Photographic
Tour
Construction of the
Lake Hodges Projects began in 2005 and is anticipated to be completed in late
2010. The construction has four components:
• Pipeline Tunnel – a 10-foot diameter underground
pipeline, contained in a 1.25 mile long tunnel, connecting the two reservoirs
• Pump Station – a pump station to move water back
and forth between the two reservoirs and generate electricity
• Electrical Switchyard – an electrical switchyard
providing electricity to the pump station and sending electricity from the pump
station to a local transmission system, SDG&E will build one part and the
Water Authority will build adjacent equipment
• Inlet-outlet Structure – an inlet-outlet structure
below the water surface that draws and discharges water between the Hodges Reservoir
and the pump station
Diagram
of Lake Hodges Projects Components
Pipeline Tunnel
Completed in spring 2007, the pipeline tunnel is 1.25 miles-long and
contains a 10-foot diameter steel pipeline that rises 770 feet in elevation
from Hodges Reservoir to Olivenhain Reservoir.
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Water will flow back and forth between Hodges and Olivenhain Reservoirs
within this 10-foot diameter steel pipe. The pipe’s epoxy coat protects
the steel pipe from internal corrosion. In total, 148 sections of pipe
were used to complete the tunnel. |
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This is a “pipe carrier.” It was used to lift and place the
steel pipe within the 1.25-mile-long pipeline tunnel |
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A mucking machine pushes the “pipe carrier” into the pipeline
tunnel. |
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In this image, the pipe section is placed within the pipeline tunnel and
attached to another installed section of pipe. |
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The pipe section is secured inside the pipeline tunnel using timber bracing.
The bracing keeps the pipe from moving and allows the area between the
outside of the pipe and the tunnel wall to be backfilled with grout. |
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One by one, each section of pipe is welded together and forms the pipeline
inside the tunnel. |
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Once
welded together, the space between the 12-foot diameter tunnel and the
10-foot diameter pipeline is filled with grout. Grout is a fluid material
injected into soil, rock, concrete, or other construction material. Once
hardened, it forms a permanent impervious, watertight bond that provides
structural strength to the pipeline tunnel. This picture shows the grout
being pumped through a grout port installed in the pipe.
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Construction
crews inspect the inside of the pipeline tunnel prior to completion in
spring 2007. |
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Once
completed, the pipeline tunnel was sealed in May 2007. The seal will be
removed when the pump station contractor connects the pump station piping. |
Pump Station
The Hodges Pump Station will extend 12-stories underground and house two 28,000
horsepower pump turbines that will generate 40 megawatts of electricity as water
flows down the pipeline tunnel from Olivenhain Reservoir to Hodges Reservoir.
Electricity generated by the pump turbines will be transmitted to an outdoor
switchyard, then to a 69kV, ¼-mile-long power line that will connect
to the existing local transmission system.
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Construction equipment and materials used in the tunneling process are
lowered and lifted in and out of the pump station pit using a crane. |
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Looking down from the top pump station pit, you can see the excavators
removing material that has been blasted. The material is put in a dumpster-sized
bucket and hauled out of the pit using a crane. |
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At the bottom of the pit that will house the pump station, construction
workers drill pilot holes horizontally towards Lake Hodges. This construction
method is referred to as drill & blast method, in which pilot holes
are drilled for explosive charges. Once the explosive charges are set-off,
the resulting debris is carried out and the process is repeated. |
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The two-pronged inlet/outlet tunnel will draw or discharge water back
and forth from the inlet/outlet structure, located at the bottom of Hodges
Reservoir, and the pump station. |
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After construction crews completed excavation of the 12-story Hodges Pump
Station pit in June 2007, construction of the pump station’s foundations,
walls, and floors started. Here, a construction worker places steel reinforcing
bars within the Pump Station floor. The reinforcing bars are encased within
concrete to strengthen and hold the concrete together. |
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Construction crews started pouring the foundation of the pump station
in June 2007. Here, concrete is lowered in a large bucket and poured onto
the steel framework. |
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Another method of delivering concrete form the top of the pump station
excavation to lower sections was the use of a concrete pump truck. |
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As concrete is poured, a construction worker smoothes-over and levels
the concrete with an extension trowel.
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Here workers smooth and level a floor within the pump station. |
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As construction continued within the pump station, steel reinforced walls
were poured. |
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Some steel-reinforced concrete walls within the pump station reached ground
level in April 2008. |
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As concrete work on floors and walls took place, some of the water pipes
and equipment was installed. This image captures the installation of equipment
that now houses the two pump turbines. The pump turbines will generate electricity as water flows from Olivenhain into Hodges Reservoir.
The pump turbines will also send water from Hodges Reservoir uphill 1.25
miles to Olivenhain Reservoir. |
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Equipment for the Lake Hodges Projects has come from all over the world.
This 98-ton section of pipe is 21 feet in length and width and arrived
on an oversized delivery truck from Fontana, Calif. in May 2009. It connects
the pump station to the 1.25-mile-long pipeline between the Hodges and
Olivenhain reservoirs and split the tunnel’s water flow to feed
two pump turbines housed in the pump station.
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This long section of pipe is part of a connecting series of pipes that link the Y-shaped bifurcated pipe that enters the pump station with the pipeline that connects to the Olivenhain Reservoir. The wood inside reinforces the pipe, keeping the pipe round, and is removed once the pipeline is encased with concrete.
