Washington Administrative Code
Title 173 - Ecology, Department of (See also Titles 197, 317, 372, and 508)
Chapter 173-351 - Criteria for municipal solid waste landfills
Section 173-351-500 - Closure and post-closure care
Universal Citation: WA Admin Code 173-351-500
Current through Register Vol. 24-06, March 15, 2024
(1) Closure criteria.
(a) Owners or operators of all MSWLF must
install a final cover system that is designed to minimize infiltration and
erosion.
(i) The final cover system must be
designed and constructed to:
(A) Have a
permeability less than or equal to the permeability of any bottom liner system
and natural subsoils present, and minimize infiltration through the closed
MSWLF by the use of an anti-infiltration layer that contains a composite layer
as defined in (a)(i)(B) of this subsection;
(B) For the purpose of this section,
"composite layer" means a system consisting of two components; the upper
component must consist of a minimum of 30 mil (0.76 mm) thickness of
geomembrane (60 mils (1.5 mm) for high density polyethylene geomembranes). The
lower component must consist of at least a two-foot (60 cm) layer of compacted
soil with a hydraulic conductivity of no more than
1X10-5 cm/sec. The geomembrane must be installed in
direct and uniform contact with the compacted soil component;
(C) Minimize erosion of the final cover by
use of an anti-erosion layer that contains a minimum of a one-foot (30 cm)
layer of earthen material of which at least six inches (15 cm) of the uppermost
layer is capable of sustaining native plant growth; and
(D) Address anticipated settlement (with a
goal of achieving no less than two to five percent slopes after settlement),
drainage and/or the need for drainage layers, gas generation and/or the need
for gas layers, freeze-thaw, desiccation and stability and mechanical strength
of the design.
(ii) The
jurisdictional health department, with the written concurrence of the
department, may approve an alternative final cover design equivalent to that
specified in (a)(i) of this subsection that includes:
(A) An anti-infiltration layer that has a
permeability less than or equal to the permeability of any bottom liner system
and natural subsoils present, and achieves an equivalent reduction in
infiltration as an anti-infiltration layer with a permeability no greater than
1x10-5 cm/sec containing at least two feet (60 cm)
of earthen material;
(B) An
anti-erosion layer that provides equivalent protection from wind and water
erosion as a layer that contains a minimum of one foot (30 cm) of earthen
material of which at least six inches (15 cm) of the uppermost layer is capable
of sustaining native plant growth; and
(C) The additional design features of
(a)(i)(D) of this subsection.
(b) The owner or operator must prepare a
written closure plan that describes the steps necessary to close all MSWLF
units at any point during its active life. The closure plan must be submitted
to and approved by the jurisdictional health department during the permit
process of WAC
173-351-700 or through the permit
modification process of WAC
173-351-720(6)
and must include the following information:
(i) A description of the final cover,
designed in accordance with (a) of this subsection and the methods and
procedures to be used to install the cover;
(ii) An estimate of the largest area of the
MSWLF unit or all MSWLF units ever requiring a final cover as required under
(a) of this subsection at any time during the active life;
(iii) An estimate of the maximum inventory of
wastes ever on-site over the active life of the facility; and
(iv) A schedule for completing all activities
necessary to satisfy the closure criteria in this subsection including
sequencing of each MSWLF unit and the use of intermediate cover.
(c) The owner or operator of
existing MSWLF units must no later than November 26, 1993:
(i) Prepare a closure plan;
(ii) Place the closure plan in the operating
record; and
(iii) Notify the
jurisdictional health department that (c)(i) and (ii) of this subsection have
occurred.
(d) One
hundred eighty days (but no sooner than November 26, 1993) prior to beginning
closure activities of each MSWLF unit or all MSWLF units as specified in (e) of
this subsection, the owner or operator must:
(i) Notify the jurisdictional health
department and the financial assurance trustee and/or insurer of the intent to
close the MSWLF unit or all MSWLF units according to the approved closure plan;
and
(ii) Submit final engineering
closure plans for review, comment, and approval by the jurisdictional health
department.
