It was constructed with a puddle clay core, which extended upward from the cut-off trench excavated into the rock foundation on the hillsides.

Faced with few methods to treat such an unsafe condition, Hawksley then adopted the novel technique of pouring[2] or pumping[4][5] cement grout into holes bored in rock below the trench alignment.

The reservoir is now used solely to maintain minimum regulatory flows on the River Wear, in support of raw water abstractions further downstream, at Chester-le-Street.

[7] The reservoir borders the Backstone Bank and Baal Hill Woods Site of Special Scientific Interest.

At the northern end of the reservoir, there is a small marshy area where the nationally scare Thread rush, Juncus filiformis, occurs; to protect this, Northumbrian Water has designated the marsh as a private nature reserve.