ALP 3

Contents
Bulkhead Dam and Entrainment System
To collect the test sample after passing it through the sleeve valve, a 20 ft wide x 4 ft high
bulkhead dam was built at the terminal end of the spillway to force the discharge into fine mesh
entrainment nets. The bulkhead dam wall was made from 4 ft x 8 ft sheets of 1/4 in marine
plywood and the framing made from 2 x 6 in boards and was reinforced by 4 sets of kicker
braces held in place by angle iron anchored into the spillway concrete. Angle iron support was
also used around the lower perimeter of the bulkhead where the frame came into contact with the
spillway concrete. At the base of the bulkhead, three - 23 x 19 in rectangular reinforced
window -type openings were made and evenly spaced apart from each other but were set two -
inches above the bottom of the bulkhead. Three rod iron net frames were also made to help
secure the entrainment nets tightly next to the bulkhead dam using 2' /2 in lag screws through the
grommets and net frame. This set -up made net attachment and replacement relatively
uncomplicated in the event that any of the nets should become damaged or detached during
sleeve valve survival testing.
Figure 12. Bulkhead dam (20 ft wide x 4 ft high) at the terminal end of RBD spillway,
entrainment nets, and upstream face of bulkhead dam.
The entrainment nets were designed and constructed by Aquatic Research Instruments, Hope,
Idaho. The nets were made from 500- micron Nitex® nylon screening material that is designed
to screen plankton size particles (larger than 500 microns) from water. The nets were 24 x 20 in
at the open end and were about 22 ft in length and had reinforced collars with '/2 in grommets
every 6 inches. The entrainment nets were conical in shape and tapered to the circumference of a
common 5 -gal bucket (figure 13). To protect the nets from abrasions, layers of heavy duty
plastic sheeting (6 MIL) was anchored to the shotcrete using metal HIT drive anchors. Five -gal
plastic buckets were used for the cod -end of the net where fish and rainbow trout embryos were
collected. To pass water through the buckets, '/4 in holes were drilled into one -half of the bucket
to allow water to vent upwards and were also screened with 500- micron Nitexe nylon screen.
The back end of the nets slipped over the 5 -gal bucket and was strapped below the top lip by two
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