OAR 690-240-0510: Abandonment of Monitoring Wells

Proper abandonment of monitoring wells will prevent both vertical movement of water within the well bore and infiltration of surface water into the well: (1) In areas where groundwater contamination has been identified, except as described in number (4) below, abandonment shall require the borehole to be completely redrilled to a minimum of the original diameter. All casing, screen, annular sealing material, drill cuttings, debris, and filter pack material shall be removed prior to sealing. (2) In areas where groundwater contamination has not been identified, if it can be verified that the monitoring well was constructed in accordance with these rules, it shall be abandoned by filling the well from the bottom up with an approved sealant as described in OAR 690-240-0475. The casing shall then be removed below grade, as compatible with local site conditions and land practices. The following are acceptable methods of original well construction verification: (a) A well report in accordance with OAR 690-240-0395; (b) Well construction information submitted to the Oregon Department of Environmental Quality; (c) Information obtained through down-hole geophysical logging; or (d) Other information as approved by the Water Resources Department. (3) In areas where groundwater contamination is not present, and if the monitoring well construction cannot be verified by means listed in section (2) of this rule, the well shall be abandoned according to section (1) of this rule. (4) In contaminated areas where remediation has occurred, an approved special standard is required to abandon a well unless it is abandoned according to section (1) of this rule. Abandonment procedures will be considered on a case by case basis. The Department will consult with the state or federal agency that supervised the remediation in determining the appropriate abandonment method. In cases where there was no agency oversight, the Department will consider any information supplied by the licensed and bonded Monitoring Well Constructor in determining the appropriate abandonment procedure. (5) Grout slurries shall be placed from the bottom up by a grout pipe to avoid segregation or dilution of the sealant. The discharge end of the grout pipe shall be submerged in the grout to avoid breaking the seal while filling the annular space. Grout slurries used to abandon monitoring wells shall conform to the requirements of OAR 690-240-0475. (6) The abandonment procedure shall be recorded on a form provided by or previously approved in writing by the Department. The form shall include, as a minimum, all the requirements as listed in OAR 690-240-0395, plus: (a) Method of abandonment; (b) If assigned, the well identification number, original start card number, and owner's well number of the abandoned well. (7) When abandoning artesian monitoring wells, in addition to sections (1)-(6) of this rule, the flow shall be confined or restricted by cement grout applied under pressure, or by the use of a suitable well packer, or a wooden plug placed at the bottom of the confining interval immediately above the artesian water bearing zone. An approved grout shall be used to fill the well to land surface as specified in OAR 690-240-0475. (8) Monitoring wells that were constructed under special standards will require the abandonment method to be approved by the Department.