The proposed synthetic field to be built at Arncliffe Park will be elevated on a suspended concrete slab at an estimated cost of up to $6 million to avoid future flooding.
Bayside Council last night voted to proceed with the suspended field rather than the more expensive option of building a detention tank to hold flood waters.
Arncliffe Park is in a floodway and special consideration needs to be given to the design of the synthetic field to ensure the development does not increase flooding to the field or adjoining properties.
This would require either the diversion of flood waters around or below the field or a combination of both, an earlier council report found.
Bayside Council has prepared designs for the proposed synthetic field to ensure that it is not subject to flooding including installation a water detention tank.
But the council decided not to proceed with water detention at Arncliffe Park as it would not provide sufficient reduction in flood levels and construction costs would outweigh the benefits.
Instead, the council has decided to elevate the field to allow floodwater to flow under it.
Cost to have the field atop a suspended concrete slab is estimated to be between $4 million to $6 million, while the cost of building a synthetic atop a spending concrete slab plus a 5400 square-metre detention slab is estimated to be between $8 million to $12 million.
The main reason to install a detention tank at Arncliffe Park is to reduce flood levels for downstream properties along the flow path between Broe Avenue and Bonar Street.
But council report found that a 5400sqm tank would not provide sufficient reduction in flood levels.
While nearby Woollongong Road is estimated to flood to a depth of 1.52m in a 100-year flood, a 5400sqm, tank would only reduce flooding by 0.123m, resulting in a flood depth of 1.39m.
A 1998 study by Rockdale Council identified flood mitigation in the form of a detention area in Arncliffe Park as a high priority to reduce flood levels on surrounding properties and roads.
Design plans for a detention basin were prepared but none of the options provided a satisfactory flood reduction solution.
Since that study the Bonar Street precinct has been redeveloped as high density and is no longer subject to flooding.
Design of the new concrete suspended structure at Arncliffe Park is expected to start this month and construction is likely to occur following the 2019 winter sports season.