WSDOT Bridge Repair Case Study: On-Site Water Treatment for Bridge Deck Milling

When the Washington State Department of Transportation needed a smarter way to manage water during bridge deck repair, Washington Stormwater built a solution from the ground up. The result was a first-of-its-kind mobile water treatment system that allowed WSDOT to treat and discharge water on-site, compliant with the 2022 Bridge and Ferry Terminal Washing General Permit.

Project Overview: The Bridge Repair Water Challenge

Bridge repair generates a significant amount of water, and managing it isn’t simple. WSDOT faced the problem of what to do with water encountered during bridge deck milling and repair work. Vac trucks are costly, off-site disposal locations aren’t always nearby or practical, and state water quality standards still apply even when the goal is on-site infiltration or discharge.

The project introduced an additional layer of complexity. WSDOT had acquired a Hydro Mill with the intention of reducing water consumption during milling operations. While that goal was achievable for partial deck repairs, traditional full deck replacement projects use thousands of gallons of water. Treating the resulting concrete slurry to meet discharge standards required a purpose-built solution.

Washington Stormwater’s Solution

Washington Stormwater designed and fabricated a trailer-mounted water treatment system built specifically for WSDOT’s bridge repair workflow.

• Custom Fabricated Treatment System: The unit was built to treat water at 50-75 GPM, with 1,000 gallons of onboard storage to handle fluctuating water volumes during active milling operations.
• Advanced Water Quality Monitoring: Onboard electronics continuously monitor pH, turbidity, and Total Dissolved Solids (TDS), ensuring the system responds in real time to changing water conditions from concrete slurry and debris.
• Chemical Treatment Capability: Integrated chemical storage and distribution allows the system to treat high-pH water and concrete-impacted runoff before discharge.
• Portable and Field-Ready: Mounted on a 12,000-pound car trailer, the system can be mobilized to bridge sites without heavy equipment or specialized transport.

What Washington Stormwater Delivered

• A fully operational mobile water treatment system capable of treating concrete slurry and construction water to meet state discharge standards on-site.
• Elimination of vac truck dependency, reducing project cost and logistical complexity.
• A computer-controlled system that tracks chemical use and logs when water is released, providing documentation for regulatory compliance.
• A scalable solution that became the first water treatment system of its kind purchased by a Washington State agency.

A New Standard for State Agencies

WSDOT gained the ability to treat and discharge water directly on-site, avoiding the expense of vac trucks and the challenge of finding compliant disposal locations. The system’s onboard monitoring and chemical dosing capabilities handled the unique demands of concrete slurry treatment, one of the trickier water quality challenges in bridge work.

By investing in a purpose-built mobile treatment unit, WSDOT set a new standard for how state agencies can approach water management during bridge repair, and Washington Stormwater delivered the engineering to make it work.

Kelly Brauhn, WSDOT Bridge Supervisor, put it plainly: “Washington Stormwater LLC provided the perfect solution to our problem. A mobile water treatment system that is low cost, easy to use and easy to maintain. It only needs a couple of hundred gallons of water to start and has a computer system to track chemicals and when the water is released. I am excited about this water treatment plant and happy we have it in our equipment inventory.”

Upcoming Bridge Repair Project?

Managing water on a bridge site doesn’t have to mean vac trucks and off-site disposal. Washington Stormwater builds mobile treatment systems sized for your flow rates and compliant with state discharge standards. Call us at (360) 625-8366 or request a quote below.