Appendix I - FCE Outlet Design Report (DRAFT)

115 Pages·2015·3.95 MB·English

by  Victor Narteh

M D R
ILLSITE AM EHABILITATION
O W E
UTLET ORKS XTENSION

DRAFT DESIGN REPORT

Prepared for

Utah Division of Water Resources

Prepared by

November 2015
Draft, Subject to Revision Millsite Dam Outlet Works  Design Report

TABLE OF CONTENTS
1 Introduction ...................................................................................................................... 1-1
2 Existing Outlet Works...................................................................................................... 2-1
2.1 Layout of Pipelines and Other Facilities .............................................................. 2-1
2.2 Outlet Discharge Valve ........................................................................................ 2-2
2.3 Plunge Pool .......................................................................................................... 2-2
3 Outlet Pipe ....................................................................................................................... 3-1
3.1 Pipe Wall Thickness ............................................................................................ 3-1
3.2 Hydraulic Analysis............................................................................................... 3-1
4 Outlet Works Extension ................................................................................................... 4-1
4.1 Vault Layout and Design ..................................................................................... 4-1
4.2 Pipe Diversions Layout and Design ..................................................................... 4-3
4.3 Discharge Valve Replacement ............................................................................. 4-4
4.4 Plunge Pool .......................................................................................................... 4-6
4.5 Miscellaneous Design .......................................................................................... 4-7
5 Conclusion and General Conditions ................................................................................ 5-1

List of Tables
Table 4.1: Roof Loading .............................................................................................................. 4-1
Table 4.2: Structural Design Software ......................................................................................... 4-2
Table 4.3: Heavyweight Nonwoven Geotextile Fabric Properties .............................................. 4-6

Appendices
Appendix A – Hydraulic Model Data
Appendix B – Structural Design Data
Appendix C – Miscellaneous Information

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1 Introduction
The existing Millsite Dam is not in compliance with current minimum Utah Dam Safety
standards. As a result, a berm will be constructed at the toe of the existing dam to stabilize the
dam for seismic conditions. This berm necessitates the extension of the outlet works further
downstream.

Franson Civil Engineers (FCE) is assisting the Utah Division of Water Resources (Water
Resources) with design work for the Millsite Dam Rehabilitation. FCE is preparing the Outlet
Works section of the Millsite Dam Rehabilitation Design Report. This section focuses on the
extension and relocation of the existing outlet works. For project background details, refer to the
Millsite Dam Rehabilitation Design Report prepared by Water Resources.

The proposed outlet works extension and relocation will include the following main construction
items:
a. Extending the existing outlet tunnel
b. Extending the existing 54-inch main outlet pipe
c. Extending all appurtenances, such as electrical wiring, air vent shaft, tunnel drains,
etc. necessary for operation of the outlet works
d. Replacing the existing 8-inch culinary pipeline with a new culinary pipeline (size is
being increased to 12-inch) along the entire length of the outlet tunnel
e. Relocating or replacing the connections for existing pipelines, including:
i. Two 36-inch diameter irrigation pipelines
ii. One 12-inch stock water pipeline, which currently connects to one of the
36-inch pipelines
iii. One 24-inch culinary pipeline (separate from the other culinary pipeline
mentioned above)
iv. One 24-inch pipeline that supplies cooling water to the power plant south of
Castle Dale
f. Replacing the existing 42-inch Howell Bunger valve with two plunger valves
g. Constructing a new vault and a building to house the relocated utilities
h. Relocating the water connection to the golf course booster station, if necessary
i. Existing or new tunnel inlet valves:
i. Replacing the electric actuator for the existing 54-inch butterfly valve with a
hydraulic actuator
ii. Installing a new 8-inch butterfly valve with manual and hydraulic actuators

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2 Existing Outlet Works
The dam was originally built in 1971. In 2000, the outlet works were modified to allow
connection of two 36-inch pipes and a 12-inch stockwater pipe for a pressurized irrigation
system. A new vault was constructed and the discharge valve was moved farther downstream to
facilitate the new connections. This section briefly explains the current configuration of the
outlet works.

