New Hampshire Code of Administrative Rules
We - Water Well Board
Chapter We 600 - STANDARDS FOR THE CONSTRUCTION, MAINTENANCE AND ABANDONMENT OF WELLS
Part We 604 - SEALING ABANDONED WELLS
Section We 604.05 - Sealing

Universal Citation: NH Admin Rules We 604.05

Current through Register No. 40, October 3, 2024

An 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;

(3) Bentonite chips;

(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.

#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

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