Abstract: In this test the samples are taken from

Abstract: In this analysis the aquifer
characteristics are determined by single well push pull test near the
chemically affected area in Mumbai region or ground water affected by
chemicals. It is important to find the aquifer the aquifer characteristics for
the future drawdown of water from the ground surface. In this test the samples
are taken from different bore holes and tested in laboratory to find out the
characteristics of ground water aquifer. A push-pull test involves the injection
(push) of a prepared test solution into an aquifer followed by the extraction
(pull) of the test solution/groundwater mixture from the same location. From
the above test it is observed that the solution or water tested by this method
is not affected by any chemical reaction and it is help full for drinking and
other daily needs. And aquifers are found may be of confined and unconfined.
From this it is observed that unconfined aquifers are found to be more affected
than confined aquifer by the chemical reaction in ground water. From this test
it is suggest that the push pull test method should be useful for obtaining
quantitative information on a wide range of any chemical reaction in ground
water.

1. Introduction

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An aquifer is
an underground layer of water-bearing permeable rock, rock fractures or
unconsolidated materials (gravel, sand, or silt) from which groundwater can
be extracted using a water well. The study of water flow in aquifers
and the characterization of aquifers are called hydrogeology.
Related terms include aquitard, which is a bed of low permeability along
an aquifer, and aquiclude (or aquifuge), which is a solid,
impermeable area underlying or overlying an aquifer. If the impermeable area
overlies the aquifer, pressure could cause it to become a confined aquifer. An
aquifer is a body of saturated rock through which water can easily move.
Aquifers must be both permeable and porous and include such rock types as sandstone,
conglomerate, fractured limestone and unconsolidated sand and gravel. Fractured
volcanic rocks such as columnar basalts also make good aquifers. The rubble
zones between volcanic flows are generally both porous and permeable and make
excellent aquifers. In order for a well to be productive, it must be drilled
into an aquifer. Rocks such as granite and schist are generally poor aquifers
because they have a very low porosity. However, if these rocks are highly
fractured, they make good aquifers. A well is a hole drilled into the ground to
penetrate an aquifer.

 

Literature survey:-

There are single
well push pull test techniques available in the literature to assess, simulate
and predict aquifer characteristics. However, the selection normally depends on
the availability of required input data, objectives of the study, some
predefined assumptions and the quality of available models. Therefore, the
choice of a test results is one of the important factors that will influence
the predicting accuracy.

Junqi Huang,et al (2010),
In this work, an exact analytical solution to two?dimensional equations
describing the governing processes acting on a dissolved compound during a
modified push?pull test (advection, longitudinal and transverse dispersion,
first?order decay, and rate?limited sorption/partitioning in steady, divergent,
and convergent flow fields) was developed.
J.d.istok el al (1997).from this study it it
found that the tests  were performed to
determine rates of aerobic respiration, denitrification,  sulfate 
reduction,  and  methanogenesis  in 
a  petroleum contaminated aquifer.
The results suggest that the push-pull test method should be useful for
obtaining quantitative information on a wide range of in situ microbial   processes for finding out auifer
characteristics.

Stefan Bachu (May 1997), this study suggested that based on a very
large set of core and formation water analyses, and drillstem tests collected
by the oil industry, the regionalscale hydrogeological regime of formation
waters was analysed for the entire sedimentary succession in the northern part
of the basin. The results of this analysis were then related to hydrocarbon
generation and accumulation, and to the current geothermal regime in the area
for testing aquifer characteristics.

 B. F. Sule,et
al,(2013),from this investigation it is found
that  the data gives  pumping test results, discharge, drawdown and
geophysical and borehole constructional methods. The determination of the
aquifer characteristics was based on the Theis Residual Recovery Method.

Magnus Uzoma Igboekwe,et,al,(2012),  The survey was aimed
at investigating the resistivity of consolidated and unconsolidated formations
of the study area and the depth of the Aquifer. The depth ranges from 16.0 to
30.0 m from the earth’s surface. This means that it is more economical to sink
boreholes in such a region than in other regions with deeply buried aquifers.

.  

