The Shire of Murray has halted progress on a proposed marina at Point Grey near Mandurah as it seeks to overturn approval of the development.

The proposal by Tian An Australia would see the Point Grey Peninsular transformed by the construction, which includes a 300-boat marina and a housing development.

Point Grey is surrounded by the Harvey Estuary and Peel Inlet, where the two meet to form the Peel-Harvey Estuary.

The site is within the Peel-Yalgorup wetlands system, which has been recognised since 1990 as a Wetland of International Significance by the Ramsar Convention. The area is regarded as the most significant location for waterbirds in the South-West.

Mandurah Environment and Heritage Group committee member Merrilee Baker said although the current health of the Peel-Harvey Estuary is degraded it is still protected under the Ramsar Convention. Ramsar is an International Convention of Wetlands that enables classification and preservation of important sites.

She said: “If you’ve got something that’s endangered and you do one more thing, it goes extinct.”

Part of the marina proposal is a 2.5km long, 50m wide, and 3.5m deep navigation channel from Point Grey, through the Peel-Harvey Estuary, to the Indian Ocean.

Creating the channel will require extensive dredging of the Estuary floor, and the removal of 95,000m³ of sediment.

The channel will require maintenance dredging every 5-10 years, which may involve the further removal of up to 50,000m³ of the Estuary floor each time.

Chair of the Peel-Harvey Catchment Council Caroline Knight is concerned the dredging will exacerbate the poor state of the Estuary and have serious impacts on the natural environment.

“The health of the Estuary already means that there’s a black ooze at the bottom,” she said.

Monosulfidic black ooze is formed when sediment containing high concentrations of acid volatile sulphides is agitated. The ooze releases nutrients into the water, which can contribute to deoxygenation of the Estuary.

Barbara Sing, member of local environment and dolphin rescue group Estuary Guardians, said the dredging of the channel would affect the pod of 80 bottlenose dolphins that call the Peel-Harvey Estuary home.

“The dolphins operate on echolocation, so the sound from the dredging and pile driving will have an impact on them,” she said.

“The ooze from the dredging is going to smother their foraging grounds too.”

The environmental concerns prompted the Shire of Murray to vote to amend their Town Planning Scheme by revoking allowance for a marina at Point Grey, at a Council meeting in June.

Tian An Australia appealed this decision at the State Administrative Tribunal, which upheld the Shire of Murray’s vote.

A consultation period win which the Council took submissions from the public concerning the proposed marina closed on October 30.

The Shire of Murray Council now has 90 days to consider the submissions received.

Within this period the Council must vote on whether they support the amendment to remove allowance for a marina at Point Grey, with or without modifications suggested in the public submissions.

If supported, the amendment will be referred to the West Australian Planning Commission, and reviewed by the Department of Planning, Lands and Heritage. Within 90 days of this occurring, the amendment must be submitted to the Minister for Planning who will make a final decision on the development’s future.

Tian An Australia’s senior development manager Grant McLennan said the company “objects in the strongest possible terms” to the Shire of Murray’s Town Planning Scheme amendment.

When asked about the environmental concerns surrounding the marina, Mr McLennan said: “The Point Grey development has been through a rigorous, open and transparent public environmental review process that culminated in State and Commonwealth Government approval.”

While awaiting an outcome on the Shire of Murray’s Scheme amendment, Tian An Australia will “continue progressing” with “technical work, environmental surveys and monitoring” at Point Grey.

Ms Knight said the Peel-Harvey Catchment Council were not against all development at Point Grey.

“This site is incredibly unique, and we would welcome the opportunity to have eco-tours or a kind of development there which would do justice to the site,” she said.