Northwoods & Popperdam Pump Station Rehabilitations

The North Charleston Sewer District (NCSD) selected Weston & Sampson for the design and construction administration of major upgrades to Northwoods and Popperdam Pump Stations. Constructed in the late 1980s, these regional pump stations each have two identical wetwells.

The new design will change the stations from triplex to quadplex with fully redundant wetwells, allowing NCSD to completely close off one side for extended periods of time for cleaning operations while handling the projected 2040 peak flows. Weston & Sampson provided civil, electrical, and structural engineering.

Hydraulics/Pumps: We performed extensive hydraulic modeling for each station to select the appropriate pumps capable of handling 2040 peak flows. Four 248HP pumps were selected for Northwoods and four 140HP pumps were selected for Popperdam. Due to significant proposed flow increases, we also evaluated forcemain manifold piping and valves for compliance with Hydraulic Institute standards.

Valves & Piping: The design includes the replacement and upsizing of all suction and discharge legs. New isolation valves, check valves, ARVs, flow meters, and surge protection valves will be added to the station piping.

Wetwell & Influent: Following removal of unstable concrete, the wetwells and influent channels will be re-lined with 1” of cementitious buildback and 125 mils of epoxy coating. A third-party coating inspector will be involved throughout the process to ensure a quality product. Additionally, a new mechanical bar screen will be added to each station. This automated bar screen will discharge screenings into a nearby dumpster significantly decreasing the O&M burden at each station.

Structural: A new suspended concrete platform will be added to support the mechanical bar screen and to allow O&M access to the screen. This platform will extend over the influent area. Because there will be new generators and significant site improvements, new slabs will be designed to support the bioxide tanks and generators for each station.

Electrical: The electrical design includes a complete overhaul of the existing conditions, including new cabinets, VFDs, generators, switchboards, control panels, new PLC, and the relocation of all electrical junction boxes to the top floor to minimize electrical impacts in the event of a flooded station.

HVAC: Existing ductwork inside of the station will be reused as much as possible to provided proper air exchanges for each facility per NFPA 820 requirements. Electrical rooms will be air conditioned to keep the controls cool and the humidity down.

Site Improvements: The design includes drainage and sub-grade improvements for each site, along with fencing/building envelope improvements as needed. Each site will be repaved with a heavy duty pavement section capable of supporting all of NCSD’s equipment.