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Overhead view of wastewater treatment holding pools and facility

Hudson Wastewater Treatment Plant 2020 Improvements


Built in the 1950s, the Hudson Wastewater Treatment Plant was designed for future expansions but with an undetermined life span due to its limited space. When commercial and residential growth in the City of Hudson removed suitable sites on which to build a new treatment facility, the City committed to expanding the plant for greater capacity with special attention given to the site limitations.

After being upgraded in 1980 and 2000 to bring the treatment plant up to its current capacity, SEH undertook a thorough facility condition and space assessment in 2017 at the City’s behest to assess the plant’s infrastructure and operations. As a result, the City uncovered approximately $10 million in needed improvements to keep the plant intact and operating efficiently for the next several decades.

The plant’s current flow is roughly 1.5 million gallons per day. In 2040, with the inviting Hudson community continuing to grow, these flows are projected to be 2.2 million gallons per day. To meet this flow volume, the City explored options for a full rebuild. However, the SEH team’s evaluation showed that renovations could not only save the City significant costs over a rebuild but also meet and exceed this flow volume while keeping the plant running efficiently beyond 2040.

SEH’s relationship with the City and deep experience in both wastewater treatment facility design and construction oversight for complex, multi-year projects led to the SEH team’s selection for this project.

The City’s treatment plant is compact and unique in that it’s bordered by the St. Croix River (running between Wisconsin and Minnesota), State Trunk Highway 35 to the west, a cliff to the east, residential housing to the south, and commercial properties to the north.


As touched on above, the Wastewater Treatment Plant 2020 Improvements project began with a condition assessment study led by SEH. This study was followed by a facility plan, design, bidding, and construction. The project was completed summer of 2023.

The project is being executed between the City and SEH via a single contract, with the SEH team also overseeing the bidding process. The close collaboration and single contract have ensured accountability, better control over the budget, and deeper relationship building.

Rehabbing and extending the life of critical infrastructure
The City's overall objective with this project is to rehab and extend the life of its existing wastewater infrastructure within the permitted flow capacity.

The most pressing needs identified by the SEH team for renovation – and now in the process of being upgraded – including converting chlorination/dichlorination disinfection to a new UV disinfection system; a new pretreatment building replacing the old static screens and aerated grit removal process; and replacing the dissolved air flotation (DAF) sludge thickening process within the existing sludge conditioning building.

Additional features of the Wastewater Treatment Plant 2020 Improvements include:

  • Construction of a new pretreatment building
  • Existing pretreatment building partial demolition, pump replacement
  • Partial demolition of existing garage in the pretreatment building
  • Aeration basin replacement of fine bubble diffusers, piping modifications, and a new turbo blower
  • Replacement of final clarifier mechanisms
  • Chlorine contact tank modification to a UV disinfection system
  • Replacement dissolved air flotation sludge thickening and chemical feed system
  • New sludge pumping equipment
  • Electrical upgrades, including conversion to LED lighting
  • Architectural and structural improvements
  • Mechanical system replacements
  • Biosolids storage tank decant pump
  • Supervisory control and data acquisition (SCADA)/controls improvements
  • Miscellaneous heating, ventilation, and air conditioning (HVAC) replacement
  • Odor control replacement
  • Aerated grit chamber retrofit to a vactor pad
  • Miscellaneous piping and valve work

Aligned with a strategic long-term vision
The City undertook the project with a close eye on its comprehensive plan – specifically, relying on the strategic plan to examine land usage and how much waste these uses generally produce. For example, transportation and high-tech developments may impact flow volume; leadership wanted to be certain its wastewater treatment plan could handle additional flow volume as the community expands.

Aligning the Wastewater Treatment Plant 2020 Improvements project with its strategic vision and plan ensured the City was making a wise investment.

Gaining buy-in: Drone filming and visualization services
Toward the conclusion of the design phase, SEH’s Drone Services team partnered with the City and overall SEH team to capture aerial footage of the existing wastewater treatment plant. SEH’s visualization experts overlaid this video with 3D design graphics illustrating the planned improvements – creating the ability for key stakeholders to experience proposed upgrades long before construction.

The video, which can be viewed at the top of this page, was used to secure buy-in from the City Council and Utilities Commission. Available publicly, it’s also a tool to engage and educate the community.


2024 Engineering Excellence State Finalist Award | American Council of Engineering Companies, Wisconsin Chapter (ACEC-WI)

Project Name
Wastewater Treatment Plant 2020 Improvements

City of Hudson, Wisconsin

City of Hudson


  • Wastewater engineering
  • Architecture
  • Civil engineering
  • Community development
  • Construction services
  • Geotechnical engineering
  • Marketing communications
  • Visualization services
  • Mechanical/electrical engineering
  • Natural resource scientists
  • Planning and landscape architecture
  • Structural engineering
  • Survey