Section 22490 - Swrcb - Mining Unit Siting and Construction Standards. (C15: S2572) (California Code of Regulations)

§ 22490. Swrcb - Mining Unit Siting and Construction Standards. (C15: S2572)

(a) Proximity to Faults -New Mining Units:

(1) for Group A and B wastes, shall not be located on Holocene faults. Units for Group C wastes may be located on Holocene faults if displacement will not allow escape of wastes or cause irreparable damage to containment structures;

(2) shall be outside of areas of rapid geologic change. Exemptions may be allowed by the RWQCB if containment structures are designed and constructed to preclude failure.

(b) Flooding -All Mining Units shall be protected from flooding as shown on Table 1.2 of this article.

(c) Construction & Discharge Standards -General construction standards are given on Table 1.3 of this article. Procedures for determining appropriate methods for discharges of Groups A and B mining wastes are outlined in Figures 1.1 and 1.2 of this article.

(d) Registered Professionals -Containment structures shall be designed by a registered civil engineer, and construction shall be supervised and certified by a registered civil engineer or a certified engineering geologist.

(e) General Containment Structure Criteria -Dischargers shall comply with general criteria for containment structures in s20320.

(f) Liners.

(1) FMLs -Synthetic liners (40 mil minimum thickness) can be used for waste piles where the discharger can demonstrate that the liner will function adequately during the active life of the waste pile and provided that the waste pile is closed in accordance with s21410.

(2) Relative Permeability -Permeabilities shall be relative to the fluids, including waste or leachate, to be contained.

(3) Clay Liners -Clay liners shall be of a minimum of two feet thick and shall be installed at relative compaction of at least 90 percent.

(4) Replaceable Clay-Liners -Single clay liners may be used for Group B surface impoundments if replaced as specified in s20330(e).

(5) Contingency Plan -If the RWQCB exempts a discharger from liner requirements for a waste pile, a contingency plan for alternative waste containment shall be developed. The plan shall be implemented if there is failure of the waste pile containment system.

(6) Dischargers shall comply with the liner criteria given in s20330 (a & d).

(g) Leachate Collection and Removal Systems (LCRSs) for Group A and B Wastes.

(1) All LCRSs shall be of the blanket type.

(2) Dischargers shall comply with leachate collection and removal system (LCRS) requirements given in s20340(b - e).

(h) Precipitation and Drainage Controls.

(1) Design Storm -Diversion and drainage facilities shall be designed and constructed to accommodate the anticipated volume of precipitation and peak flows from surface runoff as follows:

(A) Group A -one 25-year, 24-hour storm;

(B) Group B -one 10-year, 24-hour storm; and

(C) Group C -one 10-year, 24-hour storm.

(2) Excess Runoff -Precipitation on Group A and B waste piles that is not diverted by containment structures shall be collected and managed through the LCRS. The RWQCB can make exemptions to this requirement if the collected fluid does not contain indicator parameters or waste constituents in excess of applicable water quality objectives.

(3) Precipitation/Drainage Controls -Dischargers shall comply with precipitation and drainage control requirements given in s20365(d & e).

(i) Incorporated Impoundment Requirements -Dischargers shall comply with special requirements for surface impoundments given in s20375. Nevertheless, for Mining Units, dischargers shall use the precipitation conditions in ¶(h)(1).

Table 1.2 Floodplain Siting Criteria

Waste Group Waste Management Unit Existing Units [FN1] New Units
A Waste Pile Protect from 100-year peak Outside 100-year floodplain
   Surface Impoundment streamflow   
   Tailings Pond      
B Waste Pile Protect from 100-year peak streamflow
   Surface Impoundment      
   Tailings Pond      
C Waste Pile Retrofit as needed to protect surface Preclude increased sediment in
   Surface Impoundment water quality surface water [FN2]
   Tailings Pond      

[FN1]

As required by the RWQCB pursuant s22470(a).

[FN2]

Mining wastes shall not be placed in perennial, intermittent, or ephemeral stream channels unless provision is made to divert runoff around the waste in a non-erosive manner. Wastes shall not be placed where they can be eroded by streamflows or where they can cause accelerated streambank erosion. Waste generated during seasonal mining operations may be exempted from these requirements provided that increased sediment in surface water is precluded.

Table 1.3 Natural and Artificial Containment Features for Mining Units

Waste Waste Management    Liner(s) Hydr. Cond. Leachate Collection
Group Unit Geologic Setting Values (Units: cm/sec) and Removal System
A Waste Pile per s2531(b)(1) of Title    required
      23, OR single clay liner [FN1]      
      <1x10 -7      
   Surface Impoundment not applicable double liner, both required [FN2]
   or Tailings Pond    <1x10 -7 outer: clay;   
         Inner: clay or synthetic   
B Waste Pile per s20250(b)(1) OR <1x10 -6 (1) required
      single clay liner      
   Surface Impoundment or not applicable double liner, both <1x10-6 // required [FN2]
   Tailings Pond outer: clay or natural permeability [FN3];         
         inner: clay or synthetic   
         OR   
         single replaceable clay liner [FN4]   
C Waste Pile, Surface not applicable not applicable not applicable
   Impoundment, or         
   Tailings Pond         

[FN1]

Synthetic liner may be used for short-term containment [see s22490(f)(1)].

[FN2]

Liner and leachate collection and removal system for tailings pond must be able to withstand the ultimate weight of wastes.

[FN3]

Permeability of <1x10 -6 cm/sec or natural geologic materials may replace outer liner of double liner system.

[FN4]

Single clay liner <(1x10 -6 cm/sec) for surface impoundment, to be removed before last 25 percent (minimum 1 foot thickness) of liner is penetrated by fluid, including waste and leachate.

(1. New section, including Table 1.2 filed 6-18-97; operative 7-18-97 (Register 97, No. 25).)

Note: Authority cited: Section 1058, Water Code. Reference: Sections 13172, 13226, and 13263, Water Code; and Section 43103, Public Resources Code.

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