1. (a) Applicability. Assessment monitoring is required whenever a statistically significant increase over background has been detected for one (1) or more of the constituents listed in:

   1. (1) Appendix 1 for Class 1 landfills;
   2. (2) Appendix 3 for Class 3 landfills and other facilities required to monitor ground water; or
   3. (3) An alternative list approved in accordance with 8 CAR § 60-1204.

2. (b) Assessment monitoring frequency.

   1. (1) Within ninety (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 2 of this part.
   2. (2) A minimum of one (1) sample from each downgradient well, and any other well which contained a statistically significant increase, must be collected and analyzed during each sampling event.
   3. (3) For any constituent detected as the result of the complete Appendix 2 analysis, a minimum of four (4) independent samples from each well (background and downgradient) must be collected and analyzed to establish background for the new constituents unless the Director of the Division of Environmental Quality approves a more appropriate background sampling scheme.
   4. (4) All detected constituents from the full Appendix 2 analysis and all Appendix 1 monitoring parameters shall be referred to as the assessment monitoring constituents (AMC) list.
   5. (5) The director may specify an appropriate subset of wells to be sampled and analyzed for Appendix 2 constituents during assessment monitoring.
   6. (6) The director may delete any of the Appendix 2 monitoring parameters for facilities 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.

3. (c) Alternative frequency. The director may specify an appropriate alternate frequency for repeated sampling and analysis for the full set of Appendix 2 constituents required by subsection (b) of this section during the active life (including closure) and post-closure care of the unit considering the following factors:

   1. (1) Lithology of the aquifer and unsaturated zone;
   2. (2) Hydraulic conductivity of the aquifer and unsaturated zone;
   3. (3) Ground water flow rates;
   4. (4) Minimum distance between up gradient edge of the landfill or facility and downgradient monitoring well screen (minimum distance of travel);
   5. (5) Resource value of the aquifer; and
   6. (6) Nature (fate and transport) of any constituents detected in response to this section.

4. (d) Assessment monitoring procedures. After obtaining the results from the initial or subsequent sampling events required in subsection (b) of this section, the owner or operator must:

   1. (1) Within fourteen (14) days, place a notice in the operating record identifying the Appendix 2 constituents that have been detected and notify the director that this notice has been placed in the operating record;

   2. (2)

      1. (A) Within ninety (90) days, and on at least a quarterly basis thereafter, resample all wells specified by 8 CAR § 60-1202(a), conduct analyses for all assessment monitoring constituents (AMC) specified in subsection (b) of this section, and record their concentrations in the facility operating record.
      2. (B) At least one (1) sample from each well (background and downgradient) must be collected and analyzed during these sampling events.
      3. (C) Following the first year of assessment monitoring, the director may approve semiannual AMC sampling and analysis or an alternative frequency as specified below.
      4. (D) The director may specify an alternative monitoring frequency during the active life (including closure) and the post-closure period for the constituents referred to in this subsection.
      5. (E) The alternative frequency for the AMC list during the active life (including closure) shall be no less than annual.
      6. (F) The alternative frequency shall be based on consideration of the factors specified in subsection (c) of this section;
   3. (3) Establish background concentrations for any constituents detected pursuant to subsection (b) of this section or subdivision (d)(2) of this section; and

   4. (4)

      1. (A) Establish ground water protection standards for all constituents detected pursuant to subsection (b) or (d) of this section.
      2. (B) The ground water protection standards shall be established in accordance with subsection (h) or (i) of this section.
5. (e) Cessation of assessment monitoring. If the concentrations of all assessment monitoring constituents are shown to be at or below background values, using the statistical procedures in 8 CAR § 60-1203(g), for two (2) consecutive sampling events, the owner or operator must notify the director of this finding and may return to detection monitoring.
6. (f) Assessment levels below protection standard. If the concentrations of any assessment monitoring constituents are above background values, but all concentrations are below the ground water protection standard established under subsection (h) or (i) of this section, using the statistical procedures in 8 CAR § 60-1203(g), the owner or operator must continue assessment monitoring in accordance with this section.

