**NATURAL RESOURCES CONSERVATION SERVICE\
CONSTRUCTION SPECIFICATION**

**WELL**

1\. SCOPE

This specification applies to drilled, driven, and dug wells developed
to supply water from an underground source. It does not include pumps
installed in the well, or above-ground installations such as pumping
plants, pipelines, or tanks.

All wells shall comply with state water laws and regulations. Wells at
recreation sites shall comply with applicable regulations of the State
Department of Health, or other state and county agencies having
jurisdiction.

2\. CASING AND MATERIALS

Wells shall be cased, except that the lower sections of a well passing
through consolidated strata do not require casing. Materials shall be in
accordance with the requirements of Section 9 of the specification.

3\. SCREENS

All wells finished in unconsolidated aquifers shall be equipped with
manufactured screen sections, well points, or field perforated sections
meeting the criteria stated below.

The screen openings for aquifer material of near uniform size shall be
slightly smaller than the average diameter of the aquifer material. For
graded aquifer materials (of non-uniform gradation), the screen openings
shall be such that 25 to 40 percent of the aquifer material is larger
than the screen opening. In wells using a gravel pack envelope, the
screen shall have openings if a size that will exclude at least 85
percent of the gravel pack material. The length and open area of the
screen shall be sufficient to maintain the entrance velocity of water
into the well at an acceptable level, preferably less than 0.1 ft. per
second.

> The position of the screen in the well will be governed by the depth
> of the aquifer below the ground surface and the thickness of the
> aquifer to be penetrated by the well. Where practical, the top
> elevation of the screen should be below the lowest water level
> expected during pumping and be located opposite the most permeable
> areas in the water-bearing strata.

4\. GRAVEL PACK

Filter packs will be used in wells developed in stratas composed of fine
material of relatively uniform grain size to prevent aquifer materials
from passing through the well screen or perforated casing. The pack
shall be 76 to 305 millimeters (3 to 12 inches) thick and shall be
composed of sand and gravel material having a D~30~ grain size 4 to 12
times the D~30~ grain size of the strata material.

> When gravel packing is used, it shall be of the specified gradation
> and thickness and shall be carefully placed to prevent segregation and
> bridging. Gravel pack materials shall extend a minimum of 10 feet
> above the top of the perforated or screened section and extend through
> the length of the water-bearing formation.

5\. SANITARY PROTECTION

Groundwater sources should be located a safe distance from sources of
contamination. The well should be located on ground that is higher than
any source of contamination. Drainage that might reach the source from
areas used by livestock should be diverted.

> Each well shall be provided with a watertight cover or seal to prevent
> contaminated water or other objectionable material from entering the
> well. The annular space around the casing shall be filled with cement
> grout, bentonite clay, or other suitable material from the surface to
> a minimum of 3 meters (10 feet) below the ground surface. A positive
> seal shall be provided between the casing and the impervious material
> overlying the aquifer or artesian wells. In addition, wells used for
> human consumption shall have the casing surrounded at the ground
> surface by a 100 millimeter (4-inch) thick concrete slab extending at
> least 0.6 meters (2 feet) in all directions. A sanitary well seal
> shall be installed at the top of the well casing to prevent the
> entrance of contaminated water or other objectionable material.

6\. ALIGNMENT

> Drilled wells shall be round, plumb, and aligned so as to permit
> satisfactory installation and operation of a pump of the proposed size
> and type, to the greatest anticipated depth of setting.

7\. CASING INSTALLATION

In consolidated formations, the casing shall extend from the ground
surface through the overburden material to an elevation at least 2 feet
into the consolidated foundation.

> In unconsolidated formations, the casing shall extend from the ground
> to the screen.
>
> For artesian aquifers, the casing shall be sealed into the overlying
> impermeable formations so as to retain the artesian pressure.
>
> When a water-bearing formation containing water of poor quality is
> penetrated, the formation shall be sealed off to prevent the
> infiltration of poor quality water into the well and the developed
> aquifer.
>
> Plastic well casing shall be equipped with a steel driving shoe and
> shall be placed with very little driving.

8\. DEVELOPING

The well shall be developed until it has stopped producing detrimental
quantities of sand when the continuous discharge rate is approximately
20 percent greater than the anticipated normal production rate.

9\. MATERIALS

> Casing materials may be pipe made of steel, wrought iron, plastic,
> concrete, or other similar material of equivalent strength and
> durability.
>
> New metal pipe or new plastic pipe shall be used for well casing in
> drilled wells. New metal pipe only shall be used for driven wells.
> Plastic casing shall be NSF-approved for transport of potable water
> supplies where the water will be used for human consumption.
>
> Polyvinyl chloride plastic well casing shall be Schedule 40 or
> Schedule 80 pipe and shall be limited to a maximum installation depth
> of 60 meters (200 feet). Specifications for wall thickness and for
> diameter of polyvinyl chloride plastic pipe (PVC), ASTM D 1785,
> NSF-approved, are given in Table 1.
>
> Plastic well casing made of virgin, white, high-impact,
> rubber-modified polystyrene material; such as Dow Chemical Company
> Styron 456 or Cosden 825-D or equal; shall be limited to an
> installation depth of 90 meters (300 feet).

10\. SIZE OF PLASTIC CASING

> Plastic well casings shall be no larger than 152 millimeters (6
> inches) diameter, nominal.

11\. JOINTS IN PLASTIC CASING

> Joints shall be other than screw type.

12\. ADDITIONAL ITEMS WHICH APPLY TO THIS JOB