(e) The
owner or operator must begin closure activities of each MSWLF unit or all MSWLF
units in accordance with the closure plan no later than thirty days after the
date on which the MSWLF unit or all MSWLF units receives the known final
receipt of wastes. If the MSWLF unit or all MSWLF units has remaining capacity
and there is a reasonable likelihood that the MSWLF unit or all MSWLF units
will receive additional wastes, the owner or operator must begin closure
activities no later than one year after the most recent receipt of wastes.
Extensions beyond the one-year deadline for beginning closure may be granted by
the jurisdictional health department if the owner or operator demonstrates
during the permit process of WAC
173-351-700 or through the permit
modification process of WAC
173-351-720(6)
that the MSWLF unit or all MSWLF units has the capacity to receive additional
waste and the owner or operator has taken and will continue to take all steps
including the application of intermediate cover necessary to prevent threats to
human health and the environment from the unclosed MSWLF unit or all MSWLF
units.
(f) The owner or operator of
all MSWLF units must complete closure activities of each MSWLF unit or all
MSWLF units in accordance with the closure plan within one hundred eighty days
following the beginning of closure as specified in (e) of this subsection.
Extensions of the closure period may be granted by the jurisdictional health
department if the owner or operator demonstrates that closure will, of
necessity, take longer than one hundred eighty days and he/she has taken and
will continue to take all steps to prevent threats to human health and the
environment from the unclosed MSWLF unit.
(g) Following closure of each MSWLF unit or
all MSWLF units, the owner or operator must submit to the jurisdictional health
department a certification or declaration of construction signed by an
independent registered professional engineer verifying that closure has been
completed in accordance with the approved final engineering plans and the
closure plan.
(h) Environmental
covenant. Following closure of all MSWLF units, the owner or operator must file
an environmental covenant conforming to the procedures and requirements of
chapter 64.70 RCW, Uniform Environmental Covenants Act. Unless waived in
writing by the department, the environmental covenant shall be in a form
approved by the department and include at a minimum the following provisions:
(i) State that the document is an
environmental covenant executed pursuant to chapter 64.70 RCW;
(ii) Contain a legally sufficient description
of the real property subject to the covenant;
(iii) Designate the department, or other
person approved by the department, as the holder of the covenant;
(iv) Be signed by the department, every
holder, and, unless waived by the department, every owner of a fee simple
interest in the real property subject to the covenant;
(v) Identify the name and location of the
administrative record for the property subject to the environmental
covenant;
(vi) Describe with
specificity the activity or use limitations on the real property subject to the
covenant. At a minimum, this shall prohibit uses and activities that:
(A) Threatens the integrity of any cover,
waste containment, storm water control, gas, leachate, public access control,
or environmental monitoring systems;
(B) May interfere with the operation and
maintenance, monitoring, or other measures necessary to assure the integrity of
the MSWLF unit and continued protection of human health and the environment;
and
(C) May result in the release
of solid waste constituents or otherwise exacerbate exposures.
(i) Grant the
department and the jurisdictional health department the right to enter the
property at reasonable times for the purpose of evaluating compliance with the
environmental covenant, including the right to take samples.
(2) Post-closure care requirements.
(a) Following closure of each
MSWLF unit or all MSWLF units, the owner or operator must conduct post-closure
care. Post-closure care must be conducted for thirty years or as long as
necessary for the landfill to become functionally stable. A landfill is
functionally stable when it does not present a threat to human health or the
environment at the point of exposure for humans or environmental receptors. The
point of exposure is identified as the closest location at which a receptor
could be exposed to contaminants and receive a dose by a credible pathway from
the MSWLF unit. Potential threats to human health or the environment are
assessed by considering leachate quality and quantity, landfill gas production
rate and composition, cover system integrity, and groundwater quality. The
post-closure care period may be adjusted as provided under (b) of this
subsection. Post-closure care must consist of at least the following:
(i) Maintaining the integrity and
effectiveness of any final cover, including making repairs to the cover as
necessary to correct the effects of settlement, subsidence, erosion,
maintaining the vegetative cover (including cutting of vegetation when needed)
or other events, and preventing run-on and runoff from eroding or otherwise
damaging the final cover;
(ii)
Maintaining and operating the leachate collection system in accordance with the
requirements in WAC
173-351-300 if applicable. The
jurisdictional health department may recommend to the department and the
department under its authority in
chapter
90.48 RCW, the Water
Pollution Control Act, may allow the owner or operator to stop managing
leachate if the owner or operator demonstrates that leachate no longer poses a
threat to human health and the environment;
(iii) Monitoring the groundwater in
accordance with the requirements of WAC
173-351-400 and maintaining the
groundwater monitoring system; and
(iv) Maintaining and operating the gas
monitoring system in accordance with the requirements of WAC
173-351-200(4).
