construction and refurbishment of earthen irrigation channel banks

A hydraulic excavator working along the centreline of the channel can create theinitial pilot cut to the design bed level, followed by excavators working from thesides pulling back the batters to the design slope.Photos\construction\cg2.pilot trench.jpgPhoto 19-5Pilot trench for new channelThe material excavated to form the channel waterway, if suitable, can be used on thebanks. Unsuitable material or surplus material is formed into spoil banks or hauledto waste.Excavated material in excess of bank requirements at any cross-section can be usedto make up deficiencies at other cross-sections.19.6.3 Borrow PitsMaterial for bank construction is obtained either from the channel excavation, if it issuitable, or from borrow. The borrow material is taken from pits constructed wellclear of the channel line. For economy, borrow pits should be located as close aspossible to the site of the channel works. However in some situations, it may benecessary to travel a considerable distance from the channel to obtain suitablematerial.In some of the larger irrigation schemes in Australia, haul distances of 5 km arecommon and can be up to 10 km, adding significantly to earthwork costs.Photos\borrow pits\shep7 excavator loading tipper with borrow.jpgPhoto 19-6Excavator loading Dump Truck at Borrow PitIn selecting borrow sites consideration should be given to:• Suitability of the type of material available• Volume of channel bank material required• Volume and depth of soil obtainable from potential borrow pit(s)• Bulking factor of borrow material (refer section 19.6.4)• Distance from borrow pit to Channel Bank Construction site• Location of the borrow pit in respect to roads• Moisture content• Amount of stripping required• Depth of watertableRefer to Section 15, Material Selection and Testing.Where a haul road can be built, scrapers can be used. If the borrow material has tobe moved several kilometres over public roads, the choice would be a front-endloader, or excavator that would load dump trucks.Construction and Refurbishment of Earthen Channel Banks August 2002 - Edition 1.0 19-13