Oklahoma Administrative Code › Title 785 - Oklahoma Water Resources Board › Chapter 35 - Well Driller and Pump Installer Licensing › Subchapter 11 - Plugging and Capping Requirements for Wells and Test Holes › Section 785:35-11-2 - Plugging requirements for site assessment observation wells, monitoring wells and geotechnical borings

Current through Vol. 41, No. 20, July 1, 2024
(a)
Monitoring wells, direct push monitoring wells and site
										assessment observation wells.
Monitoring wells, direct push monitoring wells and site assessment
										observation wells shall be plugged to prevent pollution of groundwater within three (3) days after completion
										of use or immediately if drilled by an unlicensed or uncertified person or if the Board determines that the
										well does not meet the minimum construction standards set forth in this Chapter. The following are minimum
										requirements for plugging monitoring wells and site assessment observation wells, and the owner of such wells
										or other federal or state agency may specify more stringent requirements:
(1) If no contaminated soil or contaminated groundwater is present in the
										well, cement grout shall be placed in the well through a tremie pipe and filled or pumped from the bottom of
										the well to an elevation four (4) feet below the land surface. In the alternative, bentonite pellets,
										granules or high solids (a minimum of twenty percent (20%) solids by dry weight) bentonite grout shall be
										placed from the bottom of the well to an elevation fourteen (14) feet below land surface and a minimum of ten
										(10) feet shall be filled with cement grout to an elevation four (4) feet below land surface, unless
										contaminated soil or contaminated groundwater is present in the well. The remaining four (4) feet to land
										surface shall be backfilled with compacted uncontaminated soil. If the depth of the well is fourteen (14)
										feet or less, cement grout shall be placed from the bottom of well to land surface.
(2) If contaminated soil or contaminated groundwater is present or was
										previously present in the well and the top of the screen is less than 20 feet below land surface,
										overdrilling of the well is required. The casing shall be removed or drilled out and the same size auger used
										to drill the borehole or larger shall be used to drill out the casing and associated seals, annular space and
										filter pack. Cement grout shall be placed from the bottom of the well to an elevation four (4) feet below
										land surface effectively grouting a minimum of 95% of the original drilled borehole depth. If the total depth
										of the well is in excess of twenty feet (20') below land surface, the cement grout shall be placed by pumping
										from the bottom of the hole to within four (4) feet of the land surface. If the top of the well screen is 20
										feet or more below land surface and the well meets current minimum construction standards, then the casing
										need not be removed and cement grout shall be placed in the well through a tremie pipe and filled or pumped
										from the bottom upward to within four (4) feet of land surface. The remaining four (4) feet to land surface
										shall be backfilled with compacted uncontaminated soil.