SOURCES OF WATER SUPPLY FOR THE REHABILITATION OF WATER

SUPPLY SYSTEM OF SCHOOL OF ENGINEERING AGP

By
ABDULRAHMAN MUHAMMAD
1902201010

A RESEARCH PROJECT SUBMITTED TO THE DEPARTMENT CIVIL ENGINEERING ,

ABDU GUSAU POLYTECHNIC TALATA MAFARA, ZAMFARA STATE.

IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE AWARD OF

NATIONAL DIPLOMA (ND) IN SCHOOL OF ENGINEERING TECHNOLOGY.

FEBRUARY, 2023.
 APPROVAL PAGE

This research project is submitted to the Department of Civil Engineering has

been read and approved by Malan Aminu Umar in partial fulfillment of the
requirement for the award of Natioanl Diploma in Civil Engineering Abdu Gusau
Polytechnic, Talata Mafara, Zamfara State.

______________________ ______________________
Project Supervisor Date
Mal. Aminu Umar

______________________ ______________________
Project Coordinator Date
Mal. Umar Ishak

______________________ ______________________
Head of Department Date
Mal. Alyasa’u Jafar
 DEDICATION
This project research is dedicated to Almighty Allah (SWT) who kept me alive to
this present time and my entire family.
 ACKNOWLEDGEMENT
I thanks the Almighty for making work successfully.
I wish to acknowledge first of all members of my family especially my
parents for their prayers, patience and encouragement. It also owe a lot to my
brothers and sisters for their back up prayers for the success of this project work.
I cannot forget encouragement given to us by my Supervisor Mal. Aminu
Umar and H.O.D Mal. Alyasa’u Jafar for their guide, advice and support on how
to conduct this project work. May Almighty Allah help them in all their respective
endeavors.
 ABSTRACT

Water’s essential function as drinking water is a significant daily intake.

Contamination by microorganisms (bacteria or viruses) on water sources and
drinking water supplies is a common cause in developing countries like
Indonesia. This paper will discuss the sources of clean water and drinking water
and their problems in developing countries; water quality and its relation to public
health problems in these countries; and what efforts that can be made to improve
water quality.
 LITERATURE REVIEW

Water quality is influenced by natural processes and human activities around the
water source Among developed countries, public health problems caused by low
water quality, such as diarrhea, dysentery, cholera, typhus, skin itching, kidney
disease, hypertension, heart disease, cancer, and other diseases the nervous
system. Good water quality has a role to play in decreasing the number of
disease sufferers or health issues due to drinking and the mortality rate. The
efforts made to improve water quality.
 CHAPTER 1

1.0 INTRODUCTION
Ground water is subsurface water occupying the zone of saturation. A water bearing
geologic formation which is composed of permeable rock, gravel, sand, earth, etc., and
yields water in sufficient quantity to be economical is called an aquifer. Unconfined
water is found in aquifers above the first impervious layer of soil or rock. This zone is
often referred to as the water table. Water infiltrates by downward percolation through
the air-filled pore spaces of the overlying soil material. The water table is subjected to
atmospheric and climatic conditions, falling during periods of drought or rising in
response to precipitation and infiltration. A confined aquifer is defined as the aquifer
underlying an impervious bed. Areas of infiltration and recharge are often some
distance away from the point of discharge. This water is often referred to as being under
artesian conditions. When a well is installed into an artesian aquifer, the water in the
well will rise in response to atmospheric pressure in the well. The level to which water
rises above the top of the aquifer represents the confining pressure exerted on the
aquifer. Materials with interconnecting pore spaces such as unconsolidated formations
of loose sand and gravel may yield large quantities of water and, therefore, are the
primary target for location of wells. Dense rocks such as granite from poor aquifers and
wells constructed in them do not yield large quantities of water. However, wells placed
in fractured rock formations may yield sufficient water for many purposes.

1.1 WATER REHABILITATION

WATER REHABILITATION as the reduction of suspended sediments, the retention of
pollutants and nutrients and the reduction of sedimentation rates downstream are
values that wetlands can contribute in a catchment resulting from the Sediment
retention function.
1.2 PURPOSE AND SCOPE. This course provides an introduction to selecting water
sources and determining water requirements for developing suitable sources of supply
from ground and retention of pollutant and nutrients.

