Treatment and management of surface runoff
Impermeable surfaces and large quantity of surface runoff
Project overview
Client: Stadsbader / BV Asphalt
Location: Belgium
Industry: Quarries & Construction
Key Results
Regulatory roadmap
Delivered a clear technical path to achieve permit renewal compliance ahead of the June 2026 deadline.
Site-wide water management design
Designed a complete collection and treatment system for a site that previously had none, covering all active zones including storage areas and access roads.
Technology selection and sizing
Defined a multi-stage treatment train with pre-dimensioned equipment and realistic cost projections.
The challenge
A sprawling asphalt production site with no system in place to collect or treat its runoff water.
The VINASPHALT asphalt plant in Wanze, part of the Stadsbader group, manufactures asphalt from minerals and recycled road millings. The site is dominated by hard, impermeable surfaces, such as storage yards, access roads, and a bitumen handling area, which means that rainfall has nowhere to soak in. Instead, it washes across the site, picking up suspended solids, hydrocarbons, and heavy metals along the way, before flowing untreated into a nearby Category 2 stream called the Fond de Roua.
With the site's environmental permit due for renewal in June 2026, that status quo was no longer an option. The renewal required the company to demonstrate two things: that peak discharge flows into the stream would be controlled and limited, and that the quality of those discharges would meet environmental standards. Existing partial measures, like a small oil separator at the fuel station and a domestic wastewater system, left the majority of the site's runoff completely unmanaged.
Stadsbader mandated Revalio to design a complete, fit-for-purpose stormwater management and treatment system that could meet regulatory requirements while remaining practical and cost-effective for an active industrial site.
What Revalio delivered
Revalio conducted a full pre-design study, combining site analysis, regulatory assessment, and engineering design into one integrated deliverable:
Site survey and topographic analysis: Mapped the full site layout, surface types, and natural drainage patterns to identify where water collects, how it flows, and what it carries. Three distinct collection zones were identified, covering approximately 2 hectares of predominantly impermeable surface.
Pollution characterisation: Based on sector benchmarks and regulatory thresholds, identified the key pollutants of concern (suspended solids, hydrocarbons, and heavy metals) and set target treatment performance levels for each.
Hydraulic design: Calculated peak flow rates using a 25-year return period storm event (300 L/s/ha over 10 minutes), and sized a 730 m³ underground retention basin to buffer those peaks before controlled discharge at 10 L/s into the stream.
Treatment train design: Engineered a cascading, multi-stage treatment system, from heavy-duty channel drains and grit traps, through a hydrodynamic vortex separator, to a final Up-Flo® filtration unit, with each stage protecting the next and progressively removing finer pollutants.
Water reuse opportunity: Identified that treated water could be stored in a 20 m³ tank and reused on-site for wetting down compactor rollers, reducing freshwater consumption by an estimated 655 m³ per year.
CAPEX and OPEX projections: Compared construction options (prefabricated steel, precast concrete, in-situ concrete) and provided realistic cost estimates to support the client's investment decision.
How it works
Rather than proposing a single oversized piece of equipment, Revalio designed a treatment train in which each stage does a specific job:
Earthworks and waterproofing: Storage areas for recycled millings are regraded and sealed to prevent pollutant infiltration and direct all runoff toward the central site road for collection.
Collection channels and primary grit traps: Heavy-duty sealed channels (rated for heavy vehicle loads) collect water from across the site. Integrated grit traps at two intermediate points capture the coarsest solids before they reach downstream equipment.
Hydrodynamic vortex separator: Water enters a cylindrical chamber tangentially, creating a spinning vortex. Heavier particles are flung outward and settle to the base. This step handles the bulk of the suspended solids load and protects the retention basin from silting up.
Underground retention basin (730 m³): Acts as a hydraulic buffer, holding stormwater during peak rain events and releasing it at a steady, regulated rate. This keeps discharge flows within the limits set by the provincial authority.
Up-Flo® gravity filtration: At the controlled outlet flow, water passes through a specialised filter medium that captures fine particles, residual hydrocarbons, heavy metals, and some dissolved pollutants, delivering a final effluent quality that meets discharge standards. Combined with the vortex separator, this system has demonstrated reductions of over 80% in fine particles and over 70% in heavy metals on comparable industrial sites.
Results
✓ A technically robust, permit-ready design delivered ahead of the June 2026 renewal deadline.
✓ Complete collection and treatment coverage for a site that previously discharged all runoff untreated.
✓ A cascading treatment architecture where each stage protects the next, minimising long-term maintenance needs.
✓ Multiple construction options compared, with realistic capital and operating cost projections to support investment decisions.
✓ A water reuse loop identified, recovering treated water for on-site use and reducing freshwater demand by ~655 m³/year.
✓ An operational maintenance plan is defined for each component, from six-monthly grit trap cleaning to annual filter servicing.
Looking for a custom solution?
Every site presents a different set of constraints: permit deadlines, surface types, pollutant profiles, or budget limits. Revalio starts with a precise study to understand your needs before recommending anything. Whether you need to manage runoff, treat complex effluents, or explore water reuse, we engineer the most cost-effective path to compliance.
Start your study with our experts.