Cliff Instability in Former Quarry

Earlwood, NSW

In the late 1960s, a conventional three-storey unit development was constructed within a former sandstone quarry in Earlwood.  The quarry face behind and beside the unit development was near vertical and up to 12 m high.  In addition, there were a number of large slabby rocks on the rock face and significant drainage issues on one side of the quarry.  The boundary with the adjoining property to the high cliff face was also aligned so that it was in places near the top of the cliff, and in other places partway down the cliff face.

When the development was constructed, it was built with part of the unit development being relatively close to the former quarry face.  It is also understood that that the unit development was approved without any geotechnical advice in relation to the stability of the quarry face.

In the early 2000s a large boulder fell from the cliff face and impacted the rear of one part of the unit block causing extensive damage to one of the units.  Subsequently, geotechnical investigations of the cliff face indicated that there were many other rocks which had a potential to fall at any time.  There was also extensive tree growth on the cliff face that continued to prise apart the cliff face and rocks on the face.

After a number of geotechnical studies, and litigation involving several property owners and the Council, extensive stabilisation works were undertaken on a shared cost basis that left all of the property owners in a difficult financial position.