Wash. Admin. Code § 173-340-720 - Groundwater cleanup standards
(1)
General
considerations.
(a) Groundwater cleanup
levels shall be based on estimates of the highest beneficial use and the
reasonable maximum exposure expected to occur under both current and potential
future site use conditions. The department has determined that at most sites
use of groundwater as a source of drinking water is the beneficial use
requiring the highest quality of groundwater and that exposure to hazardous
substances through ingestion of drinking water and other domestic uses
represents the reasonable maximum exposure. Unless a site qualifies under
subsection (2) of this section for a different groundwater beneficial use,
groundwater cleanup levels shall be established using this presumed exposure
scenario and be established in accordance with subsection (3), (4) or (5) of
this section. If the site qualifies for a different groundwater beneficial use,
groundwater cleanup levels shall be established under subsection (6) of this
section.
(b) In the event of a
release of a hazardous substance at a site, a cleanup action complying with
this chapter shall be conducted to address all areas where the concentration of
the hazardous substance in groundwater exceeds cleanup levels.
(c) Groundwater cleanup levels shall be
established at concentrations that do not directly or indirectly cause
violations of surface water, sediments, soil, or air cleanup standards
established under this chapter or other applicable state and federal laws. A
site that qualifies for a Method C groundwater cleanup level under this section
does not necessarily qualify for a Method C cleanup level in other media. Each
medium must be evaluated separately using the criteria applicable to that
medium.
(d) The department may
require more stringent cleanup levels than specified in this section where
necessary to protect other beneficial uses or otherwise protect human health
and the environment. Any imposition of more stringent requirements under this
provision shall comply with WAC
173-340-702 and
173-340-708. The following are
examples of situations that may require more stringent cleanup levels:
(i) Concentrations that are necessary to
protect sensitive subgroups;
(ii)
Concentrations that eliminate or minimize the potential for food chain
contamination;
(iii) Concentrations
that eliminate or minimize the potential for damage to soils or biota in the
soils which could impair the use of the soil for agricultural or silvicultural
purposes;
(iv) Concentrations that
eliminate or minimize the potential for the accumulation of vapors in buildings
or other structures to concentrations which pose a threat to human health or
the environment; and
(v)
Concentrations that protect nearby surface waters.
(2)
Potable groundwater
defined. Groundwater shall be classified as potable to protect drinking
water beneficial uses unless the following can be demonstrated:
(a) The groundwater does not serve as a
current source of drinking water;
(b) The groundwater is not a potential future
source of drinking water for any of the following reasons:
(i) The groundwater is present in
insufficient quantity to yield greater than 0.5 gallon per minute on a
sustainable basis to a well constructed in compliance with chapter 173-160 WAC
and in accordance with normal domestic water well construction practices for
the area in which the site is located;
(ii) The groundwater contains natural
background concentrations of organic or inorganic constituents that make use of
the water as a drinking water source not practicable. Groundwater containing
total dissolved solids at concentrations greater than 10,000 mg/l shall
normally be considered to have fulfilled this requirement; (NOTE: The
total dissolved solids concentration provided here is an example. There may be
other situations where high natural background levels also meet this
requirement.) or
(iii) The
groundwater is situated at a great depth or location that makes recovery of
water for drinking water purposes technically impossible; and
(c) The department determines it
is unlikely that hazardous substances will be transported from the contaminated
groundwater to groundwater that is a current or potential future source of
drinking water, as defined in (a) and (b) of this subsection, at concentrations
which exceed groundwater quality criteria published in chapter 173-200 WAC.
In making a determination under this provision, the department shall consider site-specific factors including:
(i) The extent of affected
groundwater;
(ii) The distance to
existing water supply wells;
(iii)
The likelihood of interconnection between the contaminated groundwater and
groundwater that is a current or potential future source of drinking water due
to well construction practices in the area of the state where the site is
located;
(iv) The physical and
chemical characteristics of the hazardous substance;
(v) The hydrogeologic characteristics of the
site;
(vi) The presence of
discontinuities in the affected geologic stratum; and
(vii) The degree of confidence in any
predictive modeling performed.
