SECTION 785:35-11-2. Plugging requirements for site assessment observation wells, monitoring wells and geotechnical borings  


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  • (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.
    (b)   Geotechnical borings except direct push geotechnical borings. Geotechnical borings shall be plugged to prevent pollution of groundwater within thirty (30) days after completion of drilling 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 geotechnical borings, and the owner of the boring or other federal or state agency may specify more stringent requirements:
    (1)   If no contaminated soil and groundwater is encountered in the boring, uncontaminated drill cuttings, uncontaminated surface clay, cement, and/or high solids (a minimum of twenty percent (20%) solids by dry weight) bentonite grout, pellets, or granules shall be placed from the bottom of the boring 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. The remaining four (4) feet to land surface shall be backfilled with compacted uncontaminated soil.
    (2)   If contaminated soil or contaminated groundwater is encountered in the boring, or if the boring is located at an underground storage tank site or within 300 feet of the outside perimeter of an existing wastewater lagoon or is located on a tract of land where a wastewater lagoon is proposed, cement grout shall be placed from the bottom of the borehole to an elevation four (4) feet below land surface. Cement grout shall be placed in the borehole through a tremie pipe and filled or pumped from the bottom upward. The remaining four (4) feet to land surface shall be backfilled with compacted uncontaminated soil.
    (3)   If the boring is twenty (20) feet or less in total depth and groundwater has not been encountered, the boring shall, at a minimum, be filled with compacted uncontaminated cuttings from the bottom of the boring to land surface.
    (c)   Direct push geotechnical borings. Direct push geotechnical borings shall be plugged to prevent pollution of groundwater within thirty (30) days after completion of drilling 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 as follows:
    (1)   Bentonite chips shall be placed and effectively compressed within the annulus space from the bottom of the borehole to within ten (10) feet of the land surface.
    (2)   Cement grout shall be installed through a tremie pipe in the remaining annulus space from ten (10) feet to land surface, provided that no cement grout shall be required if the boring is less than ten feet (10') in total depth and no groundwater and no contaminated soil was encountered.
    (d)   Cement grout requirements. If cement grout is used, the grout shall have a mix ratio of one 94 pound sack of cement to a maximum of six U.S. gallons of water.
    (e)   Abandonment after equipment removed. If a site assessment observation well, monitoring well or geotechnical boring is abandoned after the drilling equipment has been removed from the site, responsibility for proper plugging within the applicable time period specified in this section shall lie with the owner of the land where the well or boring is located
[Source: Revoked and reenacted at 9 Ok Reg 1679, eff 5-11-92; Amended at 10 Ok Reg 3299, eff 6-25-93; Amended at 11 Ok Reg 2947, eff 6-13-94; Amended at 12 Ok Reg 2703, eff 7-1-95; Amended at 15 Ok Reg 2440, eff 6-11-98; Amended at 16 Ok Reg 2686, eff 7-1-99; Amended at 19 Ok Reg 2498, eff 6-27-02; Amended at 20 Ok Reg 2608, eff 7-11-03; Amended at 21 Ok Reg 2632, eff 7-1-04; Amended at 22 Ok Reg 1598, eff 7-1-05; Amended at 23 Ok Reg 3078, eff 7-27-06; Amended at 25 Ok Reg 1444, eff 5-27-08; Amended at 27 Ok Reg 1313, eff 5-27-10; Amended at 30 Ok Reg 891, eff 6-13-13]