Current through Register Vol. 24-06, March 15, 2024
(1) Detection monitoring must be conducted at
MSWLF units at all groundwater monitoring wells required under WAC
173-351-405. At a minimum, a
detection monitoring program must include monitoring for the constituents
listed in Appendix I and II of this regulation.
(2) Background data.
(a) Background data development for new MSWLF
units.
(i) A minimum of eight independent
samples must be collected from each monitoring well and analyzed for Appendix I
constituents for the first year of groundwater monitoring unless background
data already exists for Appendix I constituents and performance criteria of WAC
173-351-400 are met.
(ii) Each independent sampling event must be
no less than one month apart from the previous independent sampling
event.
(iii) Sampling for Appendix
II parameters must be done quarterly.
(b) Total metals background data development
for existing MSWLF units.
(i) An owner or
operator must follow the permit modification process in WAC
173-351-720(6)
to amend the sampling and analysis program to address (b)(ii) and (iii) of this
subsection by May 31, 2013. Amendments must meet the standards of WAC
173-351-410(1) and
(2).
(ii) Beginning at the first sampling event
after jurisdictional health department approval of amendments to the sampling
and analysis program in (b)(i) of this subsection, independent samples must be
collected from each monitoring well and analyzed for the parameters in (ii)(A)
and (B) of this subsection. Samples must be collected and analyzed over eight
sampling periods, which may be quarterly or semi-annually to coincide with
routine monitoring as approved by the jurisdictional health department.
(A) Total metals from Appendix I Inorganic
Constituents 1-15.
(B) Dissolved
metals:
Antimony (Dissolved).
Arsenic (Dissolved).
Barium (Dissolved).
Beryllium (Dissolved).
Cadmium (Dissolved).
Chromium (Dissolved).
Cobalt (Dissolved).
Copper (Dissolved).
Lead (Dissolved).
Nickel (Dissolved).
Selenium (Dissolved).
Silver (Dissolved).
Thallium (Dissolved).
Vanadium (Dissolved).
Zinc (Dissolved).
(iii) After collecting and analyzing samples
for total and dissolved metals for eight sampling periods, collection and
analysis of Appendix I Inorganic Constituents 1-15 (total metals) must continue
and collection and analysis of dissolved metals under (b)(ii)(B) of this
subsection can cease.
(3) Routine sampling. Except as allowed under
WAC 173-351-450, the monitoring
frequency for all constituents listed in Appendix I and II must be quarterly in
each well during the active life of the MSWLF unit including the closure and
the post-closure period and begins after background data development.
(4) If the owner or operator determines,
pursuant to WAC
173-351-420, that there is a
statistically significant increase over background for one or more of the
constituents listed in Appendix I, at any monitoring well at the boundary
specified under WAC
173-351-405, the owner or
operator:
(a) Must, within fourteen days of
this finding, place a notice in the operating record indicating which
constituents have shown statistically significant changes from background
levels, and send the same notice to the jurisdictional health department and
the department; and
(b) Must
establish an assessment monitoring program meeting the requirements of
WAC-173-351-440 within ninety days except as provided for in (c) of this
subsection; or
(c) May demonstrate
that a source other than a MSWLF unit caused the contamination or that the
statistically significant increase resulted from error in sampling, analysis,
statistical evaluation, or natural variation in groundwater quality. A report
documenting this demonstration must be prepared by a geologist or other
licensed professional in accordance with the requirements of chapter 18.220
RCW, Geologists, and approved by the jurisdictional health department and be
placed in the operating record. If a successful demonstration is made and
documented, the owner or operator may continue detection monitoring as
specified in this section. If, after ninety days, a successful demonstration is
not made, the owner or operator must initiate an assessment monitoring program
as required in WAC
173-351-440.
(5) A geochemical evaluation of Appendix II
parameters must be conducted at each well on a quarterly basis and include all
of the following methods:
(a) A cation-anion
balance evaluating the difference between the cation and anion sums expressed
in milliequivalents per liter. If the following threshold limits are exceeded,
the owner or operator must provide a summary explanation and examine whether
the difference is due to a laboratory error, poor well conditions, or other
ions not accounted for in natural or impacted groundwater conditions. A ten
percent difference threshold is used if the total cation-anion sums are less
than 5.0 meq/liter. A five percent difference threshold is used if the total
cation-anion sums are greater than or equal to 5.0 meq/liter.
(b) A plot of cations and anions for each
well on a trilinear diagram, as recommended in hydrogeologic texts and/or the
department guidance documents.
Statutory Authority:
RCW
70.95.020(3),
70.95.060(1), and
70.95.260(1),
(6). 12-23-009 (Order 07-15), §
173-351-430, filed 11/8/12, effective 12/9/12. Statutory Authority:
Chapter
70.95 RCW and 40 CFR 258.
93-22-016, § 173-351-430, filed 10/26/93, effective
11/26/93.