Canal Work Project at IGI Airport, Delhi

Ocean Global supplied and installed 4000 sq m of 1.0 mm HDPE geomembrane for a canal work project at Indira Gandhi International Airport (IGI), Delhi, part of the airport’s water conservation arrangements. This page covers why canals are lined with geomembrane, how the airport uses its water, and the lining specification on this job.

Why canals leak

Canals carry water from where it is available to where it is needed, for cities, farms and large campuses. Many were historically lined with compacted clay or concrete, or left unlined.

Earthen canals are cheap to build but lose a large share of the water they carry to seepage, and they erode and choke with vegetation, so their capacity falls over time. Concrete lining reduces erosion and weed growth, but it costs more and cracks as it ages, through shrinkage, thermal movement and settlement. Water then escapes through the cracks and joints, so a concrete canal can still lose a significant amount of water.

Water conservation at IGI Airport

Delhi airport has adopted a range of environmental and water-saving measures, including green cover planting across the airport and an automated irrigation system. Around four lakh square metres of land is watered by this system, which runs on treated water from four underground sewage treatment plants.

According to the terminal facilities, water conservation arrangements were made alongside Ocean Global’s canal work project. Water used at the airport goes to the four underground treatment plants, which have a combined capacity of 3.5 million litres, for filtration and treatment, and is then distributed for irrigation through a 90-kilometre pipe network. Microprocessor-controlled treatment prepares the water before use. Irrigation is by sprinkler and drip, which cuts water and power waste and helps maintain soil quality. A total of four lakh square metres of the airport area has been planted.

How geosynthetics improve a canal lining

Geosynthetics improve a canal lining on their own or combined with a concrete veneer. A geomembrane is effectively impermeable, so seepage through the lining drops sharply compared with earth or concrete alone, and erosion and weed growth are controlled as well.

In a composite lining, the geomembrane sits beneath the concrete. If the concrete cracks, the membrane behind it keeps holding water until the slab is repaired. A geotextile beneath the geomembrane cushions it against stony or uneven subgrade, and geogrids can support the lining where the subgrade is weak.

Construction

Geomembrane canal liners can be left exposed or covered. HDPE geomembranes are UV stabilised with carbon black and can sit in the sun for long periods. Even so, most lined canals should have a concrete cover, or at least an earth cover for ballast, because exposed membranes are more easily damaged by rocks, debris, equipment, animals and vandalism. The concrete cover can be cast in place with reinforcing steel, pumped into geotextile forms, laid as precast panels or sprayed.

Geomembranes suit new canals and the relining of existing earthen or concrete canals that are cracked and leaking. Where the budget does not allow a full reline, the worst sections can be relined first and the rest done in stages.

Scope and specification

The project required 4000 sq m of 1.0 mm HDPE Geomembrane. Ocean Global’s scope covered delivery, installation and welding of the 1.0 mm geomembrane on the bottom and slopes. The geomembrane is 97.5 percent polyethylene and 2.5 percent carbon black, within the 2 to 3 percent carbon black range GRI-GM13 specifies for UV protection. It is formulated to resist environmental stress cracking, and its UV stabilisation allows exposed as well as covered use.

The client specified the layer system, with the stated aim of preventing leachate seeping from the bottom of the landfill: a 1000 mm embankment, the 1.0 mm geomembrane, 300 mm of coarser material and 2 mm drainage aggregate. The top of the geomembrane was secured with a layer of cement concrete and a 3 m lap.

More lining projects are on our case studies page.