Washington Regulatory

Question 1

Resource protection wells (standard vs DP: minimum annulus size relative to casing

Answer 1

Annulus must be 4 inches greater diameter than well casing/screen
DP: 1 inch greater

Question 2

Resource protection wells (standard vs DP): sand pack height relative to screen

Answer 2

Sand pack must be 1-5 feet above screen
DP: Sand pack must be 1-3 feet above screen and 0-1feet from bottom of screen

Question 3

RP well decommissioning - with and without well log information

Answer 3

If you have well log:
Wells greater than or equal to 1 inch diameter: fill casing with bentonite chips, grout, cement, surface seal.
Wells less than 1 inch (DP): pressure fill with grout and seal at surface
If you don’t have the well log:
Perforate casing and pressure fill with grout or pull casing and seal boring

Question 4

Water wells - minimum length and diameter of surface seal

Answer 4

18 feet below ground surface and 4 inches greater than maximum casing diameter. Seal must extend to and through the confining layer

Question 5

Well sealants include

Answer 5

Bentonite (slurry or dry - slurry must have 20% by weight bentonite solids content)
Neat cement (6 lb water per 94 lb cement solids - portland or high alumina)
Cement grout (neat cement, with up to 5% bentonite by weight)
Concrete (portland cement with aggregate)

Question 6

Sealing of wells penetrating confined aquifers

Answer 6

Must be sealed from ground surface to bottom of upper aquitard, or ground surface to minimum 18 feet

Question 7

Decommissioning of water wells

Answer 7

Either perforate the casing to within 5 feet of the surface, then pressure seal,
or
withdraw casing and fill with sealant.
Flowing artesian wells must be filled with grout from bottom to surface using tremie