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Title: SLUG TEST INTERPRETATION FOR A SITUATION IN INTERBEDDED SAND AND CLAY

Author
item HEATHCOTE, RICH - DEP OF JUSTICE, IOWA
item Bouwer, Herman

Submitted to: Iowa Groundwater Quarterly
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/1/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Dependable soil permeability data are needed for many projects involving drainage, irrigation, well design, groundwater recharge, pollutant transport, etc. The Bouwer and Rice slug test is a simple technique to measure how rapidly or slowly water can move through underground soils (hydraulic conductivity) below the groundwater table. A well is drilled with the top of the screen and gravel envelope below the water table, wate is quickly removed from, or added to the well and the subsequent rise or fall of the water level in the well is measured for calculation of the permeability of the soil or aquifer material around the well screen. The technique is widely used, including for conditions for which it was not intended, like a layered soil profile or with the screen and envelope extending above the groundwater table. This paper describes how the method can then be used to get estimates of the permeability, even though it stretches the validity of the technique. There is no escaping the fact, however, that good slug tests start with good wells. This paper benefits water managers, engineers, hydrologists, geologists, planners, regulators, and attorneys.

Technical Abstract: The Bouwer and Rice slug test applies to uniform soils, a well screen and envelope that are below the water table, and quick rise (slug out) or fall (slug in) measurements so that drawdown or upconing of the groundwater table around the well are still negligible. When these conditions are not met, the slug test procedure loses validity and only estimates of hydraulic cconductivity can be obtained. This paper discusses how such estimates can be obtained where the soil profile consists of a permeable upper layer (sand) underlain by less permeable material (silt, clay), and where the screen and envelope extend above the groundwater table.