(d) Even if groundwater is classified as a
potential future source of drinking water under (b) of this subsection, the
department recognizes that there may be sites where there is an extremely low
probability that the groundwater will be used for that purpose because of the
site's proximity to surface water that is not suitable as a domestic water
supply. An example of this situation would be shallow groundwaters in close
proximity to marine waters such as on Harbor Island in Seattle. At such sites,
the department may allow groundwater to be classified as nonpotable for the
purposes of this section if each of the following conditions can be
demonstrated. These determinations must be for reasons other than that the
groundwater or surface water has been contaminated by a release of a hazardous
substance at the site.
(i) The conditions
specified in (a) and (c) of this subsection are met;
(ii) There are known or projected points of
entry of the ground-water into the surface water;
(iii) The surface water is not classified as
a suitable domestic water supply source under chapter 173-201A WAC;
and
(iv) The groundwater is
sufficiently hydraulically connected to the surface water that the groundwater
is not practicable to use as a drinking water source.
(3)
Method A cleanup levels
for potable groundwater.
(a)
Applicability. Method A groundwater cleanup levels may only be
used at sites qualifying under WAC
173-340-704(1).
(b)
General requirements. Method
A cleanup levels shall be at least as stringent as all of the following:
(i) Concentrations listed in Table 720-1 and
compliance with the corresponding footnotes;
(ii) Concentrations established under
applicable state and federal laws, including the following requirements:
(A) Maximum contaminant levels established
under the Safe Drinking Water Act and published in 40 C.F.R. 141 ;
(B) Maximum contaminant level goals for
noncarcinogens established under the Safe Drinking Water Act and published in
40 C.F.R. 141;
(C) Maximum
contaminant levels established by the state board of health and published in
chapter 246-290 WAC.
(iii) For hazardous substances deemed
indicator hazardous substances for groundwater under WAC
173-340-708(2)
and for which there is no value in Table 720-1 or applicable state and federal
laws, concentrations that do not exceed natural background or the practical
quantitation limit, subject to the limitations in this chapter.
(iv)
Protection of surface water
beneficial uses. Concentrations established in accordance with the
methods specified in WAC
173-340-730 for protecting
surface water beneficial uses, unless it can be demonstrated that the hazardous
substances are not likely to reach surface water. This demonstration must be
based on factors other than implementation of a cleanup action at the
site.
(4)
Method B cleanup levels for potable groundwater.
(a)
Applicability. Method B
potable groundwater cleanup levels consist of standard and modified cleanup
levels determined using the procedures in this subsection. Either standard or
modified Method B groundwater cleanup levels based on drinking water beneficial
uses may be used at any site.
(b)
Standard Method B potable groundwater cleanup levels. Where the
groundwater cleanup level is based on a drinking water beneficial use, standard
Method B cleanup levels shall be at least as stringent as all of the following:
(i)
Applicable state and federal
laws. Concentrations established under applicable state and federal
laws, including the requirements in subsection (3)(b)(ii) of this
section;
(ii)
Protection of
surface water beneficial uses. Concentrations established in accordance
with the methods specified in WAC
173-340-730 for protecting
surface water beneficial uses, unless it can be demonstrated that the hazardous
substances are not likely to reach surface water. This demonstration must be
based on factors other than implementation of a cleanup action at the
site.
(iii)
Human health
protection. For hazardous substances for which sufficiently protective,
health-based criteria or standards have not been established under applicable
state and federal laws, those concentrations which protect human health as
determined by the following methods:
(A)
Noncarcinogens. Concentrations that are estimated to result in no
acute or chronic toxic effects on human health as determined using Equation
720-1.
Click to view image
(B)
Carcinogens. For known or suspected carcinogens, concentrations
for which the upper bound on the estimated excess cancer risk is less than or
equal to one in 1,000,000 (1 [MULTIPLICATION]- 10-6)
as determined using Equation 720-2.
