Apex was tasked by the City of St. Cloud to assist with a city-wide water distribution system master plan. Cavalry Hill Booster Pump Station was one of the major components of the master plan. The first phase of the project addressed the inadequate generator and associated electrical equipment.

The pumping capacity of the station had been a bottleneck for the city for some time. Its pumping capacity barely reached the minimum requirement with all pumps in service. Because the generator was sized for a single pump, the station was a significant source of anxiety for the city during utility outages.

Flexibility for the city to accommodate outages for performing the upgrades was impossible due to the pumping limitations. Upgrading the station required a design approach that limited outages to less than 4 hours with construction during low usage times only. Anything outside those parameters risked exceeding the station’s storage capacity.

In addition to the operational requirements, the new generator and electrical system needed to be sized for the ultimate build-out of the pumping station. The site layout was extremely compact with little flat, usable space for a new generator. Based on the master plan, additional distribution piping changes would be needed, further limiting the generator’s location. Ultimately, a suitable site was selected, requiring minimal prep to accommodate the new 300KW natural gas generator to power future pumps.

The electrical room posed some design challenges. The city requested Variable Frequency Drives (VFD) used on the future pumps versus the soft starters they were using. New VFDs were significantly larger than the soft starters. Apex worked on a layout that included future electrical gear to ensure adequate space in the room. By relocating some existing control equipment, it was possible to accommodate the needed equipment.

The final element was the evaluation of the Automatic Transfer Switch (ATS). Luckily, the ATS was oversized and reusable without any significant modifications. Otherwise, the entire electrical gear would have needed replacement with a complete temporary electrical system which would have been at a high cost to the city.