The company proposes to convert it into a $600 million-plus residential complex comprising 600 dwellings in buildings ranging from two to six storeys in height.
The site, leased to IBM, is “not viable – the buildings are redundant” in its current form, said Adrian Checchin, of Mirvac Capital.
The 25.87-hectare site, at 55 Coonara Avenue, underwent a two-year set of works between 2008 and 2010 characterised as an "end-of-life upgrade" for what was already a 25-year-old facility.
Mr Checchin said a residential complex with townhouses, terraces and apartments was now the most viable option for the site.
Residents groups are concerned about the entire site being used for accommodation at the expense of the green space and additional vehicle traffic on Castle Hill Road.
The proposal has been forwarded by The Hills Shire Council to the Department of Planning and Environment for Gateway Determination.
The site is currently occupied by seven interconnected low-rise buildings totalling 36,000 square metres of commercial floor space, two car parks comprising 1687 car spaces, and a levelled grass area.
An economic assessment prepared by Hill PDA, in January 2016, concluded that the site would face considerable challenges in maintaining commercial office uses once the current tenants vacated the site.
Among the challenges were the existing floor plate was out-of-date, the unsuitability of the site for commercial functions and the competitiveness of the site compared Macquarie Park, Norwest, Rhodes and Parramatta
These employment centres were noted to offer greater amenity, transport access, retail services and flexible range of employment space compared to the subject site, the PDA report said.