1.3 WATER WORKS. All construction (structures, pipe, equipment, etc.) required for
the collection, transportation, pumping, treatment, storage and distribution of water.

1.4 SUPPLY WORKS. Dams, impounding reservoirs, intake structures, pumping

stations, wells and all other construction required for the development of a water supply
source.

1.5 SUPPLY LINE. The pipeline extending from the supply source to the treatment
works or distribution system.

1.6 DESIGN POPULATION. The population figure is obtained by multiplying the

effective-population figure by the appropriate capacity factor as follows:
 Design Population = Effective Population x Capacity Factor

1.7 REQUIRED DAILY DEMAND. This is the total daily water requirement. Its value is
obtained by multiplying the design population by the appropriate per capital domestic
water allowance and adding to this quantity any special industrial, aircraft-wash,
irrigation, air-conditioning, or other demands. Other demands include the amount
necessary to replenish in 48 hours the storage required for fire protection and normal
operation. Where the supply is from wells, the quantity available in 48 hours of
continuous operation of the wells will be used in calculating the total supply available for
replenishing storage and maintaining fire and domestic demands and industrial
requirements that cannot be curtailed.

1.8 PEAK DOMESTIC DEMAND. For system design purposes, the peak domestic
demand is considered to be the greater of:

• Maximum day demand, i.e., 2.5 times the required daily demand.

• The fire flow plus fifty percent of the required daily demand.

1.9 FIRE FLOW. The required number of L/min (gal/min) at a specified pressure at the
site of the fire for a specified period of time.

1.10 FIRE DEMAND. The required rate of flow of water in L/min (gal/min) during a
specified fire period. Fire demand includes fire flow plus 50 percent of the required daily
demand and, in addition, any industrial or other demand that cannot be reduced during
a fire period. The residual pressure is specified for either the fire flow or essential
industrial demand, whichever is higher. Fire demand must include flow required for
automatic sprinkler and standpipe operation, as well as direct hydrant flow demand,
when the sprinklers are served directly by the water supply system.

1.11 RATED CAPACITY. The rated capacity of a supply line, intake structure, treatment
plant or pumping unit is the amount of water which can be passed through the unit when
it is operating under design conditions.

1.12 CROSS CONNECTION. The two types recognized are as follows:

• A direct cross connection is a physical connection between a supervised, potable

water supply and an unsupervised supply of unknown quality. An example of a
direct cross connection is a piping system connecting a raw water supply, used
for industrial fire fighting, to a municipal water system.
 • An indirect cross connection is an arrangement whereby unsafe water, or other
liquid, may be blown, siphoned or otherwise diverted into a safe water system.
Such arrangements include unprotected potable water inlets in tanks, toilets, and
lavatories that can be submerged in unsafe water or other liquid. Under
conditions of peak usage of potable water or potable water shutoff for repairs,
unsafe water or other liquid may backflow directly or be back-siphoned through
the inlet into the potable system. Indirect cross connections are often termed
"backflow connections" or "back-siphonage connections." An example is a direct
potable water connection to a sewage pump for intermittent use for flushing or
priming.

1.13 GROUND WATER SUPPLY DEFINITIONS. The meanings of several terms used
in relation to wells and ground waters are as follows:

1.14 SPECIFIC CAPACITY. The specific capacity of a well is its yield per foot of
drawdown and is commonly expressed as liters per minute per meter (Lpm/m) of
drawdown (gpm/ft).

1.15 VERTICAL LINE SHAFT TURBINE PUMP. A vertical line shaft turbine pump is a
centrifugal pump, usually having from 1 to 20 stages, used in wells. The pump is located
at or near the pumping level of water in the well, but is driven by an electric motor or
internal combustion engine on the ground surface. Power is transmitted from the motor
to the pump by a vertical drive shaft.

1.16 SUBMERSIBLE TURBINE PUMP. A submersible turbine pump is a centrifugal

turbine pump driven by an electric motor which can operate when submerged in water.
The motor is usually located directly below the pump intake in the same housing as the
pump. Electric cables run from the ground surface down to the electric motor.
 CHAPTER 2

WATER REQUIREMENTS

2.1 DOMESTIC REQUIREMENTS. The per-capita allowances, given in Table 2-1 are
illustrative only of domestic water requirements. These allowances do not include
special purpose water uses, such as industrial, commercial, institutional, air-
conditioning, and irrigation.

