GROUNDWATER DRILLING AND CONSTRUCTION

Groundwater is a unique resources but can easily be tapped with proper technology. The selection of construction technique and size of well depend on several factors but finally it rest on the water demand and budget of the user.

The type of groundwater among others are as listed below:

        i.   Traditional well (manually open dug well)
        ii.  Monitoring well (piezometer)
        iii. Tube well (shallow and deep well)
        iv. Well point System (series of drainage well)
         v. Horizontal Collector Well (HCW)


Type of groundwater production well and its comparison can be shown in Fig.3 below:

Fig.3: Type of Groundwater Production Well and its Discharge Capacity

1. Traditional Well

Groundwater in the olden days in most villages are commonly tapped by construction of simple hand dug Traditional Well and its walls cased up with supporting structure such as concrete culvert or caisson. This simple hand dug well has construction limitations due to difficulties to dug deeper upon reaching water logged conditions upon striking the first aquifer zone.  The design of this open dug well do not provide any screen intake, only depend on groundwater recharge from the bottom opening of the well and some seepage at the joints of the caisson. The discharge capacity of the open dug is small yet able to support a small demand due to the caisson structure that able to act as part of a storage structure.

2. Monitoring Well (piezometer)

Monitoring well is usually been constructed for the purpose of monitoring the local groundwater conditions for it physical (eg. pH, color, turbidity etc), chemical (eg. Iron, Manganese, chloride etc.) and biological (eg. E-Coli form, Total Coli form etc.) parameters. The monitoring groundwater in some cases become mandatory due to specific monitoring qualities required by the authority.

The monitoring well size and depth of installation shall depend on the specific requirement but the standard monitoring well usually of size, the largest diameter is 100mm diameters and the smallest is 40mm diameters.
The usual depth of monitoring installation is that to be installed at least below the existing static water table.

The monitoring well is constructed by drilling borehole of adequate size to enable the installation of the required tubewell pipe casing and screen diameter.

Drilling technique to construct the monitoring well shall depend on the size and depth required. For small and shallow depth monitoring well in the alluvium formation, the following drilling technique is adequate.
a. Water jetting method using simple mud pump.
b. Wash boring method by soil investigation machine.
c. Percussion drilling using bailer method.

..break time....to be continue...

STUDYING THE POTENTIAL AND NEED OF WATER RESOURCING

In water resourcing, among the main objectives are to really understand the water demand and its fluctuating effects besides the potential of the available resources, i.e. surface water or groundwater.

A good water resourcing studies shall evaluate every angles of the available water potential in terms of quantity, quality, economical to develop and even to the extend of conjunctive usage between surface and ground water resources.

Surface water seem to be popular to the local authority since it can be easily identified, measured and treated, but the major disadvantages of surface water, it can be easily affected by pollution, especially in an urban environment.

The next best alternative is to tap ground water from the local area. Ground water in most cases can easily be developed and utilized, provide that proper abstraction methodology is applied.

The ground formation in which ground water is confine known as aquifer can be visualized as in fig.2 below:

Fig.2: Ground water aquifer

Ground water aquifer potential varies due to several factors, mainly its geology and hydro geology, in other words, the type of soil formation and its properties, and depth that contribute the piezometric pressure to speed up the flow rate of ground water upon abstraction.  

In Malaysia, shallow aquifer being highly utilized in the East Coast region such as Kota Bharu, Kelantan. The deep aquifer is more popular in the West Coast region such as in Selangor and Kuala Lumpur.

The shallow aquifer of depth less than 30 meters exist in old river bed, valley and coastal area of sandy formation, while the deep aquifer of depth greater than 30 meters and even reached to 200 meters is tapped from the fractured zone of hard rock formation such as in granite, meta sediments of shale, schist etc. or cavities of limestone. 

The flow rates of these ground water wells depend much on the geology and hydro geology, and also dependent on the construction technology and the well design of the production well.

The selection and the design of a good groundwater production well shall required ground water expertise of good knowledge and experience. 

coming next... groundwater well drilling and construction technology...

WATER RESOURCING

Water as what we seen, exist in two common forms known as surface water and groundwater. What we see at the surface such as river, lakes etc are known as surface water while groundwater exist and stored underneath the ground level. Both supplies eventually come from rainfall and evaluate in cycle known as Hydrology Cycle and the summarized image sample as shown in Fig.1.