2.1 Layout of Pipelines and Other Facilities
The existing vaults consist of the following pipelines and controls as described in a report
prepared by Water Resources:
• An 8-inch steel pipe which serves the Castle Valley Special Service District. It has an
exterior paint coating. The existence of an interior coating is uncertain. It runs from the
bulkhead of the inlet tower, down through the tunnel and control house, and into a meter
box to the south of the control house. This pipe joins with a 12-inch steel pipe in this box,
which then transitions into a 24-inch pipe and serves the special service district. The
upper end of the pipe has a gate valve and two gate valves in the meter box which can
isolate the meter. This entire pipe up to the upstream gate valve will be replaced as part of
this project due to corrosion of the pipe and a desire of the special service district to
increase the size of this pipe.
• A 12-inch steel pipe which serves the special service district. It has an exterior epoxy
coating in the tunnel, transitioning to a painted coating outside the tunnel. The existence
of an interior coating is uncertain. The pipe tees off of the 54-inch pipe in the control
house, and then runs to the same meter box as the 8-inch steel pipe previously mentioned.
This 12-inch pipe transitions to a 24-inch pipe that runs southeast, and then bends to the
east on the south side of the maintenance shed, continuing east towards the service
district’s facilities. The 24-inch pipe is reported to be ductile iron. The 12-inch pipe has a
gate valve in the tunnel, a valve just upstream of the meter box, and one in the meter box.
There is an older dysfunctional meter in the meter box, and a saddle type magmeter or
paddle wheel meter.
• A 24-inch steel pipe serving PacifiCorp that tees off of the 54-inch mainline in the
control house, and then runs into a metering building to the north of the control house,
where it is metered using an orifice meter. The pipe then transitions to a 26-inch
fiberglass pipe after the metering building. The pipe has one main butterfly valve in the
control house, but has a 6-inch bypass line around the main valve with two gate valves
and a globe valve, the gate valves being able to isolate the globe valve. PacifiCorp has
specifically requested that their steel pipe be replaced with ASTM grade B, 24-inch O.D.
pipe with 3/8-inch wall thickness, and that a custom spigot x flanged fitting, which they
would provide, and a JCM Style 304 adapter be used to join the new steel pipe to the
existing fiberglass pipe.

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• The Ferron Canal and Reservoir Company has a newer control vault downstream of the
historical control house. In this structure, two 36-inch steel pipes tee off of the main pipe.
Each pipe has a butterfly valve, but each also has a 6-inch bypass line around the
butterfly valve. Each bypass has two gate valves and a globe valve, the gate valves being
able to isolate the globe valve. The 36-inch lines turn east after exiting the control box.
The 36-inch pipes transition to PVC pipe downstream of the control box.
• A 12-inch steel stock waterline branches off of one of the 36-inch pipes, upstream of the
main 36-inch butterfly valve. This stock waterline has one butterfly valve. It turns east
after exiting the control vault. This stock waterline transitions to PVC pipe downstream
of the control vault.
• There are floor drains and groundwater drains under the canal company’s newer control
vault which run into a manhole southeast of the structure, and then drain into the stream
channel.
• A drain which collects seepage in the old tunnel, and the left toe drain, currently runs
through the newer control vault where they can be diverted into buckets for measurement.
The drain pipes then run out of the vault and into the stream channel.
• The golf course has diversions coming off of the special service district’s line, and off of
the stock waterline owned by the canal company. Both of the golf course’s lines run to
the west side of the maintenance shed where they feed a pump. Both of these lines are
6-inch PVC until they transition to HDPE pipe just before they enter the pump.

2.2 Outlet Discharge Valve
Also housed in the vault is the existing discharge valve. This is a 42-inch Howell-Bunger (HB)
valve that serves as the primary outlet and drains into the existing irrigation canal. The HB valve
is fitted with a concrete valve chamber to convert the valve discharge from a spray to a
concentrated jet. This HB valve was put in when the dam was built in 1971. The canal personnel
indicated that it is difficult to get replacement parts for the current HB valve and servicing the
valve is a complicated process. For these reasons, and also because the valve is past its design
life, the existing HB valve will need to be replaced with a new control valve. The HB valve is
currently being operated at 20% of its maximum capacity, and much of the time it is open.

