S.C. Code Regs. § § 61-107.19.V.E.258.55

Current through Register Vol. 48, No. 10, October 25, 2024

Section 61-107.19.V.E.258.55 - Assessment Monitoring Program

a. Assessment monitoring is required whenever a statistically significant increase over background has been detected and validated, in accordance with Section258.54.d., for one or more of the metals listed in Appendix IV, or above the MCL or PQL, as applicable, for any volatile organic compound (VOC) listed in Appendix IV, unless a successful demonstration has been made in accordance with Section258.54.d. (5).

b. Within 90 days of triggering an assessment monitoring program, and annually thereafter, the permittee shall sample and analyze the groundwater for all constituents identified in Appendix V. A minimum of one sample from each downgradient well shall be collected and analyzed during each sampling event. For any constituent detected in the downgradient wells as the result of the complete Appendix V analysis, a minimum of four (4) independent samples from each well (background and downgradient) shall be collected and analyzed to establish background for the new constituents.

c. The Department may approve an appropriate subset of wells to be sampled and analyzed for Appendix V constituents during assessment monitoring, provided the permittee provides sufficient technical rationale for the subset of wells. The Department may delete any of the Appendix V monitoring parameters for a Class Three landfill if it can be shown that the removed constituents are not reasonably expected to be in or derived from the waste contained in the landfill.

d. The Department may allow an appropriate alternate frequency for repeated sampling and analysis for the full set of Appendix V constituents required by Section258.55.b., during the active life and post-closure care of the landfill considering the following factors:

(1) Lithology of the aquifer and unsaturated zone;

(2) Hydraulic conductivity of the aquifer and unsaturated zone;

(3) Groundwater flow rates;

(4) Minimum distance between upgradient edge of the Class Three landfill 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.

e. After obtaining the results from the initial or subsequent sampling events required in paragraph b. above, the permittee shall:

(1) Within 14 days, submit to the Department analytical results identifying the Appendix V constituents that have been detected and place a copy in the operating record;

(2) Within 90 days, and on at least a semiannual basis thereafter, resample all wells specified by Section258.51.a., conduct analyses for all constituents in Appendix IV and for those constituents in Appendix V that are detected in response to paragraph (b) above, and record their concentrations in the facility operating record. At least one sample from each well (background and downgradient) shall be collected and analyzed during these sampling events;

(3) Establish background concentrations for any constituents detected pursuant to paragraphs b., c., d. or e. (2) above; and,

(4) Establish groundwater protection standards for all constituents detected pursuant to paragraph b. or e. above. The groundwater protection standards shall be established in accordance with paragraph j. or k. below.

f. The Department may specify an alternative monitoring frequency during the active life and the post closure care period for the constituents referred to in this paragraph. The alternative frequency for Appendix V constituents 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 (d) above.

g. If the concentrations of all Appendix V constituents are shown to be at or below background values, using the statistical procedures in Section258.53.g., for two consecutive sampling events, the permittee may request approval from the Department to return to detection monitoring.

h. If the concentrations of any Appendix V constituents are above background values, but all concentrations are less than the groundwater protection standard established in paragraph j. or k. below, using the statistical procedures in Section258.53.g., the permittee shall continue assessment monitoring in accordance with this section.

i. If one or more Appendix V constituents are detected at or above the groundwater protection standard established in paragraph j. or k. below in any sampling event, the permittee shall, within 14 days of this finding, submit to the Department analytical results identifying the Appendix V constituents that have exceeded the groundwater protection standard and notify the Department and all appropriate local government officials that the notice has been placed in the operating record. The permittee shall do one of the following:

(1) Either:

(a) Submit to the Department within 60 days of this finding, a groundwater quality assessment plan for characterizing the nature and extent of the release.

(b) Upon approval of the groundwater quality assessment plan, shall characterize the nature and extent of the release by installing additional monitoring wells as necessary;

(c) Install at least one additional monitoring well at the facility boundary in the direction of contaminant migration and sample this well in accordance with Section258.55.d. (2);

(d) 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 as indicated by sampling of wells in accordance with Section258.55.i. (1); and,

(e) Initiate an assessment of corrective measures as required by Section255.56. within 90 days; or,

(2) Demonstrate that a source other than a Class Three landfill caused the contamination, or that the statistically significant increase (SSI) resulted from error in sampling, analysis, statistical evaluation, or natural variation in groundwater quality. A report documenting this demonstration shall be certified by a qualified professional, submitted to the Department for approval, and placed in the operating record. If a successful demonstration is made, the permittee shall continue monitoring in accordance with the assessment monitoring program pursuant to Section258.55., and may return to detection monitoring if the Appendix V constituents are at or below background as specified in Section258.55.g. Until a successful demonstration is made, the permittee shall comply with Section258.55.i. including initiating an assessment of corrective measures.

j. The permittee shall establish a groundwater protection standard for each Appendix V constituent detected in the groundwater. The groundwater protection standard shall be:

(1) For constituents for which a maximum contaminant level (MCL) has been promulgated under South Carolina R.61-58, State Primary Drinking Water Regulations, 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 258.51.a. (1); or,

(3) For constituents for which the background level is higher than the MCL identified in paragraph j. (1) above or health based levels identified in Section258.55.k. (1), the background concentration.

k. The Department may establish an alternative groundwater protection standard for constituents for which MCLs have not been established. These groundwater protection standards shall be appropriate health based levels that satisfy the following criteria:

(1) The level is derived in a manner consistent with Federal Environmental Protection Agency (EPA) guidelines for assessing the health risks of environmental pollutants (51 FR 33992, 34006, 34014, 34028, September 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) of 1 x 10^-6; 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.

l. In establishing groundwater protection standards in paragraph j. or k. above, the Department may consider the following:

(1) Multiple contaminants in the groundwater;

(2) Exposure threats to sensitive environmental receptors; and,

(3) Other site-specific exposure or potential exposure to groundwater.

S.C. Code Regs. § 61-107.19.V.E.258.55