Potomac Filtration Plant Improvements Phases 1 & 2


Washington Suburban Sanitary Commission


Potomac, MD

Date Completed

April 2011



The Potomac Water Filtration Plant supplies fresh water to Montgomery and Prince George’s Counties in Maryland.  Singleton was a subcontractor on the two-phase project to replace and install power substations servicing the plant.

For Phase 1, Singleton was responsible for all construction activities (e.g., electrical, civil, GC, etc.). The job consisted of replacing the existing Outdoor Substation #1 in place and also adding a new Outdoor Substation #4.  Each substation consisted of 35kV switchgear, four 34.5kV to 4.16kV transformers, 5kV switchgear in weatherproof housing, and underground cable vaults.

Singleton developed a temporary power plan to maintain power to Substation #1, as it still fed a number of pumps and other equipment at the plant. First, the team relocated two of the transformers to just outside the yard, then installed temporary cables to the transformers and temporary cables to the switchgear.  They then demolished the existing yard and built an underground electric vault for the outdoor switchgear house.  Singleton also installed new cables, bus duct, outdoor metal-enclosed switchgear, the 5kV switchgear and transformers.  After energizing the new Substation #1, the team tied in the existing pumps and equipment and demolished the temporary setup.

Phase 1 also included construction of a new outdoor 34.5kV-4.16kV substation (#4), which consisted of 35kV switchgear, four transformers, and 5kV switchgear to serve future rapid mix, flocculation, pumping, and UV disinfection facilities.  The new construction included concrete-encased duct banks, new electrical and communications manholes, and an underground cable vault. At the main incoming 34.5kV switchgear yard, Singleton added two 34.5kV outdoor switch gear sections to the existing lineup.

For Phase 2 of this project, Singleton installed four 5kV to 480V network transformers, two 5kV to 480V outdoor dry-type transformers, two 480V 2000A Outdoor Switchboards, two large 480V outdoor walk-in substations, and thousands of feet of 5 kV and 35kV cable.  The team also installed a 34.5 kV power circuit breaker in an existing overhead outdoor substation.  Singleton self-performed all of the medium voltage terminations and splices for the entire project.