Canal^3® Lining with a Shotcrete Cover

The situation:

The Dryden Canal was constructed in the early 1900’s to provide hydroelectric power and irrigation water to the Wenatchee Valley. The power plant was decommissioned in the 1950's but the delivery of irrigation water continues to be an important function of the canal. Since 1990, a rearing and acclimation pond for endangered species has been operated successfully adjacent to the old powerhouse. The canal delivers a vital water supply to the pond of up to 32 cubic feet per second.

The problem:

For five years, several geosynthetic lining systems were tried in this problem area. In 2003, the District evaluated the risk of a canal failure, the potential damage to the Wenatchee River ecosystem, and the temporary shutdown of an essential water supply outweighed the cost of installing a lining system. Various lining alternatives were evaluated, and HUESKER’s 8208 geocomposite liner with a 3-inch shotcrete cover offered the most cost effective lining option to be installed along 1,600 feet of the canal. The canal had not been cleaned in this area for some time. Extensive work was needed to bring the canal invert to grade and clean the side slopes of vegetation. Due to the lack of access, all preparation and placing of the composite liner and shotcrete had to be completed within the canal prism. A trackhoe was used to smooth the sides and invert, and to place the liner. Because the liner has a high puncture resistance, concrete trucks and the shotcrete application crew were able to drive on the material to apply the shotcrete. Batten strips were used to fasten the liner to the structures. Seaming was accomplished using either hot melt glue or a two part high strength epoxy.

The advantages:

When compared to other lining methods, Canal³ offers several advantages.

• Reduced excavation. Use of PVC requires overexcavation of the canal by 18 to 24 inches, backfilling with a 6-inch layer of sand for bedding, placing the PVC membrane over the sand layer, then covering the PVC with another 6-inch layer of sand for protection. This is followed by the placement of 6 to 12 inch layer of armor stone. By using Canal^3®, excavation is not required (just normal shaping & anchoring trenching) and no sand bedding or sand cover material is required because the polyester fabric protects the membrane.
• Steeper side slopes can be achieved, increasing the canal’s water holding capacity due to the interface friction advantage that Canal^3® provides.
• Shotcrete can be placed directly over the Canal^3® which provides protection from animals, vandalism, fire, sunlight, etc.
  According to studies by the Bureau of Reclamation, this method provides the highest effectiveness (95%+) and longevity (50 years).• Canal^3® can be installed by the irrigation districts own work force.