Eighteen months after the Salt Creek Remediation Working Party (SCRWP) was formed, the first on-ground works have commenced to bring back the former recreational amenity of the creek at Middle Beach.
The working party, comprising four community representatives in partnership with representatives of District Council of Mallala, have taken core samples from the bed of Salt Creek to determine the type, depth and volume of material that has clogged the creek over the past several decades.
SCRWP members John Drexel and Malcolm Frost were joined in the water by co-member and DCM deputy mayor Mark Wasley, and sediment-coring specialist Bobbie Rice, on Tuesday August 12 to take nine core samples spread over a distance of 350m of the creek bed.
On-shore assistance was provided by Wayne Hage and Andrew Stewart.
Mr Drexel said the coring device comprised a petrol-driven vibrator attached to three-metre hollow tubes that were sunk in the creek bed until stopped by hard material.
“Most people familiar with the creek expected the tubes to sink to their full depth but, surprisingly, the thickest sediment was found to be only 1.5m, near the old boat ramp,” he said.
“Below that was hard clay of the original creek bed, probably belonging to what is known geologically as the Glanville Formation, a clay-silt-shellbed unit estimated at around 125 000 years old.
“West of the old ramp the original creek bed is covered by as little as a half-metre of shellgrit, while around the ramp shellgrit up to 1m thick lies over a half-metre layer of brown mud.
“East of the ramp, shellgrit is up to 1.5m thick mixed with dead seagrass and some mud.
Mr Drexel, formerly principal geologist with mobile casino the State Government, believes most of the shellgrit in the creek originated from storm-surge erosion of the shellgrit foredune and adjacent beach deposits.
The brown mud was most likely eroded from the surface of the open lagoon area inside the mangroves, he added.
Sediment cores taken from the creek have been stored at Mr Drexel’s Middle Beach shack awaiting further analysis.
The SCRWP, which also includes Foreshore Advisory Committee president Barb Reid, Two Wells Regional Action Team president Eddie Stubing, Councillor Steve Jones, Mallala Council General Manager, Infrastructure & Planning Services Gary Mavrinac, and Mallala Council Strategic Projects Coordinator, Infrastructure & Planning Services Carol Muzyk, is planning to remediate the creek by removing as much recently deposited sediment as possible.
“At least two potential methods of excavation are feasible, and this is where it is hoped that University of South Australia students can assist with projects such as cost-benefit analysis and surveying,” Mr Drexel said.
“The volume of sediment in the creek needs to be estimated, along with an assessment of areas where it can be reused.
“Two potential sites are the old shellgrit pit at the north end of the beach, and the Stage 2 carpark immediately east of the new boat ramp.”
The SCRWP is also looking to the future, particularly with respect to an influx of new residents when the Hickinbotham residential development comes to fruition on the northern side of Two Wells.
Apart from returning the creek to its former depth to allow better boating access, the working party is investigating the creation of a water-sports hub at Middle Beach.
This will include a salt water swimming pool and separate wading pool refreshed on a regular basis by the tide, landscaping of the creek bank to allow viewing areas and safer access to the water, and BBQ and seating facilities nearby.
Mr Drexel said the members of the SCRWP wished to thank former DCM chief executive officer, Charles Mansueto, for his enthusiastic participation and input to the project over the past 18 months.