Evaluation of Canal Lining Projects in the Lower Rio Grande Valley
Since 1999, seven (7) irrigation districts in the Lower Rio Grande Valley of Texas have installed six (6) different types of synthetic canal lining materials, totaling approximately 21 miles. In 2005, we began a program to track the long‐term effectiveness and durability of these lining projects and to document the damage caused by such factors as UV, animal traffic, intentional and unintentional vandalism, and normal irrigation district operational and maintenance activities. Each project was evaluated using a visual inspection process during which performance/condition ratings were assigned. Without question, the best lining system is a synthetic liner with a protective barrier of shotcrete. The synthetic liner significantly reduces seepage, while the shotcrete protects it from damage. This lining system needs little to no maintenance. There were two types of liners used: PVC and polyester. Each performed equally as well. The performance of synthetic liners without a protective barrier varied dramatically. One important factor was the location of the project. Liners located in high traffic areas (people and animals) showed significantly more damage than those installed in remote areas. Damage was also common which appeared to be caused by mowing and canal cleaning operations. The PVC alloy is the toughest of the 4 liners installed without a protective barrier, is more difficult to cut and less likely to be damaged by unintentional vandalism. We also observed that liners carelessly or improperly installed were more susceptible to intentional and/or unintentional damage. For example, liners which are not properly stretched leave folds which can easily be caught by machinery or pulled by children swimming in the canals. Additional details are provided in this report, along with suggested considerations when planning a lining project. A summary of the findings for each individual lining project is presented in the Appendix B of this report which is published separately.