The proposal
To address the historic contamination and make the site safe to build new homes, Bellway’s engineers propose the placement of a clean capping layer and surcharge above the landfill.
These two methods will allow the site to be remediated safely and permanently. The two metre deep clean capping layer will sit immediately above the landfill material to hold it permanently in place.
The clean capping layer
The capping layer will ensure that the installation and maintenance of services and private drainage can be carried out in clean, safe conditions. Above the capping layer will sit a small drainage blanket that will help act as filter for water from the surface and deeper down within the existing landfill.
A temporary surcharge
A four metre temporary surcharge will sit above both the clean capping layer and the drainage blanket. In order to reduce the extent of future settlement for the former landfill area and ensure the contaminated land is compressed and contained, surcharging of the soil is considered the most appropriate approach. This will require clean soil to be transported to site over an extended period of time to provide both the capping layer and the surcharge element.
Slurry wall barrier
As surface ground water flows west towards the River Roding, the proposal includes the construction of a slurry wall barrier along the western boundary in the form of a slurry trench. This will help to prevent site contamination from polluting the river and local watercourse.
Redline boundary image of the site. The area in yellow marks the extent of contamination. The dark dotted line on the western boundary marks the location of the slurry wall barrier.
The benefits
Bellway’s proposals will address the historic contamination caused by the years of use as an unregistered and uncontrolled local tip.
For human health, the works will prevent the release of any pollution into the air.
For the environment more widely, the proposed works will improve the quality of the local watercourse and will significantly improve the quality of these important environmental assets.
Safety
The remediation works will be carried out in a way that avoids releasing any dust, odour or pollution into the air.
The ground conditions, air quality and overall pollution levels will be monitored both during the enabling works and throughout the lifetime of the development to ensure ongoing safety.
Bellway will work closely with the Council, Environment Agency and Lead Local Flood Authority (LLFA) throughout the process to ensure safety and maximise the benefits for the environment.
Construction
An onsite waiting area is proposed so lorries can enter the site directly from the public highway so as not to block the road and prevent unplanned waiting offsite.
The management plan will be finalised in consultation with highways officers at Redbridge Council and where possible movements will avoid peak school hours (8:15am to 9:00am and 3:10am to 4:00pm).
The proposal for the enabling works will be accompanied by a Construction and Environmental Management Plan that will detail strict routes for construction traffic, particularly during sensitive hours, wheel washing procedures and the details of the dedicated site manager. This information will be publicly available for residents to see.
A Construction Logistics Plan will also support the proposals which will help to manage vehicle movements to and from the site and to reduce impacts on the road network.
Privacy
The current site falls gently from north to south and by raising the site with the clean capping layer in the future there will be a gentle rise from Billet Road by a maximum of approximately two metres.
Nevertheless, the overall masterplan will be carefully designed to promote the privacy of residents who border the site.
That’s why Bellway are working with landscape consultants to design a dense planted buffer which will not only promote the privacy of existing residents along the length of the eastern boundary of the site, but also provide useful green amenity space and improve local biodiversity.
Timescales
The full process to remediate the site is expected to take place across six phases. The busiest period of work will take place across the first two phases that could take up to 60 weeks to complete.
Much fewer traffic movements will take place after the second phase as no additional material importation for the capping and surcharge process being necessary. Overall, it is estimated that all six phases of decontamination work could take place across the next three years.
The planning application for the enabling works was submitted to Redbridge Council in October 2022 and was approved in March 2023. The enabling works process will only begin once the Environment Agency provide Bellway a permit to start work.