CRANWORTH APARTMENTS, ST HELIER
PROJECT OVERVIEW
In January 2021, CJ Associates were instructed by RSK to undertake a ground investigation at St Helier, Jersey. The purpose of the GI was to provide ground data for the design of an apartment block requiring an extensive cut into a slope comprising Jersey Shale Formation. The GI scope designed by RSK comprised 2 no. boreholes to 30 m bgl, downhole geophysics, and groundwater monitoring instrumentation. Due to the location of the boreholes, a crane was required to lift the rig and ancillary plant into position on the slope crest.
Following contract award, the nominated drilling foreman from CJA undertook a site visit to meet with the crane provider, along with engaging with local suppliers for the provision of ancillary plant, including a compressor and water bowser. Our foreman was able to input into the design of the crane lift and advise on the optimum location for the landing of the plant.
In order to construct the boreholes, we mobilised a Commachio 205 drilling rig with 30 m of PWF size downhole tooling with air mist as the flushing medium. Due to the remote nature of the site, we mobilised alternative tooling and drill bits to provide resilience with respect to unforeseen ground conditions.
The drilling plant and installation equipment were mobilised to Jersey via 3 no. vehicles. In order to reduce transport costs and ensure there were no potential delays with the geophysical testing, we also mobilised the geophysical equipment so that the equipment was available as soon as the drilling was completed
We constructed 2 no. 30 m deep rotary boreholes and achieved 100% core recovery. Upon BH completion we flushed the holes with clean water, thereby providing an optimum borehole for the completion of the geophysics, including an optical and acoustic televiewer complete with structure picking. Temporary casing was left in each of the boreholes during the geophysics, which was then removed to facilitate groundwater monitoring instrumentation. We provided on-site training to the site owner on the use of groundwater monitors, thereby reducing any associated costs and carbon footprint with weekly visits from a mainland-based engineer to monitor groundwater.
GENERAL PROJECT DETAILS
Location: St Helier, Jersey
Sector: Commercial Development
Client: RSK
Consultant: RSK
Contract Value: £50,000
Services: Dynamic sampling, rotary coring, down hole geophysics, remote working
