Infiltration Trench


EGRP Supported Infiltration Trench

Increased property development has resulted in a larger proportion of land with non-permeable surfaces which, when combined with prolonged periods of rainfall, can give rise to nuisance groundwater and flooding. Whilst traditional piped drainage systems require an outflow to already over stressed storm drains, the Energy-Passive Groundwater Recharge Pump (EGRP) system enables you to deal with rainfall at source, cost effectively, environmentally and with minimal disruption.
The EGRP technology enhances and accelerates the soils ability to absorb water and the system is used for natural turf drainage as well Surface Water Management for SUDS solutions in urban drainage schemes.

The concept of our EGRP supported linear soakaway is based on maximising permeable surfaces and minimising the distance water needs to travel before coming into contact with either the walls or the floor of the trench. The traditional cubic soakaway design only has circa one third of the permeable surfaces which a long narrow soakaway has to offer – and given that water requires contact with a permeable surface in order to drain away then a long narrow trench is the most effective means of buffering storm water before it permeates into the ground.

Before the Infiltration Trench is excavated the positions and depths of each EGRP device is marked out, the boreholes drilled and EGRP devices installed respectively. The 6 metre EGRP devices, which are installed 300mm below the base of the trench, are put into position before excavations commence (as drilling in the base of an excavated trench quickly refills the trench with arising’s – which in turn has to be excavated out).

The EGRP System comprises a series of vertical 90mm diameter boreholes at depths of 3 metres along the side walls of the trench and 6 metres along the floor of the trench. The objective of these devices is to increase the rate at which storm water is able to drain from the trench into the earth surrounding it. The boreholes also add to the overall storage capacity of this drainage system and as the EGRP devices “acclimate” (a term used to describe the 12 weeks or so that it takes for the boreholes to close in around each device respectively) a connection is made between the infiltration trench and the boreholes surrounding it.

The result is a drainage asset which;

- Has significant storage capacity which matches the specified storm return event.

- Is specifically designed for purpose using a site specific Drainage Design Statement.

- Is installed in accordance with an independent Drainage Design Statement specifying the dimensions of the trench and the amount & locations of EGRP devices.

- Is easily augmented in future should additional storage be required.

- Deals with storm water at source without the need to connect to storm drains or sewers.

Our Infiltration Trench design, typically a 300mm wide by 2 metre deep x varying length depending on drainage storage calculations, increases the volume of permeable surfaces by approximately 3 times that of a traditional cubic soakaways. Also, water entering the Infiltration Trench has a much shorter path to contact with permeable surfaces leading to quicker more efficient percolation rates.


Filled Infiltration Trench

Filled Infiltration Trench