A Viridor residents newsletter [PDF] tells us that:
Viridor intends to submit a planning application in June 2014, accompanied by an Environmental Statement, relating to the infill and restoration of the Site of Special Scientific Interest (SSSI) area at the Horton Clay Pit.
In 1991, the former clay pit was granted planning consent for restoration using landfilling. A condition of this consent was that the SSSI would be retained and as a result the landfill was designed around it. The SSSI now forms one side of a shallow excavation with the landfill lying on the other side.
A recent technical stability report found that long-term remediation of the SSSI was not feasible. The only practical and sustainable solution is burial by
inert infill and restoration of the whole SSSI void to prevent any further erosion. Natural England has agreed in principle, subject to the Gault clay being protected by a marker layer.
The scheme will establish additional grassland married into the existing adjacent restoration profile. It will also provide further woodland planting and establishment to enable habitat linkages across the restored landfill.