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2 <br />(ii) It should contain no chemicals or substances which have toxic properties, <br />(iii) It should contain no chemicals or substances which may decompose in the <br />hole to produce toxic properties, <br />(iv) It should contain no flocculating agent, <br />(v) The liquid phase of the mud should be non-saline water with no oil or other <br />soluble substances that would be toxic if ingested, in the concentration present in the liquid phase. <br />(c) The abandonment mud should be placed in the hole by pumping through the drilling <br />pipe, or equivalent, to totally displace any fluid in the hole. Injections should cease when the hole is filled <br />with abandonment mud and recirculation of the abandonment mud should be avoided. <br />(d) Following the injection of the abandonment mud, a non-slip hole plug should be <br />installed in the drill hole and a minimum 5 foot column of Portland cement concrete placed atop the non-slip <br />plug. The top of the Portland cement concrete plug should be at a minimum depth compatible with local <br />cultivation practices, or at a minimum of 2 feet below either the original land surface, or the collar of the <br />hole, whichever is the lower elevation. <br />(e) Following the setting of this Portland cement concrete plug, the remainder of the <br />drill hole can be backfilled as described in Section 5.41(3) of the regulations. <br />(f) If the operator so elects, aquifers encountered in volcanic or sedimentary rock may <br />be sealed in accordance with the artesian zone interval grouting procedures described in Section 5.41(1) of <br />the regulations. <br />(3) Permanent abandonment of any drill hole which is limited to unconsolidated material and <br />less than 10 feet of penetration into bedrock: <br />(a) Any drill hole limited to unconsolidated material and less than 10 feet of penetration <br />into bedrock, should be backfi lied with materials removed from the drill hole. If the materials removed from <br />the hole during drilling are inadequate to backfill the drill hole, materials representative of the undisturbed <br />unconsolidated materials should be backfilled into the drill hole. <br />(4) Permanent abandonment of any drill hole which penetrates saturated unconsolidated <br />materials and continues more than 10 feet into bedrock: <br />(a) The .segment of the drill hale from the bottom to a paint 5 feet below the contact of <br />the bedrock with the overlying unconsolidated materials should be abandoned by the methods described in <br />5.41(2ya), (b) and (c). A non-slip hole plug topped by a Portland cement concrete column should be <br />installed from the top of the abandonment mud seal to the level of the contact. `rhe remainder of the drill <br />hole can be backfilled as described in 5.41(3) of the regulations.