California Code of Regulations
Title 23 - Waters
Division 3 - State Water Resources Control Board and Regional Water Quality Control Boards
Chapter 15 - Discharges of Hazardous Waste to Land
Article 3 - Waste Management Unit Classification and Siting
Section 2531 - Class I: Waste Management Units for Hazardous Waste

Universal Citation: 23 CA Code of Regs 2531

Current through Register 2024 Notice Reg. No. 38, September 20, 2024

(a) Class I disposal units shall be located where natural geologic features provide optimum conditions for isolation of wastes from waters of the state. The classification criteria for new disposal units in this section shall be applied to new treatment and storage units, and shall be used for reclassification of existing waste management units according to the following categories:

(1) existing units at disposal sites approved as Class I under previous regulations and any expansion or reconstruction thereof (designated as "I" in Table 3.1);

(2) existing units at disposal sites approved as limited Class I ("I") or Class II-1 ("II-1") under previous regulations;

(3) existing units used for treatment or storage of hazardous wastes ("T/S"), whether or not classified under previous regulations; and

(4) reconstruction ("REC") or Expansion ("EX") of existing units described in subsections (a)(2) and (a)(3) of this section.

(b) Geologic Setting

(1) New and existing Class I units shall be immediately underlain by natural geologic materials which have a permeability of not more than 1 x 10-7 cm/sec, and which are of sufficient thickness to prevent vertical movement of fluid, including waste and leachate, from waste management units to waters of the state as long as wastes in such units pose a threat to water quality. Class I units shall not be located where areas of primary (porous) or secondary (rock opening) permeability greater than 1 x 10-7 cm/sec could impair the competence of natural geologic materials to act as a barrier to vertical fluid movement. These provisions do not apply to Class I land treatment facilities.

(2) Natural or artificial barriers shall be used to prevent lateral movement of fluid, including waste and leachate.

(c) Flooding--New disposal units and existing units in Category I other than existing land treatment units, shall be located outside of floodplains subject to inundation by floods with a 100-year return period. Other existing units and new treatment and storage units may be located within such floodplains provided that such units are designed, constructed, operated, and maintained to prevent inundation or washout due to floods with a 100-year return period.

(d) Ground Rupture--New units and existing units in Categories I, I', REC, and EX, other than existing land treatment units, shall have a 200-foot setback from any known Holocene fault. Existing units in Categories II-1 and T/S and existing land treatment units may be located within 200 feet of a known Holocene fault, provided that containment structures are capable of withstanding ground accelerations associated with the maximum credible earthquake.

(e) Rapid Geologic Change--New disposal units and existing units in Categories I, I', and EX, other than existing land treatment units, shall be located outside areas of potential rapid geologic change. Other units may be located in such areas if containment structures are designed, constructed, and maintained to preclude failure, as a result of such changes.

(f) Tidal Waves--New disposal units shall be located outside areas subject to tsunamis, seiches, and surges. Other units may be located within these areas if designed, constructed, and maintained to preclude failure due to such events.

1. Amendment of subsections (a)(1)-(3) and (b)(1) and Table 3.1 filed 6-18-97; operative 7-18-97 (Register 97, No. 25).

Note: Authority cited: Section 1058, Water Code. Reference: Sections 13172 and 13360, Water Code.

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