Drop Rack Trap

Drop Rack Trap

The Drop Rack trap uses a specifically designed inclined rack to "divide" the pollutants out of the water flow and into the containment bay. We use the available energy in the water flow to transport the Gross Pollutants into the containment bays where is can drain dry upon the abatement of the flow. This is the basis of our catch phrase

Removing the water flow from below the Gross Pollutants  is how we achieve "Dry Rubbish".

Where Used

The Drop Rack trap is used in sites with low to high velocity flows where there is an available headloss (height difference between inlet and outlet inverts) . If no headloss is available then one of our "Vane" based traps would be suitable.

Site Requirements

Target Pollutant Class

The Drop Rack trap is targeted at capturing the Gross Pollutant class of pollutants. 

Water Sources/Velocity

The Drop Rack trap can be used for sites with low velocity flows to very high velocity flows. In fact the more velocity the better they work! 

The Drop Rack trap is suitable for treating the following water sources:

  • Pipes
  • Small Channels
  • Small Box Culverts

Note: While we can cater for high velocities, some trap design modification may be required.


The Drop Rack trap is suitable for grades from less than 0.05%  to 10% (For grades outside this range a Baramy pre-treatment solution may be required). 

Treatable Flow

The Drop Rack trap is suitable for treating flows from as low as a 3 month ARI to a 5 Year ARI.  (Be aware that although we can treat higher events than a 5 Year ARI with a Drop Rack trap, it may be more cost effective to use one of our "Vane" based traps).

We don't just treat the "first flush", we can treat the whole flow for the duration of the event if required. High flow storms should be treated, not ignored!



The size of the Dual Vane Trap is dependent on the:

  • Cross Sectional area of the Water Source, 
  • Velocity, 
  • Tail Water Condition,
  • Maintenance Regime
  • Catchment Type and Size
  • Required Treatable Flow 

To give you an idea of sizing here is a sample set of configurations. (The dimensions below assume full pipe 1% inlet grade and 0.6m pipe cover)

Sample Configuration Sizing Without Ramp

Cross Sectional Area Height Width Length
0.16m2 (450 pipe) 2.1m 1.45m 3.53m
0.28m2 (600 pipe) 2.4m 1.8m 4.81m
0.87m2 (1050 pipe) 3.0m 2.8m 7.50m
1.13m2 (1200 pipe) 3.0m 3.6m 7.56m

Sample Configuration Sizing With Ramp

Cross Sectional Area Height Width Length
0.16m2 (450 pipe) 1.8m 9.91m 5.53m
0.28m2 (600 pipe) 2.4m 11.28m 6.31m
0.87m2 (1050 pipe) 3.0m 16.90m 7.50m
1.13m2 (1200 pipe) 3.0m 18.60m 7.65m


Note: These figures are indicative only and do not represent the largest or smallest sizes we can treat. If you need an estimate size for your plans please contact us and we will be able to provide this information to you over the phone if you can provide some or all of the Site Requirements.


The Drop Rack trap is suitable as a lidded solution or unlidded solution.

Pollutant Storage

The Drop Rack trap utilised on-line storage.

Trap Access

Depending on the site and cleaning requirements the Drop Rack trap can be accessed via a ramp or internal step irons


Standard equipment and modular construction combine to make installation convenient with minimum interruption or alteration to existing conditions. Deep excavation is not required with the Drop Rack Trap.


Cleaning of the Drop Rack Trap is dependant on the site requirements but any of the following can be used with this design of trap.

  • Eductor Vacuum
  • Backhoe/Bobcat (dependent on size of containment bay)
  • Clam Shell (dependent on size of containment bay)
  • Manual

Please Note: If a trap is to be cleaned manually, there is minimal Occupation Health and Safety issues as the captured pollutants are dry. 

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