Photo credits: PC/Leeper Construction

Project Description

Charlotte Water’s Mallard Creek WRRF Phase 1 Project has earned Envision Verified for sustainable infrastructure achievements. The facility is one of five major water resource recovery facilities owned and operated by the City of Charlotte. The Mallard Creek WRRF serves a 47 square-mile drainage basin northeast of Uptown Charlotte in Mecklenburg County and encompassing the growing University of North Carolina at Charlotte campus. It provides preliminary and primary treatment, activated sludge biological treatment, secondary clarification, tertiary effluent filter polishing and UV disinfection, and is permitted to treat 13.1 million gallons per day (MGD) maximum monthly flow (MMF).

Population growth and the development of a regional light rail transportation corridor have contributed to continued fast growth in the drainage basin served by the Mallard facility. The Mallard Creek WRRF Expansion Phase 1 Project will expand the facility’s treatment capacity from 13.1 to 16 MGD to meet the demand.

Scope of the Project

● A new influent pump station (IPS) building — a three-level 60-foot-deep structure that will include new mechanical multi-rake bar screens, Parshall flumes and dry-pit submersible pumps pulling from a dual trench style wet well.
● Upgrades and improvements to the grit removal and intermediate pump station (IMPS), including addition of baffles to the grit removal chambers and replacement of the grit classifiers.
● New Flow Equalization (EQ) Facilities – Two new prestressed concrete EQ tanks to address diurnal flow peaking and extreme wet weather events. The smaller tank, with a volume of 5.3 MG, will be used daily for diurnal peak flow shaving whereas the larger tank, with a volume of 14.7 MG, will be used during wet weather flow events.
● Replacement of the magnesium hydroxide chemical storage and feed system with a new containment, storage, and feed system.
● Improvements to the existing polymer system, and the addition of a new centrifuge – changes that will increase the plant’s capacity for treating residuals.

Quotes

Owner

“Charlotte Water is proud that the Mallard Creek Expansion has earned Envision Certification, recognizing the project’s commitment to enhancing community well‑being, protecting local waterways, and strengthening long‑term environmental resilience.”
— Charlotte Water

Design Engineer and Program Manager

“Charlotte Water continues to demonstrate what it looks like to lead with purpose—advancing infrastructure that is both resilient and sustainable while meeting the region’s growing demands. Brown and Caldwell, as program manager and design lead, values the opportunity to partner in delivering solutions that align operational performance with practical, cost-effective sustainability outcomes.”
— Leslie Jones, Brown and Caldwell Program Manager

Contractor/CMAR

“The PC Construction / RJ Leeper Joint Venture is honored to be part of the transformative work at the Mallard Creek Water Reclamation Facility. Achieving the Envision Verified Award is a testament to the team’s commitment to sustainable infrastructure, collaborative partnerships and delivering long-term value to the Charlotte community.”
— Matt Cooke, PC Construction President and CEO

Institute for Sustainable Infrastructure (ISI)

“Congratulations to Charlotte Water on the success of Mallard Creek WRRF Phase 1 Project. The owner and the project team approached the planning, design and construction aspects of this important plant upgrade and expansion with a comprehensive view of the opportunities available to realize community, sustainability and resilience benefits.”
— Kailey Eldredge, Director of Verification

Verified Sustainability Achievements

Community Health – Surrounding community health is protected by increasing the treatment capacity of Mallard Creek WRRF in line with the increasing wastewater flows in facility’s catchment basin. Highest flows to the plant are most likely to occur during or after wet weather events. In recognition of this risk, this expansion adds two equalization basins with a total capacity of 20 million gallons to help manage wet weather flow.

Public Safety – Charlotte Water also went above and beyond by choosing to have the project conform to NFPA 820: Standard for Fire Protection in Wastewater Treatment and Collection Facilities, an optional industry standard for fire safety. This means that all areas potentially exposed to the combustible gases generated by wastewater have combustible gas detectors (CGDs), alarm horns/lights, and go/no-go panels.

Management of water resources – The increased treatment capacity also helps protect the aquatic health of Mallard Creek and its receiving bodies. Modelling shows that despite increases in total effluent, Mallard Creek water quality will not decrease and could actually increase thanks to this project. Much of the treatment infrastructure installed is highly automated, leading to gains in plant efficiency and resource management.

Climate and Resilience – The project identified two potential site hazards: near-surface groundwater and flood risk associated with Mallard Creek’s 100-year floodplain. Several project structures were located specifically to avoid these hazards (EQ tanks, Influent Pump Station). While the EQ Underdrain Station had to be located within the floodplain, its design specifically mitigates the risk from flooding to the structure. A detailed construction erosion & sedimentation control plan as well as new stormwater infrastructure help mitigate flooding risk on the project site.

Infrastructure Integration – The new flow equalization capabilities will increase internal systems integration by reducing peak flows through the plant. This is a simple, cost-effective way to lessen the need for additional downstream treatment equipment. External systems integration is also achieved, since the project is occurring concurrently with a project to increase capacity of the facility’s sewer network.

Workforce Development – Charlotte Water has a long history of serving its community via workforce development initiatives. Between 2020 and 2024, 46 participants were trained and hired into full-time positions with Charlotte Water via apprenticeship and academy programs. Workers hired through these programs make valuable contributions to Charlotte Water and the operation of Mallard Creek WRRF. In addition, PC Construction implemented a workforce development plan for this project to hire construction workers from local disadvantaged populations, with 30 new hires expected over the four-year project duration.

Byproduct Synergies – Residuals (or “biosolids”) production at Mallard Creek WRRF will go up as total flow to the plant continues to increase. Three new centrifuges are being installed to account for the increased solids-treatment demand. A residuals management study was conducted to project future residual production at the plant, and concluded that current land application practices can continue with the greater output.