Current through Register Vol. 63, No. 12, December 1, 2024
(1) If data collected during the initial site
characterization do not identify the full nature, magnitude, and extent of soil
and groundwater contamination, the responsible person must conduct an
investigation for this purpose.
(a) The areal
and vertical extent of soil contamination must be determined.
(b) The areal extent of groundwater
contamination must be determined, including an estimate of groundwater velocity
and flow direction.
(c)
Representative samples of all affected media must be analyzed for reasonably
likely contaminants of concern based on the nature of the release and
applicable remedial options under OAR
340-122-0217.
(d) Expedited site assessment tools (e.g.,
push-probe samplers) may be used to provide a preliminary measure of the
magnitude and extent of groundwater contamination.
(e) If groundwater contamination appears to
have migrated beyond the immediate vicinity of the tank pit, additional
groundwater investigation must be performed in accordance with section (2) of
this rule unless the responsible person can demonstrate to the Department that
the contamination presents no potential threat to human health or the
environment.
(2)
Groundwater investigations required by section (1) of this rule, and
groundwater monitoring under corrective action plans required by OAR
340-122-0250 must be carried out
as follows:
(a) Groundwater monitoring
systems must include a minimum of one hydraulically upgradient and two
hydraulically downgradient groundwater monitoring wells, capable of adequately
characterizing both site hydrogeology and the vertical and horizontal magnitude
and extent of groundwater contamination. Additional monitoring wells may be
required by the Department if necessary to adequately characterize the site or
to establish compliance monitoring points. All monitoring wells must be
designed, completed and, when appropriate, removed according to the Water
Resources Department's administrative rules, OAR
690-240-0005 through
690-240-0180 (Construction and
Maintenance of Monitoring Wells and Other Holes in Oregon).
(b) When the installation of monitoring wells
is impractical due to specific site conditions, the responsible person must
notify the Department and develop an alternative course of action which must be
approved by the Department.
(c)
Groundwater sampling events must meet the following minimum requirements:
(A) Initially, samples must be collected at
quarterly intervals. After four consecutive quarters of groundwater monitoring,
if site conditions warrant more or less frequent sampling, an alternative
sampling schedule may be proposed;
(B) Water elevation measurements must be made
in all monitoring wells during each sampling event, unless the Department has
approved measurements from a reduced number of wells that provide sufficient
data for the determination of the groundwater flow direction;
(C) Formal chain-of-custody records must be
prepared and maintained for each sample; and
(D) All sampling events for purposes of
identifying contaminants of concern, or for verifying either preliminary
compliance or final compliance, must include adequate quality assurance and
quality control (QA/QC) measures.
(3) The responsible person shall submit the
information collected under sections (1) and (2) of this rule to the Department
within 45 days of completing field work, or within a longer period of time
approved by the Department. Groundwater monitoring reports must be submitted
after each monitoring event unless an alternative schedule has been approved by
the Department, and must contain the following information:
(a) A site map, drawn to scale, showing the
location of all monitoring wells and the direction of groundwater
flow;
(b) A summary of all
sampling, handling, and chain-of-custody procedures followed, including, as
appropriate, a discussion of any routine maintenance procedures performed
during the quarter and any problems encountered (e.g., failure of a pump,
clogging of a well screen, an unexplained change in the quality of the water,
or any other unusual event) and what actions were taken, or will be taken, in
response to such occurrences;
(c) A
summary of the analytical data, including QA/QC results for the sampling
event;
(d) Water elevation
measurements from each monitoring well, unless the Department approves
elevation measurements from a reduced number of wells; and
(e) A written evaluation of data, describing
trends or other pertinent information derived from the sampling event, and
specifying the method or methods of statistical analysis used to describe the
significance of these trends.
Stat. Auth.: ORS
465.400 & ORS
466.746
Stats. Implemented: ORS
465.200 - ORS
465.455 & ORS
466.706 - ORS
466.835
