WATER WELL SERVICES
DIAGRAM OF WATER WELL
NEED FOR WATER WELL REQUIREMENTS
WATER WELL PRINCIPLES
REQUIREMENTS & RESPONSIBILITIES
BORE DESIGN & TYPES
CLASSIFICATION SYSTEM & DRILLING METHODS
SITING A WATER SUPPLY BORE
Bore Casing Principles:
Water bore casings and joints shall:
Prevent the collapse of the strata penetrated
Assist in construction and sealing, and prevent intermixing
Be strong enough to withstand installation, construction,
and operational pressures
Provide access to the water-producing zone
Be of sufficient size to act as a safe housing for
the pump selected for the hole
Provide an adequate operational life
The casing provides the conduit from the water-producing zone to the surface. It is also important in assisting in the construction of the bore, and must be of sufficient strength and composition to withstand the pressure exerted by the surrounding strata and other forces imposed during installation, bore development, and any cementing operations.
It should provide a secure and leakproof conduit from the water source to the surface through unstable formations and through zones of actual or potential contamination.
Casing joints should be watertight and have the same structural integrity as the casing itself.
The selected casing material and overall diameter of the bore casing should be adequate to accommodate the size of pump that has been selected.
It should take into account:
The efficiency of the pumping unit
The expected pump life
The extra clearance required in the event that the casing is not perfectly straight
The possibility of welds and other fasteners projecting inside the joints of the casing
The possibility of weld intrusions on steel casing
Any potential corrosion issues.
A range of casing materials are available,
and casing selection depends on several major factors.
Ease of handling
Type of formation
The particular bore design
The method of drilling
Bore permit requirements
Where resistance to collapse is the most critical strength requirement for boreholes with unstable formations, steel or FRP casing is usually selected to meet the strength characteristics required.
For corrosive water, PVC-U, ABS, FRP, or stainless steel casing provides the longest life possible. Because of the many and sometimes conflicting factors involved in selecting the most suitable casing material, the driller should consult with the manufacturer/supplier and bore owner before selecting the casing.