Table 2-1

Illustrative Domestic Water Allowance

Use Liters/Capita/Day Gallons/Capita/Day

Residential 570 150
Hospitals 2300/bed 600/bed
Hotels 260 70
Industrial/Commercial 190/employee/8-hour shift 50/employee/8-hour shift

2.2 FIRE-FLOW REQUIREMENTS. The system must be capable of supplying the fire
flow specified plus any other demand that cannot be reduced during the fire period at
the required residual pressure and for the required duration. The requirements of each
system must be analyzed to determine whether the capacity of the system is fixed by
the domestic requirements, by the fire demands, or by a combination of both. Where
fire-flow demands are relatively high, or required for long duration, and population
and/or industrial use is relatively low, the total required capacity will be determined by
the prevailing fire demand. In some exceptional cases, this may warrant consideration
of a special water system for fire purposes, separate, in part or in whole, from the
domestic system. However, such separate systems will be appropriate only under
exceptional circumstances and, in general, are to be avoided . Rowett, Anthony Jr (7
October 2019).

2.3 IRRIGATION. The allowances indicated in Table 2-1 include water for limited
watering or planted and grassed areas. However, these allowances do not include
major lawn or other irrigation uses. Lawn irrigation provisions for facilities, such as
family quarters and temporary structures, in all regions will be limited to hose bibs on
the outside of buildings and risers for hose connections. Where substantial irrigation is
deemed necessary and water is available, underground sprinkler systems may be
considered. In general, such systems should receive consideration only in arid or
semiarid areas where rainfall is less than about 635 mm (25 in) annually. Glossary (7
October 2021).

2.3.1 BACKFLOW PREVENTION. Backflow prevention devices, such as a vacuum

breaker or an air gap, will be provided for all irrigation systems connected to potable
water systems. Installation of backflow preventers will be in accordance with the
applicable local plumbing code. Single or multiple check valves are not acceptable
backflow prevention devices and will not be used. Direct cross connections between
potable and nonpotable water systems will not be permitted under any circumstances.

2.3.2 USE OF TREATED WASTEWATER. Effluent from wastewater treatment plants

can be used for irrigation when authorized. Only treated effluent having a detectable
chlorine residual at the most remote discharge point will be used. Where state or local
regulations require additional treatment for irrigation, such requirement will be complied
with. The effluent irrigation system must be physically separated from any distribution
systems carrying potable water. A detailed plan will be provided showing the location of
the effluent irrigation system in relation to the potable water distribution system and
buildings. Provision will be made either for locking the sprinkler irrigation control valves
or removing the valve handles so that only authorized personnel can operate the
system. In addition, readily identifiable "nonpotable" or "contaminated" notices,
markings or codings for wastewater conveyance facilities and appurtenances will be
provided. Another possibility for reuse of treated effluent is for industrial operations
where substantial volumes of water for washing or cooling purposes are required. For
any re use situation, great care must be exercised to avoid direct cross connections
between the reclaimed water system and the potable water system.
 CHAPTER 3

CAPACITY OF WATER SUPPLY SYSTEM

3.1 CAPACITY FACTORS. Capacity factors, as a function of "Effective Population"

are shown in Table 3-1, as follows:

Table 3-1
Capacity Factors
Effective Population Capacity Factors
5,000 or less 1.50
5,001 to 10,000 1.50
10,001 to 20,000 1.25
20,001 to 30,000 1.15
30,001 to 40,000 1.10
40,001 to 50,000 1.05
50,001 or more 1.00

3.2 USE OF CAPACITY FACTOR. The "Capacity Factor" will be used in planning water
supplies for all projects, including general hospitals. The proper "Capacity Factor" as
given in Table 3-1 is multiplied by the "Effective Population" to obtain the "Design
Population." Arithmetic interpolation should be used to determine the appropriate
Capacity Factor for intermediate project population. (For example, for an "Effective
Population" of 7,200 in interpolation, obtain a "Capacity Factor" of 1.39.) Capacity
factors will be applied in determining the required capacity of the supply works, supply
lines, treatment works, principal feeder mains and storage reservoirs. Capacity factors
will NOT be used for hotels and similar structures. Capacity factors will NOT be applied
to fire flows, irrigation requirements, or industrial demands.

