PROJ00061

• Contract/PO #: C153366
• Contractor Name: Ridges Metropolitan District
• Contract Type: Loan
• Water District: 72
• County: Mesa
• Bill Number: SB 81-439
• Loan Projects - Doc Type: Feasibility Study

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The inflow design flood and volume and peak discharge will be determined
in accordance with the U. S. Department of the Interior, Bureau of Reclama-
tion "Design of Small Dams", Chapters III and IX and Appendix C. The com-
putational procedure for the proposed dams is shown in Table 5-b. The one-
hour point precipitation for Zone II, west of the 1050 meridian has been
selected as the design storm. The probable flood type has been selected as
less than maximum probable - Assumption A. Assumption A provides criteria
for inflow design floods for structures where failure would not increase
danger to human life and some risk of failure may be tolerated. The flood
hazard and routing criteria shall be in accordance with Chapter IX of the
"Design of Small Dams".

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Since the intake structure of the primary pump station is located at the
tailrace of the Redlands Power Canal the water level fluctuations are mini-
mal and range from 4532 ~ to 4534 +. It should be noted also that the channel
between the tailrace and the pump station is protected from a 100-year flood.
This prevents a large quantity of silt from being deposited in the channel
during a flood period.

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Ample flexibility in meeting the minimal varying water demand will be pro-
vided by utilizing four turbine type pumps at various stages of demand. See
the preliminary design layout in Appendix C of this report for further design
information.

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The pumping station sumps will have the sump inlet below the minimum liquid
level. Additionally, the center-to-center distance of multiple pumps will be
l~ to 2 times the diameter of the suction bell. The backwall clearance will
be 9/16 times the diameter of the suction bell. Velocities within the sump
will be less than 2 feet per second.

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Basic water hammer analysis will be conducted using references from Joukousky
and Allievi. Water hammer solutions for the pumping systems with various
surge control devices will be examined. Several possible solutions will be
reviewed and are as follows:

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1. Hydraulic transients at the pump and midlength of the pump discharge
lines with reverse flow passing through the pumps.

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2. Surge tanks.

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Surge suppressors.

4. Air chambers.

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5.

One-way surge tanks.

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6. Water column separation.

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Most materials such as concrete, reinforcing steel, structural steel, elec-
trical equipment and piping are readily available with the project area. In
addition, three phase electrical power is available within the project area.

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