PROJC00189

• Contract/PO #: C150006
• Contractor Name: Palisade, Town of
• Contract Type: Loan
• Water District: 72
• County: Mesa
• Bill Number: HB 95-1155
• Loan Projects - Doc Type: Feasibility Study

V-u

I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I

Pipe Sections. The following piPe sections will be evaluated independently:

a. Section 1 - Outlet works under dam (intake screen to outlet box)
(Segment 1)
b. Section 2 - Cabin Reservoir outlet box to Kruzen Springs box
(Segments 2 & 3)
c. Section 3 - Kruzen Springs box to Wye (Segments 4-7)
d. Section 4 - Wye to WTP (Se~ment 7)

Capacity Based on Ground Profil~ The main item that determines the pipe
diameter required to carry a given flow is the pipe hydraulic gradient. For
open channel flow, the hydraulic gradient on a long pipeline equals the slope
of the pipe, which is usually panillel to ground slope. There will be different
pipe slopes (hydraulic gradients) along the route. Pipes with flatter slopes will
flow fuller than slopes on a steePer gradient. In some cases, a surcharge may
occur if the pipe gradient is not Meep enough.

Because the water depth varies d~nding on pipe slopes, it will be necessary
to provide air release and vacuum valves at certain locations to prevent air
locking and pipe collapse. Vent pipes are preferable to air release vacuum
valves since their cost is significantly less, and there is much less maintenance.
However, greater care must be taken in their placement to prevent overflow.

2. Methods for Calculation of CapaQity for Individulll Pipe Segments

For outlet control calculations, both the Manning and Hazen-Williams formulas
were used to calculate pipe diam~ters needed to carry a specified flow. All
calculations assumed use of C1.5~ ductile iron pipe, with a Mannings 'n' of
.009. Slopes were estimated by plotting prof1les off a USGS map. For inlet
control calculations, the orifice equation was used to calculate flows from
concrete boxes.

A ground prof11e was plotted for the pipeline route using USGS maps. For
each pipe segment, 3 different scenarios for pipe capacity were evaluated as
follows:

a. CllPllcity R:l<P1l on Average Ov..",n Slope. When using the standard pipe
formulas for calculating pipe diameter, the first step is to determine overall
head and total length and froQ! this, calculate the average overall pipe slope
(HGL). The formula then calculates the minimum size pipe, but must be
used with caution. First, this approach is only possible if the entire pipe
prof11e is concave shaped. If it has a convex prof11e (flatter sections exist
in the upstream areas), the hYdraulic grade line will pass below the prof11e
of the pipe and a vacuum collld occur. Second, this approach only works
if there is one specific flow Tate. At lower flow rates than the ideal flow,