[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: 40CFR258.54]

[Page 409-410]
 
                   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. 258.54  Detection monitoring program.

    (a) Detection monitoring is required at MSWLF units at all ground-
water monitoring wells defined under Secs. 258.51 (a)(1) and (a)(2) of 
this part. At a minimum, a detection monitoring program must include the 
monitoring for the constituents listed in appendix I to this part.
    (1) The Director of an approved State may delete any of the appendix 
I monitoring parameters for a MSWLF unit if it can be shown that the 
removed constituents are not reasonably expected to be in or derived 
from the waste contained in the unit.
    (2) The Director of an approved State may establish an alternative 
list of inorganic indicator parameters for a MSWLF unit, in lieu of some 
or all of the heavy metals (constituents 1-15 in appendix I to this 
part), if the alternative parameters provide a reliable indication of 
inorganic releases from the MSWLF 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 
wastes managed at the MSWLF unit;
    (ii) The mobility, stability, and persistence of waste constituents 
or their reaction products in the unsaturated zone beneath the MSWLF 
unit;
    (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 thispart, 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 facility (including closure) and the post-closure 
period. A minimum of four independent samples from each well (background 
and downgradient) must be collected and analyzed for the appendix I 
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 
constituents, or the alternative list approved in accordance with 
paragraph (a)(2) of this section, during the active life (including 
closure) and the post-closure care period. The alternative frequency 
during the active life (including closure) 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 MSWLF 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. 258.53(g) 
of this part, that there is a statistically significant increase over 
background for one or more of the constituents listed in appendix I to 
this part 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. 258.51(a)(2), the owner or operator:

[[Page 410]]

    (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. 258.55 of this part 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 a 
MSWLF 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. 258.55.