Each plumbline presently consists of the original strand of stainless steel wire suspended from an aluminum spider by the original stainless steel holding chuck. The assemblies are located in the former tank enclosures in the utility gallery at the upper ends of the lines. The enclosures are accessible by removing covers immediately above the reading stations. Each plumbline supports a 26-pound cylindrical weight at the bottom. At the lowest reading station on each plumbline, a container of oil is provided for vibration dampening of the suspended mass.

At the reading stations, doorframes are set in the concrete of the gallery wall, and doors seating against sponge-rubber seals are provided as closures. At each reading station on each plumbline, an anchorplate assembly is installed horizontally for supporting the measuring apparatus. The anchorplate assembly is positioned so that the upstream and downstream movement, as well as the cross stream movement, of the plumbline is measured in the planes of radial and tangential movement. Measurements are made using pairs of a measuring apparatus which consists of a peep sight mounted on a micrometer slide carriage. The apparatus is attached to the anchorplate assembly by knurled headed hold-down screws. Movement of the plumbline is determined in terms of the differences between successive readings of the measurements with respect to indexes on the anchorplate and the position of the plumbline. Figure 52 shows the plate assembly as installed in the reading stations, the reference targets, and the measurement devices.

The doors of the reading station are kept locked, except when readings are being made to prevent unauthorized personnel from disturbing the plumblines. Observed data are recorded on an appropriate data sheet. Computing is done by punched cards and an electronic computer.

Measurements of the wells which extend into the foundation from near the base elevation of each plumbline area are made at less frequent intervals than measurements at the plumblines. In the well measurements, a target at the bottom of each well is used for optical plumbing from the gallery elevation using an optical plummet. Thus, horizontal movement at the gallery is with respect to the target at the bottom of a well.

Plots with respect to time of the plumbline data are made in the form of radial and tangential deflections of

the top of the dam and of each intermediate elevation. The plots furnish a time record of the movement of the four arch and three cantilever elements of the dam in which the plumbline data are obtained. Foundation well data are plotted in a similar manner, and these data are correlated with data from the triangulation measurements for information to detect possible deformation of the dam foundation.

47. UPLIFT PRESSURE PIPES. Hydrostatic uplift at the base of the dam is measured by 23 pipes in five lines of four or five pipes each. The lines of pipes are located in blocks 7, 12, 15, 18, and 22. The layout of the system of pipes is shown on figure 53.

When a pipe is under pressure, the pressure is measured by means of a Bourdon-tube pressure gage calibrated in feet of water, attached through a gage cock to the uplift pipe. When zero pressure is indicated in a pipe, the water level is determined by sounding. Continued zero pressure with water standing at the level of the top of the pipe is investigated further by adding a transparent standpipe section to the pipe and observing the level to which the water rises. Uplift pressure readings and sounding are recorded on an appropriate data sheet.

2/

48. RECORDS AND REPORTS. Readings of the instruments in the dam, in the foundation, on the penstocks, and on the reinforcing steel; readings of the uplift pressure pipes and the drainflow; and measurements on the plumblines and at foundation wells are made in accordance with the schedule shown by the designers' operating criteria prepared for the structure. These data are recorded on appropriate data sheets and transmitted as a monthly report to the Denver Office. Daily records of air and water temperature, reservoir and tailwater elevations, and any other data that may have an affect on the structural action of the dam, along with comments concerning the operation of the apparatus or the measurements, are included with the report.

Blocked out and placed separately

Bushing

Each uplift pressure pipe to be locoted and installed approximately
as shown with the bottom 6" above rock surface. Minor changes
may be mode when advisable.

All pipes are to be tightly capped or plugged during foundation
grouting operations.

Where pipes through which holes are to be drilled extend to
galleries, the holes are to be drilled through the pipes into
foundation rock after completion of high pressure grouting in
the surrounding area. Remainder of holes to be drilled as soon
as possible after first aft of concrete is placed, ond preliminary
grouting completed in the surrounding area. Minimum diameter
of holes to be ", minimum depth of holes into foundation
rock to be 3 ft.

For details of installation of uplift pressure pipes, see Denver
Office Drowing 40-0-5291.

All pipes are 2 standard black steel except as otherwise noted.
All fittings are standard malleable iron

Details of installation of goges are to be determined of
beginning of uplift pressure measurements.

For gallery and odit locations and dimensions, see Denver

pressure pipe E Office Drowings:

2; Pipes

"Wash header El 3:48 5: E1 3:46 0

El 3155.00 1-2 Pipes

Rock El 3144 0

Rock E1 3145.4

DETAIL

A

Rock E13:453

(AS BUILT)

Line of excovotion

Rock E-3443

· Adit to power plant service oreo

-2×12×12 recess for pressure 9795.

LINE 3
BLOCK 18
STA 10+40

Foundation gallery

All stations are measured along axis of dom.

After pipes have been placed, o drowing showing actual details
of installation including final location of pipes, elevation of
foundation rock at each pipe and notes on condition of the
foundation rock adjacent to the pipe locations is to be
prepared in the field and forwarded to the Office of the
Assistant Commissioner and Chief Engineer for record.
Wash headers to be installed on all uplift pressure
pipes which include bends and elbows as shown on
Denver Office Dwg 40-0-5291

For details of uplift pressure gage installations, see Denver
Office Drawing 459-D-1691

For details of adit to power plant service area, see
Denver Office Drawing 459-0-1327

deformation is done by punched cards and an electronic computer.

Check measurements of embedded instrument cable resistances are made semiannually. The Bourdon-tube

pressure gages used for uplift pressure measurements are cleaned and recalibrated annually. As these data which are recorded on appropriate forms become available, they are transmitted to the Denver office with the monthly reports of instrument readings.