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13.12. SEALING THE UPPER ANNULAR SPACE 13.12.1. The annular space shall be sealed from the top of the filter pack, or the Bentonite transition seal (refer to 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. 13.13. TEMPORARY COVER 13.13.1. The well or borehole opening shall be covered to prevent the entry of foreign material, contaminants and pollutants and ensure public safety whenever work on the well is interrupted. 13.13.2. The cover shall be watertight and held in place in such a manner that it cannot be removed except by equipment or tools. 13.14. SURFACE SEALS 13.14.1. Surface construction features of a monitoring well shall serve to prevent physical damage to the well; prevent entrance of surface water, pollutants, and contaminants; and prevent unauthorized access. 13.14.2. The top of a monitoring well shall be protected by a locking cover or equivalent level of protection to prevent unauthorized access. 13.14.3. The top of a monitoring well casing shall be fitted with a watertight sanitary seal to prevent surface water, pollutants, and contaminants from entering the well. 13.14.3.1. Openings or passages for water level measurements, venting, pump power cables, discharge tubing, and other access, shall be protected against entry of surface water, pollutants, and contaminants. EHD 43-03 Page 24 of 27 WELL STANDARDS 10/9/07