Mandurah residents have expressed their frustrations about the annual process of dredging off the coast of Silver Sands, raising concerns about the health and safety of the water and the visual appeal of the beach.
Every year in June, sand from one side of the Mandurah ocean entrance channel is excavated from a sand trap and fed directly into a mobile pumping plant which mixes it with water to form a “slurry”.
The slurry is then pumped to the other side of the channel and along the coastline of the Silver Sands beach.
Comet Bay used to be crystal clear, now you can see the plume of [dredging] in the water.
- Silversands resident, Rhonda Griechen
Information from the Department of Transport website states that dredging is necessary in Mandurah to “ensure safe navigation of the channel” and continue “the natural flow of sand along the coast”.
Local resident Rhonda Griechen has lived near Town Beach for almost a decade and said she is “disappointed” the City of Mandurah continues to dredge into the “best best tourist destination” in town.
“Comet Bay used to be crystal clear, now you can see the plume of [dredging] in the water and it’s grey and the waves are grey and black,” she said.
“The literature from the [City of Mandurah] says that it dissipates within 24 hours but after ten years of watching the decline of the clarity of water in Comet Bay, I beg to differ.
“The sediment dredged up from the bottom of the ocean is piped into the bay and it stays suspended in the ocean for years.”
Ms Griechen said she has concerns for the health and safety of swimmers after seeing, and smelling, the change in the water at her local beach over the years.
“Pumping up sludge from the bottom that’s full of bacteria and dropping it into a bay that's a huge recreational area is folly,” she said.
“Citizens are swimming in pollution – visitors and locals in a very popular beach are swimming in stuff that may be harmful to their health.
“It has very poor visibility now, you can’t see your feet it’s that bad – the crabs and crayfish and many other sea creatures and birds looking for feed have disappeared a lot over the years.”
I believe Town Beach and Cygnet Bay have the potential to become an international holiday resort but first we have to clean up with water quality.
- Silversands resident, Gordon Lynch
Her neighbour, Gordon Lynch, has lived in Mandurah for 20 years and has been visiting the local beaches with his family since the early 1960’s.
He said he has also noticed “deterioration in the water quality” over time.
“You dive into the water and can’t see a metre in front of you and you are walking on rocks of solidified silt,” he said.
“It used to be like Rottnest water – beautiful, just crystal clear.
“I believe Town Beach and Cygnet Bay have the potential to become an international holiday resort but first we have to clean up with water quality.”
The Department of Transport are responsible for all dredging and sand bypassing works in the Peel region, in conjunction with the City of Mandurah.
A Department of Transport spokeswoman said sand bypassing has occurred annually since 1995.
“Annual mechanical sand bypassing is conducted at the Mandurah Ocean Entrance Channel to maintain the natural eastward flow of sand along the coast, prevent infilling of the channel allowing for safe navigation and maintain beach areas and volumes on Town Beach, east of the ocean entrance,” she said.
“The process involves excavating sand from the sand trap using a conventional land-based earthmoving plant located on Doddi’s Beach, mixing the collected material with water using specialised equipment and pumping it through a permanent pipeline to Town Beach.”
At present, mechanical sand bypassing is the most effective method for operations due to the large volumes excavated annually.
- Department of Transport spokeswoman
She said the weather can be sometimes be to blame for the noticeable difference in water colour during dredging, but that it was still the most successful process to bypass sand.
“During bypassing operations, a milky white or light grey plume that is typically confined to the surf zone is visible,” she said.
“Plumes generally dissipate rapidly under calm weather conditions.
“The current bypassing operations have been successful in maintaining a stable coastline and navigational channels.
“At present, mechanical sand bypassing is the most effective method for operations due to the large volumes excavated annually.”
Ms Griechen said she understood dredging was necessary but believes the City of Mandurah needs to take more responsibility when it comes to maintenance of Town Beach during dredging season.
“Take it out to sea or reuse it. It has to be dredged, we get that, but we can do it differently,” she said.
“It needs to be monitored all the time that it’s fine for people to swim in, to make sure our beaches are healthy and kept clean – they need to test, not just for fecal matter, but for what it looks like and for the marine life.
“Maybe check the sediment levels daily and post them on the City of Mandurah website so people know when to stay out of the water.
“I also ask the [City of Mandurah] to explain why don’t they just pump it back on the beach if it’s needed to preserve the sand in the beach? They can always dredge up to the land and use that material somewhere else, they don’t need to dump it in the ocean.”
