16 - PRESENTATION ABOUT TRENCHLESS PIPE BURSTING

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This was an email from AECOM project manager Matt Abbe: We confirm that this type of technology is not practical or a lower cost alternative for the Paris project. My thoughts on why insert methods, or trenchless methods like pipe- bursting are impractical: 1. Insert type methods reduce the existing pipeline diameter and maintain existing capacity. In most cases, we are increasing capacity of both water and sewer lines by increasing the pipe diameter. Insert technology would not work in these situations. 2. Traditionally, trenchless technologies are more expensive than trenching options (can be less expensive under roadway over long distances). 3. The existing water /sewer are too close together (less than TCEQ minimum requirements). Placing a new line within the existing line does not solve the issue of proper TCEQ separation. The sewer line will have to be relocated a greater distance away from the water line, which does not work in all situations. 4. The water line (if pipe burst) has to be reconnected to all residential services (with new service lines) and other existing water line connections. Thus, the contractor will have to open cut all service connections, which increases the cost of trenchless methods. 5. Typically, pipe bursting or trenchless methods are good for maintaining the same size line, or going to the next larger diameter pipe (ex. 6 -in to 8 -in). There are many locations where we are going from 6 -in to 12 -in, which is not recommended for trenchless technologies (although can be done). 6. Many existing water lines are AC. After pipe bursting, the AC particles remain in the trench. When reconnecting existing lines, such as residential service lines, there is a risk of the asbestos contaminating the new connections. 7. Pipe Bursting can be done in sewer lines and is cost effective for lines that are deep. Most of the sewer lines that we are replacing, we are having to change the flow lines, which does not allow for the pipe burst options. 8. Regarding sewer lines, the majority of the manholes need to be replaced, which is an open cut option. Further, all residential sewer line connections need to be installed by open trenching techniques. When looking at the amount of trenching, required, trenching becomes more advantageous. 9. Lastly, we are changing a lot of flow lines for the sewer to increase pipe slope to achieve TCEQ slope criteria. Pipe slope cannot be adjusted when pipe- bursting /trenching. The reasons above show why we opted with trenching options vs. trenchless methods. Note that there are several areas where we are installing pipe by bore /jack /tunnel (technically trenchless), to avoid deep cuts, particularly around the loop. I point this out to say that we do look for construction advantages during the design phase. Please let me know if you have further questions /comments. Matthew Abbe, PE Project Manager, South Region AECOM