HIGH PERFORMANCE SOAKAWAY CONDUIT

The HPSC system is a high performance soakaway system that is intended to be installed at shallow depths. The very high strength of the system makes it possible to locate the HPSC units in all areas, including beneath car parks and driveways with as little as 150mm cover, therefore only 450mm overall depth.

The intention is to take advantage of high infiltration rates of shallow sub soils and open graded aggregate sub-base as part of the overall project design. The system is particularly useful where there are high groundwater levels or on contaminated sites or where poor, unstable ground exists and excavation of deep trenches needs to be avoided.

The Building Regulations (requirement H3 3.25a.), states that soakaways should not be located within 5m of a building or road. However, a relaxation on this point is allowable as the HPSC system is not a conventional concentrated point soakaway but is conversely a uniformly distributed infiltration device that provides very gentle and widespread conditioning of the soils by replicating the natural catchment as closely as possible. This philosophy is in accordance with the part H3 guidance note c which states that “In the Secretary of State’s view the requirements of H3 will be met if rainwater soaking into the ground is distributed sufficiently so that it does not damage the foundations of the proposed building or any adjacent structure”.

A sensible approach, therefore, is to consider the foundation type of the building (or road), the available space for the infiltration device and the properties of the foundation subsoils to establish suitability of the system. It may be considered beneficial to consider this type of system to maintain properly conditioned subsoils to avoid potential desiccation problems associated with drying out of cohesive soils.

Go to the downloads section where you can find a collection of pdf's on the HPSC system and components.