Methodology:-

The
single well push pull test is used for calculating the aquifer characheristics
and it is observed to be best method for computation of aquifer
characteristics. The methods of finding out the characteristics of aquifers are
as follows:

1.
Single well push pull test

2. Two
well push pull test

3.
Tidal method

1. What is a Push-Pull Test?

A
push-pull test involves the injection (push) of a prepared test solution into
an aquifer followed by the extraction (pull) of the test solution/groundwater
mixture from the same location .Tests may be performed in existing monitoring
wells or multilevel samplers. The test solution consists of water containing
one or more tracers and one or more other solutes; the type, combination, and
concentration of solutes are selected to investigate specific aquifer
characteristics. During the injection phase, the test solution is injected into
the aquifer where it flows away from the well and penetrates a roughly
cylindrical volume of aquifer (Figure 1A). During the extraction phase, flow is
reversed concentrations of tracer, reactive solutes, and possible reaction
products are measured as a function of time at the same well (Figure 1B).
Tracer concentrations are used to adjust concentrations of test solution
components for dilution. Mass balances are computed by integrating
dilution-adjusted concentrations during the extraction phase. Reaction rates
are computed from the mass of solute consumed and/or product formed.

(A) Injection
(“Push”) Phase & (B) Extraction (“Pull”) Phase

 

Fig.Injection and extraction phases of a “push-pull”
test

 

 

 

 

 

 

 

 

2. Designing A Pumping Test:-

The following concepts and reconnaissance work
should be taken for the design of a pumping test:

The time
required in year for pumping test
The natural
agents of groundwater fluctuation such as barometric pressure changes,
earth tides and tidal variations which may affect water levels in
observation wells during the pumping test
The off-site
groundwater use which may influence water levels during the pumping test
The effects
of pumping test on surrounding water users
The depth
of setting and type of pump in control well
The
duration and rate of pumping
pumping
rate measurement and control
The
frequency and water
level measurement
The
withdrawal of water from the well
The collection
of water quality samples during pumping
The location
and orientation of streams, faults, lithologic contacts and other
potential aquifer boundaries
The
potential of  salt water intrusion
in coastal areas
The preparation
of list of  needed field equipment

2. Well Reports and Pump Tests:-

Some
aquifer characteristics can be estimated from the data found in well reports
(drillers’ logs). The static water level, location of water-bearing zones,
geologic materials, and pump test data are examined to obtain information such
as aquifer depth, thickness, and nature. The description and location of
geologic formations and water-bearing zones within the formations can give
clues as to whether an aquifer is shallow (water is located near the land
surface) or deep (water is located deeper, perhaps greater than 30 meters, or
100 feet), and whether it is made of consolidated or unconsolidated
materials.The nature of the aquifer refers to whether the aquifer is confined
or unconfined. A confined aquifer has a layer of less porous material above the
aquifer, resulting in the groundwater being under pressure. When a well is drilled,
the water level in the well will rise above the top of the aquifer. An
unconfined aquifer does not have a layer of less porous rock above it, and so
when a well is drilled, the water level in the well will be at the same level
as the top of the aquifer.

Pumping
Rate Measurement and Control:-

Fig:-Well
head and discharge setup for a constant-rate pumping test

A controlled pumping stress is
imposed on an aquifer system during a pumping test. Therefore, carefully measuring, controlling and recording the flow rate throughout the test is essential for a successful outcome.

3. Rate measurement:-

Measuring
the flow rate during a
pumping test can be accomplished in a number of ways including the following:

·        
Container and stopwatch

·        
In-line flow
meter

·        
Orifice weir

·        
Weir or flume

Flow
rates should be recorded with sufficient frequency to demonstrate a constant
rate or to monitor planned rate changes. In the event of temporary test
interruption (e.g., power failure), pumping stop and restart times should be
noted to allow for proper interpretation of the test. Bear in mind that the
discharge rate often decreases with time as the water level in the control well
drops. Kruseman and
de Ridder (1994) recommend
checking and, if necessary, adjusting the flow rate at least once every hour;
however, one should consider more frequent measurements until it becomes
evident how often rate adjustments are required (Stallman 1971).

Estimating
discharge from a pumped well by use of a circular orifice weir.

Fig.In-line flow
meter for discharge measurement

 

Fig.Circular orifice weir for
discharge measurement

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Rate control:-

Controlling the flow rate is also important for a successful
pumping test. As a general rule, Stallman
(1971) recommends controlling
the pumping rate within ±10% for a constant-rate
test or for each constant-rate
step. USBR (1995) suggests a tolerance of ±5% for the pumping rate. State and
local regulations may offer additional guidance regarding an acceptable
tolerance for rate variation during a pumping test.

