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Ameron International delivered 16 miles of Reinforced
Concrete Cylinder Pipe (RCCP) to supply water to thirsty Californians
in the San Francisco Bay area. Known as the Los Vaqueros Water Supply
Project, it consisted of a new dam and a 100,000 acre-foot reservoir,
two pumping plants and a total of 104,000 feet of large diameter
pipeline.
 The
project had been under study for a number of years with a major
concern being the potential for discovery of prehistoric archaeological
sites. According to "Archaeological and Geoarchaeological Investigations
of the Los Vaqueros Project Area," by Jack Meyer and Jeff Rosenthal,
after fifteen years of negotiations and effort, test excavations
for the Los Vaqueros Archaeological Project began in 1994. In all,
testing was conducted at nine prehistoric archaeological sites located
near the proposed dam or within the flood pool of the reservoir.
Five of the sites required limited testing. However, the other four
required extensive archaeological excavations with some surface
deposits associated with late prehistoric occupations, but three
sites contained deep buried deposits that dated to 1,000 or more
years old. Archaeological excavations revealed the presence of numerous
artifacts, several intact features, and over 150 prehistoric Native
American burials. Ameron supplied nearly 16 miles of 78 to 96-inch
diameter Reinforced Concrete Cylinder Pipe for the Los Vaqueros
Reservoir Project in Northern California.
 Some
of the artifacts recovered from the deeper deposit included a wide
stemmed obsidian projectile point, hand stones, and milling slabs.
Preliminary evaluation suggested that they were 6,000 to 8,000 years
of age, and may therefore represent some of the oldest cultural
materials discovered so far in the San Francisco Bay Region.
With a strong archaeological program underway, the project owner,
the Contra Costa Water District, awarded the pipeline contract to
ARB, Inc., of Brentwood, California, and issued the notice to proceed
in November 1994. The first major water supply project in California
for over 20 years, the reservoir will provide a new source of drinking
water for nearly a half-million residents.
Briefly, the intake pump station, the Old River Pumping Plant,
lifts water from the Sacramento/San Joaquin Delta into 34,000 feet
of 78-inch diameter pipeline and then to a transfer reservoir. The
transfer reservoir provides hydraulic grade control for the system
and serves as the intake for the second pumping plant.
 That
plant discharges to 24,000 feet of 72-inch diameter pipeline, which
in turn delivers water to Los Vaqueros Reservoir. A third pipeline,
which consists of 28,000 feet of 90-inch diameter and 19,000 feet
of 96-inch diameter pipe, feeds the Contra Costa Canal from either
the Old River Pumping Plant or the Los Vaqueros Reservoir.
ARB chose the rigid AWWA Standard C300, Reinforced Concrete
Pressure Pipe, Steel-Cylinder Type (RCCP) for the 78inch, 90-inch
and 96-inch diameter pipelines over the flexible pipe alternative.
The pipe supply contract was awarded to Ameron, which supplied the
pipe from its Tracy, California, plant, located close to the project
site. Selection of rigid Reinforced Concrete Cylinder Pipe (RCCP)
resulted in substantially reduced costs to the owner since the supporting
strength of the soil was poor and substantial over-excavation would
have been required to provide for the high levels of compaction
needed to support steel pipe.
The design pressure for the 78-inch, 90-inch and 96-inch pipeline
varied from 50 psi to 175 psi, and earth cover loads varied from
8 feet up to 40 feet. ARB did much of its excavation on a 3/4 to
1 slope. Scrapers were used to remove the first 4 to 5 feet and
then an excavator to complete the trench. Pipe bedding was a 6-inch
layer of pea gravel.
The design requirements were stringent and required two processes
to fabricate the pipe cylinders, and three processes to fabricate
the reinforcing cages. The principal features of the RCCP for the
project were:
- A welded steel cylinder with joint rings welded to its ends,
and with cylinder thickness varying from 0.1046 inch up to 0.25
inch. The steel spigot had two grooves for two gaskets in order
to have a testable joint.
- Continuous reinforcing bar was wrapped helically over the cylinder
for the inner steel when the diameter of the bar was up to 1/2
inch.
- An outer reinforcing cage was included when the bar diameter
increased from 1/2 inch up to 3/4 inch.
he pipe wall, consisting of dense concrete, encased the steel cylinder
and inside and outside reinforcing cages. The required wall thicknesses
were:
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