Seasonal tourist demand is met in Malaga
The ancient port of Malaga has been a favourite wintering place for travellers since the 19th century. In the 1960s, the nar-row strip of coast to its east and west was claimed by the nascent European tourist industry as the 'Costa del Sol' and the boom began.
Today, although agriculture is still
important, service industries -tourism
especially – predominate. In
2000, they accounted for approxi-mately
70% of the region’s GNP,
compared with 8% for agriculture
and fishing. With a population of
over 1 million, Malaga is the sixth
largest city in Spain, but during the
high tourist season this can swell by
an additional 500,000, with a major
stress on the local infrastructure.
The plan was to take water from
the new Casasola dam, which has a
high water level 145 metres above
mean sea level, and transport the
water through a 9.5 km pipeline in a
seasonally dry river bed to the
Guadalhorce river. The water is then
discharged into the main channel of
the Guadalhorce where it flows to
the two main water treatment plants,
Atabal and Pilones.
As the water quality of the
Campanillas River is superior to that
of the saline Guadalhorce, an added
benefit is the improved water quality
in the Guadalhorce downstream.
Construction and service group,
OHL was contracted to carry out the
works and had the option of select-ing
the type of pipe used to develop
the project. After considering all per-formance
and installation require-ments
for the project, OHL selected
GRP pipe supplied by
Flowtite Iberica of Camarles, Spain.
The project required over 9.5 kms
of DN1300. Although the maximum
service pressure (static head) in the
DN1300 transmission line would be
8 bars, a pipe with a pressure rating
of 10 bars was selected. The 1300 mm
dia pipeline was designed to trans-port
/sec of water.
The major part of the project
required the installation of 8,897
metres of DN1300 pipe in a dry river
bed trench which provided the ideal
right-of-way for this gravity flow
pipeline. The GRP pipe was installed
with 2-3.5 metres of cover after
backfilling to final grade. The exca-
vated soil – a coarse granular mater-ial
– made for an excellent pipe zone
backfill material. A pipe with a spe-cific
stiffness (EI/D3) of 2500 N/m² was used throughout the installa-tion.
Vertical pipe deflections,
measured after final backfilling,
confirmed the appropriateness of the
SN2500 product selection. Pipe
deflections did not exceed 1.5%,
with an average around 1%.
Compacted bedding of 250mm
was placed along the trench bottom.
Pipe with 12 metre laying lengths
was used. Small over-excavations
were made every 12 metres at the
joint so the pipe had uniform sup-port.
After joint assembly, the pipe
zone backfill was placed on each side
of the pipe in 300mm lifts and com-pacted
to 90% standard Proctor den-sity.
This was continued until the
backfill reached a level of 300mm
over the pipe crown. The remaining
native soil was returned to the trench
with no further compaction.
The project specifications called
for the pipeline to be field
hydrotested to 140% of the maxi-mum
service pressure. Prior to ship-ment
to the site, Flowtite Iberica
hydrotested each 12 metre length of
pipe, and separately each coupling,
to 20 bars of pressure, or 200% of the
rated pressure class. OHL then tested
the installed pipe to 11 bars for 30
minutes with no reduction in line
pressure. In addition to this field test,
a leak tightness test was also per-formed
by OHL. A small head of
water was placed on the upstream
end of the 9.5 km lone pipeline and
the amount of water required to
maintain this same elevation in the
reservoir was measured over a 24-
hour period. The addition of only
300 litres of water was needed,
indicating the good tightness of the
overall system, which included
fittings and valves.
Concrete thrust blocks were used
at changes in direction, restraining
the movement of fittings. To accom-modate
settlement between a concrete block
and the flexible pipeline, rocker
pipes were used immediately adja-cent
to each thrust block. The close
proximity of the coupling joint to
the concrete interface will accommo-date
more translation and rotation
than the pipe alone.
In addition to the supply of pipe,
Flowtite Iberica also undertook to
fabricate and supply all the necessary
fittings required by OHL to build the
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