CWC Technology Brief

Soil Stabilization For Irrigation Canal Lining

Each year, irrigation canals in Washington and other states suffer tremendous water losses. A substantial portion of these losses is attributed to the failure of canal liners. Not only do these failures represent considerable financial cost, but canal leakage on slopes could cause slope failure, and further cause considerable hazard to individuals. Water losses in individual irrigation districts can cost over $500,000 annually. Properly lining the canals can reduce water loss. Concrete or plastic film can line canals, or, as this technology brief describes, the soil can be stabilized.

Project Overview

The goal of this project were to test stabilized soil to determine if it would meet the strength and permeability necessary to line an irrigation canal. Tests on different blends of soil and stabilization materials determined the best formulation.

Materials for Soil Stabilization

Materials have been used to stabilize soils for 2,000 years. Lime and bentonite are two materials used for soil stabilization. Roads, hillside stabilization, reservoir lining, or irrigation canal lining can use the stabilized soil. For this project, tests used a product called Econolime to provide the lime for the soil stabilization. Econolime is a by-product generated during the lime-production manufacturing process and some pulp and paper mills also generated it.

The estimate for the amount of Econolime produced at two Washington plants generating this by-product is 7,800 tons per year. One plant has approximately 30,000 tons of the Econolime stockpiled.

Although the soil stabilizer selected and used for this project was Econolime, another potential lime source could stabilize soil. This source is a by-product from controlled atmosphere warehouses that store apples.

Formulation and Testing

Stabilized soil samples were prepared using different amounts of Econolime and other additives. The amount of Econolime used ranged from 10 to 20 percent of the dry soil mixture.

Samples underwent two types of testing: the strength test (for 3 days and for 7 days) and the permeability test. After the initial testing, the best-performing formula was mixed again for further strength and permeability testing.

The formula that produced the best test results used the following components:

The strength after 3 days was 297 psi and, after 7 days, was 305 psi. (The local water district requires a minimum strength of 100 psi.) The permeability showed a hydraulic conductivity of 10-6 cm/s.

Cost Considerations

Using stabilized soil for irrigation canal lining has performance and cost advantages over concrete lining or plastic film lining. Lining canals with concrete can cost three times more than soil stabilization. Plastic lining is more expensive than concrete lining and animal migration can damage the plastic lining. The low cost of Econolime, which is less than $10 per ton, makes its use as a soil stabilizer advantageous. Heedless of this advantage, this material is currently going to landfills or stockpiles.

Conclusions

The tests performed in this project demonstrated that soil stabilization using 20% Econolime per soil weight can produce soil strengths and permeability that would be acceptable for use in irrigation canal lining. The testing performed was for a specific regional soil content. Soils from different regions would need additional testing.

Acknowledgments

The testing on this project was performed by Wedge Engineering, a soils laboratory and engineering firm located in Rainier. The soils supplied and the formulations to be tested were developed by Soil 2001, located in Yakima, with the assistance of Continental Lime of Tacoma.

Fact Sheet Update: April 1997