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t 0 0 ' casing may require perforation, or puncturing, to allow for proper placement of sealing materials. ' If the well casing is left in place during sealing operations, a hole at least one foot larger in diameter than the originally drilled hole shall be excavated ' around the outside of the well casing to a depth of 3 feet below the ground surface, and the well casing shall then be cut off 6 inches above the bottom of this excavation and removed. The grout used to fill the well shall be allowed ' to spill over into the excavation during the sealing operation, and fill the excavation up to a thickness of one foot forming a "cap" which has a diameter ' of at least one foot greater than the diameter of the originally drilled hole. After the sealing operation is completed and the sealing material has set, the remaining excavation shall be filled with clean soil. ' If the well casing is not left in place (for example, well construction is unknown, the well is located in an area of known or suspected pollution or contamination, or well casing removal is the destruction method of choice), the well shall be destroyed by removing all material within the original borehole including the well casing, screen, filter pack and annular seal. ' Material to be extracted from the original borehole shall be removed by means of drilling, including over-drilling if necessary. The excavated well boring shall be filled with sealing materials by use of a tremie pipe or ' equivalent, proceeding upward from the bottom of the well or boring. Sealing materials shall be placed in one continuous operation, and the pressure required for the placement of sealing material shall be maintained long enough for sealing materials to properly set. • Sealing material shall be selected based on the required structural, handling, ' and sealing properties, and the chemical environment into which it is placed. Sealing materials shall have such low permeability that the volume of water passing through them is of little consequence. Suitable materials can include ' neat cement, sand-cement grout, and bentonite clay. Used drilling mud or cuttings from drilling shall not be used for any part of the sealing material. The sealing material used must be approved by RWQCB staff. Potable water shall be used for sealing mixtures. Any deviations from these procedures shall be described in the Well Project tDescription Addenda and require prior approval from RWQCB staff. 7.0 REPORTING The WDRs require the Discharger to submit this document, the Master Well Workplan, prior to the first scheduled construction or destruction of any groundwater monitoring well. A Groundwater Well Project Description Addendum is also required prior to monitoring well construction or destruction. The Well Project Description Addenda shall provide site specific information and 1 ' 10 -