3.3 SYSTEM DESIGN CAPACITY. The design of elements of the water supply system,
except as noted, should be based on the "Design Population."
3.4 SPECIAL DESIGN CAPACITY. Where special demands for water exist, such as
those resulting from unusual fire fighting requirements, irrigation, industrial processes
and cooling water usage, consideration must be given to these special demands in
determining the design capacity of the water supply system.

3.5 EXPANSION OF EXISTING SYSTEMS. Few, if any, entirely new water supply
systems will be constructed. Generally, the project will involve upgrading and/or
expansion of existing systems. Where existing systems are adequate to supply existing
demands, plus the expansion proposed without inclusion of the Capacity Factor, no
additional facilities will be provided except necessary extension of water mains. In
designing main extensions, consideration will be given to planned future development in
adjoining areas so that mains will be properly sized to serve the planned developments.
Where existing facilities are inadequate for current requirements and new construction
is necessary, the Capacity Factor will be applied to the proposed total Effective
Population and the expanded facilities planned accordingly.
5.3.2 SPECIAL CONSIDERATIONS. In some geologic environments, the aquifer may
be too thin or for some other reason is unable to provide the required quantity of water
to a standard vertical well. In such instances, it may be economical to install collector
wells. A collector well is typically constructed with a large caisson having one or more
horizontal screens extending into the saturated zone (Figure 5-2). The caisson can be
used as a storage tank. The disadvantage of this system is that collector wells are more
expensive than standard vertical wells.

Figure 5-2

Collector Well
5.5.1.1 STATIC WATER LEVEL. The distance from the ground surface to the water
level in a well when no water is being pumped.

5.5.1.2 PUMPING LEVEL. The distance from the ground surface to the water level in a
well when water is being pumped. Also called dynamic water level.

5.5.1.3 DRAWDOWN. The difference between static water level and pumping water
level.

5.5.1.4 CONE OF DEPRESSION. The funnel shape of the water surface or piezometric
level which is formed as water is withdrawn from the well.

5.5.1.5 RADIUS OF INFLUENCE. The distance from the well to the edge of the cone of
depression.

5.5.1.6 PERMEABILITY. The ease of which water moves through the rock or sediment.

5.5.1.7 HYDRAULIC CONDUCTIVITY. Also called coefficient of permeability. The rate

at which water moves through the formation (gallons per day per square foot. It is
governed by the size and shape of the pore spaces.

5.5.2 WELL DISCHARGE FORMULAS. The following formulas assume certain

simplifying conditions. However, these assumptions do not severely limit the use of the
formulas. The aquifer is of constant thickness, is not stratified and is of uniform
permeability. The piezometric surface is level, laminar flow exists and the cone of
depression has reached equilibrium. The pumping well reaches the bottom of the
aquifer and is 100 percent efficient. There are two basic formulas (Ground Water and
Wells) one for water table wells (Equation 5-1) and one for artesian wells (Equation 5-
2). Figure 5-3 shows the relationship of the terms used in Equation 5-1 for available
yield from a water table well.

where:

Q = pumping rate in gpm

K = hydraulic conductivity of water bearing unit in

gpd/ft2 H = static head from bottom of aquifer in feet.
h = pumping head from bottom of aquifer in
feet R = radius of influence in feet r = radius of
well in feet

Figure 5-3

Diagram of Water Table Well (unconfined aquifer)

 CHAPTER 4

WATER SUPPLY SOURCES

4.1 GENERAL. Water supplies may be obtained from surface or ground sources, by
expansion of existing systems, or by purchase from other systems. The selection of a
source of supply will be based on water availability, adequacy, quality, cost of
development and operation and the expected life of the project to be served. In general,
all alternative sources of supply should be evaluated to the extent necessary to provide
a valid assessment of their value for a specific installation. Alternative sources of supply
include purchase of water as well as consideration of development or expansion of
independent ground and surface sources. A combination of surface and ground water,
while not generally employed, may be advantageous under some circumstances and
should receive consideration. Economic, as well as physical, factor must be evaluated.
The final selection of the water source will be determined by feasibility studies,
considering all engineering, economic, energy and environmental factors.