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This section of pipe connects to the 10-foot diameter pipeline already encased in the 1.25 mile long tunnel that connects to the Olivenhain Reservoir.
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Several maintenance hatches are visible in this aerial view of the pump station, looking straight down. The two four-foot diameter penstock pipes exiting the left side meet at the Y-shaped pipe and then form one pipe going under a construction access road visible at the far left of the photo. |
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This 48-inch diameter pipe inside the pump station connects to one of the two 28,000 horsepower pump turbines. The pipe will be completely enclosed by the pump station when work is completed. |
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Workers are preparing to pour concrete to secure the two pump turbines inside the pump station.
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Workers created wood forms to prepare for pouring concrete to erect a concrete encasement around a 200-foot section of pipe. The pipe connects the pump station to the 1.25 mile tunnel originating at Olivenhain Reservoir. The encasement and pipe are now located under 25 feet of soil.
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Two 28,000 horsepower pump turbines will move the water in and out of the pump station. Each pump turbine can generate up to 40 Megawatts of energy, enough for 26,000 homes. This photo shows the top of one turbine in place inside the pump station. A centering device used during installation is visible on the top of the head cover.
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In April 2009, community members from the Lake Hodges surrounding communities viewed sample varnish colors on the concrete walls of the pump station. Their preferred color choice was applied to the structure to help blend it in with the natural surroundings. The pump station extends 19 feet above ground and 10 stories below ground.
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A small jib crane will remain on the roof of the pump station. It will be used to lower heavy equipment in and out of the pump station for repairs or maintenance. The crane was painted brown at the recommendation of the Lake Hodges Community Landscape Committee.
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Electrical Switchyard
- Power line and Substation
The electrical
switchyard will provide electricity to the pump station and send electricity
from the pump station to a local transmission system. As water flows downhill
from the Olivenhain Reservoir, it will generate up to 40-megawatts of peak hydroelectric
energy, enough power to annually sustain nearly 26,000 homes. This energy will
help offset project operating costs and support future Water Authority projects.
SDG&E is building one part of the electrical switchyard and the Water Authority
will build adjacent equipment.
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Electricity generated by the pump turbines will be transmitted to an outdoor
switchyard. San Diego Gas & Electric’s construction crews started
work on the switchyard in June 2007. |
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This 69kV, ¼-mile-long power line connects the electrical switchyard
to the existing San Diego Gas & Electric local transmission system. |
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The San Diego Gas & Electric substation was completed in February
2008. The Water Authority will construct electrical facilities adjacent
to the substation prior to the completion of the project. |
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This picture shows an overall view of the construction site with the electrical substation seen in the left foreground.
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Inlet/Outlet Structure
The Hodges
Inlet/Outlet Structure will be located below the surface of Hodges Reservoir.
The structure is connected to the pump station by a 200-foot-long tunnel. The
pump station will draw or discharge water from the reservoir through the inlet-outlet
structure. There will be a trash rack at the west end of the structure that
will prevent large debris from entering the pump station. At the east end of
the pump station, water travels through a 10-foot diameter underground pipeline
to the Olivenhain Reservoir, 1.25 miles away. See graphic at beginning of photo
tour section.
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A cofferdam was constructed around the work site in Hodges Reservoir. The
cofferdam is a temporary enclosure from which water is pumped to create
a dry area to allow construction of the inlet/outlet tunnel and structure.
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The inlet/outlet structure was constructed within the walls of the cofferdam. Crews excavated material until they reached the lake bottom. |
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The cofferdam walls were reinforced with shotcrete and rock-bolts, which
supported the excavation of the inlet/outlet structure. |
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Pumps inside the cofferdam cells in the dam structure kept the area dry so that workers could install the inlet-outlet structure and tailrace tunnel.
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The cofferdam was completely installed by March 2007. Dismantling began in April 2009. The horse-shoe shaped structure held back the reservoir water while the contractor built the inlet-outlet structure and its connecting tunnel on the lake floor. (photo February 2009)
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Two large cranes were brought on to the site to dismantle the cofferdam. As the cofferdam was dismantled, the components were removed from the site and hauled to a metal scrap yard for recycling. The small rocks that had been inside each cell were removed by an excavator and then used as backfill around the pump station walls.
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Before the contractor could begin dismantling the cofferdam, the entire area had to be flooded so that the water level inside the cofferdam could be the same as the reservoir water level.
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The cofferdam was made of 13 connecting cells of steel sheets and pilings. A crane lifts up one of the pilings from a cell. The pilings extended 5 to 15 feet below the reservoir bottom, depending on their location. At the shoreline, the exposed portion was about 55 feet high.
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A crane lowered a circular template into the center of each cofferdam cell to stabilize it. Then each of the cell’s steel sheets could be removed and the pilings could be pulled out from the reservoir bottom.
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The template is lowered into place and secured.
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During construction for the inlet-outlet structure and related equipment, a string of buoys helped keep boaters from the cofferdam. Connected to the string of buoys was a mesh-like underwater net called a silt curtain, which reduced the amount of underwater dirt that could flow out into the reservoir.
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Once the cofferdam was completely removed in September 2009, the shoreline was stabilized with riprap made of large rocks. A new buoy system was installed (visible red line) to protect the submerged inlet-outlet structure from boaters.
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