Seawall Realignment

Lower Sandy Bay

Client: Hobart City Council

 Realignment of a seawall at Lower Sandy Bay required significant earthworks in the wave zone.

Movement of silt and sediment had the potential to impact on breeding habitat of the Spotted Handfish (Brachionichyths hirsutus) which is a threatened species under both State and Federal legislation.

Advice on potential impact and mitigation measures during works was sought by the Hobart City Council.

Key Issues included the siltation and contamination of a recreational beach, community concern regarding water appearance and construction nuisance and potential impacts on the Spotted Handfish.

Project components included the review of beach and bay hydrodynamics and sand movement, assessment of impacts and preparation including production of bathymetry maps. Siltation and sediment impacts on habitat areas were then assessed through delineation of habitat areas and underwater surveys of egg masses. Assessment was undertaken in conjunction with Marine Solutions. 

A Construction Environmental Management Plan was then prepared which included mitigation measures to be implemented during construction.

Mitigation options included placement of a silt curtain and modifying works to reduce silt and sediment sources.