THE CHALLENGE:
Dewatering of a Grade II listed Victorian gasholder was required to allow an internal drone survey to be carried out to inspect its internal structure. A total volume of 25,000m³ water was removed reducing the water level to 8.5m below ground level. This significant volume removal was required within a maximum 12 week program to allow the client to proceed with its survey and subsequent liaison with English Heritage.
Particular constraints included tight site access, minimal site space and limited access to the holder. These constraints resulted in specific design considerations for the installation of the pumps and layout of the water treatment system.
OUR SOLUTION:
Overall objectives were agreed for the works based on a Soilfix designed and implemented remediation scheme, which included:
- Pumping and on-site treatment of heavy metals and hydrocarbon contaminated gasholder water through a water treatment system, prior to discharge to the foul sewer under a discharge to sewer consent;
- Comprehensive testing of treated waters, along with assessment of results, to ensure discharged water remained below permit levels;
- Completion of environmental monitoring with assessment of controls to provide particular focus on Odour/VOC emissions along with excessive noise due to location of site being near residential areas;
- Upgrading of the water treatment system to increase the flow rate allowance from 12m³/hr to 25m³/hr due to an increased discharge permit allowance. This resulted in the project being completed ahead of program;
- Detailed telemetry was installed across the system. This allowed real-time monitoring 24/7 which allowed for planned preventive maintenance thus ensuring consistent reliability and minimising downtime; and,
- Carrying out treatability trials for basal sludges recovered from the annulus of the gasholder to inform future dewatering requirements.
Soilfix successfully completed all specified works 2 weeks ahead of program with zero lost time accidents, enabling a swift sign-off and handover back to client.
