There are several steps involved between the time you decide to invest in a borehole and getting water pumped out of the earth. We have outlined the steps for you here below.
01. Site Pre-Visit
Before a borehole is drilled, a hydrogeological survey is carried out. it comprises of a site pre-visit, geophysical & hydrogeological investigations. A site pre-visit is carried out as the initial step so as to generate a datum reference for further borehole site investigations. This involves studying the general topography and understanding the geological set up of the area to be investigated. Geophysical methods are further used in hydrogeological assessment of the subsurface conditions.
02. Site Survey
A Hydro-geological survey is necessary at the proposed site before drilling of the borehole begins. The surveys help to ascertain suitable sites for exploration of significant quantities of groundwater. In return this ensure the best point is selected according to the geological data and the client’s need. The hydro geological data, graphs, maps, and cross section profiles obtained from the survey are used in determining drilling depth and other aspects.
03. Drilling authorization
Once the drilling point is identified, the hydro geologist will do a report of the findings and have it submitted to the Water Resource Authority who will in turn evaluate it and give written authority to construct the borehole. This authorization gives the go ahead to drill.
It is also important to carry out an E.I.A (Environmental Impact Assessment) of the project. This will allow the issuance of the NEMA license.
This is in conformity with the requirement of the Environment management and coordination amendment act (2015) and the environmental impact assessment and audit regulations,2013 for approval of the proposed borehole development project.
04. Site Mobilization
Involves the preparation and the movement of equipment, personnel, supplies and incidentals to the project site. It includes the transferring to the job site all plants, equipment, materials, personnel, supplies and all items necessary for the commencement and completion of the work. It also entails the setting up of all equipment, plants and other accessories until they are ready for use.
After everything has been set up and inspected at the site, drilling starts The drilling can either be done using the rotary mud flush technique or rotary air percussion and flush method.
06. Rock Sampling
To develop relevant and accurate geotechnical evaluations and assessments it is necessary to collect representative subsurface rock/soil samples. These samples are collected at set intervals. Struck and water rest levels are constantly recorded. The process allows an estimate to be made of the yield of each individual aquifer.
07. Well Development
Is the act of cleaning out the clay and silt introduced during the drilling process as well as the finer part of the aquifer directly around the well screen prior to putting the well into use. This helps increase the rate of water movement from the aquifer into the well, stabilizes the aquifer to prevent sand pumping, and removes organic and inorganic material which may inhibit effective well disinfection.
This prevents contamination of fresh water well zones. It also prevents unstable upper formations from carving in and sticking the drill string or forming large caverns.
09. Test Pumping
Involves pumping of a well from a measured static water level at a known yield and recording the rate and pattern by which the water level within the well charges. Water samples are then collected for chemical analysis. The test is done for 24hrs and an addition 8 hrs recovery test. This will enable the hydro geologist to calculate the ideal pumping rate, the installation depth and the drawdown for a given discharge.
10. Final Stage
The next stage depends on the use of the water. This is best discussed and agreed with the client.