(a) The monitoring frequency for all constituents listed in §330.419 of this title (relating to Constituents for Detection Monitoring) shall be at least semiannual during the active life of the facility and the closure and post-closure care period.
  (1) A minimum of four statistically independent samples from each background and each point of compliance well shall be collected and analyzed for the constituents listed in §330.419 of this title to establish background groundwater quality. Initial background sampling for a well shall be completed on a quarterly basis, unless an alternative schedule is approved by the executive director. Background data sets may be updated once every two years with semiannual detection monitoring results that are demonstrated to be representative of background groundwater quality. Upon completion of background monitoring and during background updates, the owner or operator shall evaluate the background data to ensure that the data are representative of background groundwater constituent concentrations unaffected by waste management activities or other sources of contamination. The evaluation shall be documented in a report and submitted to the executive director before the next subsequent groundwater monitoring event following the updated background period. At least one sample from each background and point of compliance well shall be collected and analyzed during each subsequent semiannual sampling event.
  (2) The executive director may specify an appropriate alternative frequency for repeated sampling and analysis of the constituents listed in §330.419 of this title during the active life and the closure and post-closure care period. The alternative frequency shall be no less than annual and shall be based on factors such as lithology and hydraulic conductivity of the aquifer and unsaturated zone, groundwater flow rates, minimum distance of travel from waste to monitoring wells, and resource value of the uppermost aquifer.
  (3) For the purpose of establishing background groundwater quality, the executive director may agree to consider analytical data acquired prior to the effective date of this chapter in addition to the data required in this subsection and in §330.409(b) of this title (relating to Assessment Monitoring Program).
(b) Not later than 60 days after each sampling event, the owner or operator shall determine whether there has been a statistically significant increase over background of any tested constituent at any monitoring well. If there has been a statistically significant increase, the owner or operator shall notify the executive director, and any local pollution agency with jurisdiction that has requested to be notified, in writing within 14 days of this determination.
  (1) If a statistically significant increase over background of any tested constituent at any monitoring well has occurred, the owner or operator shall immediately place a notice in the operating record describing the increase and shall establish an assessment monitoring program meeting the requirements of §330.409 of this title within 90 days of the date of the notice to the executive director required under this subsection, except as provided for in paragraphs (2) and (3) of this subsection.
  (2) If a statistically significant increase over background of any tested constituent at any monitoring well has occurred, the owner or operator may submit the results of resampling as appropriate for the statistical method being used within 60 days of determining the statistically significant increase. The resample data may be used to statistically confirm or disprove the determination made in this subsection.
  (3) If a statistically significant increase over background of any tested constituent at any monitoring well has occurred and the owner or operator has reasonable cause to think that a source other than a landfill unit caused the contamination or that the statistically significant increase resulted from error in sampling, analysis, statistical evaluation, or natural variation in groundwater quality, then the owner or operator may submit a report providing documentation to this effect. In making a demonstration under this paragraph, the owner or operator must:
    (A) notify the executive director, and any local pollution agency with jurisdiction that has requested to be notified, in writing within 14 days of determining a statistically significant increase over background at the compliance point that the owner or operator intends to make a demonstration under this paragraph;
    (B) within 90 days of determining a statistically significant increase, submit a report to the executive director, and any local pollution agency with jurisdiction that has requested to be notified, that demonstrates that a source other than a monitored landfill unit caused the contamination or that the statistically significant increase resulted from error in sampling, analysis, statistical evaluation, or natural variation in groundwater quality. The report must be prepared and certified by a qualified groundwater scientist;
    (C) not filter the groundwater sample for constituents addressed by the demonstration prior to laboratory analysis. The executive director may also require the owner or operator to provide analyses of the landfill leachate to support the demonstration; and
    (D) continue to monitor in accordance with the detection monitoring program established under this section.
  (4) If the owner or operator does not make a demonstration satisfactory to the executive director within 90 days after the date of the notice to the executive director required under this subsection, the owner or operator shall initiate an assessment monitoring program as required in paragraph (1) of this subsection. The executive director may require the owner or operator to install additional wells at the point of compliance to further characterize the release.
(c) The owner or operator shall submit an annual detection monitoring report within 90 days after the facility's last groundwater monitoring event in a calendar year that must include the following information determined since the previously submitted annual report:
  (1) a statement regarding whether a statistically significant increase has occurred over background values in any well during the previous calendar year period and the status of any statistically significant increase events;
  (2) the results of all groundwater monitoring, testing, and analytical work obtained or prepared under the requirements of this permit, including a summary of background groundwater quality values, groundwater monitoring analyses, statistical calculations, graphs, and drawings;
  (3) the groundwater flow rate and direction in the uppermost aquifer. The groundwater flow rate and direction of groundwater flow shall be established using the data collected during the preceding calendar year's sampling events from the monitoring wells of the detection monitoring program. The owner or operator shall also include in the report all documentation used to determine the groundwater flow rate and direction of groundwater flow;
  (4) a contour map of piezometric water levels in the uppermost aquifer based at a minimum upon concurrent measurement in all monitoring wells. All data or documentation used to establish the contour map should be included in the report;
  (5) recommendation for any changes; and
  (6) any other items requested by the executive director.
(d) If the owner or operator determines that the detection monitoring program no longer satisfies the requirements of this section, the owner or operator must, within 90 days of this determination, submit an application for a permit amendment or modification to make any appropriate changes to the program.

Source Note: The provisions of this §330.407 adopted to be effective March 27, 2006, 31 TexReg 2502