California Code of Regulations › Title 27 - Environmental Protection › Division 2 - Solid Waste › Subdivision 1 - Consolidated Regulations for Treatment, Storage, Processing or Disposal of Solid Waste › Chapter 3 - Criteria for All Waste Management Units, Facilities, and Disposal Sites › Subchapter 5 - Closure and Post-Closure Maintenance › Article 2 - Closure and Post-Closure Maintenance Standards for Disposal Sites and Landfills › Section 21090 - SWRCB-Closure and Post-Closure Maintenance Requirements for Solid Waste Landfills. (C15: Section 2581 // T14: Section 17777, Section 17779)

Current through Register 2024 Notice Reg. No. 28, July 12, 2024
[
Note: For SWRCB's final cover performance
						  standard, see §
													20950(a)(2)(A);
						  for related CIWMB requirements, see §
													21790 et seq.
]
(a) Final Cover Requirements--Final cover
						slopes shall not be steeper than a horizontal to vertical ratio of one and
						three quarters to one, and shall have a minimum of one fifteen-foot wide bench
						for every fifty feet of vertical height. Designs having any slopes steeper than
						a horizontal to vertical ratio of three to one, or having a geosynthetic
						component [under ¶(a)(2)], shall have these aspects of their design
						specifically supported in the slope stability report required under §
												21750(f)(5). The
						RWQCB can require flatter slopes or more benches where necessary to ensure
						preservation of the integrity of the final cover under static and dynamic
						conditions. The cost estimate, under §
												21769, for the final cover shall
						include a description of the type and estimated volume (or amount, as
						appropriate) of material needed for each component of the final cover based
						upon the assumption that all materials will need to be purchased; if on-site
						materials are to be used, the submittal shall include test results confirming
						the availability of such on-site materials and their suitability for such use.
						The RWQCB can allow any alternative final cover design that it finds will
						continue to isolate the waste in the Unit from precipitation and irrigation
						waters at least as well as would a final cover built in accordance with
						applicable prescriptive standards under ¶(a)(1-3).
(1) Foundation Layer--Closed landfills shall
						be provided with not less than two feet of appropriate materials as a
						foundation layer for the final cover. These materials may be soil, contaminated
						soil, incinerator ash, or other waste materials, provided that such materials
						have appropriate engineering properties to be used for a foundation layer. The
						foundation layer shall be compacted to the maximum density obtainable at
						optimum moisture content using methods that are in accordance with accepted
						civil engineering practice. A lesser thickness may be allowed for Units if the
						RWQCB finds that differential settlement of waste, and ultimate land use will
						not affect the structural integrity of the final cover.
(2) Low-Hydraulic-Conductivity Layer--In
						order to protect water quality by minimizing the generation of leachate and
						landfill gas, closed landfills shall be provided with a
						low-hydraulic-conductivity (or low through-flow rate) layer consisting of not
						less than one foot of soil containing no waste or leachate, that is placed on
						top of the foundation layer and compacted to attain an hydraulic conductivity
						of either 1x10-6 cm/sec (i.e., 1 ft/yr) or less, or equal to the hydraulic
						conductivity of any bottom liner system or underlying natural geologic
						materials, whichever is less permeable, or another design which provides a
						correspondingly low through-flow rate throughout the post-closure maintenance
						period. Hydraulic conductivity determinations for cover materials shall be as
						specified in Article 4, Subchapter 2, Chapter 3 of this subdivision [§
													20310 et seq.], but using water as
						the permeant, and shall be appended to the closure and post-closure maintenance
						report. For landfills or portions thereof in which the final cover is installed
						after July 18, 1997, as part of the final closure plan for the Unit, the
						discharger shall provide a plan, as necessary [see ¶(a)(4)], for
						protecting the low-hydraulic-conductivity layer from foreseeable sources of
						damage that could impair its ability to prevent the throughflow of water
						(
e.g., desiccation, burrowing rodents, or heavy equipment
						damage
).
(3)
						Erosion-Resistant Layer--The low-hydraulic-conductivity layer of ¶(a)(2)
						shall be directly overlain by an erosion-resistant layer, as follows.
