HARRISON GROUP ENVIRONMENTAL was appointed as one of three companies to carry out the ground investigation of a number of sites across the Olympic Park. We were the first ground investigation company on this prestigious project to break ground in December 2005, with a cable percussive drilling rig on Hackney allotments.

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

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

A variety of drilling techniques have been utilised on the site to drill boreholes up to 50m deep. These include the use of: -

• Cable percussive rigs
• Hollow stem auger rigs
• Window sampling rigs
• Sonic rigs

Standard soil sampling regimes have been followed and in addition to this, piston sampling and continuous undisturbed samples - U100's have been incorporated into the works.

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

There is the potential for a wide range of contaminants across the Olympic Park area. As a result of this we are assuming all sites on this project to be category 'RED' for ground investigation purposes, and the specific PPE and welfare/decontamination facilities associated with this are made available on site. More specifically this means: -

Drillers and engineers go through decontamination procedures each time they leave site and use clean gloves for all sampling procedures.

Clean method techniques are applied to all drilling operations, drilling initially with 250mm diameter casing, with reductions in diameter at the base of made ground and again at thebase of RTD. In order to prevent cross-contamination a 2.0m bentonite seal is placed at each reduction.

Rigs are checked daily and audited weekly and all tools are cleaned between borehole positions. A gas alarm is located at every drilling rig, with both engineer and driller being trained in its use. A head space test using a PID is carried out on every sample.

All site staff have available personal universal fitted vapour masks as part of their standard PPE.

Occasional monitoring for radiation has been required

The Olympic Park site covers a wide area geographically and at the present time the land usage is varied. Some areas remain quite 'wild' and this has raised important considerations with regards to ecology. As a result of this, we have carried out walkovers on all sites - prior to mobilising any drilling crews or equipment - in order to highlight such issues. Subsequent programming of our work and the site investigation methods selected, have been dependent on the findings of these surveys.

Specific issues that we have successfully worked with are: -

The Arena fields site was held up for 2 months while a Newt survey was completed. As a result of this we were unable to carry out machine dug trial pitting in the area. Window sampling and hand dug trial pits were carried out as a suitable alternative pit.

Certain areas of scrub land could not be cleared due to ground nesting birds and the work in these areas this had to be re-programmed.

An area of breeding/nesting kingfishers was identified. An exclusion zone was designated and affected boreholes were re-positioned outside the exclusion zone. Hand augering only was carried out inside the area once we were given the go-ahead.

Japanese Knotweed has been a problem across the Olympic Park site. To eliminate risk of spreading, a wash down point was set up to decontaminate all equipment, vehicles and staff, and sampling was restricted.

This has been a high profile project for the industry and has 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 have successfully taken 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 is now being reviewed by the HSE.

We are proud to report that we have had zero reportable incidents in over 1400 drilling, monitoring and surveying days on the Olympic Park Site.