Irrigation District Observations on Large Diameter, Low Pressure Pipeline Materials

There are approximately 1,400 miles of low pressure non-reinforced cast-in-place ( monolithic or CIP ) concrete pipe in California irrigation districts. Cast-in-place pipe was irrigation districts’ material of choice for large diameter pipelines from 1930 to at least 1980. Many of these pipelines were installed in the early 1900’s. They are predominately found on the east side of the San Joaquin Valley, from Manteca in the north to Visalia in the south. Most of these pipes are deteriorating and will need to be replaced within the next 10-20 years. Irrigation districts have attempted to find new ways to repair these pipes. However, their uneven dimensions (they were often made with crude local installation equipment), high density of repairs (meaning that the pipe wall thicknesses and cross sections now vary), numerous connections, and non-linear placement have ruled out using available pipe liner technology. The cost to line these pipes is about the same as the cost to completely replace them. Due to the high replacement cost and need for repair, the last decade has seen a switch away from cast-in-place pipelines to pipelines of other materials. However, up until now there has been no general consensus as to the best replacement option. In November 2002, the California Polytechnic State University (Cal Poly) Irrigation Training and Research Center (ITRC) met at Madera ID with representatives from eight irrigation districts and one engineering firm to discuss reasons for switching types of pipes, and what alternative materials might be available