Tipner Regeneration, Portsmouth

Client: Tipner Regeneration Company
Date: 2016 – Ongoing (68 Weeks)
Nature of Works: Soil & Groundwater Remediation
Contract Value: £4.0m ICC Design & Construct Contract

This 6Ha former chemical (tar) works, fuel depot, timber yard and ship breakers yard situated on the shores of Tipner Lakes, a RAMSAR protected SSSI is grossly contaminated with a variety of contaminants including tars, oils, creosote compounds and asbestos containing materials (ACMs). Several stands of Japanese Knotweed (JK) infestation are also present. An additional challenge was the presence of historically landfilled materials, significant in-ground obstructions including buried concrete barges and risk of encountering unexploded ordnance (UXO). Soilfix is currently carrying out remediation works in support of a large regeneration scheme to return previously derelict land to 525nr residential houses / apartments with coastal footpath and amenity space.

Soilfix has designed and is currently implementing a multi-disciplinary remediation scheme, comprising:

• Installation & CQA testing of a 325m length slurry cut-off barrier around the foreshore to protect Tipner Lakes, with depths up to 7.5mbgl – Soilfix’s first in-house installation of such a barrier. Upon completion of remediation works, 2nr Permeable Reactive Treatment Sections will be constructed within the barrier to polish groundwater’s prior to discharge into protected waters;
• Excavation and processing of 50,000m3 prior to further treatments. Ex-situ augmented bioremediation of 20,000m3 gross hydrocarbon contaminated soils using cultured bacteria and 40,000m3 lime/cement stabilisation will be undertaken;
• Sheet-piling carried out to facilitate deep excavation works, up to 6.2mbgl;
  Comprehensive groundwater treatment system with multi-stage separation and settlement tanks to remove free phase and dissolved hydrocarbons prior to discharge;
• Comprehensive odour neutralisation measures during soil excavation and processing, including portable rotary atomisers and fixed nozzle systems;
• Excavation, pre-treatment and encapsulation of JK contaminated soils within copper-woven root barriers;
• Targeted obstructions removal in the larger infilled former shipyard area to clear pile cluster locations of impediments;
• Modular treatment of excavated soils containing ACM fragments using screening / hand-picking in accordance with CAR2012; and,
• Process/crushing of segregated clean hard-core arising from the works for re-use as a granular lower capping layer on hi-visibility marker geotextile.

Off-site disposal will be limited to grossly contaminated materials and residues arising from the works, with approximately 99% materials recovery envisaged. All works are being carried out in full compliance with CL:AIRE Code of Practice and Environmental Permitting requirements.