construction and refurbishment of earthen irrigation channel banks

Tight specifications and construction tolerances add significantly to costs, and realisticrequirements need to be established for general channel bank work. In some situations,stringent specifications have been adopted that are really more appropriate to major earthworks projects, rather than the construction of channel banks that are typically not muchmore than one metre high. Wherever possible, the liberalisation and simplification ofchannel bank specification should be pursued to lower construction costs.12.18 SeepageAll channels will seep to some extent. When the rate of seepage is unacceptably high,some form of control is required.Earthen channel design should therefore include an assessment of likely seepage rates,limits that can be considered tolerable, and control measures that are appropriate in eachparticular case.Where the costs of seepage control are high, alternatives such as a change in channellocation or modification of the channel network to eliminate a high seepage section ofchannel should be explored.The subject of channel seepage because of its importance is treated separately. Refer toSection 21, Channel Seepage and Section 22, Channel Lining.12.19 Rights over LandAn irrigation authority requires legal rights to occupy lands for the purposes ofconstructing, operating and maintaining channel works. It requires access to those worksand the rights to protect them from damages by stock, farming activities or any othercause.Where an authority channel crosses private property, an appropriate form of land tenurewill be required to adequately protect the channel works and secure access rights.In these situations the channel, including any access track, berms or spoil banks, shouldbe located on an adequate but not excessive width of land, over which the irrigationauthority has suitable rights.Careful consideration of land acquisition issues from the planning to construction stagescan significantly expedite a project and reduce its costs. Modifications of location andalignment can ease land acquisition problems.Some landholders argue against freehold acquisition on the grounds that it reduces thesaleable area of their property title. Other landholders request freehold acquisitionbecause they would otherwise have to pay municipal rates on lands held under easement.The methods of land tenure over the areas occupied by channel works vary acrossAustralia and can include:- Reserves- Freehold- Easements- Fenced easements- LeasesConstruction and Refurbishment of Earthen Channel Banks August 2002 - Edition 1.0 12-49