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Sadds Wharf


Case Study : Remediation of Former Sawmill and Timber Treatment


Contract In Brief:  
Location: Client:
Maldon, Essex London based consortium
HBR Role:
Form of Contract:
Design and build specialistremediation contractor

Contract Value: Contract Start: Contract Period:
£0.4M June 2014 5 Months

HBR Site Management

Contracts Manager: Project Manager: Technical Manager:
John Harrison Suzanne Thorpe Simon Hockin
Services Included:           
In-situ soils & groundwater ü DQRA & Regulatory Liaison                   ü Stabilisation/solidification                ü
Bioremediation ü Asbestos management ü DNAPL recovery ü

In situ chemical oxidation ü

Project Summary:

HBR have recently completed a turnkey design and build remediation project at a waterfront site in Maldon, Essex.

The site was formerly a sawmill, timber yard and railway sidings that fronted directly onto sensitive estuarine wetland habitat and was also next to residential properties. Contamination present in the soils included coal tars, polyaromatic hydrocarbons, total petroleum hydrocarbons, heavy metals and asbestos. The groundwater was found to be heavily impacted by weathered creosote.

Remediation included a variety of techniques including;

-: Bioremediation of soils;

-: Stabilisation/Solidification (S/S) of soils;

-: Removal of Dense Non Aqueous Phase Hydrocarbons (DNAPLs) , primarily creosote;

-: Management of asbestos contaminated soils;

-: Dissolved phase water treatment.

Sadds Wharf Case Study3.bmp

Due to the impending expiry of Planning Consent - for mixed residential/commercial use, the works had to be completed within a strict timescale and be well planned and managed due to the limited site area.

The initial works involved a delineation exercise to better quantify the contaminants and their spatial dispersion. This enabled HBR to undertake the completion of a Detailed Quantitative Risk Assessment (DQRA) in order to define the remediation criteria, and a Remediation implementation Plan (RIP) detailing the methods by which these criteria would be achieved.

The trial trenches revealed a hitherto undiscovered plume of weathered creosote as free product within the superficial alluvial deposits which was a continuing source of contamination to the groundwater. The removal of the creosote was undertaken using targeted pumping of DNAPL from large diameter wells installed to depth in the London Clay and total fluids pumping of emulsified product until asymptotic conditions were achieved. This was followed by In Situ Chemical Oxidation to further polish the groundwater contaminants.Sadds Wharf Case Study2.bmp

Treatment trials were undertaken on representative soil samples, subsequent to which stabilisation/solidification was utilised to treat metal and high levels of organic wastes. Ex-situ bioremediation using windrows with targeted additives was used to successfully treat the PAH and TPH contaminated soils.

The bioremediation took place over a period of 8-12 weeks and contaminants were reduced by up to 90%of the baseline conditions thus allowing reuse on site. The project was successfully completed on time and within budget and the scheme was signed off by the Environment Agency and Local Planning Authority.

                 Chemical v Physical v Biologicalv Complex Sorting v Water Treatmentsv Complimentary Processes