the relevant point of compliance at 

existing units, the down-gradient monitoring system may be installed at 

the closest practicable distance hydraulically down-gradient from the 

relevant point of compliance specified by the Director of an approved 

State under Sec.  258.40 that ensure detection of groundwater 

contamination in the uppermost aquifer.

    (b) The Director of an approved State may approve a multiunit 

ground-water monitoring system instead of separate ground-water 

monitoring systems for each MSWLF unit when the facility has several 

units, provided the multi-unit ground-water monitoring system meets the 

requirement of Sec.  258.51(a) and will be as protective of human health 

and the environment as individual monitoring systems for each MSWLF 

unit, based on the following factors:

    (1) Number, spacing, and orientation of the MSWLF units;

    (2) Hydrogeologic setting;

    (3) Site history;

    (4) Engineering design of the MSWLF units, and

    (5) Type of waste accepted at the MSWLF units.

    (c) Monitoring wells must be cased in a manner that maintains the 

integrity of the monitoring well bore hole. This casing must be screened 

or perforated and packed with gravel or sand, where necessary, to enable 

collection of ground-water samples. The annular space (i.e., the space 

between the bore hole and well casing) above the sampling depth must be 

sealed to prevent contamination of samples and the ground water.

    (1) The owner or operator must notify the State Director that the 

design,



[[Page 416]]



installation, development, and decommission of any monitoring wells, 

piezo meters and other measurement, sampling, and analytical devices 

documentation has been placed in the operating record; and

    (2) The monitoring wells, piezometers, and other measurement, 

sampling, and analytical devices must be operated and maintained so that 

they perform to design specifications throughout the life of the 

monitoring program.

    (d) The number, spacing, and depths of monitoring systems shall be:

    (1) Determined based upon site-specific technical information that 

must include thorough characterization of:

    (i) Aquifer thickness, ground-water flow rate, ground-water flow 

direction including seasonal and temporal fluctuations in ground-water 

flow; and

    (ii) Saturated and unsaturated geologic units and fill materials 

overlying the uppermost aquifer, materials comprising the uppermost 

aquifer, and materials comprising the confining unit defining the lower 

boundary of the uppermost aquifer; including, but not limited to: 

Thicknesses, stratigraphy, lithology, hydraulic conductivities, 

porosities and effective porosities.

    (2) Certified by a qualified ground-water scientist or approved by 

the Director of an approved State. Within 14 days of this certification, 

the owner or operator must notify the State Director that the 

certification has been placed in the operating record.