USGS Bridge Board - Model 4200
The bridge board was
designed for use in making discharge measurements and obtaining water
quality samples from off of bridges. It is a free-standing support,
accommodating A-Pack, A- 55 or B-56 sounding reels. It comes with an
adjustable foot rest which makes it easily adaptable to bridge
railings of different heights and walkways of various widths. In use,
the Bridge Board is set to the approximate height of the bridge rail
at the measurement site. With the sounding reel secured to the
mounting plate, the boom is positioned so the sheave extends out past
the bridge rail. The suspension cable is now stretched out over the
sheave at the end of the 4 foot long boom. The current meter or
sampler is then suspended from the cable and is in position to be
lowered into the water below. The maximum sounding weight to be used
with the bridge board is 50 pounds (23 kg).
