3 August 1998
(2) Prevention of subsurface contamination. Formations containing water of poor
quality above the target aquifer may be sealed off by grouting an outer casing in place before
installing the deeper well casing. If the undesirable aquifer is the lower one, care should be
taken during drilling so as not to penetrate or breach the confining unit separating the two
aquifers. Any portion of the confining unit that is breached should be replaced with grout.
g. Accessibility. The well location shall be readily accessible for pump repair, cleaning,
disinfection, testing and inspection. The top of the well shall never be below surface grade. At
least 600 mm (2 ft) of clearance beyond any building projection shall be provided.
h. Details relating to water quality. In addition to grouting and sealing, features that are
related to water quality protection are:
(1) Surface grading. The well or wells should be located on the highest ground
practicable, certainly on ground higher than nearby potential sources of surface pollution. The
surface near the site should be built up, by fill if necessary, so that surface drainage will be
away from the well in all directions. Where flooding is a problem, special design will be
necessary to insure protection of wells and pumping equipment from contamination and
damage during flood periods and to facilitate operation during a flood.
(2) Surface slab. The well casing should be surrounded at the surface by a concrete
slab having a minimum thickness of 100 mm (4 in) and extending outward from the casing a
minimum of 600 mm (2 ft) in all directions. The slab should be finished a little above ground
level and slope slightly to provide drainage away from the casing in all directions.
(3) Casing. The well casing should extend at least 300 mm (12 in) above the level of
the concrete surface slab in order to provide ample space for a tight surface seal at the top of
the casing. The type of seal to be employed depends on the pumping equipment specified.
(4) Well house. While not universally required, it is usually advisable to construct a
permanent well house, the floor of which can be an enlarged version of the surface slab. The
floor of the well house should slope away from the casing toward a floor drain at the rate of
about 1 mm per 50 mm (1/8 inch per foot). Floor drains should discharge through carefully
jointed 100 mm (4 in) or larger pipe of durable water-tight material to the ground surface 6 m
(20 ft) or more from the well. The end of the drain should be fitted with a coarse screen. Well
house floor drains ordinarily should not be connected to storm or sanitary sewers to prevent
contamination from backup. The well house should have a large entry door that opens out-
ward and extends to the floor. The door should be equipped with a good quality lock. The well
house design should be such that the well pumps motor, and drop-pipe can be removed
readily. The well house protects valves and pumping equipment and also provides some
freeze protection for the pump discharge piping beyond the check valve. Where freezing is a
problem, the well house should be insulated and a heating unit installed. The well house
should be of fireproof construction. The well house also protects other essential items. These
- Flow Meter
- Depth Gage