Click to view image
(C)
Petroleum mixtures. For noncarcinogenic effects of petroleum
mixtures, a total petroleum hydrocarbon cleanup level shall be calculated
taking into account the additive effects of the petroleum fractions and
volatile organic compounds present in the petroleum mixture. Equation 720-3
shall be used for this calculation. Cleanup levels for other noncarcinogens and
known or suspected carcinogens within the petroleum mixture shall be calculated
using Equations 720-1 and 720-2. See Table 830-1 for the analyses required for
various petroleum products to use this method. A total petroleum hydrocarbon
cleanup level for petroleum mixtures derived using Equation 720-3 shall be
adjusted when necessary so that biological degradation of the petroleum does
not result in exceedances of the maximum contaminant levels in chapter 246-290
WAC or natural background, whichever is higher.
Click to view image
(c)
Modified Method B potable
groundwater cleanup levels. Modified Method B groundwater cleanup levels
for drinking water beneficial uses are standard Method B groundwater cleanup
levels modified with chemical-specific or site-specific data. When making these
adjustments, the resultant cleanup levels shall meet applicable state and
federal laws and health risk levels for standard Method B groundwater cleanup
levels. Changes to exposure assumptions must comply with WAC
173-340-708(10).
The following adjustments may be made to the default assumptions in the
standard Method B equations to derive modified Method B groundwater cleanup
levels for drinking water beneficial uses:
(i)
The inhalation correction factor is an adjustment factor that takes into
account exposure to hazardous substances that are volatilized and inhaled
during showering and other domestic activities. When available, hazardous
substance-specific information may be used to estimate this factor;
(ii) Where separate toxicity factors
(reference doses and carcinogenic potency factors) are available for inhalation
and oral exposures, the health hazards associated with the inhalation of
hazardous substances in groundwater during showering and other domestic
activities may be evaluated separately from the health hazards associated with
ingestion of drinking water. In these cases, the groundwater cleanup level
based on ingestion of drinking water shall be modified to take into account
multiple exposure pathways in accordance with WAC
173-340-708(6);
(iii) The toxicity equivalency factor
procedures described in WAC
173-340-708(8)
may be used for assessing the potential carcinogenic risk of mixtures of
chlorinated dibenzo-p-dioxins, chlorinated diben-zofurans and polycyclic
aromatic hydrocarbons;
(iv)
Adjustments to the reference dose and cancer potency factor may be made if the
requirements in WAC
173-340-708(7) and
(8) are met; and
(v) Modifications incorporating new science
as provided for in WAC
173-340-702(14), (15) and
(16).
(d)
Using modified Method B to evaluate
groundwater remediation levels. In addition to the adjustments allowed
under (c) of this subsection, other adjustments to the reasonable maximum
exposure scenario or default exposure assumptions are allowed when using a
quantitative site-specific risk assessment to evaluate the protectiveness of a
remedy. See WAC
173-340-355,
173-340-357, and
173-340-708(3)(d) and
(10)(b).
(5)
Method C cleanup levels for potable
groundwater.
(a)
Applicability. Method C potable groundwater cleanup levels consist
of standard and modified cleanup levels as described in this subsection.
The department may approve of both standard and modified Method C groundwater cleanup levels based on drinking water beneficial uses only at sites qualifying under WAC 173-340-706(1).
(b)
Standard Method C potable
groundwater cleanup levels. Where the groundwater cleanup level is based
on a drinking water beneficial use and the site qualifies for a Method C
groundwater cleanup level, the standard Method C cleanup levels for groundwater
shall be at least as stringent as all of the following:
(i)
Applicable state and federal
laws. Concentrations established under applicable state and federal
laws, including the requirements in subsection (3)(b)(ii) of this
section;
(ii)
Protection of
surface water beneficial uses. Concentrations established in accordance
with the methods specified in WAC
173-340-730 for protecting
surface water beneficial uses, unless it can be demonstrated that the hazardous
substances are not likely to reach surface water. This demonstration must be
based on factors other than implementation of a cleanup action at the
site.
(iii)
Human health
protection. For hazardous substances for which sufficiently protective,
health-based standards or criteria have not been established under applicable
state and federal laws, those concentrations that protect human health as
determined using the following methods:
(A)
Noncarcinogens. Concentrations that are estimated to result in no
significant acute or chronic toxic effects on human health and are estimated
using Equation 720-1, except that the average body weight shall be 70 kg and
the drinking water intake rate shall be two liters/day;
(B)
Carcinogens. Concentrations
for which the upper bound on the estimated excess cancer risk is less than or
equal to one in 100,000 (1 [MULTIPLICATION]- 10-5),
using Equation 720-2;
(C)
Petroleums. Cleanup levels for petroleum mixtures shall be
determined as specified in subsection (4)(b)(iii)(C) of this section except
that the average body weight shall be 70 kg and the drinking water rate shall
be two liters/day.
