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Vol. 9  No. 11

SLUG TESTS

&
THE ***NEW*** COMPLETE SLUGTEST PACKAGE

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Slug Tests

Slug tests can be used as an alternative to aquifer tests. There are many advantages to conducting a slug test;

• they can be less expensive to conduct

• they can be performed in small diameter monitoring wells

• they can be performed in areas with hydraulic conductivities too low for a pumping test

There are a variety of slug test analysis methods, this newsletter will highlight three of the common methods:

• The Cooper-Bredehoeft-Papadopulos Method (Confined aquifer)

• Hvorslev Method (Screened piezometers that do not fully penetrate)

• Bouwer and Rice Method (Open or screened piezometers; fully or partially penetrating)

In all cases, the slug test is conducted by inserting a volume of water or a slug into the well, which then causes the water table to rise to a maximum height above the initial water level (Ho). The water level will then decrease as the water drains into the aquifer, and this decrease is monitored in order to determine the hydraulic properties of the aquifer. It is also possible to bail out a volume of water and monitor the rising of the water table back to the initial water level.

Cooper-Bredehoeft-Papadopulos Method

The Cooper-Bredehoeft-Papadopulos method is applied to confined aquifers that are completely penetrated by an open borehole or well screen. The results of the slug test are plotted on semilogarithmic paper with time (log scale) and the ratio of measured head to maximum head (H/Ho) on the arithmetic scale. The plot is then matched against a series of type curves.

(From Fetter, 1994)

Click on image to see full size

The vertical time-axis, t₁, which overlays the vertical axis for Tt/r_c²=1.0 is then selected and the transmissivity (T) is found from:

        T=1.0r_c²/t₁

        Where r_c is the well casing radius.

Hvorslev Method

The Hvorslev Method is used for piezometers that do not fully penetrate an aquifer. As with the Cooper-Bredehoeft-Papadopulos method, H/Ho is plotted against time, however in this method time is the arithmetic scale, and H/Ho on the log scale. In this case, the time-drawdown data should plot in a straight line.

(From Fetter, 1994)

Click on image to see full size

The time associated with H/Ho=0.37 (T_o) is then used in the equation below to determine the hydraulic conductivity (K) of the aquifer:

        K=r²ln(L_e/R)/2L_eT_o

Where r is the well casing radius, Le is the length of the well screen, and R is the radius of the well screen.

Bouwer and Rice Method

The Bouwer and Rice Method has been highlighted in a previous newsletter, and includes a slug test calculator. Click here to read more.

References

Domenico P.A. and Schwartz, F.W. (1998). Physical and Chemical Hydrogeology. Published by John Wiley & Sons, Inc. New York, NY.

Fetter, C.W. (1994). Applied Hydrogeology; Third Edition.  Published by Prentice-Hall, Inc., Englewood Cliffs, NJ.

 

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***NEW*** Complete Slugtest Package

The Complete Slugtest Package is a new package available only at GroundwaterSoftware.com. This package contains everything you need to conduct and analyze slugtests or single well pumping tests!

• Solinst Waterlevel Meter - 100 ft waterlevel meter
• Solint Levelogger - Measures waterlevel over time
• Solinst Barologger - Corrects waterlevel measurements for changes in barometric pressure
• Solinst Communications Package - Allows you to setup and download data from levelogger/barologger
• Solinst Wire/Hooks - Used to hang the levelogger in well
• Slug to displace water - 3ft x1.75" pvc closed pipe
• ESI AquiferWin32 - Aquifertest software for graphing and evaluating slugtest and pumping test data.

This package has everything you need and you save 10% on cost!

For more info or to purchase click here:  Complete Slugtest Package

YSI 556 
 (Temp,Cond.DO,pH) 

Solinst Levelogger
$565
What's the basic setup?


RBCA Tool Kit