INTRODUCTION
The project consisted of site investigation at a number of sites directly affected by proposed extensions to the existing East London Line. This extensive project is designed to provide a link into the National Rail Network in north and south London. The site was split into three sections - from Dalston Bridge in the north through to Shoreditch and Surrey Quays in the central section and non-operational parcels of land in the south. The Harrison Group investigation formed a vital link in a chain of enabling works to assess infrastructure, improve operational stations and ultimately construct a new station at Surrey Canal Road.

SCOPE OF WORK
Site works included the drilling of cable percussion and rotary boreholes, machine and hand excavated trial pits and in-situ permeability and cone penetration testing (CPT).

Many of the hand dug trial pits were excavated to assess the foundations of existing bridge arches and structures along a derelict viaduct in the northern section of the site. Some of the pits were greater than 5m deep, requiring shoring. The sensitivity and potential historic importance of other parts of the site meant that a representative of the Museum of London Archaeological Services (MOLAS) was present to observe and advise personnel.

Rotary drilling was undertaken in the southern section through the base of cable percussion boreholes using a 76mm triple barrel coring system, with a water and air flush to core the chalk. The cores were then logged and photographed on site to CIRIA approved standards.

SPECIAL CONSIDERATIONS
Key considerations whilst planning of our work were the limited access and sensitive nature of some of the locations. In order to overcome the challenges that were encountered, we used bespoke and ingenious methods in carrying out our work.

In addition, the varied requirements of landowners along the route meant Harrison Group managed individual and complex access requirements, obtaining permits to work, providing required-format method statements and producing risk assessments at all stages. On sites close to railway lines personnel were PTS qualified to ensure both safety and best practice.

CONCLUSION
This was a sensitive and demanding project that required a flexible working approach due to the many landowners and varied nature of the locations where investigations were taking place. Close liaison with authorities and interested parties such as museums/ heritage bodies ensured that Harrison Group’s contribution to this major regeneration project was completed successfully and with minimal disruption to infrastructure and local heritage.