We designed, supervised, implemented and reported a multi-phase investigation to support the site remediation and construction a Place of Worship in Consett. The seemingly straightforward scheme encountered a range of challenges, including potential ground subsidence associated with historical coal mining, generally poor ground conditions and contamination including “Blue Billy” and hydrocarbons.
Although the emerging conditions proved challenging, our robust desk-based assessment provided a reliable Conceptual Ground Model and anticipated a number of the hazards encountered. We worked closely with our client and Local Authority to ensure the execution of a comprehensive site investigation, remediation planning and implementation to enable the development.
We were engaged to undertake an Integrated Site Investigation and Remediation to support the development of a Place of Worship on a brownfield site in Consett. The investigation was in response to a number of planning conditions imposed by the Local Authority relating to coal mining and contaminated land. The Stage 1 Desk Study identified that the site was formerly occupied by a coal depot, adjacent to railway land. The underlying geology comprise Glacial Diamicton over Coal Measures bedrock, with Made Ground anticipated on site.
Trial pits and rotary cored boreholes in accordance with BS5930 were undertaken to confirm the ground conditions at the site. The rotary drilling encountered shallow coal mine workings which presented a significant subsidence risk.
We designed, scoped and implemented drilling and grouting in accordance with CIRIA C758; this enabled us to inject ~200 tonnes of grout into the shallow coal mine workings to reduce the subsidence risk. We provided full-time supervision throughout the works and subsequent confirmatory reporting.
During the Integrated Site Investigation and Remediation, localised cyanide contamination was identified at the site as Blue Billy. A hot spot of hydrocarbon contamination was also identified.
‘Blue Billy’ is a distinctive bright Prussian blue making it immediately obvious on #ContaminatedLand sites-These materials are #hazardous ferric cyanide compounds by-products of former #gasworks Today we deal with their legacy remediating & returning land to new uses #Brownfield pic.twitter.com/0LGuMzyAVX
— Geoscience EnvAgency (@GeoscienceEA) July 15, 2019
During supplementary works, we worked with the Client and Local Authority to manage the risks in accordance with the Environment Agency Land Contamination Risk Management (LCRM) guidelines.
We prepared a Remediation Method Statement and supervised on-site remediation works, including material removal and validation testing. We provided ongoing support throughout to ensure completion of the remediation and on completion we produced a Remediation Verification Report.