LOCATION:   Stratford - London

PROJECT TYPE:   Contaminated land investigation

VALUE:   £3.75M

BACKGROUND

HARRISON GROUP ENVIRONMENTAL was appointed as one of three companies to carry out the geotechnical ground investigation on approximately 70No. sites across the Olympic Park area . We were the first site investigation company on the project to break ground in December 2005, with a cable percussive drilling rig on Hackney allotments.

SCOPE OF WORK

By working closely with the client, we were able to successfully overcome a number of challenges in order to meet the deadlines set. These involved:

• Unexpected ground conditions
• Liasing with landowners and occupiers
• Access difficulties
• Scheduling fieldworks to cause least disruption to breeding kingfishers

Intrusive work across the Olympic Park area included:

• Borehole drilling with cable percussive rigs
• Machine dug trial pits
• Borehole drilling with hollow stem auger rigs
• Small diameter boreholes using window sampling rigs

Standard soil sampling regimes were followed and in addition to this, piston sampling and continuous undisturbed samples – U100’s – were incorporated into the works.

In addition to the drilling crews, we also had a dedicated team on site to carry out continuous gas and water monitoring, permeability testing and in-situ water quality testing.

Environmental Considerations

There was the potential for a wide range of contaminants across the Olympic Park area. As a result of this, we assumed at the time, that all sites on this project would be category ‘RED’ for ground investigation purposes, and that the specific PPE and welfare/decontamination facilities associated with this were made available on site. More specifically this meant that:

• Drillers and engineers go through decontamination procedures each time they left site and used clean gloves for all sampling procedures
• Clean method techniques were applied to all drilling operations, drilling initially with 250mm diameter casing, with reductions in diameter at the base of made ground and again at the base of the river terrace deposits. In order to prevent cross-contamination a 2.0m bentonite seal was placed at each reduction
• Rigs were checked daily and audited weekly and all tools cleaned between borehole positions. A gas alarm was located at every drilling rig, with both engineer and driller being trained in its use. A head space test using a PID was also carried out on every sample
• All site staff had available personal, universal fitted vapour masks as part of their standard PPE
• Occasional monitoring for radiation was required

Health and Safety

This was a high profile project for the industry and presented an opportunity to fine tune the health and safety standards for industry drilling operations. As a result of working closely with the HSE we successfully took on board new recommendations to enhance the safety of drilling crews on site. We also commissioned an in-depth assessment of manual handling issues on behalf of the Olympic Delivery Authority, which has been reviewed by the HSE.

OUTCOME

We are proud to report that we had zero reportable incidents in over 1400 drilling, monitoring and surveying days on the Olympic Park Site. All work was completed in the timescales that were set and to the satisfaction of the clients that we were working for.