Combined Flood Risk Assessment & SuDS Drainage Strategy
Civilistix Consulting Engineers were appointed to undertake a combined Flood Risk & Drainage Strategy to support the accommodation of 36,000m3 of imported fill material at an existing 13.40ha quarry site, raising existing levels by up to 3.0m.
Our drainage strategy overcome two principle problems; preventing existing drainage pathways becoming blocked by ground raising proposals and attenuating the additional runoff caused by the fill material.
For the former, we provided a ~400m dry swale around the ground raising extends to intercept existing runoff and convey it to existing ditches (to mimic the pre-developed state).
For the latter, we proposed a ~1150m3 attenuation pond to attenuate additional runoff at the 1 in 1 year greenfield runoff for all events up to and including the 100yr+40%cc event creating a betterment when compared to the predeveloped site. Dry swales where used to convey and treat runoff.
The measures we implemented ensured greenfield runoff rates and volumes were never exceeded and the necessary level of surface water treatment provided.