4.2 USE OF EXISTING SYSTEMS. Most water supply projects involve expansion or
upgrading of existing supply works rather than development of new sources. If there is
an existing water supply, thorough investigation will be made to determine its capacity
and reliability and the possible arrangements that might be made for its use with or
without enlargement. The economics of utilizing the existing supply should be compared
with the economics of reasonable alternatives. If the amount of water taken from an
existing source is to be increased, the ability of the existing source to supply estimated
water requirements during drought periods must be fully addressed. Also, potential
changes in the quality of the raw water due to the increased rate of withdrawal must
receive consideration.

4.3 OTHER WATER SYSTEMS. If the development is located near a municipality or

other public or private agency operating a water supply system, this system should be
investigated to determine its ability to provide reliable water service to the installation at
reasonable cost. The investigation must consider future as well as current needs of the
existing system and, in addition, the impact of the military project on the water supply
requirements in the existing water service area. Among the important matters that must
be considered are: quality of the supply; adequacy of the supply during severe
droughts; reliability and adequacy of raw water pumping and transmission facilities;
treatment plant and equipment; high service pumping; storage and distribution facilities;
facilities for transmission from the existing supply system, and costs. In situations where
a long supply line is required between the existing supply and the installation, a study
will be made of the economic size of the pipeline, taking into consideration cost of
construction, useful life, cost of operation, and minimum use of materials. A further
requirement is an assessment of the adequacy of management, operation, and
maintenance of the public water supply system.
4.4 ENVIRONMENTAL CONSIDERATION. Environmental policies, objectives, and
guidelines must be observed.

4.5 WATER QUALITY CONSIDERATIONS. Guidelines for determining the adequacy of

a potential raw water supply for producing an acceptable finished water supply with
conventional treatment practices must be observed.

4.5.1 HARDNESS. The hardness of water supplies is classified as shown in Table 4-1.

Table 4-1
Water Hardness Classification

Total Hardness (mg/L as CaCO3) Classification

0-100 Very Soft to Soft
100-200 Soft to Moderately Hard
200-300 Hard to Very Hard
Over 300 Extremely Hard

Softening is generally considered when the hardness exceeds about 200 to 250 mg/L.
While hardness can be reduced by softening treatment, this may significantly increase
the sodium content of the water, where zeolite softening is employed, as well as the
cost of treatment.

4.5.2 TOTAL DISSOLVED SOLIDS (TDS). In addition to hardness, the quality of

ground water may be judged on the basis of dissolved mineral solids. In general,
dissolved solids should not exceed 500 mg/L, with 1,000 mg/L as the approximate
upper limit.

4.5.3 CHLORIDE AND SULFATE. Sulfate and chloride cannot be removed by

conventional treatment processes and their presence in concentrations greater than
about 250 mg/L reduces the value of the supply for domestic and industrial use and
may justify its rejection if development of an alternative source of better quality is
feasible. Saline water conversion systems, such as electrodialysis or reverse osmosis,
are required for removal of excessive chloride or sulfate and also certain other dissolved
substances, including sodium and nitrate.

4.5.4 OTHER CONSTITUENTS. The presence of certain toxic heavy metals, fluoride,
pesticides, and radioactivity in concentrations exceeding recognized standards, will
make rejection of the supply mandatory unless unusually sophisticated treatment is
provided.
4.5.5 WATER QUALITY DATA. Water quality investigations or analysis of available
data at or near the proposed point of diversion should include biological, bacteriological,
physical, chemical, and radiological parameters covering several years and reflecting
seasonal variations. Sources of water quality data are local records, U.S. Geological
Survey District or Regional offices and Water Quality Laboratories, U.S. Environmental
Protection Agency regional offices, state geological surveys, state water resources
agencies, state and local health departments, and nearby water utilities, including those
serving power and industrial plants, which utilize the proposed source. Careful study of
historical water quality data is usually more productive than attempting to assess quality
from analysis of a few samples, especially on streams. Only if a thorough search fails to
locate existing, reliable water quality data should a sampling program be initiated. If
such a program is required, the advice and assistance of an appropriate state water
agency will be obtained. Special precautions are required to obtain representative
samples and reliable analytical results. Great caution must be exercised in interpreting
any results obtained from analysis of relatively few samples.

4.5.6 CHECKLIST FOR EXISTING SOURCES OF SUPPLY. The following items, as

well as others, if circumstances warrant, will be covered in the investigation of existing
sources.

