(a) In the closure plan under 40 Code of Federal Regulations (CFR) §265.112 and the post-closure plan under 40 CFR §265.118, the owner or operator must address the following objectives and indicate how they will be achieved:
  (1) control of the migration of hazardous waste and hazardous waste constituents from the treated area into the groundwater;
  (2) control of the release of contaminated run-off from the facility into surface water;
  (3) control of the release of airborne particulate contaminants caused by wind erosion; and
  (4) compliance with 40 CFR §265.276, concerning the growth of food-chain crops.
(b) The owner or operator must consider at least the following factors addressing the closure and post-closure care objectives of subsection (a) of this section:
  (1) type and amount of hazardous waste and hazardous waste constituents applied to the land treatment facility;
  (2) the mobility and the expected rate of migration of the hazardous waste and hazardous waste constituents;
  (3) site location, topography, and surrounding land use, with respect to the potential effects of pollutant migration (e.g., proximity to groundwater, surface water, and drinking water sources);
  (4) climate, including amount, frequency, and pH or precipitation;
  (5) geological and soil profiles and surface and subsurface hydrology of the site, and soil characteristics, including cation exchange capacity, total organic carbon, and pH;
  (6) unsaturated zone monitoring information obtained under 40 CFR §265.278; and
  (7) type, concentration, and depth of migration of hazardous waste constituents in the soil as compared to their background concentrations.
(c) The owner or operator must consider at least the following methods in addressing the closure and post-closure care objectives of subsection (a) of this section:
  (1) removal of contaminated soils;
  (2) placement of a final cover, considering:
    (A) functions of the cover (e.g., infiltration control, erosion and run-off control, and wind erosion control), and
    (B) characteristics of the cover, including material, final surface contours, thickness, porosity and permeability, slope, length of run of slope, and type of vegetation on the cover;
  (3) collection and treatment run-off;
  (4) diversion structures to prevent surface water run-on from entering the treated area; and
  (5) monitoring of soil, soil-pore water, and groundwater.
(d) In addition to the requirements of 40 CFR Part 265; Subpart G, relating to closure and post-closure, §335.118 of this title (relating to Closure Plan; Submission and Approval of Plan) and §335.119 of this title (relating to Post-Closure Plan; Submission and Approval Plan), during the closure period the owner or operator of a land treatment facility must:
  (1) continue unsaturated zone monitoring in a manner and frequency specified in the closure plan, except that soil pore liquid monitoring may be terminated 90 days after the last application of waste to the treatment zone;
  (2) maintain the run-on control system required under §335.121(b) of this title (relating to General Operating Requirements (Land Treatment Facilities));
  (3) maintain the run-off management system required under §335.121(c) of this title; and
  (4) control wind dispersal of particulate matter which may be subject to wind dispersal.
(e) For the purpose of complying with 40 CFR §265.115 concerning certification of closure, when closure is completed, the owner or operator may submit to the executive director certification both by the owner or operator and by an independent licensed professional geoscientist, in lieu of an independent licensed professional engineer, that the facility has been closed in accordance with the specifications in the approved closure plan.
(f) In addition to the requirements of 40 CFR §265.117 concerning post-closure care and use of property during the post-closure care period, the owner or operator of a land treatment unit must:
  (1) continue soil-core monitoring by collecting and analyzing samples in a manner and frequency specified in the post-closure plan;
  (2) restrict access to the unit as appropriate for its post-closure use;
  (3) assure that growth of food chain crops complies with 40 CFR §265.276 concerning food chain crops; and
  (4) control wind dispersal of hazardous waste.

Source Note: The provisions of this §335.123 adopted to be effective May 28, 1986, 11 TexReg 2347; amended to be effective July 14, 1987, 12 TexReg 2106; amended to be effective November 15, 2001, 26 TexReg 9135; amended to be effective September 1, 2003, 28 TexReg 6915