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First Defense® High Capacity Stormwater Separator System

First Defense® High Capacity Stormwater Separator System

As the world becomes more aware of the full impact of climate change, the Provincial and Federal governments continue to regulate environmental concerns in every industry, including construction. The liability that a construction project takes on from transforming previous water absorbing surfaces (i.e. soils, vegetation, low-lying areas) into impervious surfaces (i.e. concrete, asphalt, buildings) is significant. This runoff water causes environmental destruction by concentrating pollutants such as oils and heavy metals and channeling them into our stormwater systems. It is more important now than ever to mitigate the liability caused by altering natural spaces, including reducing environmental contamination from the deposition of sediment, oils, and other contaminants.

The Province of British Columbia is facing a climate crisis. Recently the Province has seen an increase in extreme weather patterns producing record breaking rainfall, causing mass flooding and leaving behind billions of dollars in damage. Scientists believe that these extreme weather events are going to be the new normal and will only grow in strength and severity as climate change accelerates. It is imperative that new and future construction projects have the proper infrastructure and systems in place to manage this rainfall and its subsequent stormwater.

Grosso Precast has partnered with Hydro International to offer our customers the First Defense® High Capacity stormwater separator system. The First Defense® High Capacity is an enhanced vortex separator that combines an effective stormwater treatment chamber with an integral peak flow bypass. It efficiently removes sediment, total suspended solids, trash and hydrocarbons from stormwater runoff without washing out previously captured pollutants. The First Defense® High Capacity is available in several model configurations to accommodate a wide range of pipe sizes, peak flows and depth constraints.

How It Works:

  1. The First Defense® High Capacity has internal components designed to remove and retain gross debris, total suspended solids and hydrocarbons.
  2. Contaminated stormwater runoff enters the inlet chute from a surface grate and/or inlet pipe. The inlet chute introduces flow into the chamber tangentially to create a low energy vortex flow regime (magenta arrow) that directs sediment into the sump while oils, floating trash and debris rise to the surface.
  3. Treated stormwater exits through a submerged outlet chute located opposite to the direction of the rotating flow (blue arrow). Enhanced vortex separation is provided by forcing the rotating flow within the vessel to follow the longest path possible rather than directly from inlet to outlet.
  4. Higher flows bypass the treatment chamber to prevent turbulence and washout of captured pollutants. An internal bypass conveys infrequent peak flows directly to the outlet eliminating the need for, and expense of, external bypass control structures. A floatables draw off slot functions to convey floatables into the treatment chamber prior to bypass.


  • Stormwater treatment at the point of entry into the drainage line
  • Sites constrained by space, topography or drainage profiles with limited slope and depth of cover
  • Retrofit installations where stormwater treatment is placed on or tied into an existing storm drain line
  • Pre-treatment for filters, infiltration and storage


Cut footprint size, cut costs:

The First Defense® provides space-saving, easy-to-install surface water treatment in standard sized chambers/manholes manufactured by Grosso Precast. They can even be delivered to the job site already installed in Grosso Precast’s precast concrete manholes, so they don’t need to take up time and space being installed on site.

Faster project completion:

The partnership between Grosso Precast and Hydro International ensures that the turnaround on manufacturing is faster than our competitors. Avoid supply chain issues by partnering with local manufacturers and suppliers.

Adapt to site limitations:

Variable configurations will help you effectively slip First Defense® into a tight spot. It also works well with large pipes, multiple inlet pipes and inlet grates.

Prevent washout:

The First Defense® retains the pollutants it captures. The low-energy vortex separation of the First Defense® eliminates excessive agitation of captured pollutants ensuring that these pollutants are not washed out during subsequent rainfall events.


YouTube Video: “First Defense High Capacity Animation”

Downloadable Spec Sheet:

Hydro International First Defense – Grosso Precast


If you think that your upcoming construction project could benefit from utilizing Hydro International’s First Defense® High Capacity stormwater separator system, please contact Grosso Precast to set up a demo.

Grosso Precast

Main: 250-392-3169

Email: [email protected]