[Code of Federal Regulations]
[Title 40, Volume 25]
[Revised as of July 1, 2005]
From the U.S. Government Printing Office via GPO Access
[CITE: 40CFR264.97]

[Page 284-286]
 
                   TITLE 40--PROTECTION OF ENVIRONMENT
 
         CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)
 
PART 264_STANDARDS FOR OWNERS AND OPERATORS OF HAZARDOUS WASTE TREATMENT, 
STORAGE, AND DISPOSAL FACILITIES--Table of Contents
 
          Subpart F_Releases From Solid Waste Management Units
 
Sec. 264.97  General ground-water monitoring requirements.

    The owner or operator must comply with the following requirements 
for any ground-water monitoring program developed to satisfy Sec. 
264.98, Sec. 264.99, or Sec. 264.100:
    (a) The ground-water monitoring system must consist of a sufficient 
number of wells, installed at appropriate locations and depths to yield 
ground-water samples from the uppermost aquifer that:
    (1) Represent the quality of background water that has not been 
affected by leakage from a regulated unit;
    (i) A determination of background quality may include sampling of 
wells that are not hydraulically upgradient of the waste management area 
where:
    (A) Hydrogeologic conditions do not allow the owner or operator to 
determine what wells are hydraulically upgradient; and
    (B) Sampling at other wells will provide an indication of background 
ground-water quality that is representative or more representative than 
that provided by the upgradient wells; and
    (2) Represent the quality of ground water passing the point of 
compliance.
    (3) Allow for the detection of contamination when hazardous waste or 
hazardous constituents have migrated from the waste management area to 
the uppermost aquifer.
    (b) If a facility contains more than one regulated unit, separate 
ground-water monitoring systems are not required for each regulated unit 
provided that provisions for sampling the ground water in the uppermost 
aquifer will enable detection and measurement at the compliance point of 
hazardous constituents from the regulated units that have entered the 
ground water in the uppermost aquifer.
    (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 collection of ground-water samples. The annular space (i.e., 
the space between the

[[Page 285]]

bore hole and well casing) above the sampling depth must be sealed to 
prevent contamination of samples and the ground water.
    (d) The ground-water monitoring program must include consistent 
sampling and analysis procedures that are designed to ensure monitoring 
results that provide a reliable indication of ground-water quality below 
the waste management area. At a minimum the program must include 
procedures and techniques for:
    (1) Sample collection;
    (2) Sample preservation and shipment;
    (3) Analytical procedures; and
    (4) Chain of custody control.
    (e) The ground-water monitoring program must include sampling and 
analytical methods that are appropriate for ground-water sampling and 
that accurately measure hazardous constituents in ground-water samples.
    (f) The ground-water monitoring program must include a determination 
of the ground-water surface elevation each time ground water is sampled.
    (g) In detection monitoring or where appropriate in compliance 
monitoring, data on each hazardous constituent specified in the permit 
will be collected from background wells and wells at the compliance 
point(s). The number and kinds of samples collected to establish 
background shall be appropriate for the form of statistical test 
employed, following generally accepted statistical principles. The 
sample size shall be as large as necessary to ensure with reasonable 
confidence that a contaminant release to ground water from a facility 
will be detected. The owner or operator will determine an appropriate 
sampling procedure and interval for each hazardous constituent listed in 
the facility permit which shall be specified in the unit permit upon 
approval by the Regional Administrator. This sampling procedure shall 
be:
    (1) A sequence of at least four samples, taken at an interval that 
assures, to the greatest extent technically feasible, that an 
independent sample is obtained, by reference to the uppermost aquifer's 
effective porosity, hydraulic conductivity, and hydraulic gradient, and 
the fate and transport characteristics of the potential contaminants, or
    (2) an alternate sampling procedure proposed by the owner or 
operator and approved by the Regional Administrator.
    (h) The owner or operator will specify one of the following 
statistical methods to be used in evaluating ground-water monitoring 
data for each hazardous constituent which, upon approval by the Regional 
Administrator, will be specified in the unit permit. The statistical 
test chosen shall be conducted separately for each hazardous constituent 
in each well. Where practical quantification limits (pql's) are used in 
any of the following statistical procedures to comply with Sec. 
264.97(i)(5), the pql must be proposed by the owner or operator and 
approved by the Regional Administrator. Use of any of the following 
statistical methods must be protective of human health and the 
environment and must comply with the performance standards outlined in 
paragraph (i) of this section.
    (1) A parametric analysis of variance (ANOVA) followed by multiple 
comparisons procedures to identify statistically significant evidence of 
contamination. The method must include estimation and testing of the 
contrasts between each compliance well's mean and the background mean 
levels for each constituent.
    (2) An analysis of variance (ANOVA) based on ranks followed by 
multiple comparisons procedures to identify statistically significant 
evidence of contamination. The method must include estimation and 
testing of the contrasts between each compliance well's median and the 
background median levels for each constituent.
    (3) A tolerance or prediction interval procedure in which an 
interval for each constituent is established from the distribution of 
the background data, and the level of each constituent in each 
compliance well is compared to the upper tolerance or prediction limit.
    (4) A control chart approach that gives control limits for each 
constituent.
    (5) Another statistical test method submitted by the owner or 
operator and approved by the Regional Administrator.