7. (g) Statistically significant assessment levels.

   1. (1) If one (1) or more assessment monitoring constituents are detected at statistically significant levels above the ground water protection standard established under subsection (h) or (i) of this section in any sampling event, the owner or operator must, within fourteen (14) days of this finding:

      1. (A) Place a notice in the operating record identifying the assessment monitoring constituents that have exceeded the ground water protection standard; and
      2. (B) Notify the director and all appropriate local government officials that the notice has been placed in the operating record.

   2. (2) The owner or operator also:

      1. (A) Must:

8. (i) Characterize the nature and extent of the release by installing additional monitoring wells as necessary;

   1. (ii) Install at least one (1) additional monitoring well at the facility boundary in the direction of contaminant migration and sample this well in accordance with subdivision (d)(2) of this section;

      1. (iii) Notify all persons who own the land or reside on the land that directly overlies any part of the contaminant migration if contaminants have migrated off-site if indicated by sampling of wells in accordance with this subdivision (g)(2)(A); and

         1. (iv) Initiate an assessment of corrective measures as required by 8 CAR § 60-1206 within ninety (90) days; or

      2. (B)

         1. (i) May demonstrate that a source other than a landfill or solid waste disposal facility caused the contamination, or that the SSI resulted from error in sampling, analysis, statistical evaluation, or natural variation in ground water quality.
         2. (ii) A report documenting this demonstration must be certified by a qualified ground water scientist or approved by the director and placed in the operating record.
         3. (iii) If a successful demonstration is made, the owner or operator must continue monitoring in accordance with the assessment monitoring program pursuant to this section, and may return to detection monitoring if the assessment monitoring constituents are at or below background as specified in subsection (e) of this section.
         4. (iv) Until a successful demonstration is made, the owner or operator must comply with this subsection including initiating an assessment of corrective measures.

9. (h) Ground water protection standard.

   1. (1) The owner or operator must establish a ground water protection standard for each assessment monitoring constituent detected in the ground water.

   2. (2) The ground water protection standard shall be:

      1. (A) For constituents for which a maximum contaminant level (MCL) has been promulgated under Section 1412 of the Safe Drinking Water Act codified under 40 C.F.R. pt. 141, the MCL for that constituent;
      2. (B) For constituents for which MCLs have not been promulgated, the background concentration for the constituent established from wells in accordance with 8 CAR § 60-1202(a)(1); or

      3. (C) For constituents for which the background level is higher than the MCL identified under subsection (h)(1) of this section or health-based levels identified under subdivision (i)(2)(A) of this section, the background concentration.

         1. (i) Alternative ground water protection standards.
   3. (1) The director may establish an alternative ground water protection standard for constituents for which MCLs have not been established.

   4. (2) These ground water protection standards shall be appropriate health-based levels that satisfy the following criteria:

      1. (A) The level is derived in a manner consistent with United States Environmental Protection Agency guidelines for assessing the health risks of environmental pollutants (51 FR 33992, 34006, 34014, 34028 (September 24, 1986));
      2. (B) The level is based on scientifically valid studies conducted in accordance with the Toxic Substances Control Act Good Laboratory Practice Standards (40 C.F.R. pt. 792) or equivalent;
      3. (C) For carcinogens, the level represents a concentration associated with an excess lifetime cancer risk level (due to continuous lifetime exposure) with the 1 x 10^-4 to 1 x 10^-6 range; and

      4. (D)

         1. (i) 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.
         2. (ii) For purposes of this section, “systemic toxicants" include toxic chemicals that cause effects other than cancer or mutation.

10. (j) Ground water protection standard criteria. In establishing ground water protection standards under subsection (i) of this section, the director may consider the following:

    1. (1) Multiple contaminants in the ground water;
    2. (2) Exposure threats to sensitive environmental receptors; and
    3. (3) Other site-specific exposure or potential exposure to ground water.

Codification Notes: “SSI” means statistically significant increase.