All wells shall be grouted in accordance with this regulation. Time Limits. All wells shall be grouted as soon as possible but not later than 24 hours after the well casing has been set in place in Hydrogeological Area’s 1 & 2. In Hydrogeological Area’s 3, 4 & 5 all wells shall be grouted within 72 hours after the permanent casing has been set. After grouting is completed, there shall be a minimum curing time before drilling may be resumed of: 18 hours for Type I and Type II Portland cement; and 12 hours for Type III Portland cement. Grouting Materials. Cement. The annular space may be filled with neat Portland or quick-setting cement in a ratio of not over 6 gallons of water per 94-pound sack of cement. Bentonite may be added to the neat cement grout in an amount not to exceed 6 pounds per 94-pound sack of cement. If bentonite is added to the neat cement grout, then additional water may be added at the ratio of 1 gallon of water per 2 pounds of bentonite. Bentonite. Bentonite with a minimum solids content of 20 percent may be used to fill the annular space in accordance with the following: When mixed as a slurry, at 2 pounds bentonite per gallon of water; or In chip or pellet form and if hydrated per the manufacturer specifications, when the annular space is less than 20 feet in depth. Bentonite may not be used for grouting where it will come into contact with ground water having a pH below 4.0 or a total dissolved solids content greater than 1,000 mg/l. Thermal Enhanced Bentonite Grout. Bentonite slurry shall be mixed per manufacturer specifications. The sand-bentonite ratio may not be greater than 250 pounds of sand per 50 pounds of bentonite. Sand shall be “000” well gravel that meets the following: 95 percent silica sand; Have a uniformity coefficient not greater than 1.7; and Have a particle size range of 0.60 mm to 0.15 mm. Thermally Enhanced Cementatious Grout: Shall be mixed per manufacturers specifications; and Have a permeability rating not less than 1 × 10^¯7. Cement alone or bentonite alone may be required as a special condition in a well construction permit for any well. If rapid loss of grout material occurs during grout emplacement, coarse fill material may be used in the zone or zones in which the loss is occurring. Other grouting materials or mixtures may be authorized as a special condition in a well construction permit for any well after review and approval by the Department. Standards for Grouting Unconfined Aquifer Wells in Hydrogeologic Areas 1 and 2. For wells screened in an unconfined aquifer under this section, the annular space shall be grouted to a depth of at least 20 feet. Standards for Grouting Confined Aquifer Wells in Hydrogeologic Area 2. Under this section: The depth of grouting may not be less than 30 feet; The annular space above the screen and below the grout shall be completely filled with clay, drill cuttings, or sand before grouting operations begin; For two part (lapped) telescoped wells, the drilling fluid may be used as fill material in the annular space if the drill fluid has a weight greater than 11 pounds per gallon; Drilling fluid less than 11 pounds per gallon may not be used as an acceptable fill material; For wells intended to have a yield greater than 5,000 gallons per day, the grout shall extend from a minimum of 5 feet into the confining bed, immediately above the aquifer being used, to the land surface; and For wells intended to have a yield of less than 5,000 gallons per day, the grout shall extend from a minimum of 5 feet into the first confining bed, which is at least 5 feet thick, to the land surface. Relative depths to confining layers are described in “MGS, Open File Report No. 12-02-20, Maryland Coastal Plain Aquifer Information System: Hydrogeologic Framework, 2013”, which is incorporated by reference. Standards for Grouting Wells in Hydrogeologic Areas 3, 4, and 5. The annular space shall be grouted completely from the bottom of the casing to the land surface. The minimum depth of grout may not be less than 18 feet in Hydrogeologic Areas 3 and, and may not be less than 38 feet in Hydrogeologic Area 4 and 5. If caving conditions are experienced on wells with greater than 30 feet of casing, the annular space shall be grouted from the point where caving occurred or from a depth of 30 feet, whichever is greater, to the land surface. If the annular space cannot be grouted in accordance with these regulations, the well shall be abandoned and sealed in accordance with this chapter. Deviation from Grouting Standards. Deviation from the grouting standards given in §§D, E, and F of this regulation may be approved by the Approving Authority for unusual conditions that prevent conformance with those standards. The deviation from the grouting standard shall be requested on a form provided by the Approving Authority. The request shall be submitted to the Approving Authority within 5 days after the well is completed. The Approving Authority shall reject or approve the request within 5 business days. Grout Height. For wells where a pump is not to be installed, the final grout height shall be at ground grade. For wells where a pump is to be installed, the final grout height shall be immediately below the pitless adapter or pitless unit.