An RMS spokesperson said the boat ramp was due to open on Tuesday, June 4, but storms and rainfall of more than 60mm in Batemans Bay on Monday, June 3, delayed completion of construction.

"The last stage of work involved placing large and heavy rocks (scour protection) along the boat ramp walls to prevent sand washing away," an RMS spokesperson said.

"This work had not been completed before the weather event."

RMS said the ramp collapsed due to a combination of high seas, a king tide, and increased flows down the Clyde River from about 80mm of rainfall in upstream catchment areas washing away sand and destabilising the foundations of the ramp.

"No pollution has entered the river and there is no impact on oyster farms," the spokesperson said.

"Marine navigation markers are still viable and there is no foreseeable impact on public/marine safety.

"Floating environmental silt curtains are in place to stop sediment escaping.

"Discussions are under way to determine the required remediation work, options and impact on construction schedule."

RMS said the existing Clyde Street boat ramp would be kept open to the public until the situation was resolved.

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Construction of new Batemans Bay Bridge | PHOTOS