WHAT SHORT OF SOAKAWAY IS MOST APPROPRIATE?
Soakaways for small catchment areas of less than 100m² are usually 3-4 m deep pits filled with granular material with a particle size of 10-150mm, or lined with dry-jointed masonry. NHBC data suggests that depending on the rate of water infiltration into the ground, smaller pits may be possible (see diagram above right). A geotextile covering should be laid over the top to ensure that no soil is washed down into the soakaway. Those serving larger areas should be designed in accordance with BS EN 752-4 or the latest BRE Digest 365. Generally, these will be lined pits, trenches or perforated precast-concrete ring units (to a similar depth as the smaller versions depending on soil characteristics) Loadbearing plastics honeycomb units are also produced to serve the same function. Very deep soakaways may use an access shaft to connect the lower perforated chamber to ground level. Whichever design is chosen, the soakaway should accommodate an above-ground silt trap and be designed for a retu