2.3 Plunge Pool
The existing plunge pool is upstream of the irrigation canal that supplies water to the North,
South, and Molen Ditches. The canal personnel indicated that the side walls of the plunge pool
channel are eroding due to the high velocity jet from the HB valve and wave action.

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3 Outlet Pipe
3.1 Pipe Wall Thickness
The existing outlet pipe is a 54-inch epoxy-coated steel pipe. As indicated in the record drawings,
the original wall thickness was 5/16 inches. Water Resources has recently commissioned a study
evaluating the integrity of the existing outlet pipe. The structural analysis showed that at some
locations there was a decrease in the wall thickness of approximately 1/16 inches, with the lowest
reading showing a loss of 5/64 inches due to water dripping on the pipe from seams in the tunnel.
The deteriorating affects have been mitigated and Dam Safety anticipates that the outlet pipe
should have at least 50 more years of service life. The analysis also indicated that the maximum
stress in the outlet pipe, as a result of the full reservoir head, bending and settlement stresses, and
seismic forces would be 7,500 psi, well under the assumed minimum yield strength of 30,000 psi.

FCE evaluated this study and determined that an additional study to determine the required wall
thickness of the outlet pipe extension was not necessary and that it would be a reasonable
assumption to maintain the original wall thickness of 5/16 inches for the new section of outlet pipe.

3.2 Hydraulic Analysis
A hydraulic model was prepared using WaterCAD to size the outlet pipe to ensure that the peak
demands are supplied even during low reservoir levels. The existing 54-inch steel pipe is extended
until after most of the demand is met and then it is reduced to a 36-inch steel pipe. The mainline
was sized to meet the following demands:
• 36-inch pipe, irrigation flow – 35.34 cfs
• 36-inch pipe, irrigation flow – 35.34 cfs
• 12-inch pipe, stock water flow – 1 cfs
• 8-inch pipe, golf course flow – 3.5 cfs (this flow was added to the 12-inch pipeline in the model)
• 24-inch pipe, culinary water flow – 10 cfs
• 24-inch pipe, power plant flow – 20 cfs
• 36-inch pipe, outlet flow to canal – 263 cfs
• 10-inch pipe, outlet flow to canal – 10.84 cfs

The outlet flow was obtained from data on the Emery Water Conservancy District website and
represents the maximum flow released from the outlet to the North, South, and Molen Ditches on
the same day between June 2002 and June 2014. The remaining peak demands were supplied by
the respective project stakeholders.

The model shows that the 54-inch and 36-inch transmission pipelines are capable of supplying the
peak demands until the reservoir level drops to approximately 12 feet of head. When the water
level in the reservoir drops to 12 feet above the inlet to the outlet works, the peak demands above
cannot be met concurrently. This water level is 38 feet below the conservation pool water level and
as such the peak demands could not be requested by the water users. Based on the model and this
observation, the 54-inch pipe and a short section of 36-inch pipe can meet the peak demands of the
system.

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4 Outlet Works Extension
4.1 Vault Layout and Design
4.1.1 Layout Considerations
The current outlet works facilities consist of the original building and four separate underground
vaults. All the facilities had their own access point to an aboveground entrance with a door and
stairs. All the stakeholders expressed support for an efficient pipe layout to be housed in a single
vault. Various versions of the pipe layout were distributed among the stakeholders for comment
until the final layout seen in the design drawings was agreed upon.

4.1.2 Structural Analysis
Vault
The loads considered for design of the concrete outlet vault were snow loads, earthquake loads,
live loads and dead loads typical for this area and type of building. Wind loads were not
considered due to the vault being mostly buried. The structural steel design of the roof joists is to
be determined by the steel joist manufacturer and coordinated by the contractor. Assumptions
were made as to the type and weight of members to be used so that an accurate dead load could
be determined. Snow loads were determined from the location and elevation of the site and are in
accordance with building code requirements. Live loads were assumed to be typical roof
maintenance loads. Table 4.1 shows the roof loads considered in the vault design. It should be
noted that the vault’s roof was not designed with the loads shown in Table 4.1. The roof loads
shown in the table were used to estimate the loading on the vertical walls of the vault.

