Project: Emergency response and clean-up of a diesel leak
Client: Confidential manufacturing company
Services: Emergency response planning, environmental assessment, regulator liaison, remediation design
Summary: Through rapid site characterisation and expert decision making ESI minimised the environmental damage associated with a major fuel leak, reduced the duration (and cost) of remediation required and avoided legal action against the client
Due to the corrosion of old fuel transmission pipe work at a large engineering plant in the West Midlands, in excess of 40,000 litres of red diesel was discharged to ground overnight. Due to the proximity of the fuel leak to on site drainage structures, diesel was rapidly conveyed alongside and within the on site drains and was subsequently discharged to a local stream.
ESI were commissioned to provide emergency response, environmental assessment and remediation services following the discovery of the fuel leak and associated pollution.
ESI’s key inputs included:
Emergency response actions
- A site visit by a senior consultant was made within 4 hours of the initial client contact. Immediate advice was provided in order to contain the effects of the leak (including isolation of the on-site drainage system and recovery of accessible free product).
- Simultaneously, data was sought to inform the conceptual site understanding (i.e., to clarify the potential controlled waters receptors and estimate contaminant travel times).
- Contact was made with the Environment Agency and the utility company with responsibility for public sewerage. Lines of communication were established and salient information was exchanged including drainage plans.
- A series of absorbent booms and matting were placed along the length of the affected water course. A damn structure was also constructed within the surface water course to isolate free phase materials and enable controlled release of ‘clean’ river water.
- A programme of pumping and off site effluent tankering was instigated from various locations along the impacted water course and selected on site locations.
- The on site drainage system was carefully managed in order to contain the pollution risks (including isolating drain runs and pumping contaminated effluent for on site treatment).
A daily watching brief was devised in order to monitor key on and off-site locations.
A site investigation programme was designed in order to both characterise the sub surface conditions across the site and delineate the extent of the contaminant ‘plume’. The site works included:
- Excavation of over 20 trial pits, including the creation of sumps in and around the leak area which were designed for subsequent product recovery.
- Drilling of 15 exploratory boreholes and subsequent piezometer installations in a radial configuration around the leak; drilling included a number of locations within buildings.
- Drain mapping and visual inspection of manholes chambers and drainage runs.
- CCTV surveying of on site drainage.
- Forensic testing of free product samples in order to verify the product composition, age and origin.
A risk assessment was undertaken in order to quantify the risks posed by contamination to both site users and the wider environment, notably local shallow groundwater and off-site surface water bodies.
Remediation and verification
ESI produced an outline remediation design, appointed appropriate sub contractors and supervised all remediation works intended to mitigate identified risks posed by the fuel leak. The main remediation activities included:
- Drilling of wide diameter boreholes for product recovery.
- Free phase product recovery from open sumps and boreholes using surface mounted vacuum pumps. These pumps afforded a safe and versatile solution to skimming the free product from the water surface (i.e., pump hoses could be rapidly transferred between boreholes, as required).
- On site effluent treatment using oil-water separation and GAC filtration.
Verification of the remediation performance included a regular programme of borehole dipping and product thickness measurement, for a period of up to two months after the cessation of pumping (to allow for rebound effects). Targets for residual product thicknesses, as previously agreed with the Environment Agency, were satisfied at all monitoring locations.
On completion of the remediation programme over 80 percent of the leak volume was calculated to have been recovered.
As a direct consequence of the robust site characterisation and remediation programme undertaken the Environment Agency elected not to fine or prosecute the client in relation to the incident.