[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: 40CFR258.55]



[Page 419-421]

 

                   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.  258.55  Assessment monitoring program.



    (a) Assessment monitoring is required whenever a statistically 

significant increase over background has been detected for one or more 

of the constituents listed in the appendix I to this part or in the 

alternative list approved in accordance with Sec.  258.54(a)(2).

    (b) Within 90 days of triggering an assessment monitoring program, 

and annually thereafter, the owner or operator must sample and analyze 

the ground water for all constituents identified in appendix II to this 

part. A minimum of one sample from each downgradient well must be 

collected and analyzed during each sampling event. For any constituent 

detected in the downgradient wells as a result of the complete appendix 

II analysis, a minimum of four independent samples from each well 

(background and downgradient) must be collected and analyzed to 

establish background for the constituents. The Director of an approved 

State may specify an appropriate subset of wells to be sampled and 

analyzed for appendix II constituents during assessment monitoring. The 

Director of an approved State may delete any of the appendix II 

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.

    (c) The Director of an approved State may specify an appropriate 

alternate frequency for repeated sampling and analysis for the full set 

of appendix II constituents required by Sec.  258.55(b) of this part, 

during the active life (including closure) and post-closure care of the 

unit considering 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);

    (5) Resource value of the aquifer; and

    (6) Nature (fate and transport) of any constituents detected in 

response to this section.

    (d) After obtaining the results from the initial or subsequent 

sampling events required in paragraph (b) of this section, the owner or 

operator must:

    (1) Within 14 days, place a notice in the operating record 

identifying the appendix II constituents that have been detected and 

notify the State Director that this notice has been placed in the 

operating record;

    (2) Within 90 days, and on at least a semiannual basis thereafter, 

resample all wells specified by Sec.  258.51(a), conduct analyses for 

all constituents in



[[Page 420]]



appendix I to this part or in the alternative list approved in 

accordance with Sec.  258.54(a)(2), and for those constituents in 

appendix II to this part that are detected in response to paragraph (b) 

of this section, and record their concentrations in the facility 

operating record. At least one sample from each well (background and 

downgradient) must be collected and analyzed during these sampling 

events. The Director of an approved State may specify an alternative 

monitoring frequency during the active life (including closure) and the 

post-closure period for the constituents referred to in this paragraph. 

The alternative frequency for appendix I constituents, or the 

alternative list approved in accordance with Sec.  258.54(a)(2), during 

the active life (including closure) shall be no less than annual. The 

alternative frequency shall be based on consideration of the factors 

specified in paragraph (c) of this section;

    (3) Establish background concentrations for any constituents 

detected pursuant to paragraph (b) or (d)(2) of this section; and

    (4) Establish ground-water protection standards for all constituents 

detected pursuant to paragraph (b) or (d) of this section. The ground-

water protection standards shall be established in accordance with 

paragraphs (h) or (i) of this section.

    (e) If the concentrations of all appendix II constituents are shown 

to be at or below background values, using the statistical procedures in 

Sec.  258.53(g), for two consecutive sampling events, the owner or 

operator must notify the State Director of this finding and may return 

to detection monitoring.

    (f) If the concentrations of any appendix II constituents are above 

background values, but all concentrations are below the ground-water 

protection standard established under paragraphs (h) or (i) of this 

section, using the statistical procedures in Sec.  258.53(g), the owner 

or operator must continue assessment monitoring in accordance with this 

section.

    (g) If one or more appendix II constituents are detected at 

statistically significant levels above the ground-water protection 

standard established under paragraphs (h) or (i) of this section in any 

sampling event, the owner or operator must, within 14 days of this 

finding, place a notice in the operating record identifying the appendix 

II constituents that have exceeded the ground-water protection standard 

and notify the State Director and all appropriate local government 

officials that the notice has been placed in the operating record. The 

owner or operator also:

    (1)(i) Must characterize the nature and extent of the release by 

installing additional monitoring wells as necessary;

    (ii) Must install at least one additional monitoring well at the 

facility boundary in the direction of contaminant migration and sample 

this well in accordance with Sec.  258.55(d)(2);

    (iii) Must notify all persons who own the land or reside on the land 

that directly overlies any part of the plume of contamination if 

contaminants have migrated off-site if indicated by sampling of wells in 

accordance with Sec.  258.55 (g)(1); and

    (iv) Must initiate an assessment of corrective measures as required 

by Sec.  255.56 of this part within 90 days; or

    (2) May demonstrate that a source other than a MSWLF unit caused the 

contamination, or that the SSI 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 placed in the operating record. If a successful 

demonstration is made the owner or operator must continue monitoring in 

accordance with the assessment monitoring program pursuant to Sec.  

258.55, and may return to detection monitoring if the appendix II 

constituents are at or below background as specified in Sec.  258.55(e). 

Until a successful demonstration is made, the owner or operator must 

comply with Sec.  258.55(g) including initiating an assessment of 

corrective measures.

    (h) The owner or operator must establish a ground-water protection 

standard for each appendix II constituent detected in the ground-water. 

The ground-water protection standard shall be:



[[Page 421]]



    (1) For constituents for which a maximum contaminant level (MCL) has 

been promulgated under section 1412 of the Safe Drinking Water Act 

(codified) under 40 CFR part 141, the MCL for that constituent;

    (2) For constituents for which MCLs have not been promulgated, the 

background concentration for the constituent established from wells in 

accordance with Sec.  258.51(a)(1); or

    (3) For constituents for which the background level is higher than 

the MCL identified under paragraph (h)(1) of this section or health 

based levels identified under Sec.  258.55(i)(1), the background 

concentration.

    (i) The Director of an approved State may establish an alternative 

ground-water protection standard for constituents for which MCLs have 

not been established. These ground-water protection standards shall be 

appropriate health based levels that satisfy the following criteria:

    (1) The level is derived in a manner consistent with Agency 

guidelines for assessing the health risks of environmental pollutants 

(51 FR 33992, 34006, 34014, 34028, Sept. 24, 1986);

    (2) The level is based on scientifically valid studies conducted in 

accordance with the Toxic Substances Control Act Good Laboratory 

Practice Standards (40 CFR part 792) or equivalent;

    (3) For carcinogens, the level represents a concentration associated 

with an excess lifetime cancer risk level (due to continuous lifetime 

exposure) with the 1x10-4 to 1x10-6 range; and

    (4) For systemic toxicants, the level represents a concentration to 

which the human population (including sensitive subgroups) could be 

exposed to on a daily basis that is likely to be without appreciable 

risk of deleterious effects during a lifetime. For purposes of this 

subpart, systemic toxicants include toxic chemicals that cause effects 

other than cancer or mutation.

    (ii) [Reserved]

    (j) In establishing ground-water protection standards under 

paragraph (i) of this section, the Director of an approved State may 

consider the following:

    (1) Multiple contaminants in the ground water;

    (2) Exposure threats to sensitive environmental receptors; and

    (3) Other site-specific exposure or potential exposure to ground 

water.