| (a) Assessment monitoring is required whenever the owner or operator determines there has been a statistically significant increase over background for one or more of the constituents listed in §330.419 of this title (relating to Constituents for Detection Monitoring). (b) Within 90 days of determining that a statistically significant increase has occurred in accordance with §330.407(b) of this title (relating to Detection Monitoring Program for Type I Landfills), and not less than annually thereafter, the owner or operator shall sample and analyze the groundwater monitoring system for the full set of constituents listed in Appendix II to 40 Code of Federal Regulations (CFR) Part 258, effective July 14, 2005, is adopted by reference. A minimum of one sample shall be collected from each point of compliance well and analyzed for the 40 CFR Part 258, Appendix II constituents during each sampling event. For any new constituent(s) detected in the point of compliance wells as a result of the complete Appendix II analysis, a minimum of four statistically independent samples from each background well shall be collected and analyzed to establish background levels for the additional constituent(s). After sampling all point of compliance wells for Appendix II constituents, the executive director may specify an appropriate subset of wells to be sampled and analyzed for the Appendix II constituents during assessment monitoring and may delete any of the Appendix II constituents for a municipal solid waste management unit if the owner or operator can document that the removed constituents are not reasonably expected to be in or derived from the waste contained in the unit. (c) The executive director may specify an appropriate alternative frequency for repeated sampling and analysis for the full set of 40 CFR Part 258, Appendix II constituents required by subsection (b) of this section during the active life and the closure and post-closure care period of the unit considering the following factors: (1) lithology and hydraulic conductivity of the aquifer and unsaturated zone; (2) groundwater flow rates; (3) minimum distance of travel from the waste nearest to any point of compliance monitoring well; (4) resource value of the uppermost aquifer; and (5) nature (fate and transport) of any constituents detected in response to this section. (d) Not later than 60 days after each sampling event, the owner or operator shall submit to the executive director the results from the initial and subsequent sampling events required in subsection (b) of this section and also place them in the operating record. The owner or operator shall also: (1) within 90 days of submittal of the results from a sampling event and on at least a semiannual basis thereafter, resample all wells specified by §330.403(a) of this title (relating to Groundwater Monitoring Systems) and conduct analyses for all constituents in §330.419 of this title and for those additional constituents in 40 CFR Part 258, Appendix II that are detected in response to subsection (b) of this section. The results must be submitted to the executive director not later than 60 days after the sampling event and shall also be placed in the operating record. At least one sample must be collected and analyzed from each background and point of compliance well at each sampling event. The executive director may specify an alternative monitoring frequency during the active life and the closure and post-closure care period for the constituents referred to in this paragraph. The alternative frequency during the active life and the closure and post-closure care period shall be not less than annual. The alternative frequency shall be based on consideration of the factors described in subsection (c) of this section; (2) establish background concentrations for any additional Appendix II constituents detected in accordance with subsection (b) of this section or paragraph (1) of this subsection; and (3) establish groundwater protection standards for all constituents in point of compliance wells detected in accordance with subsection (b) of this section or paragraph (1) of this subsection. The groundwater protection standards shall be established in accordance with subsection (h) or (i) of this section. (e) If the concentrations of all 40 CFR Part 258, Appendix II constituents are shown to be at or below background values, using the statistical procedures in §330.405(f) of this title (relating to Groundwater Sampling and Analysis Requirements) for two consecutive sampling events, the owner or operator must notify the executive director in writing and return to detection monitoring if approved. (f) If the concentrations of any 40 CFR Part 258, Appendix II constituents are above background values, but all concentrations are below the groundwater protection standard established under subsection (h) or (i) of this section, using the statistical procedures in §330.405(f) of this title, the owner or operator shall continue assessment monitoring in accordance with this section. (g) Not later than 60 days after each sampling event, the owner or operator shall determine whether any 40 CFR Part 258, Appendix II constituents were detected at statistically significant levels above the groundwater protection standard established under subsection (h) or (i) of this section in any sampling event. If the groundwater protection standard has been exceeded, the owner or operator shall notify the executive director and appropriate local government officials in writing within seven days of this determination. (1) The owner or operator shall also: (A) characterize the nature and extent of the release by installing additional monitoring wells as necessary; (B) install at least one additional monitoring well between the monitoring well with the statistically significant level and the next adjacent wells along the point of compliance before the next sampling event and sample these wells in accordance with subsection (d)(1) of this section; (C) notify in writing all persons that own or occupy the land that directly overlies any part of the plume of contamination if contaminants have migrated off-site as indicated by sampling of wells in accordance with subsection (d)(1) of this section; and (D) initiate an assessment of corrective measures as required by §330.411 of this title (relating to Assessment of Corrective Measures) all within 90 days of the notice to the executive director. (2) The owner or operator may demonstrate that a source other than the monitored solid waste management unit caused the contamination or that the statistically significant level resulted from error in sampling, analysis, statistical evaluation, or natural variation in groundwater quality. In making a demonstration under this paragraph, the owner or operator must: (A) notify the executive director in writing within 14 days of determining a statistically significant level above the groundwater protection standard at the point of compliance that the owner or operator intends to make a demonstration under this paragraph; (B) within 90 days of determining a statistically significant level above the groundwater protection standard, submit a report to the executive director that demonstrates that a source other than the monitored solid waste management unit caused the contamination or that the statistically significant level resulted from error in sampling, analysis, statistical evaluation, or natural variation in groundwater quality. The report shall be prepared and certified by a qualified groundwater scientist; (C) not filter the groundwater samples for constituents addressed by the demonstration prior to laboratory analysis. The executive director may also require the owner or operator to provide analysis of landfill leachate to support the demonstration; and (D) continue to monitor in accordance with the assessment monitoring program established under this section. (3) If a successful demonstration is made, the owner or operator shall continue monitoring in accordance with the assessment monitoring program required by this section and may return to detection monitoring if the 40 CFR Part 258, Appendix II constituents are at or below background as specified in subsection (e) of this section. Until a successful demonstration is made, the owner or operator shall comply with paragraph (1) of this subsection, including initiating an assessment of corrective measures. (4) If the owner or operator determines that the assessment monitoring program no longer satisfies the requirements of this section, the owner or operator must, within 90 days, submit an application for a permit amendment or modification to make any appropriate changes to the program. (h) The owner or operator shall establish a groundwater protection standard for each 40 CFR Part 258, Appendix II constituent detected in the point of compliance monitoring wells. The groundwater protection standard must be: (1) for constituents for which a maximum contaminant level (MCL) has been promulgated under 40 CFR Part 141, Safe Drinking Water Act (codified), §1412, the MCL for that constituent; Cont'd... |
