Delph Lane Quarry Remediation & Restoration
Delph Lane Quarry was a 30 m deep vertical sided Triassic red sandstone quarry in Whiston, Merseyside, which remained undeveloped for years despite being in an area short of development land. Permission to infill and restore the quarry was constrained by it being located on a principal aquifer and adjacent to a water supply borehole. The availability of suitable excavated spoil from a quarry in St. Helens provided a potential catalyst to restore the site at an economic cost.
The quarry was reclaimed by placing 120,000 m3 of the quarry spoil as an engineered fill and regarding the site to provide a development platform for an 80-unit housing development.
Following extensive geochemical testing, numerical modelling and a detailed hydrogeological risk assessment, the Environment Agency removed their objections to infilling the quarry, provided it was undertaken in accordance with a Quality Assurance regime with professional full-time supervision by TerraConsult. This was provided throughout the contract and included control of loading at source, chemical testing of the fill placed and supervision of the fill placement. The geotechnical aspects of the design were key to ensuring that post infilling settlement and differential settlement constraints were addressed. Compaction trials were undertaken, and a method specifically developed for the earthworks. Following the infilling settlement, monitoring confirmed the suitability of the site for development with residential housing. The site was subsequently purchased by a national house builder and successfully developed.