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
programmed according to the as-built drawings as well as to installed conditions.
HAMMER 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. At a cost of
$14,800, this solution was significantly less than the alternatives.
The goal of this $1.5 million project was to determine if the relocation of a water
supply line would reduce the $750,000 annual cost to pump 20 million gallons
per day. The goal was achieved by using WaterGEMS to model a scenario in
which water supplied from an alternative location flows by gravity during part
of the year so the total dynamic head of the pump would be substantially less.
Hatch Mott MacDonald
Supply Optimization and Energy Reduction
Newark, New Jersey, United States
Using WaterGEMS, the concept was quickly validated, reducing annual
pumping costs to $187,000. Based upon securing a low-interest loan to finance
construction of a new booster station, hydropower facility, and minor piping
infrastructure improvements, it was determined that the electrical savings
would be greater than the debt service and the return on investment would