WAC 173-351-430
Detection monitoring program. (1)
Detection monitoring is required at MSWLF units at all
groundwater monitoring wells defined under WAC 173-351-405. At a minimum, a detection monitoring program must include the
monitoring for the constituents listed in Appendix I and II of
this regulation.
(2) Background data development.
(a) A minimum of eight independent samples shall be
collected for each well (background and downgradient) and must
be collected and analyzed for the Appendix I constituents for
the first year of groundwater monitoring.
(b) Each independent sampling event shall be no less than
one month apart from the previous independent sampling event.
(c) Sampling for Appendix II parameters shall be done
quarterly.
(d) MSWLF units which have previously developed
background for those constituents listed in Appendix I will be
waived from (a) of this subsection on a parameter by parameter
basis providing all performance criteria of WAC 173-351-400
are met.
(3) Foreground data development. The monitoring
frequency for all constituents listed in Appendix I and II
shall be quarterly during the active life of the MSWLF unit
including closure and the post-closure period and begins after
the first year of background data development, for all
monitoring wells (upgradient and downgradient).
Note:
Foreground denotes the period of time following the development of the back ground data set, for all monitoring wells
(upgradient and downgradient).
(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;
(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;
(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 hydrogeologist or other qualified groundwater
scientist 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; and
(d) Must submit the assessment monitoring program to the
jurisdictional health department at the end of ninety days as
provided in (b) of this subsection.
(5) A geochemical evaluation of Appendix II parameters
shall 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 a greater than a five to ten
percent difference occurs then the owner or operator shall
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; if the total cation-anion sums are
less than 5.0 meq/liter then a ten percent difference
threshold, may be used.
(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.