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Highbarns chalk mines

Following the discovery of abandoned chalk mine workings in the Highbarns area in 2007, the area has been treated and stabilised, with the final report available in the published technical reports section below.
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Background information

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  • Background information on the mines

    Chalk mining was carried out in Hertfordshire from the 1700s to the 1900s. Mined chalk was used for a number of different purposes.

    The first sign that there might be chalk mines in the Nash Mills area came in May 2007, when there was a partial ground collapse in a garden (now established to have been caused by a shaft collapse). At that time, Hertfordshire County Council, in consultation with us, commissioned a specialist consultant to assess the condition of the land within a 50-metre radius of the affected site. This assessment involved a geological survey and an investigation of historical activity on the site in order to establish the cause of the incident and establish if any further remedial work was needed.

  • The extent of the mines

    The chalk mine was located around the road junction of Highbarns, Pond Road, Meadow Road and East Green.

    The area that we have data on extends 50 metres around the point where we believe the access shaft was.

    We commissioned further geological surveys around the area. The results confirmed the initial findings regarding the location and extent of the mine.

  • What work was carried out?

    The initial collapse in 2007 caused damage to the garden of a property in Highbarns, so the repair work and stabilisation costs were covered by the property owner's insurance company.

    A nearby mine, which was discovered beneath the road and pathway, was found to need urgent filling. We funded this urgent work, which was completed in 2008.

    Between 2008 and 2011 we coordinated the work to secure funding from central government to fully investigate and repair the mines. Funding was approved by the Homes and Communities Agency in November 2011, and, following the surveys, work was undertaken to treat the mine. The complexity of the mine and the conditions of the ground meant that the treatment required was much more extensive than predicted. Altogether some 8,300 cubic metres of material (equivalent to 83 double decker buses) has been used to treat the mine - over four times as much as originally estimated based on works undertaken at similar sites elsewhere.

    In October 2013, a further ground collapse at the junction of Highbarns and Meadow Road, meant that the treatment works had to be extended further still. This treatment has been completed and a final treatment report is available in the published technical reports section below.

Letters and reports

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Contacts

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