THE CHALLENGE:
A housing development had been partially completed due to the developer having gone into administration. Previous works had left 8,250m3 stockpiles of mixed clean subsoils and made ground containing polyaromatic hydrocarbons (PAH)s & Asbestos. Further works were therefore required to render the 0.5Ha area suitable for Public Open Space (POS) including a children’s playground.
Upon further inspection, the Soilfix team noticed that the stormwater attenuation pond serving the development had been previously constructed to the wrong design (slope angles far too steep), and the unprotected, exposed liner had become badly deteriorated by sunlight.
OUR SOLUTION:
The works were designed following further assessment by the client’s environmental consultants in full collaboration and agreement with both the Environment Agency and Local Authority to work under the CL:AIRE DoWCoP for sustainable materials re-use. Works included:
- Further characterisation testing and careful segregation of clean topsoil / subsoils (suitable for re-use) from contaminated made ground;
- Hand-picking of visible asbestos cement sheeting fragments, double-bagging for removal;
- Disposal of 5,000m3 of surplus / unsuitable soils off site under full Duty of Care;
- Reprofiling the POS area to final design contours using selected sub-capping fill;
- Placement of a freely draining orange marker geotextile, clean capping subsoil and imported BS3882 compliant topsoil to form a clean cover system prior to landscaping and playground construction (by others);
- Draining of the stormwater pond, stripping/disposal of the deteriorated liner, re-contouring the pond to the engineer’s design; and,
- Placement of a new welded geo-membrane liner, protective geotextile and protective layer of clean subsoil across the stormwater pond—sides of pond dressed with topsoil and hydroseeded to establish vegetative grown.
All works were completed with no health, safety or environmental incidents, on programme and to the administrator’s financial budget. Follow-on construction works could thereafter continue and complete the development for much needed new housing in North Essex.
