Chester’s St Werburgh dip will cost £250K to fix

Jan 12 2012 Chester Chronicle

St Werburgh Street

ONE of Chester’s best known streets is sinking into a 16th century quarry along with the adjacent Chester Cathedral gardens.

Cheshire West and Chester Council insists neither St Werburgh Street nor the cathedral is about to disappear into a hole although the quarry is just 3m from the cathedral’s south west transept door .

A £250,000 engineering solution is needed to fix the ‘St Werburgh Street dip’ by the Halifax bank which extends under the cathedral gardens up to the war memorial.

A council report reveals the street is subsiding so much that one pillar supporting Grade II-listed buildings in St Werburgh’s Row has sunk by 15cm over the last 10 years, although the properties themselves are believed to be stable.

The road has been sinking for the past 40 years but the problem has accelerated over the last two years although it does not need immediate attention.

Bore hole test results reveal a quarry filled with loose sand and soft clay to a maximum depth of 26 metres above the bedrock which cannot support the weight of the road.

The affected area may be unstable because it is moist but the water source has not been traced.

The design solution involves removing the top 1.5 metres of surface then laying light-weight aggregate on which concrete slabs would be ‘floated’.

The three-month programme would need to be carried out in the summer months for the concrete to set. Ideally, the repairs would be carried out at the same time as the proposed public realm work at the cathedral but this is on hold so no dates have been set.

Analysis has revealed the underground quarry fill is of considerable archaeological interest but would be ‘prohibitively expensive’ to investigate. Sandstone from the 16th century quarry was extracted for a cathedral rebuilding programme.

There are two other unrelated and less serious areas of subsidence in St Werburgh Street. Props are holding up Grade II-listed buildings in St Werburgh Mount, but the cause requires further investigation by the owners, while a depression near the junction with Eastgate Street is due to buried cellars.