N.M. Admin. Code § 20.9.9.13

Current through Register Vol. 35, No. 23, December 10, 2024

Section 20.9.9.13 - ASSESSMENT MONITORING

A. Owners and operators shall conduct assessment monitoring whenever the AML has been exceeded for one or more constituent of Subsection A of 20.9.9.20 NMAC or an alternate constituent list approved under Subsection A of 20.9.9.11 NMAC unless a demonstration has been approved pursuant to Paragraph (3) of Subsection C of 20.9.9.11 NMAC. Assessment monitoring shall be conducted in accordance with an assessment monitoring plan, approved in accordance with Subsection C of 20.9.9.11 NMAC.

B. Within 90 days of the determination of an exceedance under Subsection M of 20.9.9.10 NMAC, and annually thereafter, the owner or operator shall sample and analyze the ground water for all constituents and parameters referenced and listed in Subsections B and C of 20.9.9.20 NMAC for each downgradient well. For any constituents detected in the downgradient wells as a result of the complete analysis, a minimum of four independent samples from each well (upgradient and downgradient) shall be collected and analyzed to establish background for the constituents for which background has not been established. Sampling data and proposed background concentration shall be submitted to the department within 180 days of the determination of an exceedance under Subsection M of 20.9.9.10 NMAC. The upgradient concentrations shall be presumed to be the background unless the owner or operator demonstrates that hydrogeological conditions are such that sampling at other points will provide an indication of background ground water quality that is as representative or more representative than that provided at the upgradient wells. The department shall approve background levels for those detected constituents for which background concentrations have not previously been determined within 60 days, or the upgradient concentrations shall be deemed to be the background concentrations.

C. The department may specifically approve an alternative frequency or subset of wells for repeated sampling for assessment monitoring during the active life and post-closure care period of the facility. In determining an alternative frequency or subset of wells, the department shall consider:

(1) lithology of the aquifer and unsaturated zone;

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

(3) ground water flow rate;

(4) minimum distance between the waste management unit boundary and downgradient monitoring well screen;

(5) resource value of the aquifer; and

(6) nature of any constituents detected.

D. After obtaining the results from the sampling required by Subsection B of this section, the owner or operator shall:

(1) within 14 days, notify the department in writing and document in the operating record any constituents that have been detected;

(2) within 90 days and at least semiannually, resample all wells and analyze for all constituents in Subsections A and C of 20.9.9.20 NMAC and any constituents in Subsection B of 20.9.9.20 NMAC or an approved alternate list that have been detected; the department may specify an alternate monitoring frequency in accordance with Subsection A of 20.9.9.11 NMAC, but all constituents in Subsection B of 20.9.9.20 NMAC shall be sampled no less frequently than once every five years during the active life and post-closure care period.

E. If the concentration of each constituents in Subsection A of 20.9.9.20 NMAC, and each detected constituent of Subsection B of 20.9.9.20 NMAC is determined to be at or below the approved AML after two sampling events, the owner or operator shall notify the department in writing and may return to detection monitoring.

F. If the concentration of any constituent in 20.9.9.20 NMAC is above the AML, but below the corrective action level (CAL), the owner or operator shall continue assessment monitoring in accordance with this section.

G. If one or more constituents in 20.9.9.20 NMAC is detected above the CALs in any sampling event, the owner or operator shall:

(1) within 14 days of this finding, notify the department and all appropriate local government officials in writing;

(2) install at least one additional monitoring well at the facility boundary in the direction of contaminant migration and sample this well in accordance with this section within six months; the department may approve an extension for this installation and sampling for good cause for up to an additional six months of the finding of the exceedance;

(3) characterize the nature and extent of the release by installing additional monitoring wells as necessary within one year of the finding of the exceedance;

(4) notify area residents and land owners in the same manner as described in Subsection B of 20.6.2.4108 NMAC; and

(5) initiate an assessment of corrective measures as required by 20.9.9.15 NMAC within 90 days; or

(6) the owner or operator may demonstrate that a source other than the facility caused the contamination, or that the increase resulted from error in sampling, analysis, statistical evaluation, or natural variation in ground water quality; a report documenting this demonstration shall be certified by a qualified ground water scientist and submitted to the department for review and approval; if a demonstration is specifically approved by the department, the owner or operator may return to detection monitoring; until a successful demonstration is made, the owner or operator shall comply with 20.9.9.12 - 20.9.9.20 NMAC, including initiating an assessment of corrective action.

H. Within 90 days after any AML exceedance, the owner or operator shall identify the ground water protection standard for each constituent in 20.9.9.20 NMAC that exceeded the AML in the ground water that was not identified pursuant to Subsection I of 20.9.9.10 NMAC. The owner or operator shall propose for department approval ground water protection standards for any constituent that exceeded the AML pursuant to Subsection B of this section and Paragraph (2) of Subsection D of this section that does not have an MCL or numeric standard in commission rules. The owner or operator shall make a demonstration that the proposed standard will be protective of the public health and the environment, in accordance with Subsection I of this section.

(1) The ground water protection standards for constituents shall be the more stringent of the MCL promulgated at 40 CFR 141, or the numeric standard established by commission rules.

(2) For hazardous constituents for which the background concentration is higher than the ground water protection standard, the background concentration shall be used as the ground water protection standard.

I. The secretary may establish an alternative ground water protection standard for constituents for which MCLs or commission standards have not been established. These ground water protection standards shall be appropriate health based levels that satisfy the following:

(1) the level is derived in a manner consistent with U.S. EPA guidelines for assessing the health risks of environmental pollutants;

(2) the level is based on scientifically valid studies conducted in accordance with the Toxic Substances Control Act good laboratory practice standards or equivalent;

(3) for carcinogens, the level represents a concentration associated with an excess lifetime cancer risk of more than one cancer per 100,000 exposed persons; and

(4) for systemic toxicants, the level represents a concentration to which the human population could be exposed on a daily basis that is likely to be without appreciable risk of deleterious effects during a lifetime; systemic toxicants include toxic chemicals that cause effects other than cancer or mutation.

J. In establishing ground water protection standards under Subsection I of this section, the secretary 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.

N.M. Admin. Code § 20.9.9.13

20.9.9.13 NMAC - Rp, 20 NMAC 9.1.VIII.806, 8/2/2007