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KIRTLAND AIR FORCE BASE ALBUQUERQUE, NEW MEXICO ...

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APPENDIX B<br />

SOP B5.7<br />

Aquifer Testing<br />

The following SOP describes the general guidelines to be used when performing several types of aquifer<br />

tests. More specific procedures will be presented in project-specific addenda, if applicable. Many<br />

factors influence the design of specific aquifer tests, such as well or borehole size, depth to water or<br />

depth of water, anticipated recovery rate, present or final use of the well/borehole, spatial location, end<br />

use of the data, or type of available testing equipment. This SOP does not attempt to address all of these<br />

variables, but provides the user with descriptions of the general types of tests available.<br />

In-Situ Hydraulic Conductivity Tests<br />

In-situ hydraulic conductivity tests approximate the hydraulic conductivity of the formation only across<br />

the interval tested. The disturbance to the formations caused by drilling and the potential turbulence<br />

from the well screen can influence the data. The diameter of the well is critical to the computation of the<br />

hydraulic conductivity, and the effective diameter of well can be increased considerably by the well<br />

development process. Poor well efficiency caused by inappropriate slot size, poor condition of the well<br />

screen, or a poorly designed gravel pack could produce results not representative of the tested formation.<br />

Hydraulic conductivity tests in wells should be conducted only after the well has been fully developed.<br />

Slug test evaluation formulas assume an instantaneous initial change in water level in the tested interval.<br />

Tests performed after extended periods of pumping or water addition may yield inaccurate results. Slug<br />

tests provide only rough estimates of hydraulic conductivity, and should not be run in preference to<br />

aquifer tests.<br />

Slug Tests in Borings<br />

Slug tests can be performed in borings while the boring is being advanced. This permits testing of<br />

formations at different depths throughout the drilling process. Boreholes to be tested should be drilled<br />

using casing or hollow stem augers, so that discrete depths may be investigated. Various tests and testing<br />

methods are described below. The decision of which test to use is dependent upon aquifer conditions,<br />

geologic conditions, drilling methods, and project objectives. The test method selected will be described<br />

in the project-specific addenda.<br />

Both rising head and falling head hydraulic conductivity tests can be performed in saturated formations<br />

during drilling. There are several ways the tests can be performed. One way entails setting the casing<br />

flush with the bottom of the boring when the desired testing depth has been reached. The hole is then<br />

cleaned out to remove loose materials, and the drill bit and rods carefully withdrawn from the boring or<br />

raised well above the water level. After the water level in the boring has stabilized, the static water level<br />

is measured and recorded. The water level should then be raised (falling head test) or lowered (rising<br />

head test) and the change in water level measured at selected time intervals.<br />

Measurements should be taken at least every ½ minute for the first 10 minutes, then at predetermined<br />

intervals after that. Depending on the response time of the aquifer, measurements may need to be taken<br />

more frequently and transducers and data loggers may be required. Figure BA5.7-1 shows a standard<br />

form for recording water level changes during testing. The rate of change of water levels will be used to<br />

calculate hydraulic conductivity. The test should be conducted until the water level again stabilizes, or<br />

for a minimum of 20 minutes. In low permeability formations it is not always practical to run the test<br />

until the water level stabilizes, as it may take a long time to do so. The top of the well casing should be<br />

used as the reference point for all water level measurements.<br />

Kirtland AFB<br />

SOPs for Field Investigations B-139 April 2004

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