(A) Closed landfills shall be provided with
						an uppermost cover layer consisting of either:
1. Erosion-Resistance Via a Vegetative
						Layer--a vegetative layer consisting of not less than one foot of soil which:
a. contains no waste (including
						leachate);
b. is placed on top of
						all portions of the low-hydraulic-conductivity layer described in
						¶(a)(2);
c. is capable of
						sustaining native, or other suitable, plant growth;
d. is initially planted--and is later
						replanted as needed to provide effective erosion resistance--with native or
						other suitable vegetation having a rooting depth not exceeding the depth to the
						top of the low-hydraulic-conductivity layer described in ¶(a)(2). For any
						proposed vegetative cover, the discharger shall propose a species mix which
						harmonizes with the proposed post-closure land use, and which requires as
						little long-term maintenance as feasible by virtue of its tolerance of the
						vegetative layer's soil conditions (
e.g., the presence of landfill
						gas
), its resistant to foreseeable adverse environmental factors
						(e
.g., climate, disease, and pests
), its rapidity of
						germination and growth, its persistence and ease of self-propagation, its high
						percentage of surface coverage (sufficient to prevent surface erosion), and its
						minimal need for irrigation and maintenance; and
e. by virtue of its composition, its
						maintained vegetation density, and its finished-and- maintained grade, will be
						resistant to foreseeable erosion effects by wind-scour, raindrop impact, and
						runoff; or
2.
						Mechanically Erosion-Resistant Layer--an erosion- and ultraviolet
						light-resistant layer which, by virtue of its composition and
						finished-and-maintained grade, resists foreseeable erosion effects by
						wind-scour, raindrop impact, and runoff (
e.g., a 1-foot thick layer of
						cobbles, the interstices of which are filled with
						gravel
).
(B) The
						discharger shall maintain all components of the erosion-resistant layer
						throughout the post-closure maintenance period, and, if closed after July 18,
						1997, shall implement such maintenance in accordance with an approved
						Cover-Integrity Monitoring and Maintenance Program, pursuant to
						¶(a)(4).
(4) Cover
						Maintenance Plan & Annual Cost Estimate--The final cover shall be designed
						and constructed to function with the minimum maintenance possible. For
						landfills and for other Units closed as landfills, if the closure occurs after
						July 18, 1997, the preliminary and final closure and post-closure maintenance
						plan shall incorporate a cover-integrity monitoring and maintenance program
						which includes at least the following components. The annualized post-closure
						maintenance plan cost analysis [of §
													21769(c)] shall
						include an itemized estimate of the annual cost of each component:
(A) Periodic Leak Search--a schedule for
						carrying out periodic monitoring of the integrity of the
						low-hydraulic-conductivity layer, including a method for effectively
						identifying and repairing breaches in that layer [
for example and where
						allowed, by temporarily discontinuing active gas extraction and using surface
						gas probes or inserted soil gas probes to identify locations where landfill gas
						is emerging
];
(B) Periodic
						Identification of Other Problem Areas--a schedule for periodically identifying
						and addressing other cover problems, including at least:
1. areas of the vegetative cover, if any,
						requiring replanting;
2. eroded
						portions of the erosion-resistant layer requiring regrading, repair, or (for
						areas where the problem persistently reoccurs) increased erosion
						resistance;
3. eroded portions of
						the low-hydraulic-conductivity layer needing repair or replacement;
4. areas lacking free drainage;
5. areas damaged by equipment
						operation;
6. [Reserved];
						and
7. localized areas identified
						in the iso-settlement survey [of ¶(e)(2)] as having sustained repeated or
						severe differential settlement.
(C) Prompt Cover Repair--a plan for
						repairing, in a timely manner, any breach or other cover problem discovered
						pursuant to ¶(a)(4)(A or B). For any repairs of the
						low-hydraulic-conductivity layer, this plan shall either contain a Construction
						Quality Assurance (CQA) plan [under §
														21710(a)(5)], or
						shall accomplish this goal through the incorporation-by-reference of
						appropriate portions of an approved CQA plan; and
(D) Vegetation Maintenance--for a final cover
						utilizing a vegetated erosion resistant layer [under ¶(a)(3)(A)1.], a plan
						for maintaining this vegetative cover, including fertilization, irrigation,
						elimination of species that violate the rooting depth limit [of
						¶(a)(3)(A)1.d.], replanting, and irrigation system
						maintenance.
(5)
						Discharges of Liquids to Covers.
(A) Leachate
						and Gas Condensate--The discharge of leachate, gas condensate, or other waste
						liquids to any final-covered portion of an MSW landfill is subject to the
						restrictions under §
														20200(d).
						[
Note: see also 1) definitions of "leachate" and "landfill gas
						condensate" in §
															20164, and
						2) §
															20705(f), re:
						daily and intermediate cover
]
(B) Other Liquids--The discharger shall
						moderate the application rate of liquids discharged to the cover for dust
						control, irrigation of the vegetative layer, or other non-disposal purpose in a
						manner that minimizes the potential for throughflow to the underlying waste.
						The RWQCB can establish cover throughflow monitoring requirements
						(
e.g., via intermittent tensiometer measurements of the cover
)
						to ensure compliance with this requirement.
(6) Stability Analysis--For any portions of
						the final cover installed after July 18, 1997 for which the RWQCB has not
						approved a slope and foundation stability report on or before that date, the
						discharger shall meet the requirements of §
													21750(f)(5).