(c)
Modified Method C potable
groundwater cleanup levels. Modified Method C groundwater cleanup levels
for drinking water beneficial uses are standard Method C groundwater cleanup
levels modified with chemical-specific or site-specific data. The same
limitations and adjustments specified for modified Method B in subsection
(4)(c) of this section apply to modified Method C groundwater cleanup
levels.
(d)
Using Modified
Method C to evaluate groundwater remediation levels. In addition to the
adjustments allowed under (c) of this subsection, other adjustments to the
reasonable maximum exposure scenario or default exposure assumptions are
allowed when using a quantitative site-specific risk assessment to evaluate the
protectiveness of a remedy. See WAC
173-340-355,
173-340-357, and
173-340-708(3)(d) and
(10)(b).
(6)
Cleanup levels for nonpotable
groundwater.
(a)
Applicability. Groundwater cleanup levels may be established under
this subsection only if the contaminated groundwater is not classified as
potable under subsection (2) of this section.
(b)
Requirements. Cleanup levels
shall be established in accordance with either of the following:
(i) The methods specified in subsections (3),
(4) or (5) of this section, as applicable, for protection of drinking water
beneficial uses; or
(ii) A
site-specific risk assessment as provided for under (c) of this subsection for
protection of other groundwater beneficial uses.
(c)
Site-specific risk
assessment.
(i)
Method B
site-specific groundwater cleanup levels. Where a site-specific risk
assessment is used to establish a Method B ground-water cleanup level under
(b)(ii) of this subsection, the risk assessment shall conform to the
requirements in WAC
173-340-702 and
173-340-708. The risk assessment
shall evaluate all potential exposure pathways and groundwater uses at the
site, including potential impacts to persons engaged in site development or
utility construction and maintenance activities. The risk assessment shall
demonstrate the following:
(A) The cleanup
levels will meet any applicable state and federal laws (drinking water
standards are not applicable to these sites);
(B) The cleanup levels will result in no
significant acute or chronic toxic effects on human health as demonstrated by
not exceeding a hazard quotient of one for individual hazardous
substances;
(C) The cleanup levels
will result in an upper bound on the estimated excess cancer risk that is less
than or equal to one in 1,000,000 (1 [MULTIPLICATION]-
10-6) for individual hazardous substances;
(D) Fc hazardous substances and petroleum
products, the cleanup levels comply with the limitation on free product in
subsection (7)(d) of this section;
(E) The cleanup levels will not exceed the
surface water cleanup levels derived under WAC
173-340-730 at the groundwater
point of compliance or exceed the surface water or sediment quality standards
at any point downstream, unless it can be demonstrated that the hazardous
substances are not likely to reach surface water. This demonstration must be
based on factors other than implementation of a cleanup action at the site;
and
(F) Where it is demonstrated
that hazardous substances are not likely to reach surface water, the use of a
groundwater cleanup level less stringent than a surface water cleanup level
will not pose a threat to surface water through pathways that could result in
ground water affected by the site entering surface water (such as use of the
water for irrigation or discharges from foundation drains or utility
corridors).
(ii)
Method C site-specific groundwater cleanup levels.
(A)
Applicability. The
department may approve of a site-specific Method C groundwater cleanup level
derived under (b)(ii) of this subsection only at sites qualifying under WAC
173-340-706(1).
(B)
Requirements. Where a
site-specific risk assessment is used to establish a Method C groundwater
cleanup level under (b)(ii) of this subsection, the site-specific risk
assessment shall comply with the requirements in (c)(i) of this subsection
except that the level of risk for individual carcinogens shall be one in
100,000 (1 [MULTIPLICATION]- 10-5).
