A constraint on all the sites was the need to identify and protect live below ground operational gas equipment, a large amount of which comprised high pressure distribution mains. DSM arranged for the precise location of the equipment to be determined by using ground penetrating radar. Using this information enabled a protection system to be installed for all equipment on site that was to remain operational.
The decommissioned gas holders to be removed were large steel multi lift structures, guided and unguided, some with concrete base tanks and were situated above and below ground. The large volume of water in each holder was treated to meet the requirements of the short term discharge consent in place for each site. By cold cutting openings were made both in the crown and through the side walls to vent each holder and allow safe access to remove the sludge in the tanks. This material was chemically treated and stabilised allowing its use as backfill in one of the below ground tanks.
Once clean the remaining structures were removed by a combination of high reach shearing and removal by lowering sections by crane after hot cutting from operatives using mobile elevated work platforms
All of the below ground tanks with a combined volume of over three thousand cubic metres, were filled with clean soils imported under the CL:AIRE, to produce a structural platform suitable for residential development.