SITE INFORMATION AND CORRESPONDENCE CASE 2

Home Browse Search

13.12. SEALING THE UPPER ANNULAR SPACE 13.12.1. The annular spacf ill be sealed from the top of the filter pac} r the bentonite transition seal (rei_ .o Section 13.11), to the ground surface. 13.12.2. The annular seal shall be a minimum of 2 inches in radial thickness. 13.12.3. Sealing material shall be selected based on required structural, handling, and sealing properties, and the chemical environment into which it is placed. Sealing material shall consist of neat cement, bentonite neat cement grout, or bentonite clay. 13.12.4. Drilling fluid or cuttings from drilling the borehole shall not be used in the sealing material. 13.12.5. Neat cement grout shall be mixed at a ratio of one 94-pound sack of Portland cement to 5-10 gallons of potable water. 13.12.6. Cement-bentonite grout shall contain not more than 3-5% bentonite. 13.12.7. Neat cement and cement-bentonite grouts shall be thoroughly mixed. 13.12.8. Water used for sealing mixtures shall be potable. 13.12.9. All bentonite used must be NSF approved or equivalent type designed by the manufacturer for the intended usage. 13.12.10. All equipment used in the construction of the well and placement of the annular space seal shall be free of debris and/or contamination. 13.17. REQUIREN�TS FOR DESTROYING MONITORING WELLS AND EXPLORATION HOLES 13.17.1. A monitoring well shall be investigated to determine its condition and details or its construction prior to its destruction. 13.17.2. The well shall be sounded immediately before it is destroyed to determine whether there are obstructions that will interfere with filling and sealing. 13.17.3. Any obstructions found in the well or boring shall be removed before filling and sealing operations begin. _ 13.17.4. If the well was constructed and maintained in accordance with these Standards, the sealing material shall be placed under pressure to ensure that the monitoring well is properly filled and sealed. 13.17.5. Casing material may require perforation, or puncturing, to allow for proper placement of sealing materials. 13.17.6. If the well construction is unknown and/or is located in an area of known or suspected pollution or contamination, the well shall be destroyed by removing all _material within,the odginal borehole.(including-the well casing, screen, filter pack, and annular seal); and the created hole filled completely with appropriate sealing material. 13.17.7. Exploratory borings, installed for sampling purposes, shall be completely grouted with appropriate sealing material. The top 3 feet of the boring may be backfilled with clean, uncontaminated fill material. 13.17.8. The well or exploratory boring shall be filled by use of a tremie pipe or equivalent, proceeding upward from the bottom of the well or boring. Any deviation from this method must be approved by the Director. 13.17.9. Sealing materials shall be placed in one continuous operation unless conditions in the well or boring dictate that sealing operations be conducted in a staged mariner and prior approval is obtained from the Director. 13.17.10. Pressure required for the placement of sealing material shall be maintained long enough for sealing materials to properly set. 13.17.11. Verification shall be made to determine that an adequate seal has been installed by a EHD representative. 13.17.12. If the well casing was 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. 13.17.13. The grout used to fill the well shall be allowed to spill over into the excavation, during the sealing operation, and fill it for a thickness of one foot and form. a "cap" which has a diameter of at least one foot greater than the diameter of the originally drilled hole. 13.17.14. After the sealing operation and the sealing material has set, the excavation shall be filled with clean soil. 13.17.15. Any deviation from this section must obtain prior approval from the Director.