NATURAL RESOURCES CONSERVATION SERVICE

**Idaho**

**CONSTRUCTION SPECIFICATIONS**

**FOR**

**WELL DECOMMISSIONING**

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(Owner/Operator) (Project Title)

GENERAL

The well sealing procedure shall be in accordance with a plan approved
by the responsible technician. Details of construction shown on the
drawings or described in the State of Idaho, Department of Water
Resources "Rules and Regulations, Well Construction Standards" for well
abandonment, but not included herein, shall be considered as part of
these specifications. Construction activities shall be in accordance
with applicable Department of Labor, Occupational Safety and Health
Administration (OSHA) regulations.

WELL PREPARATION

Equipment/Debris Removal -- Pumping equipment, screens, liners, any
obstacles or debris and foreign materials shall be removed from the well
before sanitation or sealing procedures begin.

Flushing -- Unless otherwise specified the well shall be flushed by
pumping in clean water or by use of an air compressor line.

SANITIZATION

Unless otherwise specified, the water in the well shall be brought to a
100 parts per million (ppm) chlorine concentration before sealing.

A 100 ppm chlorine solution will require one of the following:

> 1 gallon of 5 per cent chlorine bleach per 500 gallons of water,
>
> 1 pint of 5 per cent chlorine bleach per 62 gallons of water, or
>
> 1.3 pounds high-test calcium hypochlorite tablets per 1000 gallons of
> water.

MATERIALS

The entire well depth shall be filled with bentonite pellets, cement or
grout. Sealing materials shall meet the requirements of ASTM D 5299,
"Standard Guide for Decommissioning Ground Water Wells, Vadose Zone
Monitoring Devices, Boreholes, and Other Devices for Environmental
Activities". Bentonite pellets shall not be installed in wells with
standing water.

Bentonite Pellets -- Commercially chipped or pelletized bentonite in a
granulated form, with a particle size of 1/4- to 3/4-inch. Powdered
bentonite is not suitable for dry placement in well sealing operations.

Cement Grout -- A mixture of one (1) bag (94 lbs.) of Portland cement
and six (6) gallons of water which is fluid enough to be pumped through
a small-diameter pipe. This mixture yields a volume of about 1.1 cubic
feet. To obtain a better flowing mixture, three to five (3-5) pounds of
powdered bentonite may be added per sack of cement and the water
increased to not more than 6 1/2 gallons per sack of cement. Other
cement grout mixes may be used. These mixes shall be mixed and installed
in accordance with American Petroleum Institute Standards API Class A
through H and ASTM D 5299.

Volume of Sealing Materials - Table 1 can be used to determine the
minimum volume of materials required per foot of depth of the well hole.

[TABLE 1]{.underline}

VOLUME OF SEALING MATERIALS

  ----------------------- ----------------------- -----------------------
  Hole Diameter           Volume per Foot of      
                          Depth                   

  (inches)                gal/foot                Cu. Ft/foot

  4                       0.7                     0.1

  6                       1.5                     0.2

  8                       2.6                     0.3

  10                      4.1                     0.5

  12                      5.9                     0.8

  14                      8.0                     1.1

  16                      10.5                    1.4

  20                      16.4                    2.2

  24                      23.6                    3.1

  36                      53.0                    7.1

  48                      94.2                    12.6
  ----------------------- ----------------------- -----------------------

SEALING PROCEDURE

Sealing materials shall be placed in the well to a point not more than
four (4) feet below the ground surface.

If there is free-standing water present in the well prior to filling,
the water shall be pumped or bailed out or its volume shall be
determined and figured into the amount of water used to mix the sealing
material.

If bentonite pellets are used, they shall be screened to remove dust and
fine particles. The bentonite shall be added slowly at a rate no faster
than one (1) bag (50 lbs.) per three (3) minutes to prevent bridging.
The bentonite shall be saturated with water as it is placed in the well,
and tamped into place to assure bridging has not occurred. Water shall
be added at a rate of eight (8) gallons per 50-lb. bag.

If cement grout or concrete is used, the well shall be filled through a
pipe (tremie), from the bottom of the well upward in one continuous
operation.

If possible without damaging, caving or blocking the drill hole bore,
the casing and/or liner pipe shall be carefully removed from the well as
sealing materials are placed. When the casing can not be removed, it
shall be ripped or perforated to ensure that sealing materials fill any
annular space that may exist between the casing and the well bore.

After filling with sealing materials, the top four (4) feet of hole
shall be dug out and, if the casing was not removed prior to sealing,
the well casing shall be cut off to a minimum of four (4) feet below the
original ground surface unless otherwise shown on the drawings. The hole
shall be filled with a one to two (1-2) foot thick plug of sealing
materials, and then covered with topsoil. The topsoil shall be tamped in
place and the area shall be graded such that surface water is directed
away from the abandoned well location and ponding of water is precluded.

Well Pits. If the abandoned well is located in a walled well pit,
proceed with the sealing process as described above. Prior to placing
the plug of sealing materials, knock down at least one wall of the pit,
then fill with sealing materials and topsoil as outlined above unless
otherwise shown on the drawings.

OPERATION AND MAINTENANCE GUIDE

Once this practice is installed, the site needs to be periodically
inspected to see that the decommissioned well surface seal and adjacent
area have not settled or eroded to affect the site. When needed, the
ground surface around the well site shall be graded to prevent water
from ponding over or around the site.

ADDITIONAL SPECIFICATIONS