[Code of Federal Regulations]
[Title 40, Volume 24]
[Revised as of July 1, 2004]
From the U.S. Government Printing Office via GPO Access
[CITE: 40CFR265.91]

[Page 480-481]
 
                   TITLE 40--PROTECTION OF ENVIRONMENT
 
         CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)
 
PART 265_INTERIM STATUS STANDARDS FOR OWNERS AND OPERATORS OF HAZARDOUS 
WASTE TREATMENT, STORAGE, AND DISPOSAL FACILITIES--Table of Contents
 
                    Subpart F_Ground-Water Monitoring
 
Sec. 265.91  Ground-water monitoring system.

    (a) A ground-water monitoring system must be capable of yielding 
ground-water samples for analysis and must consist of:
    (1) Monitoring wells (at least one) installed hydraulically 
upgradient (i.e., in the direction of increasing static head) from the 
limit of the waste management area. Their number, locations, and depths 
must be sufficient to yield ground-water samples that are:
    (i) Representative of background ground-water quality in the 
uppermost aquifer near the facility; and
    (ii) Not affected by the facility; and
    (2) Monitoring wells (at least three) installed hydraulically 
downgradient (i.e., in the direction of decreasing static head) at the 
limit of the waste management area. Their number, locations, and depths 
must ensure that

[[Page 481]]

they immediately detect any statistically significant amounts of 
hazardous waste or hazardous waste constituents that migrate from the 
waste management area to the uppermost aquifer.
    (3) The facility owner or operator may demonstrate that an alternate 
hydraulically downgradient monitoring well location will meet the 
criteria outlined below. The demonstration must be in writing and kept 
at the facility. The demonstration must be certified by a qualified 
ground-water scientist and establish that:
    (i) An existing physical obstacle prevents monitoring well 
installation at the hydraulically downgradient limit of the waste 
management area; and
    (ii) The selected alternate downgradient location is as close to the 
limit of the waste management area as practical; and
    (iii) The location ensures detection that, given the alternate 
location, is as early as possible of any statistically significant 
amounts of hazardous waste or hazardous waste constituents that migrate 
from the waste management area to the uppermost aquifer.
    (iv) Lateral expansion, new, or replacement units are not eligible 
for an alternate downgradient location under this paragraph.
    (b) Separate monitoring systems for each waste management component 
of a facility are not required provided that provisions for sampling 
upgradient and downgradient water quality will detect any discharge from 
the waste management area.
    (1) In the case of a facility consisting of only one surface 
impoundment, landfill, or land treatment area, the waste management area 
is described by the waste boundary (perimeter).
    (2) In the case of a facility consisting of more than one surface 
impoundment, landfill, or land treatment area, the waste management area 
is described by an imaginary boundary line which circumscribes the 
several waste management components.
    (c) All 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 sample collection at depths where appropriate aquifer flow 
zones exist. The annular space (i.e., the space between the bore hole 
and well casing) above the sampling depth must be sealed with a suitable 
material (e.g., cement grout or bentonite slurry) to prevent 
contamination of samples and the ground water.

[45 FR 33232, May 19, 1980, as amended at 50 FR 4514, Jan. 31, 1985; 56 
FR 66369, Dec. 23, 1991]