Section We 604.05 - SealingAn abandoned well shall be sealed as follows:
(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;(b) Subject to (e), below, a drilled well penetrating bedrock shall be sealed as follows: (1) The bore hole shall be filled with clean 1/2 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) A 4-foot seal comprised of bentonite pellets, chips, or cement shall be installed between each layer of crushed stone; and(3) The remainder of the borehole and casing shall be grouted using materials specified for grouting casings, as specified in We 602.05;(c) A drilled well constructed in unconsolidated materials shall be sealed as follows: (1) The screened area and casing shall be filled with sand, gravel, washed stone, or cement up to 15 feet below finished grade;(2) A 4-foot seal comprised of bentonite, pellets, chips, or cement shall be installed; and(3) The remainder of the casing shall be grouted using materials specified for grouting, as specified in We 602.05;(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) 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) 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) 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;(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;(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 |
(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;(h) Commercially available premixed bentonite grouts shall be mixed with water according to the manufacturers specifications;(i) Acceptable sealing materials for non-contaminated drilled wells shall include: (1) Portland cement otherwise known as neat cement, mixed with 5 to 6 gallons of clean water per 94 pound bag;(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;(4) Bentonite and sand grout slurry with a mix ratio no greater than 50 pounds of bentonite to 400 pounds of sand; and(5) Commercially available premixed grouts mixed with water according to the manufacturers specifications; and(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.N.H. Admin. Code § We 604.05
#3046, eff 7-2-85; ss by #4730, eff 1-15-90; ss by #4898, eff 8-13-90; EXPIRED: 8-13-96
New. #6327, INTERIM, eff 8-24-96, EXPIRED: 12-22-96
New. #6449, eff 1-29-97; ss by #7307, eff 6-13-00; ss by #9179, eff 6-13-08
Amended by Volume XXXVII Number 2, Filed January 12, 2017, Proposed by #12083, Effective 3/1/2017, Expires 3/1/2027.