Remediation Works Langbaurgh Mineshaft

Tender description

Langbaurgh Closed Landfill Site ('the site') is located on Langbaurgh Ridge, just north of Great Ayton,North Yorkshire. The site is a former Whinstone quarry, which was active from the early 1800s until 1964 and include surface and below ground workings. The site was used as a landfill between 1978 and 1991, infilling the excavation left by surface quarrying to a recorded depth of around 15m. Numerous shafts, adits and below ground voids are understood to underlie the site. The site boundaries are generally very steep, formed by the former quarry walls. One of the shafts near the western end of the site has previously collapsed and been remediated. However, further collapse of the shaft (and remediation) has occurred, forming a roughly circular surface depression above the shaft location. The depression is estimated (from remote surveying) to be 10-15m wide and approximately 6-8m deep. The scheme involves the remedial work for this collapsed mine shaft. The remedial solution adopted comprises the infilling of the existing depression with lightweight aggregates contained by a geotextile 'bag' and covering with a high-strength geogrid reinforced 'soft cap'. The design has been progressed and updated in consultation with various specialist geogrid and lightweight aggregate suppliers in an attempt to deliver a constructible solution. The remedial design is focussed on providing 'betterment' to the site and does not provide a 'designed' solution; nor is the solution to be warranted by WSP or the Contractor against future failures / deviations / collapse.