(iii)
Limitations on the use
of site-specific risk assessment. If the site-specific risk assessment
results in a Method B or Method C groundwater cleanup level that exceeds the
applicable potable ground-water cleanup level derived under (b)(i) of this
subsection, then the potable groundwater cleanup level shall be used unless the
following conditions are met:
(A) All
potentially affected property owners, local governments, Indian tribes and
water purveyors with jurisdiction in the area potentially affected by the
groundwater contamination have been provided a notice of the proposal and
provided an opportunity to comment. The notice shall specifically ask for
information on existing and planned uses of the groundwater. The notice shall
be in addition to any notice provided under WAC
173-340-600. In determining
whether it is appropriate to use a cleanup level less stringent than the
potable groundwater cleanup level, the department will give greater weight to
information based on an adopted or pending plan or similar preexisting
document.
(B) For sites where the
groundwater is classified as nonpotable under WAC
173-340-720(2)(d),
the cleanup action includes institutional controls complying with WAC
173-340-440 that will prevent the
use of contaminated groundwater for drinking water purposes at any point
between the source of hazardous substances and the point(s) of entry of
groundwater into the surface water.
(C) For sites where the risk assessment
includes assumptions of restricted use or contact with the groundwater (other
than for the reason of being nonpotable), or restricted use of the land above
the groundwater, the cleanup action includes institutional controls complying
with WAC 173-340-440 that will implement
the restrictions.
(7)
Adjustments to cleanup
levels.
(a)
Total site risk
adjustments. Groundwater cleanup levels for individual hazardous
substances developed in accordance with subsection (4), (5) or (6) of this
section, including those based on applicable state and federal laws, shall be
adjusted downward to take into account exposure to multiple hazardous
substances and/or exposure resulting from more than one pathway of exposure.
These adjustments need to be made only if, without these adjustments, the
hazard index would exceed one or the total excess cancer risk would exceed one
in 100,000 (1 [MULTIPLICATION]- 10-5). These
adjustments shall be made in accordance with the procedures in WAC
173-340-708(5) and
(6). In making these adjustments, the hazard
index shall not exceed one and the total excess cancer risk shall not exceed
one in 100,000 (1 [MULTIPLICATION]- 10-5).
(b)
Adjustments to applicable state and
federal laws. Where a cleanup level developed under subsection (3), (4),
(5), or (6) of this section is based on an applicable state or federal law and
the level of risk upon which the standard is based exceeds an excess cancer
risk of one in 100,000 (1 [MULTIPLICATION]- 10-5) or
a hazard index of one, the cleanup level be adjusted downward so that the total
excess cancer risk does not exceed one in 100,000 (1 [MULTIPLICATION]-
10-5) and the hazard index does not exceed one at
the site.
(c)
Natural
background and PQL considerations. Cleanup levels determined under
subsection (3), (4), (5), or (6) of this section, including cleanup levels
adjusted under subsection (7)(a) and (b) of this section, shall not be set at
levels below the practical quantitation limit or natural background
concentrations, whichever is higher. See WAC
173-340-707 and
173-340-709 for additional
requirements pertaining to practical quantitation limits and natural
background.
(d)
Nonaqueous
phase liquid limitation. For organic hazardous substances and total
petroleum hydrocarbons, the cleanup level determined under subsection (3), (4),
(5), or (6) shall not exceed a concentration that would result in nonaqueous
phase liquid being present in or on the groundwater. Physical observations of
groundwater at or above the cleanup level, such as the lack of a film, sheen,
or discoloration of the groundwater or lack of sludge or emulsion in the
groundwater, may be used to determine compliance with this
requirement.
(8)
Point of compliance.
(a)
Point of compliance defined. For groundwater, the point of
compliance is the point or points where the groundwater cleanup levels
established under subsection (3), (4), (5), or (6) of this section must be
attained for a site to be in compliance with the cleanup standards. Groundwater
cleanup levels shall be attained in all ground-waters from the point of
compliance to the outer boundary of the hazardous substance plume.
(b)
Standard point of compliance for
all sites. The standard point of compliance shall be established
throughout the site from the uppermost level of the saturated zone extending
vertically to the lowest most depth which could potentially be affected by the
site.
