The remediation process
Remediation simply means the activities that are used to clean up contaminated land to a standard suitable for that land to be used in the future.
Activity on site will start in Spring 2012 with the setting up of site cabins and access arrangements, and preparing the treatment areas. Once the treatment areas are complete, we will start the bioremediation process itself.
‘Blue Billy’ removal
The first task is the removal of the ‘Blue Billy’ (ferroferricyanide) rich soils which were tipped at Grassmoor prior to the 1970s, as by-product from the town gas manufacturing process. In the early 20th century Blue Billy was used as a dye known as Prussian Blue and also as a weed killer. A link still exists for us today, as blue printer cartridges are often described as cyan in reference to the original source.
The small volumes of soil contaminated with Blue Billy cannot be remediated on site and will be safely disposed to a landfill built specially to take this sort of contamination. The removal will mean that you will see a few lorries leaving the site during March. The trucks will be covered and the wheels washed before they are inspected and allowed to leave the gated area. Trucks can only turn right on to Mansfield Road and head for the A617 dual carriageway.
The bulk of the contaminated soils on site will be remediated using a process called bioremediation. This processes uses the activity of bacteria naturally present in soil to break down contaminants like those found in the tars at Grassmoor. The process of bioremediation can occur on its own or it can be speeded up by creating the right conditions, such as by aeration, heating or the addition of organic materials to the contaminated soils.
We plan to aid the remediation process at Grassmoor Lagoons by excavating the estimated 50 thousand cubic metres (that’s the volume of 25 Olympic-sized swimming pools) of tar-contaminated soils, and mix them with 200 thousand cubic metres of shale that is already on site and 25 thousand cubic metres of compost that we will need to bring in. Think of it as every bucket of tar being mixed with four buckets of shale and half a bucket of compost.
The mixture will be laid out in long rows (windrows) onsite and turned regularly, for the eight weeks or so that it will take to bioremediate, by a special machine called a windrow turner. We are planning to complete the bioremediation activity in approximately two years. The treated soils will be reused in landscaping the remediated area of the site to the agreed master plan. (See Landscape master plan.)
Lorries delivering compost will begin arriving in April. This is a clean material and presents no health implications to local residents or park users. In total, we expect 2500 (10 cubic metre) compost lorry movements onsite over the two year period so, on average, there should be no more than 5 deliveries a day. The trucks will be washed and inspected on exit. Work will commence slowly with a small windrow machine arriving onsite in March. A new larger windrow machine is expected on site in April/May 2012.
Finally, the lagoons area will be reprofiled by landscaping and replanting.
The restored area will open to the public in 2015.