Environmental Engineering Reference
In-Depth Information
Fig. 3.40 Staff gages
installed in a wetland in the
Nebraska sandhills with a
surveyor standing on the
frozen wetland surface and
holding a survey rod at the
distant gage. Note that ice
movement has tilted the staff
gage in the distance. Staff-
gage movement is an annual
occurrence in locations
where ice forms on the
wetland surface during
winter, requiring re-surveys
to maintain year-to-year
continuity of wetland
stage data
staff gage in Fig. 3.40 will also record the angle from vertical of the staff gage so
that corrections can be made to any stage measurements obtained while the gage is
tilted. Once straightened, the gage will need to be re-surveyed.
Construction of the staff gage in the foreground is typical of many
installations. A steel fence post is attached to a piece of lumber that is treated
to resist rot (the example in Fig. 3.40 uses U-clamps to attach a wooden board
to the post). An incremented staff section, usually made of enameled metal or
fiberglass, is screwed to the wood. The fence post can be attached to the wood
and then driven into the wetland bed, or if the wetland sediments are very
resistant, the fence post can be driven first and then the board complete with
face plate is subsequently attached. A length of steel pipe is often substituted for
the fence post. Many installations also have a bolt or screw projecting out of the
wood next to the face plate so that a survey rod can be placed on the bolt and
held in a constant position relative to the values on the face plate while surveying
the relative elevation of the staff gage.
Monitoring Well Installation
Two types of monitoring wells, or piezometers, will be installed as part of this field
activity, one constructed to indicate the elevation of the water table adjacent to a
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