Table 4.1: Roof Loading
Roof Load Description Load (lb/ft2)
Snow 40.3
Tin 0.75
Structural Panels 3.5
Joists 4.1
Live Loads 20
Earthquake Equivalent 28.9

The design loads in various loading combinations were considered and the most conservative
loading was taken and used for the rest of the design. The design load was distributed over the
roof structure and the resulting loads on the walls were determined. These roof loads in
combination with backfilling and soil loads were then used to design the walls of the vault. Two
methods were used for the wall design. Some of the walls were supported internally by other
walls. These walls were designed using the Portland Cement Association’s design guide for
rectangular concrete tanks. All other walls that were completely or partially unsupported by other

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walls were designed as retaining structures using QuickRWall structural design software. The
results of both design methods were compared and the more conservative rebar configuration
was used for all walls for consistency.

The design of the wall footings was taken from the QuickRWall analysis of the walls as retaining
structures. The loads considered for the floor design included the resulting loads from the wall
design, the supporting soil under the structure, the weight of the pipes and equipment in the
vault, the water weight for filled pipes, and dead and live loads according to building code
requirements. Several critical sections were considered for the flood design, and each were
analyzed for maximum shear and moments. The results of the analysis of all the critical sections
were compared and the critical rebar section was determined. This rebar section was used
throughout the floor for consistency, with the exception of the floor that is also the wall footing.

A concrete support beam was needed to span the vault from the end of the tunnel to the adjacent
internal corner of the vault to support the south wall of the concrete masonry unit (CMU)
building. The loads on this beam include the typical roof loads, the weight of the CMU wall, and
dead and live loads from the steel floor to be used on the upper level of the structure. The beam
was analyzed using spSlab software and the critical rebar section was determined. The outside
dimensions of the beam were determined by the necessary elevations of the supported roof
section and by the necessary connections of the CMU building and the steel floor.

The end of the beam near the tunnel will be supported by the thicker wall of the tunnel. The wall
on the other end of the beam could not support the loads transferred by the beam, so a column
had to be designed to create a strong enough support for the beam. The cross section of this
column was designed using spColumn structural design software. Refer to Table 4.2 for the
structural design software details.

Table 4.2: Structural Design Software
Software Version Publisher Building Codes
QuickRWall 2.01.0007 Integrated Engineering Software, Inc. IBC 2006
spSlab v3.60 StructurePoint, LLC ACI 318-11
spColumn v4.81 StructurePoint, LLC ACI 318-11

Tunnel
The existing tunnel was designed in 1969. It is designed conservatively and the structure has not
had any problems to date. The extension of the tunnel will use the same design as the original
based on details from the 1969 drawings created by the U.S. Department of Agriculture Soil
Conservation Service.

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4.2 Pipe Diversions Layout and Design
4.2.1 Castle Valley Special Service District 8-inch Pipe
The special service district has requested that the existing 8-inch pipe connected at the head of
the tunnel be replaced with a 12-inch pipe based upon future demands of their system. The
options of Fusible PVC, Polypropylene, HDPE, and Steel pipe were evaluated to replace the
steel line. The evaluation criteria included stiffness, design life, thermal expansion,
constructability, and cost. A summary of the criteria was presented to the Natural Resources
Conservation Service (NRCS) and Water Resources for their recommendation. It was conveyed
to FCE that steel pipes are the standard for use in dam tunnel applications. This 12-inch pipeline
will connect to the main special service district pipeline in the vault and will be equipped with a
new magnetic flow meter and control valve. Fusible PVC and polypropylene pipe are viable
alternatives. The selection of steel pipe was based on the recommendation of Water Resources
and NRCS.