• Quality history of the supply; estimates of future quality.

• Permits from regulating authorities and compliance history.

• Description of source.

• Water rights.

• Reliability of supply.

• Quantity now developed.

• Ultimate quantity available.

• Excess supply not already allocated.

• Raw water pumping and transmission facilities.

• Treatment works.

• Treated water storage.

• High service pumping and transmission facilities.

• Rates in gal/min at which supply is available.

• Current and estimated future cost per 1,000 gallons.

• Current and estimated future cost per 1,000 gallons of water from alternative
sources.

• Distance from installation site to existing supply.

• Pressure variations at point of diversion from existing system.

• Ground elevations at points of diversion and use

• Energy requirements for proposed system.

• Sources of pollution, existing and potential.

• Assessment of adequacy of management, operation, and maintenance.

• Modifications required to meet additional water demands resulting from supplying

water system expansion
 CHAPTER 5

GROUND WATER SUPPLIES

5.1 GENERAL. Ground water is subsurface water occupying the zone of saturation. A
water bearing geologic formation which is composed of permeable rock, gravel, sand,
earth, etc., and yields water in sufficient quantity to be economical is called an aquifer.
Unconfined water is found in aquifers above the first impervious layer of soil or rock.
This zone is often referred to as the water table. Water infiltrates by downward
percolation through the air-filled pore spaces of the overlying soil material. The water
table is subjected to atmospheric and climatic conditions, falling during periods of
drought or rising in response to precipitation and infiltration. A confined aquifer is
defined as the aquifer underlying an impervious bed. Areas of infiltration and recharge
are often some distance away from the point of discharge. This water is often referred to
as being under artesian conditions. When a well is installed into an artesian aquifer, the
water in the well will rise in response to atmospheric pressure in the well. The level to
which water rises above the top of the aquifer represents the confining pressure exerted
on the aquifer. Materials with interconnecting pore spaces such as unconsolidated
formations of loose sand and gravel may yield large quantities of water and, therefore,
are the primary target for location of wells. Dense rocks such as granite from poor
aquifers and wells constructed in them do not yield large quantities of water. However,
wells placed in fractured rock formations may yield sufficient water for many purposes.

5.1.1 ECONOMY. The economy of ground water versus surface water supplies needs
to be carefully examined. The study should include an appraisal of operating and
maintenance costs as well as capital costs. No absolute rules can be given for choosing
between ground and surface water sources. Where water requirements are within the
capacity of an aquifer, ground water is nearly always more economical than surface
water. The available yield of an aquifer dictates the number of wells required and thus
the capital costs of well construction. System operating and maintenance costs will
depend upon the number of wells. In general, groundwater capital costs include the
wells, disinfection, pumping, and storage with a minimum of other treatment. Surface
water supply costs include intake structures, sedimentation, filtration, disinfection,
pumping, and storage. Annual operating costs include the costs of chemicals for
treatment, power supply, utilities, and maintenance. Each situation must be examined
on its merits with due consideration for all factors involved.

5.1.2 COORDINATION WITH STATE AND LOCAL AUTHORITIES. Some States

require that a representative of the state witness the grouting of the casing and collect
an uncontaminated biological sample before the well is used as a public water supply.
Some States require a permit to withdraw water from the well and limit the amount of
water that can be withdrawn. All wells and well fields must be located and designed in
accordance with State Well Head Protection Programs and the Safe Drinking Water Act.
5.1.3 ARCTIC WELL CONSIDERATIONS. Construction of wells in arctic and subarctic
areas requires special considerations. The water must be protected from freezing and
the permafrost must be maintained in a frozen state.

5.2 WATER AVAILABILITY EVALUATION. After the projected water demand and
proposed usage use have been determined, the next step is to evaluate the quality of
available water resources. The quality of the groundwater will be influenced by its ph or
corrosivity; and the presence of constituents such as iron, lead, calcium, zinc, and
gasses such as carbon dioxide, nitrogen, oxygen, and sulphur dioxide. Recommended
quality standards for domestic and municipal water are published by the US
Environmental Protection Agency. Step-by-step procedures are illustrated in Figure 5-1.

