THE EXTENT of unmapped historical chalk mines in Reading, Berkshire is greater than had previously been assessed.
Investigations following the Field Road collapse in January (GE February) have shown instability could threaten an area more than 250m across.
John Talbot of Peter Brett Associates, consultant to Reading Borough Council, said: 'To date more than 800 dynamic probes, 50 boreholes, several CCV surveys and two microgravity geophysical surveys have been completed. These show the problems of past chalk mining and instability threatening the local area is more extensive than first thought. '
With the large-scale investigations complete and the full extent of the problem determined, Reading council last month announced the award of a major stabilisation programme designed to ensure the 17 families affected will be able to return to their homes.
'Stabilisation treatment could not begin until the greater extent of the problem was assessed, as any earlier on-site works may have resulted in further damage and risk to life and property, 'added Talbot.
Keller Ground Engineering is expected to start this month on compaction and pressure grouting to fill the mine and stabilise the ground.
Jo Lovelock, deputy leader of Reading Borough Council, said: 'This looks like marvellous news for the residents of Field Road. I am delighted that, subject to legal formalities, we should soon have the funding for the repair work. The council will continue to work with the residents to ensure they return to their homes at the earliest possible date. '
Funding of £2. 6M will be provided to the council under English Partnerships' Land Stabilisation Programme. Peter Brett Associates has provided technical assistance and also liaised closely with White Young Green, English Partnership's consultant - particularly in connection with the complex details of the grant application.
The collapse at Field Road occurred on 4 January this year, when the front walls of two properties fell into an 8m crater and all services were cut. Some 200 people were evacuated as part ofReading Borough Council's emergency plan. Investigations concluded the incident was a result of the collapse ofpreviously unmapped former chalk workings, possibly triggered by a leaking water main.