Clearing a medical legacy - 777 at Harold Wood

The Harold Wood hospital first opened as a children's convalescent home in 1909 and was turned into a hospital for wounded soldiers during World War II. It finally closed its doors in 2006 and the site is now being redeveloped as a residential complex of 780 new houses.

777 was awarded the contract for the demolition of nearly all of the old hospital buildings on the site and to remediate the ground on which they stood. However, because of the way the hospital developed over its 100 year of use and the damage inflicted on some of the vacant structures by vandals, the demolition phase posed a number of challenges.

777 contract manager Dave Willcott said: "The hospital was a sprawl of randomly placed structures from different eras that took different forms. A 25 m (82 ft) high chimney stood amongst five-storey office buildings from the 1960s, post-war accommodation blocks and older, antiquated buildings housing the hospital's utilities such as boilers and generators. Most of the buildings contained asbestos and all had suffered damage due to vandals and thieves. The site housed a mile-long, 3 m (9.9 ft) deep utility tunnel as well as numerous unmarked water pits. All these factors meant the demolition stage had to be well-thought-out and closely managed."

Asbestos remediation was carried out by the Group's Environmental Division and was no small task given the estimated 315 tonnes of the material having to be handled and then disposed of. With this work complete, soft strip was done to remove all interior fittings and fixtures. A total of 18 machines were then employed on the site to clear the antiquated structures across the site.

The demolition produced a considerable volume of waste, including 88 tonnes of timber and 600 tonnes of metal, which was all segregated and then recycled. Three mobile crushers were brought onto the site to process more than 15,000 cubic metres (530,000 cubic feet) of concrete and brick waste, with one third of the resulting crushed material being kept back on the site for use as fill during the construction of the housing development.

Once the majority of the site had been cleared, 777 began remediation of the land. It was understood that during World War II, munitions had been taken from nearby railway sidings and stored underground on the site. Ground analysis indicated the presence of several areas that showed likely areas containing munitions. These were carefully excavated with a Banksman in attendance at all times and with work ceasing periodically to allow for full inspection by operatives.

Drainage outside the footprint of the site's buildings had been frequently modified and some drain runs on the site contained clay, cast iron, steel and non-notifiable asbestos, which also had to be removed. Once again, this work was carried out the by the Environmental Division in areas with restricted access to ensure that contamination was contained.