Seasonal tourist demand is met in Malaga

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

Flowtite

®

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

2.5 metres

³

/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

potential differential

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

pipeline.