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Groundwater Monitoring Well Drilling, Construction and Decommissioning

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Groundwater Monitoring Well Drilling, Construction and Decommissioning GROUNDWATER MONITORING WELL DRILLING, CONSTRUCTION, AND DECOMMISSIONING DEQ GUIDANCE DOCUMENT D1 D2 Filter-Pack Seal WATER LEVEL IN WELL H H1 2 August 24, 1992 D3 PRINTED ON RECYCLED PAPER This page intentionally left blank. NOTE This is a reprint of a Department of Environmental Quality guidance document that was first issued on August 24, 1992. Although the format has been updated, the contents of the document have not been changed. The original document was approved for use by: Stephanie Hallock Division Administrator Hazardous and Solid Waste Division* Mike Downs Division Administrator Environmental Cleanup Division Lydia Taylor Division Administrator Water Quality Division * The Hazardous and Solid Waste Division is now the Waste Prevention and Management Division. i This page intentionally left blank. ii TABLE OF CONTENTS 1.0 INTRODUCTION ............................................................................................................................... 1 2.0 APPLICABILITY OF GUIDELINES ; DISCLAIMER; RELATIONSHIP TO OAR CHAPTER 690, DIVISION 240 .................................................................................................................................. 1 3.0 DEFINITIONS ................................................................................................................................... 2 4.0 DESIGN OF MONITORING WELLS AND SUPERVISION OF CONSTRUCTION; DEPARTMENT REVIEW OF WORK PLANS .................................................................................................................................. 7 5.0 MONITORING WELL DRILLING AND CONSTRUCTION ...................................................................... 7 5.1 Well Placement and Protection ............................................................................................................................................7 5.2 Drilling And Sampling...........................................................................................................................................................8 5.3 Monitoring Well Construction ...........................................................................................................................................11 5.4 Well Development................................................................................................................................................................16 5.5 Field Testing of Hydraulic Conductivity..........................................................................................................................17 5.6 Location and Elevation Survey...........................................................................................................................................17 6.0 MONITORING WELL DECOMMISSIONING ...................................................................................... 17 6.1 Introduction ...........................................................................................................................................................................17 6.2 Decommissioning Procedures ............................................................................................................................................18 7.0 GROUTING .................................................................................................................................... 19 7.1 Introduction ...........................................................................................................................................................................19 7.2 Grout Slurries ........................................................................................................................................................................20 7.3 Grouting with Unhydrated Sodium Bentonite.................................................................................................................21 8.0 WELL CONSTRUCTION AND DECOMMISSIONING DOCUMENTATION............................................... 22 8.1 Well Construction Report....................................................................................................................................................22 8.2 Well Decommissioning Report ..........................................................................................................................................24 9.0 EXCEPTIONS FROM GUIDELINES FOR PIEZOMETERS ..................................................................... 25 10.0 SPECIAL CIRCUMSTANCES AND EXCEPTIONS .......................................................................... 25 FIGURE 1: TYPICAL MONITORING WELL CONSTRUCTION ................................................................. 26 FIGURE 2: CALCULATION OF WELL VOLUMES ................................................................................... 27 TABLE 1: WELL CASING AND ANNULAR SPACE VOLUMES ................................................................. 28 TABLE 2: WATER CONTENT AND MUD WEIGHT OF CEMENT-BENTONITE GROUT MIXTURES ........... 28 REFERENCES .................................................................................................................................... 29 APPENDIX A: REQUIREMENTS FOR DESIGN APPROVAL ...................................................................... 31 APPENDIX B: CALCULATION OF WELL BORING VOLUME.................................................................. 32 APPENDIX C: SUBMITTAL REQUIREMENTS FOR DEPARTMENT CONSIDERATION AND APPROVAL OF SPECIAL STANDARDS FOR MONITORING, WELL CONSTRUCTION, ALTERATION, OR DECOMMISSIONING....................................................................................................................... 33 iii This page intentionally left blank. iv Oregon Department of Environmental Quality – Monitoring Well Guidance 1.0 INTRODUCTION These Guidelines have been developed by the Department of Environmental Quality (DEQ) in recognition of the need for uniform standards regarding the drilling, construction and decommissioning of groundwater monitoring wells. The technique used to install a groundwater monitoring well can influence the accuracy and reliability of: (1) Water quality samples obtained from the well, (2) Information on the position of the water table or potentiometric surface, or (3) Test results to determine physical properties of the aquifer, such as hydraulic conductivity. An improperly constructed well may produce water samples that do not accurately reflect the chemical composition of the water, or may yield data that is not representative of the physical properties of the aquifer. An improperly constructed or abandoned well can act as a conduit for the migration of contaminants from the surface into a water-bearing zone, or between water-bearing zones in the well. Proper monitoring well design and construction: (1) Includes consideration of, and is compatible with, site specific hydrogeologic conditions, including site stratigraphy and the physical and chemical properties of the groundwater and any contaminants known or suspected to be present in site soils or groundwater; (2) Allows collection of accurate and representative water quality samples; (3) Maximizes well efficiency, while minimizing sediment or turbidity in water samples; (4) Prevents introduction of surface water or contaminants into groundwater; (5) Prevents vertical movement of water or contaminants between water-bearing zones in either the well bore or well annulus; (6) Prevents waste or contamination of groundwater resources; and (7) Results in permanent wells which will last for the duration of the monitoring period, including any post-closure monitoring requirements. 2.0 APPLICABILITY OF GUIDELINES ; DISCLAIMER; RELATIONSHIP TO OAR CHAPTER 690, DIVISION 240 These Guidelines apply to the installation and abandonment (decommissioning) of monitoring wells, piezometers and exploratory borings at facilities requiring hydrogeologic site characterization and/or groundwater monitoring pursuant to a DEQ operating permit or other DEQ regulatory authority. These facilities include, but are not limited to, solid and hazardous waste storage, treatment or disposal facilities, sewage treatment and storage facilities, wastewater treatment and storage facilities, underground storage tank installations or cleanup projects, sites being evaluated or cleaned up under the authority and oversight of the State Environmental Cleanup Program, or area-wide non-point source groundwater pollution monitoring. These Standards are intended solely as guidance for employees of the DEQ. They do not constitute rule making by the Environmental Quality Commission (EQC) and may not be relied upon to create a right or benefit, substantive or procedural, enforceable at law or in equity, by any person. The DEQ may take action at variance with these Standards. -1- Oregon Department of Environmental Quality – Monitoring Well Guidance On August 3, 1990, the Water Resources Commission (WRC) adopted Administrative Rules OAR Chapter 690, Division 240, effective January 1, 1991, relating to monitoring well construction and monitoring well constructor licensing. Concepts, definitions and procedures described in these Guidelines may differ from those in OAR Chapter 690, Division 240. Compliance with or use of these Guidelines does not waive compliance with OAR Chapter 690, Division 240. 3.0 DEFINITIONS Annular Space, Annulus or Well Annulus: The space between the well casing and borehole wall, or between two concentric casings. Annular Seal:
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