CASE STUDY: SITE INVESTIGATION, OSNABURGH STREET, LONDON
Project: Pre-land sale investigation
Location: Osnaburgh Street, London City Centre
Client: WSP
A potentially valuable site in the heart of London required site investigation to inform the pre-sale process. The current site held an old office block and before this could be sold or developed WSP had to know the ground conditions.
We were contracted to carry out the borehole works. Because the site already had a building on it we had to operate within these confines, drilling inside the basement of the existing building.
We knew that given the confines of the basement, the diameter of the casings and access issues that there was only one rig for the job, our unique Vetrak®. The Vetrak® is only 780mm wide, it offers the site access of a window sampling rig with the drilling capabilities of a cable percussion rig. Its working height is between four and six metres, making it perfect for this type
of job.
We were on site four weeks as planned. Our equipment was kept on site but the engineers commuted by tube every day.
4 No boreholes were constructed to 25m below the basement floor level using our Vetrak® restricted access rig including in-situ testing and sampling. Each borehole was completed as a combined gas/groundwater monitoring well. Additional works included 2 No 50m deep boreholes using a traditional cable percussion rig commencing in 10" diameter casing, reducing to 8" and 6" as dictated by the ground conditions.
1 to 1.5 fill, 6m gravel onto London Clay, U100's and SPTs at 1m centres all the way down the boreholes - quite an achievement for this rig.
Rig used: Vetrak® and traditional cable percussion rig.