5.3 TYPES OF WELLS AND CONSTRUCTION METHODS.

5.3.1 CONSTRUCTION METHODS. Wells are constructed by a variety of methods.

There is no single optimum method; the choice depends on the purpose of the well,
size, depth, formations being drilled through, experience of local well contractors, and
cost. The most common methods of installing wells are compared in Table 5-1. The
performance of different drilling methods in different formations is given in “Groundwater
and Well.” The most common type of small diameter well is the driven well.

5.4 WATER QUALITY EVALUATION. Both well location and method of construction
are of major importance in protecting the quality of water derived from a well.
Groundwater may become contaminated as a result of leakage from sources as diverse
as improperly sealed wells, septic tanks, garbage dumps, industrial and animal wastes.

5.4.1 SELECTION OF A WELL SITE. Prior to selecting the well location, a thorough
survey of the area should be undertaken. The following information should be obtained
and analyzed:

5.4.1.1 Local hydro geology such as terrain, soil type, depth, and thickness of water
bearing zone.

5.4.1.2 Location, construction, and disposal practices of nearby sewage and industrial
facilities.

5.4.1.3 Locations of sewers, septic tanks, cesspools, animal farms, pastures, and feed
lots.

5.4.1.4 Chemical and bacteriological quality of ground water, especially the quality of
water from nearby wells.

5.4.1.5 Histories of water, oil, and gas well exploration and development in area.
5.4.1.6 Location and operating practices of nearby industrial and municipal landfills and
dumps.

5.4.1.7 Direction and rate of travel of ground water. Recommended minimum distances
for well sites from commonly encountered potential sources of pollution are shown in
Table 5-2. It is emphasized that these are minimum distances which can serve as rough
guides for locating a well from a potential source of groundwater contamination. The
distance may be greater, depending on the geology of the area. In general, very fine
sand and silt filter contaminants in ground water better than limestone, fractured rock,
coarse sand and gravel. Chemical contaminants may persist indefinitely in untreated
groundwater. If at all possible, a well should be located up gradient of any known
nearby or potential sources of contamination. It is a good practice to consult local
authorities for aid in establishing safe distances consistent with the subsurface geology
of the area. Dry wells should be abandoned and plugged in conformance to local
regulations.

Table 5-2

Minimum Distances from Pollution Sources

Source Minimum Horizontal Distance

(Meters) (Feet)
Building Sewer 15 50
Disposal Field/Septic Tank 30 100
Seepage Pit 30 100
Dry Well 15 50
Cesspool/leaching pits 45 150

Note: The above minimum horizontal distances apply to wells at all depths. Greater distances are
recommended when feasible.

5.4.2 SAMPLING AND ANALYSIS. It is mandatory to review the stipulations contained

in the current U.S. Environmental Protection Agency's drinking water standards and
state/local regulations and to collect and chemically analyze samples as required for the
determination of all constituents named in the drinking water standards. Heavy metals
and arsenic are rarely encountered in significant concentrations in natural ground
waters, however, they may be of concern in areas with metamorphic rock. Radioactive
minerals may cause occasional high readings in granite wells.
5.5.4 AQUIFER TESTING. Where existing wells or other data are insufficient to
determine aquifer characteristics, a pumping test may be necessary to establish values
used for design. Testing consists of pumping from one well and noting the change in
water table at other wells as indicated in Figures 5-3 and 5-4. Observation wells are
generally set at 15 to 150 m (50-500 ft) from a pumped well, although for artesian
aquifers they may be placed at distances up to 300 m (1000 ft). A greater number of
wells allows the slope of the drawdown curve to be more accurately determined. The
most common methods of aquifer testing are:

• Step Drawdown Method. Involves pumping one well and observing what
happens in observation wells. The well is pumped at slow constant rate until the
water level stabilizes. It is then pumped at a higher rate until the water level again
stabilizes. At least three steps are normally performed.

• Recovery Method. Involves shutting down the pumping well and noting the
recovery water levels in the pumping well and its observation wells.

• Slug Test. Involves the introduction or removal of a “slug” or volume of water into
the well then measuring the rise or fall in water level. The test can also be
performed by inserting and removing a solid cylinder into the water.

• Bailer Test. Water is removed from the well using a bailer of known volume, as
rapidly as possibly until the well is empty or the water level stabilizes. The
volume and unit of time are noted.

