Washington Administrative Code
Title 173 - Ecology, Department of (See also Titles 197, 317, 372, and 508)
Chapter 173-351 - Criteria for municipal solid waste landfills
Section 173-351-405 - Performance standards for groundwater monitoring system designs
Current through Register Vol. 24-06, March 15, 2024
Groundwater monitoring well placement.
The groundwater monitoring system design must meet the following performance criteria:
(1) A sufficient number of wells must be installed at appropriate locations and depths to yield representative groundwater samples from those hydrostratigraphic units which have been identified as the earliest target hydraulic pathways and conduits of flow for groundwater and contaminant movement, and storage.
(2) The number, spacing, and depths of monitoring wells must be based on the site characteristics including the area of the MSWLF unit and the hydrogeological characterization of WAC 173-351-490, and requires a demonstration based on all of the following information:
(3) Hydraulically placed upgradient wells (background wells) must meet the following performance criteria:
(4) Hydraulically placed down-gradient wells (compliance wells) must meet the following performance criteria:
(5) All monitoring wells must be cased in a manner that maintains the integrity of the bore hole. This casing must be screened or perforated and packed with gravel or sand, where necessary, to enable collection of samples. The annular space between the bore hole and well casing above the sampling depth must be sealed to prevent corruption of samples and contamination of groundwater. All wells must be constructed in accordance with chapter 173-160 WAC, Minimum standards for construction and maintenance of water wells and chapter 173-162 WAC, Regulation and licensing of well contractors and operators. All wells must be clearly labeled, capped, and locked.
(6) The owner or operator must apply for a permit modification under WAC 173-351-720(6) or must apply during the renewal process of WAC 173-351-720(5), for any proposed changes to the design, installation, development, and decommission of any monitoring wells, piezometers, and other measurement, sampling, and analytical devices. Upon completing changes, all documentation, including date of change, new well location maps, boring logs, and well diagrams must be submitted to the jurisdictional health department and must be placed in the operating record of WAC 173-351-200(10).
(7) All monitoring wells, piezometers, and other measurement, sampling, and analytical devices must be operated and maintained so that they perform to design specifications throughout the life of the monitoring program.
(8) The groundwater monitoring system and hydrogeologic report including any changes to the groundwater monitoring system must be prepared by a geologist or other licensed professional in accordance with the requirements of chapter 18.220 RCW, Geologists.
(9) The groundwater monitoring system design and hydrogeologic report must be made a part of the permit application in accordance with WAC 173-351-730(1)(b)(iii).
Statutory Authority: RCW 70.95.020(3), 70.95.060(1), and 70.95.260(1), (6). 12-23-009 (Order 07-15), § 173-351-405, filed 11/8/12, effective 12/9/12. Statutory Authority: Chapter 70.95 RCW and 40 CFR 258. 93-22-016, § 173-351-405, filed 10/26/93, effective 11/26/93.