[Code of Federal Regulations]
[Title 40, Volume 21]
[Revised as of July 1, 2002]
From the U.S. Government Printing Office via GPO Access
[CITE: 40CFR257.24]

[Page 381-382]
 
                   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. 257.24  Detection monitoring program.

    (a) Detection monitoring is required at facilities identified in 
Sec. 257.5(a) at all ground-water monitoring wells defined under 
Secs. 257.22 (a)(1) and (a)(2). At a minimum, a detection monitoring 
program must include the monitoring for the constituents listed in 
appendix I of 40 CFR part 258.
    (1) The Director of an approved State may delete any of the appendix 
I (Appendix I of 40 CFR part 258) monitoring parameters for a unit if it 
can be shown that the removed constituents are not reasonably expected 
to be contained in or derived from the waste contained in the unit.
    (2) The Director of an approved State may establish an alternative 
list of indicator parameters for a unit, in lieu of some or all of the 
constituents in appendix I to 40 CFR part 258, if the alternative 
parameters provide a reliable indication of releases from the unit to 
the ground water. In determining alternative parameters, the Director 
shall consider the following factors:
    (i) The types, quantities, and concentrations of constituents in 
waste managed at the unit;
    (ii) The mobility, stability, and persistence of waste constituents 
or their reaction products in the unsaturated zone beneath the unit;

[[Page 382]]

    (iii) The detectability of indicator parameters, waste constituents, 
and reaction products in the ground water; and
    (iv) The concentration or values and coefficients of variation of 
monitoring parameters or constituents in the groundwater background.
    (b) The monitoring frequency for all constituents listed in appendix 
I to 40 CFR part 258, or in the alternative list approved in accordance 
with paragraph (a)(2) of this section, shall be at least semiannual 
during the active life of the unit plus 30 years. A minimum of four 
independent samples from each well (background and downgradient) must be 
collected and analyzed for the appendix I (Appendix I of 40 CFR part 
258) constituents, or the alternative list approved in accordance with 
paragraph (a)(2) of this section, during the first semiannual sampling 
event. At least one sample from each well (background and downgradient) 
must be collected and analyzed during subsequent semiannual sampling 
events. The Director of an approved State may specify an appropriate 
alternative frequency for repeated sampling and analysis for appendix I 
(Appendix I of 40 CFR part 258) constituents, or the alternative list 
approved in accordance with paragraph (a)(2) of this section, during the 
active life plus 30 years. The alternative frequency during the active 
life shall be no less than annual. The alternative frequency shall be 
based on consideration of the following factors:
    (1) Lithology of the aquifer and unsaturated zone;
    (2) Hydraulic conductivity of the aquifer and unsaturated zone;
    (3) Ground-water flow rates;
    (4) Minimum distance between upgradient edge of the unit and 
downgradient monitoring well screen (minimum distance of travel); and
    (5) Resource value of the aquifer.
    (c) If the owner or operator determines, pursuant to Sec. 257.23(g), 
that there is a statistically significant increase over background for 
one or more of the constituents listed in appendix I to 40 CFR part 258, 
or in the alternative list approved in accordance with paragraph (a)(2) 
of this section, at any monitoring well at the boundary specified under 
Sec. 257.22(a)(2), the owner or operator:
    (1) Must, within 14 days of this finding, place a notice in the 
operating record indicating which constituents have shown statistically 
significant changes from background levels, and notify the State 
Director that this notice was placed in the operating record; and
    (2) Must establish an assessment monitoring program meeting the 
requirements of Sec. 257.25 within 90 days except as provided for in 
paragraph (c)(3) of this section.
    (3) The owner/operator may demonstrate that a source other than the 
unit caused the contamination or that the statistically significant 
increase resulted from error in sampling, analysis, statistical 
evaluation, or natural variation in ground-water quality. A report 
documenting this demonstration must be certified by a qualified ground-
water scientist or approved by the Director of an approved State and be 
placed in the operating record. If a successful demonstration is made 
and documented, the owner or operator may continue detection monitoring 
as specified in this section. If, after 90 days, a successful 
demonstration is not made, the owner or operator must initiate an 
assessment monitoring program as required in Sec. 257.25.