TM 5-818-5/AFM 88-5, Chap 6/NAVFAC P-418
types of soil:
properly by filling with water and observing the rate
Approximate
of fall. A lo-foot minimum positive head should be
Time of
Period of
Type of Soil in
maintained in the piezometer following breakdown of
50 Percent Fall
Observation
Which Piezometer
the drilling fluid. After at least 30 minutes have
minutes
minutes
Screen Is Set
elapsed, the piezometer should be flushed with clear
30
30
Sandy silt (>50% silt)
water and pumped. For the piezometer to be consid-
Silty sand (<50% silt,
ered acceptable, it should pump at a rate of at least 2
>12% silt)
10
5
5
1
Fine sand
gallons per minute, or when the piezometer is filled
If the piezometer does not function properly, it will be
with water, the water level should fall approximately
developed by air surging or pumping with air if neces-
half the distance to the groundwater table in a time
sary to make it perform properly.
slightly less than the time given below for various
5-8
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