5.5.5 TESTING OBJECTIVES. A simplified example is given in appendix B. When

conducting aquifer tests by methods such as the drawdown method, it is important to
note accurately the yield and corresponding drawdown. A good testing program,
conducted by an experienced geologist, will account for, or help to define, the following
aquifer characteristics:

• Type of aquifer
 water table
 confined
 artesian
 Slope of aquifer
 Direction of flow
 Boundary effects
 Influence of recharge
 stream or river
 lake
 Non-homogeneity
 Leaks from aquifer
5.6 WELL DESIGN AND CONSTRUCTION. Well design methods and construction
techniques are basically the same for wells constructed in consolidated or
unconsolidated formations and only one aquifer is being penetrated. Typically, wells
constructed in an unconsolidated formation require a screen to line the lower portion of
the borehole. An artificial gravel pack may or may not be required. A diagrammatic
section of a gravel packed well is shown on Figure 5-5. Wells constructed in sandstone,
limestone or other creviced rock formations can utilize an uncased borehole in the
aquifer. Screens and the gravel pack are not usually required. A well in rock formation is
shown in Figure 5-6. Additional well designs for consolidated and unconsolidated
formations are shown in AWWA A100.

5.6.1 DIAMETER. The diameter of a well has a significant effect on the well's
construction cost. The diameter need not be uniform from top to bottom. Construction
may be initiated with a certain size casing, but drilling conditions may make it desirable
to reduce the casing size at some depth. However, the diameter must be large enough
to accommodate the pump and the diameter of the intake section must be consistent
with hydraulic efficiency. The well shall be designed to be straight and plumb. The
factors that control diameter are (1) yield of the well, (2) intake entrance velocity, (3)
pump size, and (4) construction method. The pump size, which is related to yield,
usually dominates. Approximate well diameters for various yields are shown in Table 5-

3. Well diameter affects well yield but not to a major degree. Doubling the diameter of
the well will produce only about 10-15 percent more water. Table 5-4 gives the
theoretical change in yield that results from changing from one well diameter to a new
well diameter. For artesian wells, the yield increase resulting from diameter doubling is
generally less than 10 percent. Consideration should be given to future expansion and
installation of a larger pump. This may be likely in cases where the capacity of the
aquifer is greater than the yield required.

5.6.2 DEPTH. Depth of a well is usually determined from the logs of test holes or from
logs of other nearby wells that utilize the same aquifer. A well that is screened the full
length of the water bearing stratum has a potential for greater discharge than a unit that
is not fully screened. Where the water bearing formations are thick, cost may be the
deciding factor in how deep the wells are installed. Cost, however, usually is balanced
by the savings from a potentially long-term source of water.

5.6.4.4 INSTALLATION. Various procedures may be used for installation of well

screens as follows:

• For cable-tool percussion and rotary drilled wells, the pull-back method may be
used. A telescope screen, that is one of such a diameter that it will pass through
• In the bail down method, the well and casing are completed to the finished grade
of the casing; and the screen, fitted with a bail-down shoe is let down through the
 casing in telescope fashion. The sand is removed from below the screen and the
screen settles down into the final position.

• For the wash-down method, the screen is set as on the bail-down method. The
screen is lowered to the bottom and a high velocity jet of fluid is directed through
a self closing bottom fitting on the screen, loosens the sand and allowing the
screen to sink to it final position. If filter packing is used, it is placed around the
screen after being set by one of the above methods. A seal, called a packer, is
provided at the top of the screen. Lead packers are expanded with a swedge
block. Neoprene packers are self sealing.

• In the hydraulic rotary method of drilling, the screen may be attached directly to
the bottom of the casing before lowering the whole assembly into the well.

5.6.4.5 FILTER PACKING. Filter packing (sometimes referred to as gravel packing) is

primarily sand placed around the well screen to stabilize the aquifer and provide a
radius of high permeability around the screen. This differs from the naturally developed
well in that the zone around the screen is made more permeable by the addition of
coarse material. Filter-pack material is more effective when it is composed of clean
rounded siliceous sand or gravel.
CONCLUSION
Water rehabilitation can remove all the unnecessary bacteria and viruses from the water
that is hazardous for our health. Water Rehabilitation may also improve the flavor and
appearance of water. It removes the unpleasant odor.

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