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.
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.