Housing Development, Powys.
Hafren Water undertook a Flood Consequence Assessment (FCA) for the proposed development of a residential property adjacent to the River Lugg. The site was identified within the Environment Agency flood map as being at risk of flooding from the 1 in 100-year event. The River Lugg, a nearby brook and surface water run-off, were all identified as possible mechanisms of flooding. An assessment was undertaken to consider the proposed development levels, the ground levels within the surrounding area and high stage readings in the river and historical flood information. From this it was possible to show that the risk of flooding at the site was very low. Assessment of impact of the development on flooding in the surrounding area was undertaken and simple mitigation measures, such as the installation of a soakaway, were recommended to reduce the risk further.
Waste Transfer Station, Avonmouth.
A FRA was undertaken for the proposed development of a waste transfer station. The site was situated in Flood Zone 3 and was considered at risk of fluvial flooding from the River Avon and tidal flooding from the Severn Estuary. Although flood defences existed in the area there was still considered to be residual risk from breaching of the defences. The proposed development did not involve the change in footprint of the buildings on-site or changes in ground levels. However, it did involve the change in use of the site to one with a greater vulnerability classification. Investigation of historical flooding at the site identified that there had been a history of surface water flooding due to insufficient capacity within the local surface water drainage system. Mitigation measures were recommended to ensure that the risk of contamination from the site during flood events was reduced and to ensure that site personnel could safely egress in the event of flooding.
Sand and Gravel Quarry, Nottinghamshire.
As part of an Environmental Impact Assessment for proposed mineral extraction and associated restoration, Hafren Water advised on the hydrology and hydrogeology of the site including undertaking a FRA. The site is situated in Flood Zone 3 and forms an integral part of the flood prevention measures in the surrounding area. Advice was given at an early stage in the design process to ensure that any proposals were appropriate. The change in floodplain storage resulting form the development was assessed to ensure there would be no adverse impact on the surrounding area. Mitigation measures were proposed to reduce the risk to site personnel.
Recycling Facility, Surrey.
Hafren Water undertook an assessment of water management issues for the proposed re-development of buildings at an existing recycling facility. Design of the surface water management system to increase the storm water storage at the site was undertaken in conjunction with manufacturers of SUDs infrastructure. Calculations were undertaken to determine run-off values from the proposed site for a range of storm events. A SUDs system consisting of wide ditches, a pool and reedbed was designed to provide the required storage potential and attenuate flows to greenfield values.
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