West Purifier - Brandon Yard
A former Bristol gas works site, which was derelict for more than 40 years, was granted planning consent for a 58 unit residential scheme.
Brandon Yard on Bristol’s harbourside contained ruins of two grade-II listed buildings, the West Purifier House and the Engine House, both were to be restored under the plans, together with the iconic chimney of the Engine House.
The site presented a number of challenges as a result of its location within an area of high tidal flood risk and legacy contamination issues relating to its historic use for both gas works and glassworks before that.
Clarkebond reviewed historic data from 44 reports and, using up-to-date assessment criteria, produced a summary report identifying the remaining contamination and geotechnical data gaps. Clarkebond then designed and managed a final site investigation to address these data gaps.
Clarkebond also undertook a Coal Mining Risk Assessment and produced a final detailed Remediation Strategy.
The site is located in an area of high tidal flood risk. Assessment of flood mitigation measures required a unique approach as the external fabric of the listed buildings could not be altered. Early consultation with the Environment Agency was therefore necessary to agree the design parameters.
It was agreed that protection up to the design flood level would be provided by demountable barriers and flood proofing of the building exterior; the specification of resilience measures on the ground floor was an additional level of protection. A robust flood evacuation plan and management plan was also produced for implementation at the site.
The final proposal incorporated SUDS measures including lined permeable paving in the external vehicle access and swales for the maximum capture of hydrocarbons prior to discharge into the Floating Harbour.
The drainage strategy positioned the outfall below the normal harbour water level to reduce hydraulic impacts. In order to avoid this surcharging the surface water system, the final lengths of the surface water system are back dropped with flap valves and penstocks to allow the system to be isolated from the harbour and to ensure that harbour water does not back up into the onsite storm sewers.
On site flood levels are predicted to be 9.8m hence all habitable buildings are set above this.