The Portsmouth Northern Quarter project is a GBP 300million re-development of the city centre to provide new commercial and residential structures and a complete revamp of the area's infrastructure.

The plans include open streets with over 80 new shops, cafes and restaurants, a John Lewis department store, a Marks & Spencer store, 200 residential apartments, a four-star 150-bed hotel, new public open spaces and car parking for 2,300 vehicles.

Harrison Group Environmental were instructed, on behalf of Centros Miller, by Waterman Environmental to act as principal contractor for the intrusive site investigation works and geotechnical consultants, providing design data and recommendations for foundation and pile design, basement design (piled walls and propping) pavement design, and environmental issues.

As principal contractor and geotechnical consultant we were required to initially plan the site investigation works, ensuring that all required data was obtained whilst keeping within an allocated budget, specified by the client. The scheduling of all geotechnical testing was carried out by the Principal Engineer in our London office, who worked closely with staff from Waterman Structural, to ensure that we fully understood the end use of specific areas and the resultant ground loadings.

Site works were extremely challenging. Before they commenced, it was found that a buried reinforced concrete slab existed across most of site, buried up to 3.0m below ground level. The thickness of the slab ranged from 300m to in excess of 1300mm and not an ideal situation for cable percussive drilling. Specialist concrete coring crews were employed on the site to work ahead of the drilling rig and release positions for us ensuring that we could work to the required programme.

The geology of the site was also not straightforward. Dense clays and limestone bands, along with a sub-artesian water table at depth, slowed the cable percussive drilling operation. As a result of this, rotary rigs were mobilised to site to drill some key positions and ensure that all required information was obtained.

Logistically the project was challenging to us, as road closures were not permitted. One of the busiest roads in Portsmouth runs through the site. We were required to minimise disruption to the public by drilling in very restricted areas and setting up detailed traffic management. In addition to this we had to coordinate all operations with the various authorities and land owners. For some of the drilling positions, we worked with Portsmouth City Council, Hampshire County Council, the Highways Agency, Colas Ltd (PCC appointed infrastructure management company) and National Car Parks, to obtain road opening licences / permits to dig and conditional surveys.

Local residents were also affected by the development with a number of compulsory purchase orders being issued.

We were very pleased to successfully complete the planning, execution of fieldworks and issue of reports within the allocated time frame.