Investigation work was located on both the north and south banks of the River Wear in Sunderland to the immediate east of the Wearmouth Bridge, an area designated for Tall Ships Race (2018) mooring facilities. Site works were commissioned to assess the structural capacity of the existing quay infrastructure and in-ground support systems, as well as to establish river bed dredge extents.
The work was undertaken on behalf of Mott MacDonald (Newcastle), who were themselves commissioned by the City of Sunderland. In order to facilitate the objectives set by the Client the company designed a cantilever platform of the required dimensions for boreholes located in the river bed at the front of the quay sheet piled wall. Overall twenty-seven cable percussion boreholes (ten using the cantilever platform) were undertaken throughout the quayside area. In addition fourteen shored (for access) mechanical/hand excavated trial pits were carried out to carefully expose the existing piled wall support system (tie-bars and anchors) as well as a supplementary survey of steel thickness by ultrasonic meter - conducted using a negative reach platform. Other services included in-situ UXO assessment, concrete coring (to assess reinforcement conditions in quayside platforms), in-situ testing and various other routine services.
Boreholes located near the piled quay walls were used to establish the toe embedment depths of adjoining sheet piles by specialist parallel seismic (PST) geophysical techniques. Plastic casing was grouted into place at the completion of selected boreholes to enable this objective. Post-site monitoring included the use of Divers® to automatically record tidal groundwater fluctuations in relation to river level, over a pre-determined duration. In-house geotechnical testing was largely routine with no specialist environmental screening required by Mott MacDonald. A detailed and descriptive factual report covering the whole of the works was provided at the conclusion of the contract period.
One key consideration during the investigation was the necessity to leave working areas in an almost pristine condition. Trial pits undertaken in paved areas were painstakingly reinstated; essentially replaced spoil arisings were densified, the granular formation replaced before individual slabs could be reset.