Newcastle CBD's mine subsidence issues

Maps published as part of a new council report have revealed clearly for the first time the extent of old underground mine workings that are hindering millions of dollars worth of development in Newcastle’s CBD.

The findings of the Hunter Street revitalisation study could force Newcastle City Council to rework existing development control plans and local environmental plans which fail to properly take into account mine subsidence problems.

And in comments likely to reignite debate about the heavy rail line’s future in Newcastle, the report shows the biggest single CBD area unaffected by mine subsidence is the railway corridor.

The rail corridor, including Hunter Street and a parcel of land at Wickham, ‘‘represent the greatest potential for higher-density development with little or no remediation penalty’’, the report says.

‘‘Clearly, the decision to retain or remove the heavy rail has a significant impact on the forward planning of Newcastle.’’

The council’s future city director, Judy Jaeger, said there was no plan to build on the Hunter Street roadway.

She declined to comment on the railway line but Newcastle lord mayor John Tate said he believed the corridor should remain dedicated for transport.

‘‘I can’t speak for the councillors but certainly I’ve always said that the railway corridor should stay as a corridor ... a transport corridor,’’ he said.

‘‘I’d like to think one day it would be light rail.’’

Member for Newcastle Jodi McKay gave an undertaking earlier this year that the rail corridor east of Wickham would stay in public hands and never be built on.

Cr Tate and Newcastle City Council general manager Lindy Hyam confirmed that existing development control plans and local environmental plans for Newcastle CBD were of little use because they did not take into account the mass of mine workings under the city.

Cr Tate said this brake on development included the areas in the CBD’s west end nominated for high-rise development by former planning minister Frank Sartor.

‘‘We might be able to approve 27-storey buildings in particular areas, but with the subsidence they might not be able to build them,’’ Cr Tate said.

The revitalisation plan says buildings over seven storeys (28metres) represented a high risk and would require substantial remediation of former mine workings.

This would impose a ‘‘significant cost’’ on developers, the report says.

The revitalisation plan lists mine subsidence as the first of five key issues affecting city redevelopment.

It is followed by the shallow water table (one metre under the Hunter Street surface), flood management, access and connections (including the rail line) and retail and commercial vacancies.

Ms Hyam said the council was working with the state government’s Mine Subsidence Board on ways to improve the situation.

As things stand, individual developers must pay to fill in old mine shafts under their buildings but the council wants the state to pick up some of the cost of remedial filling in or ‘‘grouting’’ of the old workings.

Subsidence board chief executive Greg Cole-Clark said the board and the council were talking about remediation strategies but the board was not set up to do mitigation work and was unlikely to do so unless the laws governing it changed.

The revitalisation plan says there has been ‘‘a lack of understanding’’ about the grid of old coalmines under the city and says ‘‘remediation is expensive and time consuming’’.