Or. Admin. Code § 340-122-0240

Current through Register Vol. 63, No. 12, December 1, 2024

Section 340-122-0240 - Investigation for Magnitude and Extent of Contamination

(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.

Or. Admin. Code § 340-122-0240

DEQ 29-1988, f. & cert. ef. 11-9-88; DEQ 13-1992, f. 6-9-92, cert. ef. 10-1-92; DEQ 23-1998, f. & cert. ef. 11-2-98

Stat. Auth.: ORS 465.400 & ORS 466.746

Stats. Implemented: ORS 465.200 - ORS 465.455 & ORS 466.706 - ORS 466.835