construction and refurbishment of earthen irrigation channel banks

Whether or not a covered geomembrane has been punctured or ruptured can bedifficult to determine. Locating the rupture can be equally difficult and repairing itcostly, requiring the section of the liner to be uncovered, dried, cleaned and patched.The use of a parabolic section for membrane lined channels instead of a trapezoidalsection can improve the efficiency of desilting operations and significantly reduce theassociated damage to the cover material.It is useful to provide markers to indicate the location of the lining to individualsinvolved in channel maintenance activities.Potential fire damage is an issue that needs consideration. Most lining material willmelt if exposed to fire and it is important that the edges of exposed linings are keptclean and clear of dead grass where fires are likely.Weeds can establish themselves on earth liner covers and maintenance costs relatedto aquatic weed control can be the same as unlined earthen channels.22.8.13 SummarySuccessful implementation of a liner requires careful choice of design and materialsas well as a comprehensive QC/QA program.The perfect geomembrane for all applications does not exist. The performance ofdifferent types of geomembrane can vary widely and a material that is well suited toone application may not be well suited to another. Care should be taken in selectinga material to look at the real performance requirements of the specific application andto review all of the associated aspects involved with the use of a particular materialincluding those related to maintenance and channel operations.These specifications and other documents are standard documents intended forguidance for standard projects. Review of the intended membrane choice andconstruction details and documentation by an experienced geosynthetic engineer isalways prudent.22.9 Hard Surface LiningsThese linings are the type placed directly on the subgrade of the channel and are exposedto the wear, erosion and deterioration of the flowing water. This category includes alllinings constructed of concrete, asphalt, brick and stone. Concrete which includes in-situ,precast, grouted fabric mats, shotcrete, reinforced and unreinforced linings, is the mostcommon hard surface linings used in Australia.Hard-surface linings are outside the scope of these Guidelines and readers should refer toSection 22.10 for detailed references on this type of lining.Construction and Refurbishment of Earthen Channel Banks August 2002 - Edition 1.0 22-68