(a) On November 19, 1981, the owner or operator of a surface impoundment, landfill, or land treatment facility which is used to manage hazardous waste must implement a groundwater monitoring program capable of determining the facility's impact on the quality of groundwater in the uppermost aquifer underlying the facility, except as provided in subsection (c) of this section.
(b) Except as provided in subsections (c), (d), and (g) of this section, the owner or operator must install, operate, and maintain a groundwater monitoring system which meets the requirements of 40 Code of Federal Regulations (CFR) §265.91, and must comply with 40 CFR §265.92 and §265.93, and §335.117 of this title (relating to Recordkeeping and Reporting). This groundwater monitoring program must be carried out during the active life of the facility, and for disposal facilities during the post-closure care period as well.
(c) All or part of the groundwater monitoring requirements of this subchapter may be waived if the owner or operator can demonstrate that there is a low potential for migration of hazardous waste or hazardous waste constituents from the facility via the uppermost aquifer to water supply wells (domestic, industrial, or agricultural) or to surface water. This demonstration must be in writing and must be kept at the facility. This demonstration shall be certified by a licensed professional geoscientist or geotechnical engineer and must establish the following:
  (1) the potential for migration of hazardous waste constituents from the facility to the uppermost aquifer, by an evaluation of:
    (A) a water balance of precipitation, evapotranspiration, runoff, and infiltration; and
    (B) unsaturated zone characteristics (i.e., geologic materials, physical properties, and depth to groundwater); and
  (2) the potential for hazardous waste or hazardous waste constituents which enter the uppermost aquifer to migrate to a water supply well or surface water, by an evaluation of:
    (A) saturated zone characteristics (i.e., geologic materials, physical properties, and rate of groundwater flow); and
    (B) the proximity of the facility to water supply wells or surface water.
(d) If an owner or operator assumes (or knows) that groundwater monitoring of indicator parameters in accordance with 40 CFR §265.91 and §265.92 would show statistically significant increases (or decreases in the case of pH) when evaluated under 40 CFR §265.93(b), he may install, operate, and maintain an alternate groundwater monitoring system (other than the one described in 40 CFR §265.91 and §265.92). If the owner or operator does decide to use an alternate groundwater monitoring system he must:
  (1) prior to November 19, 1981, develop a specific plan certified by a Texas licensed professional geoscientist or geotechnical engineer which satisfies the requirements of 40 CFR §265.93(d)(3), for an alternate groundwater monitoring system. This plan is to be placed in the facility's operating record and maintained until closure of the facility;
  (2) prior to November 19, 1981, initiate the determinations specified in 40 CFR §265.93(d)(4);
  (3) prepare a written report in accordance with 40 CFR §265.93(d)(5) and place it in the facility's operating record and maintain until closure of the facility;
  (4) continue to make the determinations specified in 40 CFR §265.93(d)(4) on a quarterly basis until final closure of the facility; and
  (5) comply with the recordkeeping and reporting requirements in §335.117 of this title.
(e) The groundwater monitoring requirements of this subchapter may be waived with respect to any surface impoundment that:
  (1) is used to neutralize wastes which are hazardous solely because they exhibit the corrosivity characteristic under 40 CFR §261.22 or are listed as hazardous wastes in 40 CFR Part 261, Subpart D, only for this reason; and
  (2) contains no other hazardous wastes, if the owner or operator can demonstrate that there is no potential for migration of hazardous wastes from the impoundment. The demonstrations must establish, based upon consideration of the characteristics of the wastes and the impoundment, that the corrosive wastes will be neutralized to the extent that they no longer meet the corrosivity characteristic before they can migrate out of the impoundment. The demonstration must be in writing and must be certified by a qualified professional.
(f) For owners and operators who have not established background concentrations or values in accordance with 40 CFR §265.92(c) by November 19, 1982, the executive director may require the implementation of a groundwater assessment plan under 40 CFR §265.93, whenever he determines that existing data indicates that there is a substantial likelihood that hazardous waste or hazardous constituents from the facility have entered the uppermost aquifer.
(g) The commission may replace all or part of the requirements of this subchapter applying to a regulated unit with alternative requirements developed for groundwater monitoring set out in a permit or a post-closure order where the commission determines that:
  (1) a regulated unit is situated among solid waste management units or area of concern, a release has occurred, and both the regulated unit and one or more solid waste management unit(s) or area of concern are likely to have contributed to the release; and
  (2) it is not necessary to apply the requirement of this subchapter because the alternative requirements will be protective of human health and the environment. The alternative standards for the regulated unit must meet the requirements of §335.8 and §335.167 of this title (relating to Closure and Remediation and Corrective Action for Solid Waste Management Units).

Source Note: The provisions of this §335.116 adopted to be effective May 28, 1986, 11 TexReg 2347; amended to be effective January 30, 2003, 28 TexReg 715; amended to be effective September 1, 2003, 28 TexReg 6915; amended to be effective October 29, 2009, 34 TexReg 7321