(b) The length of the post-closure
care period may be:
(i) Decreased by the
jurisdictional health department if the owner or operator demonstrates that the
reduced period is sufficient to protect human health and the environment and
this demonstration is approved by the jurisdictional health department;
or
(ii) Increased by the
jurisdictional health department if the jurisdictional health department
determines that the lengthened period is necessary to protect human health and
the environment;
(iii) The
jurisdictional health department and owner or operator will consider at least
the following factors when determining when a landfill unit is functionally
stable or whether to decrease or increase the post-closure care period:
(A) Leachate. Leachate production and quality
must be such that maintenance and operation of the leachate collection system
can be ceased beyond the post-closure care period without posing a threat to
human health or the environment.
(B) Landfill gas. Landfill gas production and
composition must be such that maintenance and operation of the gas collection
system can be ceased beyond the post-closure care period while meeting the
criteria in WAC
173-351-200(4)(a)(i) through
(iii) and not pose a threat to human health
or the environment from methane or nonmethane compounds.
(C) Settlement and cover integrity. The cover
system must attain geotechnical stability for slope and settlement. Vegetation
and other erosion controls must prevent exposing waste or otherwise threaten
integrity of the cover system. The cover system must stabilize such that no
additional care is required beyond the post-closure care period to ensure its
integrity from settlement or erosion.
(D) Groundwater quality. Groundwater quality
must remain in compliance with the protection standards established in WAC
173-351-440(8)
at the relevant point of compliance.
(c) The owner or operator of all MSWLF units
must prepare and submit a written post-closure plan to the jurisdictional
health department through the permit process of WAC
173-351-700 or through the permit
modification process of WAC
173-351-720(6)
that includes the following information. Owners or operators must prepare and
submit modifications to existing post-closure plans to incorporate the criteria
in (b)(iii) of this subsection or environmental covenants in subsection (1)(h)
of this section by November 1, 2013.
(i) A
description of the monitoring and maintenance activities required in (a) of
this subsection for each MSWLF unit or all MSWLF units, and the frequency at
which these activities will be performed;
(ii) A description of the monitoring
performed and an estimate of the time required following closure of each MSWLF
unit or all MSWLF units to meet the criteria in (b)(iii) of this
subsection;
(iii) Name, address,
and telephone number of the person or office to contact about the facility
during the post-closure period; and
(iv) A description of the planned uses of the
property during the post-closure period and activity or use limitations placed
on the real property by the environmental covenant (1)(h) of this section.
Post-closure use of the property must not disturb the integrity of the final
cover, liner(s), or any other components of the containment system, or the
function of the monitoring or control systems unless necessary to comply with
the requirements of this regulation. The jurisdictional health department may
approve any other disturbance if the owner or operator demonstrates that
disturbance of the final cover, liner or other component of the containment
system, including any removal of waste, will not increase the potential threat
to human health or the environment.
(d) Following completion of the post-closure
care period for each MSWLF unit or all MSWLF units, the owner or operator must
submit to the jurisdictional health department a certification or declaration
of construction signed by an independent licensed professional engineer
verifying that post-closure has been completed in accordance with the
post-closure plan.
Statutory Authority: RCW 70.95.020(3), 70.95.060(1), and 70.95.260(1), (6). 12-23-009 (Order 07-15), § 173-351-500, filed 11/8/12, effective 12/9/12. Statutory Authority: Chapter 70.95 RCW and 40 CFR 258. 93-22-016, § 173-351-500, filed 10/26/93, effective 11/26/93.
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