An abandoned well shall be sealed as follows:

1. (a) A well constructed by excavation shall be filled and sealed by placing clean fill material free of organic matter into the well. The upper 2 feet shall be filled with impervious material such as clay or hardpan;

2. (b) Subject to (e), below, a drilled well penetrating bedrock shall be sealed as follows:

   1. (1) The bore hole shall be filled with clean ½ inch diameter crushed stone at intervals of 100 feet or less, to a depth of 20 feet below the bottom of the well casing;
   2. (2) A 4-foot seal comprised of bentonite pellets, chips, or cement shall be installed between each layer of crushed stone; and
   3. (3) The remainder of the borehole and casing shall be grouted using materials specified for grouting casings, as specified in We 602.05;

3. (c) A drilled well constructed in unconsolidated materials shall be sealed as follows:

   1. (1) The screened area and casing shall be filled with sand, gravel, washed stone, or cement up to 15 feet below finished grade;
   2. (2) A 4-foot seal comprised of bentonite, pellets, chips, or cement shall be installed; and
   3. (3) The remainder of the casing shall be grouted using materials specified for grouting, as specified in We 602.05;

4. (d) A well, other than a drilled well, constructed in unconsolidated materials with a casing diameter 2 inches or less shall be sealed as follows:

   1. (1) The casing shall be removed from the ground, to the extent possible, and any remaining casing shall be cut away to a depth of one foot below the ground surface;
   2. (2) The hole, together with any remaining casing and screen, shall be filled with bentonite pellets or chips, with a maximum diameter of 3/8 of an inch, up to the ground surface; and
   3. (3) Well cover components shall be removed and the resulting void shall be backfilled with materials similar to the adjacent ground up to the surrounding surface grade;
5. (e) Notwithstanding the sealing requirements in We 604.05(b) and We 604.05(c) above, abandoned drilled wells penetrating bedrock may be sealed by grouting the entire length of the well;

6. (f) A drilled well penetrating bedrock or constructed in unconsolidated materials that has been contaminated or is causing an environmental hazard, including a salt contaminated well, shall be sealed by the pressure grout method with the use of a conductor pipe, otherwise known as a tremie pipe, from the bottom of the well to the top with a grout mixture of Portland cement with up to 5 percent high solids bentonite clay mixed according to the water-to-cement ratio in Table 604-1 below:

   Table 604-1 Water-to-cement ratio for mixing cement bentonite grout

   applicable for use with portland cement API class A or B and ASTM Type I or II

   Percent

   Bentonite

   (by weight)

   Maximum Mix-Water

   Requirements

   Gallons/Sack

   Slurry Weight

   (Density)

   Pounds/Gallon

   Neat cement

   5.2

   15.6

   1

   6.0

   15.0

   2

   6.5

   14.7

   3

   7.2

   14.4

   4

   7.8

   14.1

   5

   8.5

   13.8

7. (g) In addition to the materials specified in We 604.05(f) above, commercially available premixed bentonite grouts designed for sealing wells may be used;
8. (h) Commercially available premixed bentonite grouts shall be mixed with water according to the manufacturers specifications;

9. (i) Acceptable sealing materials for non-contaminated drilled wells shall include:

   1. (1) Portland cement otherwise known as neat cement, mixed with 5 to 6 gallons of clean water per 94 pound bag;
   2. (2) Portland cement with not more than 5 percent high solids bentonite clay mixed according to the water-to-cement ratio in Table 604-1;
   3. (3) Bentonite chips;
   4. (4) Bentonite and sand grout slurry with a mix ratio no greater than 50 pounds of bentonite to 400 pounds of sand; and
   5. (5) Commercially available premixed grouts mixed with water according to the manufacturers specifications; and
10. (j) Bentonite chips used for sealing 6 inch diameter or larger wells shall be a minimum of 3/8 inch diameter and shall be hydrated and as specified by the manufacturer.

Source. (See Revision Note at chapter heading for We 600) #12083 eff 3-1-17