Control the Seepage Exits
Constructing sandbag or other types of ring dikes around sand boils can be used to control the
seepage exit. The dike allows the development of a pool or head of water to backpressure the
boil, thus decreasing the net head and upward flow of water, and reducing the loss of material.
Seepage exits can often be controlled with a weighted filter constructed by placing a layer of
filter material over the seepage exit and overlaying that with pervious drainage material. A
geotextile can be substituted as the filter material. These procedures are depicted in Figure V-
1. If relief wells or standpipe piezometers are nearby, they can be pumped to reduce the uplift
pressure. These emergency measures should be carefully monitored until permanent solutions
are constructed. Standby personnel, equipment, and filter/drain material should be readily
available, because the exit may shift to an unprotected location. Readily available concrete
sand is a very good filter/drain material for emergency use.