Water-Level
Measurement

1. Measuring Water Levels:-

During
a pumping test, water levels in wells may be measured by means of manual
techniques or through the use
of sensors with
data loggers.

2. Manual Methods

Manual
water-level measurement techniques include chalked steel
tape, electric
water-level sounders and
airline methods.

Fig .Applying
carpenter’s chalk to steel tape prior to water-level measurement

 

Fig.Electric
tape for water-level measurement

Test Duration:-

The decision to terminate a pumping test is best
made on the basis of hydro geologic conditions at the test site and the
objectives of the test. Longer tests may be necessary to estimate specific
yield in an unconfined
aquifer or to observe boundary
effects.

Plotting
and inspecting pumping test data as they are collected in the field can help
you to decide when it’s appropriate to end a pumping test.

Have the
objectives of the test been achieved?
Have
sufficient late-time data been collected to estimate specific yield in an
unconfined aquifer?
Has the
test continued long enough to detect and locate aquifer boundaries?

Other factors may influence the planned duration of a pumping test
including budgetary constraints and regulatory requirements. Often, applicable
regulations may establish a minimum duration required for a test, but longer
tests may be necessary to achieve other test objectives.

Conclusion:-

Form this study it is concluded that for finding out characteristics of
aquifer this method is more accurate than the other method and the results
obtained are more accurate than other methods and the characteristics
determined are satisfied the all conditions required for the ground water area
and this methods is suggested for all types of dam construction for testing the
ground water characteristics and aquifer characteristics. From this study it is
also suggested that for any area which may be near to chemically affected or
near to sea area this methods gives an results for calculating the aquifer
characteristics .This  methods uses less
time as compared to others methods and initial cost is less as compared to
others methods. And operating system is also easy and time consuming methods
and suggested to all civil engineering and water resource engineering works. A
well is a hole drilled into the ground to penetrate an aquifer. Normally such
water must be pumped to the surface. If water is pumped from a well faster than
it is replenished, the water table is lowered and the well may go dry. When
water is pumped from a well, the water table is generally lowered into a cone
of depression at the well. Groundwater normally flows down the slope of the
water table towards the well.

References

1.     
Junqi
Huang,n, John A. Christ,and Mark N. Goltz ,”ANALYTICAL SOLUTIONS FOR EFFICIENT
INTERPRETATION OF SINGLE?WELL PUSH?PULL TRACER TESTS”WATER RESOURCES RESEARCH,
VOL. 46, W08538, doi:10.1029/2008WR007647, 2010.

 

2.     
Istok,
J.D.Humphrey, M.D.Schroth, M.H.Hyman, M.R.O’Reilly, K.T.,”SINGLE-WELL,
“PUSH-PULL” TEST FOR IN SITU DETERMINATION OF MICROBIAL ACTIVITIES”,GROUND
WATER,volume-35,Issue no-4,July 1997.

3.     
Cassiani,
G., L. F. Burbery, and M. Giustiniani (2005), ”A NOTE ON IN SITU ESTIMATES OF
SORPTION USING PUSH?PULL TESTS”, Water Resource. Res., 41, W03005, doi:
10.1029/2004 WR003382.

4.     
K. S.
Novakowski, P. A. Lapcevic, and J. W. Voralek,”A NOTE ON A METHOD FOR
MEASURING THE TRANSPORT PROPERTIES OF A FORMATION USING A SINGLE WELL”, WATER
RESOURCES RESEARCH, VOL. 34, NO. 5, PAGES 1351-1356, MAY 1998.

 

5.     
Sinclair,
W.C., 1974,” HYDROGEOLOGIC CHARACTERISTICS OF THE SURFICIAL AQUIFER IN
NORTHWEST HILLSBOROUGH COUNTY”, Florida: Florida Bureau of Geology Information
Circular 86, 98 p.

 

6.     
Kruseman
G.P, de Ridder N.A., “ANALYSIS AND EVALUATION OF PUMPING TEST DATA”,
2nd edn. Publ 47(ILRI), Wageningen , ISBN 90-70754-20-7, 1990

 

7.     
Sonawane
S. B., and Ukarande S. K., “Effect of Field Parameters on Saltwater Ingression
in Coastal Aquifers” and published in the proceedings of the sixth,
“International Congress on Computational Mechanics and Simulation (ICCMS2016)”,
at Indian Institute of Technology Bombay, Mumbai, pp 1028-1032, (27th June – 1
st July 2016 )