North America faces significant environmental challenges due to population growth and our aging infrastructure. The need to improve sanitary sewer facilities includes conveyances for new and upgraded wastewater treatment plants, and the mitigation of combined sewer overflows (CSOs) and sanitary sewer overflows (SSOs).
However, many of the areas requiring new conveyances are either heavily urbanized or established residential neighborhoods. Due to the environmental impacts associated with open-cut construction, and the long-term operational concerns associated with pump stations, more municipalities are identifying tunneling methods as their preferred means of installing gravity-based conveyance systems
Mott MacDonald’s expertise in CSO and wastewater conveyances ranges from small-diameter pipelines constructed using microtunneling and horizontal directional drilling methods, to large machine-bored openings in excess of 40 feet in diameter.
The design of wastewater conveyance systems is dictated by the need to provide storage and/or conveyance of dry weather and/or wet weather flows. Depending on each project's design and operational criteria, we bring the right balance of tunnel alignment control, construction engineering, and suitability of final linings to meet the project's requirements.
A key element of our tunneling business is the engineering of CSO facilities. By combining our tunnel, shaft, and hydraulics engineering expertise, we are advancing the state of knowledge in the engineering of drop structures required to convey shallow flows to deep storage and conveyance tunnels. In combination with numerical and/or physical modeling, we can tailor innovative drop structure designs to meet unique project requirements.
Our wastewater-related capabilities include these:
- Facilities plan development
- Consent decree mitigation strategies
- Tunnel & shaft engineering
- Hydraulic engineering
- Corrosion control methods
- Odor control methods
- Drop shaft modeling
- Alternative final lining evaluations
- Construction schedules & estimates