Lean, Green, and Mean: The IPL Project

The Integrated Pipeline (IPL) project is a 240-km (150-mile) 2100-mm to 2700-mm (84- to 108-inch) diameter pipeline that will furnish raw water to the cities of Dallas and Ft. Worth, Texas. To reduce costs and be environmentally friendly, the project is seeking construction methods that re-use as much of the native soil as possible. Re-use can result in a leaner budget for the project. Transportation costs are now significant. Re-use of the native soils reduces the cost and the traffic for importing soils. Ways to reduce handling of materials, to limit laborious compaction of soils, and to speed the installation are key for cost savings. Re-use will reduce the impact on the environment. Reduced transportation, handling, compaction, and spoil removal will reduce emissions and fuel needs. Re-use requires innovation and flexibility in the design and construction of the pipeline. While conventional methods are being considered, the IPL management team strongly encourages new approaches that can safely and economically provide a more sustainable project. One of the possibilities is making flowable fill for the pipe embedment using native soils. Much of the alignment has soils that could be used to make flowable fill. Laboratory trial mixes and field trial installations have both successfully demonstrated the viability of using native soils to make flowable fill. Both Portland cement and Type C flyash for the flowable fill have been investigated. However, a significant portion of the pipeline goes through areas of the Eagle Ford Formation, which consists of weathered shale and Fat Clay (CH). A highly expansive and plastic soil, the Eagle Ford presents challenges for re-use. The field trials have experimented with various processing, mixing, and placing methods for flowable fill using the Eagle Ford Formation. Special procedures may have to be identified for using these materials.