Tunstall Reservoir - 845-6047468

Tunstall Reservoir was a water supply storage reservoir completed in 1879, and now used solely to maintain minimum regulatory flows on the River Wear. It is situated in the north Pennines of the United Kingdom, and lies 3.5 km north of the village of Wolsingham, in Weardale, County Durham. The earthen embankment dam, which impounds the reservoir, is recognized as the location where pressure grouting with cement grout was first utilized in 1876 by engineer Thomas Hawksley, to reduce leakage within the rock foundation under an earth dam. Pressure grouting has since become normal practice for construction and remediation at dams and related water resource projects.Dam constructionThe reservoir was created for the Weardale and Shildon District Waterworks Company, with construction of the dam between 1873 and 1879. The earth embankment dam was built across the valley of Waskerley Beck, and measures 1020 feet long and 82 feet high. It was constructed with a puddle clay core, which extended upward from the cut-off trench excavated into the rock foundation on the hillsides. A seven foot diameter draw-off tunnel in one abutment controls reservoir elevation.Early groutingIn 1876, with the reservoir partially filled, water was found percolating through fissures in rock to downstream of the cut-off trench. The supervising engineer, Thomas Hawksley, initially extended the cut-off with brickwork and concrete, but the leakage continued. Faced with few methods to treat such an unsafe condition, Hawksley then adopted the novel technique of pouring or pumping cement grout into holes bored in rock below the trench alignment.

Tags: Reservoir