MWWTP Effluent FM Surge & Transient Design Build Services (UN 1282)

The County Commissioners of Charles County are hereby requesting sealed proposals from qualified firms to design and construct an upgrade to the Effluent Filters and associated structural, mechanical equipment, piping, and accessories for a Wastewater Treatement Plant located in Charles County, MD.

The primary purpose of the Project is for the Design and Construction of a new standpipe with separate influent and effluent pipes that join with the existing force main. This Project will construct a new 40-ft. diameter standpipe with spiral staircase, platform, piped overflow, overflow swale, influent, effluent and bypass vaults, new ductile iron pipe, fittings, valves, and miscellaneous improvements such as sump pumps and drainage, electrical and instrumentation and pavement and yard restoration. The Design-Build Teams will be required to provide complete turn-key services for the Project including design, permitting, furnishing and installing and equipment, testing and start up, contract close out to provide a complete and fully functioning system.

The Mattawoman Wastewater Treatment Plant (MWWTP) is rated for an average daily flow of 20 million gallons per day. In 2020, a major Project to improve he effluent pump station occurred. During this Project, the Design peak flow of the effluent pump station increased to 60 mgd. Treated effluent is pumped two miles through 54-inch diameter, 50-year old prestressed concrete cylinder pipe (PCCP) before transitioning to gravity flow for final discharge into the Potomac River.

The County experiences transient surges in their effluent force main when effluent pumps turn on and off, causing the intermediate high point air release valve (ARV) located approximately 7,000 ft. from the pump station to actuate. With the recent increase to design peak flow, the County is concerned that future transient surges caused by cyclical pump operation or multiple pump trips may damage the existing force main and ARV.