This mixed residential development of 2 to 3 storey houses and 4 storey flats, by Barratt Kent was under taken on a highly contaminated former gas works. The site was bound, to the east by an operational gas works and to the north by a main line railway.
The scheme included significant remediation works, including installation of a bentonite cut off wall on the boundary line with the current gas works, excavation and removal of highly contaminated back fill from historic gas storage tanks, bio-remediation , temporary sheet piling within 1m of a 24 inch live gas main and piling adjacent to the railway.
The scheme also allowed for the removal of existing culverts across the site and replacement with a new ‘open’ water course. The revised levels necessitated the construction of a new weir structure and culverted bridge structure, to full Highway Authority approval.
The re-modelling of the local water course took into account flood levels and surface water discharge from the site. Significant surface water attenuation was required to meet Environment Agency limits on discharge. Residual contamination, beneath a clay capping layer prevented the use of soakaways.
Earthwork modelling and arising calculations were undertaken, to limit costly off site tipping of ‘hazardous’ waste and to provide positive falls within soft landscape areas towards the watercourse.
Levels to the west of the site rose sharply requiring slope stability analysis and careful consideration of levels.
‘Green’ reinforced earth embankments we adopted in a number of locations, in part beneath new section 38 highways.
Negotiations with Kent Highways, the Environment agent, Transco, Network Rail and NHBC were required for various elements of the scheme, including Party Wall matters.
Off site, section 106 works included highway improvements under a 278 agreement and cycle path though adjoining wood and park land.
All foundations were piled, through varying depths of historic and recent fill (9m plus in part). Piling adjacent to the railway was subject to Network Rail approval.
The scheme also involved the design and detailing of an offsite cycle path, and foundation design for a proprietary timber footbridge in adjacent wooded park land.
JNP Group services provided:
- Crane foundations design.
- Pile mat designs.
- Bridge, culvert and water course design.
- Highway and drainage design.
Project Value: £15m
Client: Barratt Kent