Permachannel is a simple, proven method of source control for large-scale paved areas such as shopping centre car parks. It functions both as a surface drainage system and as a silt and oil interceptor. Laid with little or no gradient, Permachannel works by 'stilling' the run-off from catchment areas to allow dirt and hydrocarbons to sink to the bottom of the channel.

Discharge into drains or further SUDS structures is through a 'weir and baffle' system that allows clean water to pass through while trapping pollution and impurities. In this way, damaging petrol and oil deposits, as well as sand and silt, are prevented from passing into the system, where they are much harder to eradicate and where their build up over time can cause significant environmental harm. Permachannel also has the added benefit of trapping large scale contamination from fuel spills or oil sump failures, allowing it to be removed quickly and easily at source.