4.2.2 Castle Valley Special Service District 12-inch Pipe
Currently, the special service district has one 12-inch line connected to the main outlet pipe. This
pipe merges with the existing 8-inch pipe running through the tunnel in a separate vault and then
transitions to a 24-inch pipeline. To simplify the operation of these two pipelines, they will
connect in the new vault. There is not a current bypass filling pipe for the culinary lines;
therefore, one will not be added.

The pipe inside the vault will be steel and will have welded or flanged connections with a
coating of fusion bonded epoxy. The wall thickness will match that of the main outlet pipe. The
diameter of this outlet was not modeled under this project and will match that of the existing
outlet.

The pipe material outside the vault connecting the steel pipe to the existing pipeline will consist
of 24-inch C905 PVC DR32.5. This pipe has a pressure rating of 125 psi and a minimum wall
thickness of 0.794 inches. Ductile iron fittings with mechanical joints and thrust blocks will be
used to make required bends.

4.2.3 PacifiCorp 24-inch Pipe
The pipeline will be configured with a 6-inch bypass filling pipe to match the existing layout.
PacifiCorp specifically requested the Endress Hauser Promag Electromagnetic Flowmeter to
meet required material standards. The pipe inside the vault will be welded and flanged fusion-
bonded epoxy-coated steel. The wall thickness will match that of the main outlet pipe. The
diameter of the PacifiCorp outlet was not modeled under this project and will match the size of
the existing outlet.

The majority of the pipeline that conveys water to the Hunter Power Plant is a 26-inch fiberglass
pipe. The dam rehabilitation requires a section of the existing fiberglass pipe to be removed for

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the plunge pool. C905 PVC pipe is being used between the steel pipe in the vault and the existing
fiberglass pipe. PacifiCorp has requested that the C905 PVC pipe be DR18 instead of the
DR32.5 needed for the anticipated pressure for mechanical strength and durability. The DR18
has a pressure rating of 235 psi and a minimal wall thickness of 1.433 inches. Ductile iron
fittings with mechanical joints and thrust blocks will be used to make required bends.

Specific fittings are required to make the connection between the C905 PVC pipe and the
fiberglass line. These fittings will be provided by PacifiCorp. The fittings consist of a spigot x
flanged fitting and a JCM style 304 adapter. PacifiCorp has indicated that the fiberglass pipe has
to be connected to at an existing bell end and there needs to be a minimum distance of 40 feet
upstream of the adapter to the nearest bend.

4.2.4 Ferron Canal and Reservoir Company (2) 36-inch Pipes
The pipelines will be configured with a 6-inch bypass filling pipe to match the existing layout.
Where possible, the existing pipes, valves and fittings will be salvaged and reused. The pipes
inside the vault will be welded and flanged fusion-bonded epoxy-coated steel. The wall thickness
will match that of the main outlet pipe. The diameter of these outlets was not modeled under this
project and will match that of the existing outlet. The piping for these two outlets was
constructed in 2000. The owner would like the valves and fittings reused in the new design. Bid
items will be included for the refurbishment of these parts as well as for furnishing and installing
new parts. Currently the water is not metered and the owner at this point does not have the need
to place meters in the vault.

The pipes outside the vault connecting the steel pipes to the existing pipelines will be 36-inch
C905 PVC DR32.5. This pipe has a pressure rating of 125 psi and a minimum wall thickness of
0.794 inches. Ductile iron fittings with mechanical joints and thrust blocks will be used to make
required bends.

4.2.5 Ferron Canal and Reservoir Company 12-inch Pipe
This pipeline services the stock water needs of the canal company. The pipe inside the vault will
be welded and flanged fusion-bonded epoxy-coated steel. The wall thickness will match that of
the main outlet pipe. The diameter of these outlets was not modeled under this project and will
match that of the existing outlet.

4.2.6 Millsite Golf Course 8-inch Pipe
The golf course line will not be affected by this project.

4.3 Discharge Valve Replacement
The controlling factor in sizing the discharge valve is typically that it should be able to drain
90% of the reservoir’s capacity within 30 days (as required by Dam Safety). Also, the

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