[[Page 286]]

    (i) Any statistical method chosen under Sec. 264.97(h) for 
specification in the unit permit shall comply with the following 
performance standards, as appropriate:
    (1) The statistical method used to evaluate ground-water monitoring 
data shall be appropriate for the distribution of chemical parameters or 
hazardous constituents. If the distribution of the chemical parameters 
or hazardous constituents is shown by the owner or operator to be 
inappropriate for a normal theory test, then the data should be 
transformed or a distribution-free theory test should be used. If the 
distributions for the constituents differ, more than one statistical 
method may be needed.
    (2) If an individual well comparison procedure is used to compare an 
individual compliance well constituent concentration with background 
constituent concentrations or a ground-water protection standard, the 
test shall be done at a Type I error level no less than 0.01 for each 
testing period. If a multiple comparisons procedure is used, the Type I 
experimentwise error rate for each testing period shall be no less than 
0.05; however, the Type I error of no less than 0.01 for individual well 
comparisons must be maintained. This performance standard does not apply 
to tolerance intervals, prediction intervals or control charts.
    (3) If a control chart approach is used to evaluate ground-water 
monitoring data, the specific type of control chart and its associated 
parameter values shall be proposed by the owner or operator and approved 
by the Regional Administrator if he or she finds it to be protective of 
human health and the environment.
    (4) If a tolerance interval or a prediction interval is used to 
evaluate groundwater monitoring data, the levels of confidence and, for 
tolerance intervals, the percentage of the population that the interval 
must contain, shall be proposed by the owner or operator and approved by 
the Regional Administrator if he or she finds these parameters to be 
protective of human health and the environment. These parameters will be 
determined after considering the number of samples in the background 
data base, the data distribution, and the range of the concentration 
values for each constituent of concern.
    (5) The statistical method shall account for data below the limit of 
detection with one or more statistical procedures that are protective of 
human health and the environment. Any practical quantification limit 
(pql) approved by the Regional Administrator under Sec. 264.97(h) that 
is used in the statistical method shall be the lowest concentration 
level tha can be reliably achieved within specified limits of precision 
and accuracy during routine laboratory operating conditions that are 
available to the facility.
    (6) If necessary, the statistical method shall include procedures to 
control or correct for seasonal and spatial variability as well as 
temporal correlation in the data.
    (j) Ground-water monitoring data collected in accordance with 
paragraph (g) of this section including actual levels of constituents 
must be maintained in the facility operating record. The Regional 
Administrator will specify in the permit when the data must be submitted 
for review.

[47 FR 32350, July 26, 1982, as amended at 50 FR 4514, Jan. 31, 1985; 53 
FR 39728, Oct. 11, 1988]