(c)
Conditional point
of compliance. Where it can be demonstrated under WAC
173-340-350 through
173-340-390 that it is not
practicable to meet the cleanup level throughout the site within a reasonable
restoration time frame, the department may approve a conditional point of
compliance that shall be as close as practicable to the source of hazardous
substances, and except as provided under (d) of this subsection, not to exceed
the property boundary. Where a conditional point of compliance is proposed, the
person responsible for undertaking the cleanup action shall demonstrate that
all practicable methods of treatment are to be used in the site
cleanup.
(d)
Off-property
conditional point of compliance. A conditional point of compliance shall
not exceed the property boundary except in the three situations described
below. In each of these three situations the person responsible for undertaking
the cleanup action shall demonstrate that, in addition to making the
demonstration required by (c) of this subsection, the following requirements
are met:
(i)
Properties abutting
surface water. Where the groundwater cleanup level is based on
protection of surface water beneficial uses under subsection (3), (4), (5), or
(6) of this section, and the property containing the source of contamination
directly abuts the surface water, the department may approve a conditional
point of compliance that is located within the surface water as close as
technically possible to the point or points where groundwater flows into the
surface water subject to the following conditions:
(A) It has been demonstrated that the
contaminated groundwater is entering the surface water and will continue to
enter the surface water even after implementation of the selected cleanup
action;
(B) It has been
demonstrated under WAC
173-340-350 through
173-340-390 that it is not
practicable to meet the cleanup level at a point within the groundwater before
entering the surface water, within a reasonable restoration time
frame;
(C) Use of a mixing zone
under WAC 173-201A-100 to demonstrate compliance with surface water cleanup
levels shall not be allowed;
(D)
Groundwater discharges shall be provided with all known available and
reasonable methods of treatment before being released into surface
waters;
(E) Groundwater discharges
shall not result in violations of sediment quality values published in chapter
173-204 WAC;
(F) Groundwater and
surface water monitoring shall be conducted to assess the long-term performance
of the selected cleanup action including potential bioaccumulation problems
resulting from surface water concentrations below method detection limits;
and
(G) Before approving the
conditional point of compliance, a notice of the proposal shall be provided to
the natural resource trustees, the Washington state department of natural
resources and the United States Army Corps of Engineers. The notice shall be in
addition to any notice provided under WAC
173-340-600 and invite comments
on the proposal.
(ii)
Properties near, but not abutting, surface water. Where the
groundwater cleanup level is based on protection of surface water beneficial
uses under subsection (3), (4), (5), or (6) of this section and the property
that is the source of the contamination is located near, but does not directly
abut, a surface water body, the department may approve a conditional point of
compliance that is located as close as practicable to the source, not to exceed
the point or points where the groundwater flows into the surface water.
For a conditional point of compliance to be approved under this provision the conditions specified in (d)(i) of this section must be met and the affected property owners between the source of contamination and the surface water body must agree in writing to the use of the conditional point of compliance. Also, if the groundwater cleanup level is not exceeded in the groundwater prior to its entry into the surface water, the conditional point of compliance cannot extend beyond the extent of groundwater contamination above the cleanup level at the time the department approves the conditional point of compliance.
(iii)
Area-wide conditional point of compliance. As part of remedy
selection, the department may approve an area-wide conditional point of
compliance to address an area-wide groundwater contamination problem. The
area-wide conditional point(s) of compliance shall be as close as practicable
to each source of hazardous substances, not to exceed the extent of groundwater
contamination at the time the department approves an area-wide conditional
point of compliance.
