Client: City of Ottawa
Location: Carp, Ontario
J.L. Richards & Associates Limited (JLR) was retained by the City of Ottawa (City) to provide preliminary and detailed design and field services for the construction of high lift pumping system upgrades at the Village of Carp Water Treatment Plant.
The Carp Water Treatment Plant consists of two groundwater wells, a two-cell below grade reservoir, sodium hypochlorite disinfection system, and a high lift pumping system. The distribution system is operated as a closed pressure zone, requiring at least one pump to always operate to maintain system pressure.
Numerous high lift pump failures were occurring in the past, likely due to pump cavitation resulting from undersized pump suction piping. The capacities of the preexisting high lift pumps were oversized, wasting pumping energy and making distribution system pressures a challenge to maintain on a consistent basis.
Hydraulic computer modelling was utilized to address distribution system pressure management and forecast pump replacement as a phased approach to correspond to future growth in the community. To accommodate the wide flow ranges for both current and future operating scenarios, high lift pumping system upgrades were designed in two phases.
Phase 1 consisted of upgrading High Lift Pumps No. 2 and No. 3 with inverter duty motors and variable frequency drives and reconfiguring the reservoir flow pattern and the suction piping to address pump cavitation. Phase 2 upgrades are to be implemented as dictated by future growth and water demands.
Due to the critical nature of the high lift pumping operations, JLR worked closely with the City on the development of a detailed construction sequence. Replacement of process piping and isolation of reservoir cells and high lift pumps were carefully staged in order to minimize service level impacts and maintain various configurations of high lift pumping operations at all times.