[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: 40CFR257.23]



[Page 385-387]

 

                   TITLE 40--PROTECTION OF ENVIRONMENT

 

         CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)

 

PART 257_CRITERIA FOR CLASSIFICATION OF SOLID WASTE DISPOSAL FACILITIES 

AND PRACTICES--Table of Contents

 

  Subpart B_Disposal Standards for the Receipt of Conditionally Exempt 

 Small Quantity Generator (CESQG) Wastes at Non-Municipal Non-Hazardous 

                          Waste Disposal Units

 

Sec.  257.23  Ground-water sampling and analysis requirements.



    (a) The ground-water monitoring program must include consistent 

sampling and analysis procedures that are designed to ensure monitoring 

results that provide an accurate representation of ground-water quality 

at the background and downgradient wells installed in compliance with 

Sec.  257.22(a). The owner or operator must notify the State Director 

that the sampling and analysis program documentation has been placed in 

the operating record and the program must include procedures and 

techniques for:

    (1) Sample collection;

    (2) Sample preservation and shipment;

    (3) Analytical procedures;

    (4) Chain of custody control; and

    (5) Quality assurance and quality control.

    (b) The ground-water monitoring program must include sampling and 

analytical methods that are appropriate for ground-water sampling and 

that accurately measure hazardous constituents and other monitoring 

parameters in ground-water samples. Ground-water samples shall not be 

field-filtered prior to laboratory analysis.

    (c) The sampling procedures and frequency must be protective of 

human health and the environment.

    (d) Ground-water elevations must be measured in each well 

immediately prior to purging, each time ground



[[Page 386]]



water is sampled. The owner or operator must determine the rate and 

direction of ground-water flow each time ground water is sampled. 

Ground-water elevations in wells which monitor the same waste management 

area must be measured within a period of time short enough to avoid 

temporal variations in ground-water flow which could preclude accurate 

determination of ground-water flow rate and direction.

    (e) The owner or operator must establish background ground-water 

quality in a hydraulically upgradient or background well(s) for each of 

the monitoring parameters or constituents required in the particular 

ground-water monitoring program that applies to the unit, as determined 

under Sec.  257.24(a), or Sec.  257.25(a). Background ground-water 

quality may be established at wells that are not located hydraulically 

upgradient from the unit if it meets the requirements of Sec.  

257.22(a)(1).

    (f) The number of samples collected to establish ground-water 

quality data must be consistent with the appropriate statistical 

procedures determined pursuant to paragraph (g) of this section. The 

sampling procedures shall be those specified under Sec.  257.24(b) for 

detection monitoring, Sec.  257.25 (b) and (d) for assessment 

monitoring, and Sec.  257.26(b) for corrective action.

    (g) The owner or operator must specify in the operating record one 

of the following statistical methods to be used in evaluating ground-

water monitoring data for each hazardous constituent. The statistical 

test chosen shall be conducted separately for each hazardous constituent 

in each well.

    (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 that meets the performance 

standards of paragraph (h) of this section. The owner or operator must 

place a justification for this alternative in the operating record and 

notify the State Director of the use of this alternative test. The 

justification must demonstrate that the alternative method meets the 

performance standards of paragraph (h) of this section.

    (h) Any statistical method chosen under paragraph (g) of this 

section 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 

experiment wise 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.



[[Page 387]]



    (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 protective of human health and the 

environment. The parameters shall 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.

    (4) If a tolerance interval or a predictional interval is used to 

evaluate ground-water monitoring data, the levels of confidence and, for 

tolerance intervals, the percentage of the population that the interval 

must contain, shall be protective of human health and the environment. 

These parameters shall 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 quantitation limit (pql) 

that is used in the statistical method shall be the lowest concentration 

level that 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.

    (i) The owner or operator must determine whether or not there is a 

statistically significant increase over background values for each 

parameter or constituent required in the particular ground-water 

monitoring program that applies to the unit, as determined under 

Sec. Sec.  257.24(a) or 257.25(a).

    (1) In determining whether a statistically significant increase has 

occurred, the owner or operator must compare the ground-water quality of 

each parameter or constituent at each monitoring well designated 

pursuant to Sec.  257.22(a)(2) to the background value of that 

constituent, according to the statistical procedures and performance 

standards specified under paragraphs (g) and (h) of this section.

    (2) Within a reasonable period of time after completing sampling and 

analysis, the owner or operator must determine whether there has been a 

statistically significant increase over background at each monitoring 

well.