Supporting this local Welsh council in the rationalisation of an existing industrial facility and divestment of vacated land for subsequent development.
The Situation
Advisian was retained by Torfaen County Borough Council (TCBC) to review technical information submitted in support of a major planning application for a key industrial site within their Borough. The development involved the rationalisation of an existing industrial facility and divestment of vacated land for subsequent development by others.
The existing facility manufactured brake parts for heavy goods vehicles, a process involving the use of significant volumes of chlorinated solvents to degrease components. Over the course of many years of operation of the existing facility volumes of chlorinated solvents (Tetrachloroethene [TCE]) had been lost to ground. A requirement of the planning consent for the works was that remediation was undertaken concurrently with the plant rationalisation works in order to remove TCE from the subsurface and mitigate associated risks to human health and the environment.
As part of the planning consent for the work, a Section 106 agreement was established and the developer was required to place funds into an escrow account as a guarantee that the works would be undertaken in accordance with the consent and to an appropriate standard. The developer was able to withdraw funds from the escrow account, and reduce the value of the guarantee as various project milestones were achieved.
Approach
- Remediation Costing
Advisian were initially contracted to review available environmental assessment data for the site and assess the value of the provision for remediation works proposed by the developer for inclusion in the Section 106 agreement. Advisian undertook a detailed review of all available information, identified an appropriate mitigation scheme and estimated the costs of the works using pricing models developed using Advisian’s years of experience in the design and management of remediation projects in the UK.
The cost estimate established by Advisian was significantly more than that proposed by the developer. Advisian provided support to TCBC during negotiations with the developer and the provision value identified by Advisian was agreed by all parties and included with the Section 106 agreement.
- Peer Review of Remediation Design
The developer’s proposed remediation strategy for the site included the injection of molasses into the subsurface to create a reducing environment and promote the rapid bio-degradation of TCE. The bio-degradation of TCE is a multistage process that ultimately results in the production of ethene. However, the intermediary degradation products are all toxic and without careful management the bioremediation process can stall and result in the production of significant concentration of vinyl chloride, which is significantly more toxic than TCE.
Advisian identified that a significant proportion of the remediation works were to be undertaken inside of the current production building. As all of the TCE degradation products have the potential to exist in the vapour phase, there existed the potential for seepage of vapours from the subsurface into the production facility where they may present a risk to human health via inhalation. The developer’s original design did not consider this scenario significant. Advisian fundamentally disagreed with the developer’s proposal and recommended to TCBC that, they require the developer to include suitable measures to mitigate the potential for uncontrolled generation of vapours in accordance with best practice. Following a series of discussions the developer revised their proposed scheme to include a soil vapour extraction system. Advisian understand that to date the soil vapour extraction system installed beneath the production building has recovered more than 600 kg equivalent mass of TCE over the course of the works.
Results
Advisian continue to provide support to TCBC on environmental aspects of the redevelopment project including the assessment of project progress against Section 106 milestones.