This provision may be applied only at areas that are affected by hazardous substances released from multiple sources that have resulted in commingled plumes of contaminated groundwater that are not practicable to address separately. A site may have more than one area-wide conditional point of compliance to address multiple sources and types of contaminants. An area-wide conditional point of compliance may be approved under this provision only if all of the following conditions have been met:
(A) The person conducting the cleanup action
has complied with WAC
173-340-350 through
173-340-390, including a
demonstration that it is not practicable to meet a point of compliance
throughout the groundwater contamination within a reasonable restoration time
frame;
(B) A plan has been
developed for implementation of the cleanup action, including a description of
how any necessary access to the affected properties will be obtained;
(C) If the contaminated groundwater is
considered to be potable under WAC
173-340-720(2),
current developments in the area encompassed by the area-wide conditional point
of compliance and any other areas potentially affected by the groundwater
contamination are served by a public water system that obtains its water from
an offsite source and it can be demonstrated that the water system has
sufficient capacity to serve future development in these areas. This
demonstration may be made by obtaining a written statement to this effect from
the water system operator;
(D) All
property owners, Indian tribes, local governments, and water purveyors with
jurisdiction in the area potentially affected by the groundwater contamination,
have been provided a notice of the proposal to establish an area-wide
conditional point of compliance and provided an opportunity to comment. The
notice shall specifically ask for information on existing and planned uses of
the ground-water. The notice shall be in addition to any notice provided under
WAC 173-340-600. The department will
give greater weight to information based on an adopted or pending plan or
similar preexisting document. When the department is providing technical
assistance under WAC
173-340-515, the department shall
also provide an opportunity to comment to the public through the
Contaminated Site Register before issuing a written
opinion.
(E) Other conditions as
determined by the department on a case-by-case
basis.
(e)
Monitoring wells and surface water compliance.
(i) The department may require or approve the
use of upland monitoring wells located between the surface water and the source
of contamination to establish compliance where a conditional point of
compliance has been established under subsection (8)(d)(i) or (ii) of this
section.
(ii) Where such monitoring
wells are used, the department should consider an estimate of natural
attenuation between the monitoring well and the point or points where
groundwater flows into the surface water in evaluating whether compliance has
been achieved.
(iii) When
evaluating how much, if any, natural attenuation will occur, the department
shall consider site-specific factors including:
(A) Whether the groundwater could reach the
surface water in ways that would not provide for natural attenuation within the
groundwater flow system (such as short circuiting through high permeability
zones, utility corridors or foundation drains); and
(B) Whether changes to the groundwater
chemistry due to natural attenuation processes would cause an exceedance of
surface water or sediment quality standards.
(9)
Compliance
monitoring.
(a) When groundwater
cleanup levels have been established at a site, sampling of the groundwater
shall be conducted to determine if compliance with the groundwater cleanup
levels has been achieved. Compliance with groundwater cleanup levels shall be
determined by analysis of groundwater samples representative of the
groundwater. Surface water analysis, bioassays or other biomonitoring methods
may also be required where the groundwater cleanup level is based on protection
of surface water. Sampling and analytical procedures shall be defined in a
compliance monitoring plan prepared under WAC
173-340-410. The sample design
shall provide data that are representative of the site.
(b) Analyses shall be conducted on unfiltered
groundwater samples, unless it can be demonstrated that a filtered sample
provides a more representative measure of groundwater quality. The department
expects that filtering will generally be acceptable for iron and manganese and
other naturally occurring inorganic substances where:
(i) A properly constructed monitoring well
cannot be sufficiently developed to provide low turbidity water
samples;
(ii) Due to the natural
background concentration of hazardous substances in the aquifer material,
unfiltered samples would not provide a representative measure of groundwater
quality; and
(iii) Filtering is
performed in the field with all practicable measures taken to avoid exposing
the groundwater sample to the ambient air before filtering.
(c) The data analysis and
evaluation procedures used to evaluate compliance with groundwater cleanup
levels shall be defined in a compliance monitoring plan prepared under WAC
173-340-410. These procedures
shall meet the following general requirements:
(i) Methods of data analysis shall be
consistent with the sampling design;
(ii) When cleanup levels are based on
requirements specified in applicable state and federal laws, the procedures for
evaluating compliance that are specified in those requirements shall be used to
evaluate compliance with cleanup levels unless those procedures conflict with
the intent of this section;
(iii)
Where procedures for evaluating compliance are not specified in an applicable
state and federal law, statistical methods used shall be appropriate for the
distribution of sampling data for each hazardous substance. If the
distributions for hazardous substances differ, more than one statistical method
may be required;
(iv) Compliance
with groundwater cleanup levels shall be determined for each groundwater
monitoring well or other monitoring points such as a spring;
(v) The data analysis procedures identified
in the compliance monitoring plan shall specify the statistical parameters to
be used to determine compliance with groundwater cleanup levels.
