| (2) for constituents for which MCLs have not been promulgated, the background concentration for the constituent established from wells in accordance with §330.405(d) of this title; or (3) for constituents for which the background level is higher than the MCL identified under paragraph (1) of this subsection or health-based levels identified under subsection (i) of this section, the background concentration. (i) The executive director may establish an alternative groundwater protection standard for 40 CFR Part 258, Appendix II constituents for which MCLs have not been established. These groundwater protection standards shall be appropriate health-based levels that satisfy either the criteria of paragraphs (1) - (4) of this subsection, inclusive or comply with paragraph (5) of this subsection: (1) 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) 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) with the 1 x 10-4 to 1 x 10 -6 range; 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 subchapter, systemic toxicants include toxic chemicals that cause effects other than cancer or mutation; or (5) the level is developed in accordance with Chapter 350 of this title (relating to Texas Risk Reduction Program). (j) In establishing groundwater protection standards under subsection (i) of this section, the executive director may consider multiple contaminants in the groundwater, exposure threats to sensitive environmental receptors, and other site-specific exposure or potential exposure to groundwater. (k) The owner or operator shall submit an annual assessment monitoring report within 60 days after the facility's second semiannual groundwater monitoring event that includes the following information determined since the previously submitted report: (1) a statement whether an statistically significant level above a groundwater protection standard established in subsection (h) or (i) of this section has occurred in any well during the previous calendar year period and the status of any statistically significant level events; (2) the results of all groundwater monitoring, testing, and analytical work obtained or prepared in accordance with the requirements of this chapter, 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 Assessment 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. |
