Siemens Wellwater Electrical Products Plant Expansion, Pomona, California

Siemens Wellwater is what an expansion looks like when the plant can’t stop. HITT Contracting built a 155,000-square-foot addition and renovation at Siemens’ electrical products campus in Pomona, Calif., while the factory kept running around the clock, and ENR named the $65.5 million job a Best Project in its 2026 West Best Projects awards on Oct. 26, 2026.

The plant makes low-voltage electrical gear, including switchboards and lighting panels, the kind of equipment data centers and grid upgrades can’t get enough of right now. Siemens has made electrical products in Pomona since the 1970s, and it’s now spending $95 million to expand there.

Project Scope

The work came in two moves. Crews first built roughly 100,000 square feet of greenfield space, moved people and production equipment into it, then went back and renovated the legacy building. Siemens opened the new hub in March 2025. The finished campus is close to three times its original footprint, and production capacity is up 116%, according to ENR.

BHDP designed the building and IMEG handled mechanical and electrical engineering. The structure uses clear-span bays and reinforced slabs so heavy equipment can sit anywhere and production lines can be rearranged later. Training rooms and offices sit inside the manufacturing floor instead of in a separate block. Trade partners came on early for design assist, which let the team resolve clashes between heavy manufacturing systems and the steel and composite deck structure and get long-lead equipment ordered on time.

The sustainability package is more than a plaque. There’s a rooftop solar canopy that Siemens says covers about a third of the plant’s electricity, an all-electric powder coat paint line, battery storage and EV charging, and the building is LEED Gold. A 5,000-square-foot community space with art commissioned through the City of Pomona faces the public side.

Why It Matters

The hard part wasn’t the steel. It was keeping vibration, dust and utility hiccups away from a production line that runs 24 hours a day. HITT’s team used real-time vibration and particulate monitoring, temporary utility redundancies, sound attenuation, fixed access routes and phased shutdowns timed to the plant’s schedule. The 24-month program finished on budget and ahead of schedule, per the award entry.

That’s the template a lot of manufacturers will need. Switchgear and panelboard makers are racing to add capacity for data centers, and most of them would rather expand a plant they already own than start from scratch on a new site. Building next to a live line, then swapping into the new space, is slower on paper and cheaper in lost output. Pomona shows it can be done without a single unplanned stop.

Project Team & Details