(A) For cleanup levels based on short-term or
acute toxic effects on human health or the environment, an upper percentile
concentration shall be used to evaluate compliance with groundwater cleanup
levels.
(B) For cleanup levels
based on chronic or carcinogenic threats, the true mean concentration shall be
used to evaluate compliance with groundwater cleanup levels.
(vi) When active groundwater
restoration is performed, or containment technologies are used that incorporate
active pumping of groundwater, compliance with groundwater cleanup levels shall
be determined when the groundwater characteristics at the site are no longer
influenced by the cleanup action.
(d) When data analysis procedures for
evaluating compliance are not specified in an applicable state or federal law,
the following procedures shall be used:
(i) A
confidence interval approach that meets the following requirements:
(A) The upper one-sided 95 percent confidence
limit on the true mean groundwater concentration shall be less than the
groundwater cleanup level. For lognormally distributed data, the upper
one-sided 95 percent confidence limit shall be calculated using Land's method;
and
(B) Data shall be assumed to be
lognormally distributed unless this assumption is rejected by a statistical
test. If a lognormal distribution is inappropriate, data shall be assumed to be
normally distributed unless this assumption is rejected by a statistical test.
The W test, D'Agostino's test, or, censored probability plots, as appropriate
for the data, shall be the statistical methods used to determine whether the
data is lognormally or normally distributed.
(ii) Evaluations conducted under subsection
(9)(c)(v)(A) of this subsection may use a parametric test for percentiles based
on tolerance intervals to test the proportion of groundwater samples having
concentrations less than the groundwater cleanup level. When using this method,
the true proportion of samples that do not exceed the groundwater cleanup level
shall not be less than 90 percent. Statistical tests shall be performed with a
Type I error level of 0.05; or
(iii) Other statistical methods approved by
the department.
(e) All
data analysis methods used, including those specified in state or federal law,
must meet the following requirements:
(i) No
single sample concentration shall be greater than two times the groundwater
cleanup level. Higher exceedances to control false positive error rates at five
percent may be approved by the department when the cleanup level is based on
background concentrations; and
(ii)
Less than 10 percent of the sample concentrations shall exceed the groundwater
cleanup level during a representative sampling period. Higher exceedances to
control false positive error rates at five percent may be approved by the
department when the cleanup level is based on background concentrations;
and
(f) When using
statistical methods to demonstrate compliance with groundwater cleanup levels,
the following procedures shall be used for measurements below the practical
quantitation limit:
(i) Measurements below the
method detection limit shall be assigned a value equal to one-half the method
detection limit when not more than 15 percent of the measurements are below the
practical quantitation limit.
(ii)
Measurements above the method detection limit but below the practical
quantitation limit shall be assigned a value equal to the method detection
limit when not more than 15 percent of the measurements are below the practical
quantitation limit.
(iii) When
between 15 and 50 percent of the measurements are below the practical
quantitation limit and the data are assumed to be lognormally or normally
distributed, Cohen's method shall be used to calculate a corrected mean and
standard deviation for use in calculating an upper confidence limit on the true
mean ground-water concentration.
(iv) If more than 50 percent of the
measurements are below the practical quantitation limit, the largest value in
the data set shall be used in place of an upper confidence limit on the true
mean groundwater calculation.
(v)
If a hazardous substance or petroleum fraction has never been detected in any
sample at a site and these substances are not suspected of being present at the
site based on site history and other knowledge, that hazardous substance or
petroleum fraction may be excluded from the statistical analysis.
(vi) The department may approve alternate
statistical procedures for handling nondetected values or values below the
practical quanti-tation limit.
Notes
Reviser's note: The brackets and enclosed material in the text of the above section occurred in the copy filed by the agency and appear in the Register pursuant to the requirements of RCW 34.08.040.
Statutory Authority: Chapter 70.105D RCW. 01-05-024 (Order 97-09A), § 173-340-720, filed 2/12/01, effective 8/15/01; 91-04-019, § 173-340-720, filed 1/28/91, effective 2/28/91.
Reviser's note: The brackets and enclosed material in the text of the above section occurred in the copy filed by the agency.
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