1. EGERTON UNIVERSITY
RESEARCH PROJECT REPORT
TITLE:-
CAUSES OF FAILURE OF BOREHOLES - A CASE STUDY OF EGERTON UNIVERSITY
BACHELOR OF SCIENCE IN WATER AND ENVIRONMENTAL ENGINEERING
3RD
SEPTEMBER, 2008

2. 1.1. INTRODUCTION
The ground water research project was carried out at
Egerton and its surroundings, Egerton University is located
in Njoro Division of Nakuru District,RiftValley Province.Itis
180-Km northwest of Nairobi off the Njoro-Mau Narok road.
It is located at an altitude of 2160 metres above sea level. It
covers an area of 1445 hectares.Records showed about42%
(10 out of 24) of the boreholes (deep wells) drilled atEgerton
University are non-operational. Approximate cost of 150m
operational borehole then was about Ksh 1,000,000
(Average drilling rates in Kenya then), the failure of these
boreholes represented a big waste of resources.
Investigation on the high failurerateof the boreholes in that
region was necessary. This study investigated the probable
causes of failure,both structural and non-structural reasons.
In the research boreholefailurerefers to a situation wherea
borehole which is deemed “successful”atthe time of drilling
and test pumping subsequently fails to deliver a sufficient
yield of safe water throughout the year
1.2. OBJECTIVES
The broad objective of the study was to establish the
possible reasons for failure of boreholes in Egerton
University. The specific objectives were as below;
a) To determine whether failure was as a result of
deterioration in the borehole screens and casings.
b) To examine probable changes in recharge into the
aquifer supplying the boreholes.
c) To investigateparameters of concern in relation to
groundwater quality in Egerton University.
1.3. METHODOLOGY
To determine whether failure was as a result of
deterioration in the borehole screens and casings.
a) Corrosion of borehole casings and the screens;
This was determined through investigation of: the presence
of Hydrogen Sulfide in the water samples, the presence of
high levels of Carbon dioxide,the presence of high levels of
Total Dissolved Solids (TDS), the pH level of the water
sample. The RSI was calculated. The Ryznar Stability Index
(RSI) uses a database of scale thickness measurements in
water systems to predict the effect of water chemistry. It is
developed from empirical observations of corrosion rates
and film formation in steel mains
b) Incrustation of the borehole casingand the screens
Determination of Carbonate hardness in the groundwater
which was achieved through the analysis for thepresence of
any of the Calcium, Magnesium and Iron compounds.
Calculation of the Ryznar Stability Index (RSI) to determine
the water’s incrusting potential.
c) Improper borehole design
The compatibility of the borehole casing and the screens
with the hydrogeology of Egerton University was
determined. The well screens used were assessed to
establish whether they were standard (Field-slotted,
perforated casing or the recommended manufactured
screens).The length and placement of the borehole screens
and casing was assessed. Size and amount of sand pack
around the well screen (if required) and location of thepump
in the well were assessed.
d) Bio-fouling
The presence of Iron bacteria, dissolved organic carbon
(DOC), nitrates and slimebuild up on plumbing fixtures was
checked.
To identify causes of non- structural failures in boreholes at
Egerton.
a) Aquifer problems
Geophysical survey of selected sampling points was carried
out and compared with the available geophysical data.
Assessment of whether there had been aquifer mining was
done by studying precipitation data and changes in
vegetation cover which affect ground water recharge. The
design water pumping rateand the current pumping ratefor
selected boreholes were compared to assist in establishing
whether over pumping had occurred.
a) Operation, maintenance and monitoring of the
boreholes
The research checked whether the correct operation and
maintenance of the boreholes was adhered to and also
established whether the boreholes had an airlineand water
meter used to monitor the water levels.
To investigate parameters of concern in relation to
groundwater quality in the study area
Assessment of proximity of the boreholes to pollution
sources that are likely to affect the water quality was done.
Assessment on whether proper sanitary protection was
done (grouting). The following tests were carried out:
Fluoride, Total hardness, pH and Coli form test.
1.4. FINDINGS
Having studied the conditions which relate to groundwater
in Egerton, the following was adduced: Thermoplastic pipes
and casings should be adopted to replace steel pipes and
casings which are susceptible to corrosion due to
interference with chemicals in water. Alternative sources of
water to meet the water demand in this area should be
provided. Rain harvesting should be enhanced to cater for
the bigger percentage of water demand. Drilling should only
be allowed after a full study of the groundwater parameters
such as annual rechargevolumes,annual dischargevolumes,
aquifer thickness,aquifer storagevolume, sustainableyield,
entitlements, yearly allocations,abstractions and water level
variations.Normally oncethesehave been studied it may be
possible to support more boreholes. Artificial recharge of
groundwater should also considered to replenish the
aquifers.

3. Key Words; Failure, Structural and Nonstructural, Borehole