Osseo Water Treatment Plant

Challenge

Residents in Osseo, Wisconsin, were experiencing staining, odor, and taste issues in their drinking water due to aging infrastructure at the City’s Well No. 3 water treatment plant. Built in 1964, the plant struggled to meet modern water quality standards, particularly for iron and manganese removal. The well itself remained in good condition, but the facility surrounding it had reached the end of its useful life. Located on a highly constrained downtown site bordered by two highways, the existing plant posed significant challenges for constructing a modern replacement while maintaining uninterrupted water service.

Solution

To address the challenge, the City partnered with SEH to design and construct a new $5.2 million water treatment plant around the existing Well No. 3 wellhead. A phased construction approach allowed the City to maintain uninterrupted water production through most of the multi-year build while ensuring operator safety, regulatory compliance, and minimal public disruption.

Well No. 3 and Treatment Process Upgrades

Well No. 3 was producing raw water with iron concentrations averaging 6 to 7 milligrams per liter, higher than recorded in a 2019 pilot study. To help the City address this challenge, the new treatment plant incorporates an advanced plate settler system ahead of the filters. This process removes about 90% of the iron before filtration, which:

• Extends filter run times and filter media life
• Reduces backwash frequency to about once per month (compared to daily with the old plant)
• Saves an estimated 6.46 million gallons of water annually by reclaiming and reusing a portion of the backwash

Compact, Modern, and Resilient Facility

The new water treatment plant integrates a full treatment train: induced draft aeration, chemical feed, rapid mixing, flocculation, lamella plate settlers, sedimentation, gravity sand filters, a clearwell, and a backwash reclaim system. A robust Supervisory Control and Data Acquisition (SCADA) upgrade automates and monitors both the plant and the broader water system, improving reliability and operational resiliency. The new plant virtually eliminates iron and manganese from the water supply, significantly improving taste, odor, and appearance while boosting public confidence in the City’s system.

Designed for efficiency and community benefit, the facility maximizes performance in a constrained downtown site. Its compact footprint minimizes environmental impact and preserves nearby transportation corridors. Architecturally, the building complements the design of City Hall, enhancing the appearance of the downtown. The inclusion of lab and office space provides staff with improved resources for water quality monitoring, public communication, and education.

Sustainable features, particularly backwash water reclamation, further reduce stress on the City’s water supply and wastewater system, potentially delaying the need for new wells or expanded treatment capacity.

Collaboration, Funding, and Outcome

SEH supported the City in securing funding through the Safe Drinking Water Loan Program, which included a low-interest loan and $500,000 in principal forgiveness, along with financial planning tools to ensure long-term affordability. Close coordination among City staff, SEH, contractors, and regulators kept the project on track, minimized disruptions, and navigated supply chain risks. The final project cost came within $9,574 of the original bid – a remarkable achievement in today’s construction environment.

The result is a future-ready, high-performing water treatment plant that improves public health, strengthens Osseo’s infrastructure, conserves millions of gallons of water annually, and blends seamlessly into the heart of the community. 

Awards

• 2025 Large Project of the Year Award | WI - American Water Works Association (AWWA)