Humberside Police HQ in Hull lies in an area particularly vulnerable to flooding. On June 23rd 2007 the worst happened and the site had to be evacuated. Within a year, plans were being developed to prevent a recurrence.
Flood-proofing would include construction of a 500-metre perimeter earth bund. Attenuation tanks would be required to cope with intensive rain run-off within this boundary. There were a number of site constraints: existing services running over the proposed tank locations, and very shallow drainage. The first project design proposed 4 tanks placed above a pipe with top perforations to feed water into the temporary storage tank via a granular distribution layer.
The suggested switch to AquaCell gave us some valuable extra flexibility for creating the buried tank capacity. When the original design was scrutinised, it was shown how we could do it with one less tank. So it also reduced the amount of excavation necessary.
Working closely with Sangwin personnel, the Wavin team was able to suggest beneficial amendments to the design. Their alternative suggestion demonstrated how time and cost could be reduced, whilst also enhancing performance. Unlike the originally specified system, the Wavin AquaCell system allows lateral flow, and is easily adaptable to avoid disturbing any buried services. Direct connection to the assembled storage tanks eliminated the need for an underlying feeder pipe. It also allowed units to be doublestacked, increasing each tank’s capacity and reducing its footprint, while keeping within the site constraints. This, in turn, meant one tank could be eliminated altogether, with savings in both time and cost of plant, excavation and spoil removal.