Horizontal directional drilling decreased disturbances to neighborhoods while replacing a 24,000-foot-long water main in Ft. Wayne, Ind.

Wastewater system modeling
A 996,200-gallon-per-day sewage pumping station for the Cascade Falls subdivision in Duluth, Ga., experienced multiple breaks in the PVC force main. Operators requested a hydraulic analysis to determine the cause, recommend remedial repairs, and evaluate a possible new alignment. A model was developed according to the as-built drawings as well as to installed conditions. Bentley System's HAMMER modeling software was used to analyze transients and evaluate what-if scenarios. Field investigation and analysis revealed that the force main was not installed as designed, resulting in high surge pressures. Four proposed solutions were compared, and the selected solution added two air relief valves, which reduced transients to an acceptable level and mitigated force main failures.

Water main replacement
The combination of 50- to 60-year-old cast iron pipes and dry, fracturing, and shifting clay soil during the summer was causing multiple water main breaks in the city of Ft. Wayne, Ind. After more than 100 repairs to one particular corroded, 24,000-foot-long water main, the city reached the end of its patience and decided to replace it. Horizontal directional drilling (HDD) was determined to be the least disruptive and most cost-effective way to install the new water main comprising CertainTeed Certa-Lok restrained-joint PVC pipe. HDD avoided disruptive excavations, replacement of street, driveway, and sidewalk pavement, and interference with other utilities in the right-of-way. The HDD contractor made more than 60 bores, averaging 380 feet in length at depths ranging from 4 to 7 feet, and installed approximately 10,000 feet of 6-inch and 13,500 feet of 8-inch PVC pipe.