St. Charles Pumping Station 3B

Johnston Construction Company

• Johnston Construction Company was selected to construct the St. Charles Pumping Station 3B project, a new 7 MGD wastewater pumping station serving the St. Charles community in Charles County, Maryland.
• The project included construction of a new submersible wastewater pumping station with two below-grade levels, wet well, pipe gallery, generator room, chemical room, electrical room, control room, and associated site and utility improvements.
• Johnston Construction Company’s scope included site work, excavation support, dewatering, structural concrete, driven H-pile-supported construction, pumping equipment, process piping, force main work, valves, chemical feed equipment, odor control, generator facility, fuel oil system, HVAC, plumbing, instrumentation, controls, electrical service, emergency power, automatic transfer switch, and system startup.
• The project required coordination with Charles County Department of Utilities to maintain operation of existing Pumping Station 3A, divert flow from existing pump stations, pig new force mains, decommission existing Pumping Stations 2, 2A, and 3, and shut down Pumping Station 3A as part of the new station startup sequence.
• Johnston Construction Company performed the work in challenging subsurface conditions that included deep excavation, groundwater, sensitive high-plasticity clay, reinforced mat foundation construction, structural floor slab and pile-supported pipe gallery work, and extensive coordination of buried utilities and existing wastewater infrastructure.