Geotechnical experts Cardno said the actual construction may not have followed design plans at all.

Katherine Times has been provided a report from Cardno, presented to Katherine Town Council in December, after it was called in to help remedy damage caused to the structure after just one year of construction.

The "revitalisation" works are being paid for by the NT Government.

As a result of erosion and slumping some of the work already done on the Hot Springs will have to be demolished and begun again.

According to plans released as part of a tender which closes this week, an already completed footpath will need to be demolished and poured again.

There will be lots more rock baskets, gabions will be removed and later replaced while deep footings are constructed to stabilise the eroded river bank.

But in a report previously not made public, the same geotechnical experts who were used to investigate the site back in 2016 before work began were called back to find out what had gone wrong, and how to fix it.

"Since construction, the slope has showed signs of failure and the structure, signs of distress," the report reads.

"As Cardno was not involved in the design or construction process of the footpath, it is uncertain whether the design chosen was entirely appropriate for the site.

"Best practice for slopes, including relatively unstable river banks such as this, would be to avoid much cutting and filling with heavy retaining walls.

"A lighter, timber framed board walk-type structure piered well into the alluvium would appear to be less risk from a geotechnical perspective."

The report goes on to say information was provided by Irwin Consult and Katherine Town Council "that the construction also may not have followed the original designs".

"We understand some elements vary and we know that the fill was neither suitable nor compacted," Cardno says.

Cardno said its original investigation recommended to council that it use a deeper pile foundation to stablilise the river bank.

"This was due to the fill encountered in the original assessment was described as uncontrolled, comprising of loose soils with high organic content and trash."

Cardno now advises council to stop watering the slope and buttress the bottom of the slope with boulders.

"Revegetate slope areas with vegetation that can survive in both the wet and dry seasons without the use of a permanent irrigation system," the report suggests.

Council this week said it plans to award tenders soon after they close on May 31.

"Works are scheduled to commence on Stage One in July, followed closely by Stage Two starting mid October, with the project concluding at the end of 2019," a council spokeswoman said.

Stage One works are believed to be the repairs on the pathway and the slope.

The second stage involves a new playground at the top of the river bank, near the Pop Rocket Cafe.

"Council understands that this has been an overly long process and would like to identify that we have kept busy over the past three years," the spokeswoman said.

She said council had been completing numerous studies on the project including the Cardno "Geo-Technical Global Slope Stability" Studies - Civil and Structural Compilation Studies - Architectural and Landscaping Compilation Studies plus the documentation of works.

"Katherine Town Council believes it has adopted and incorporated the responsible approach to a long awaiting panacea with the proposed works to commence in July," project manager Joe Tag said.

Despite the re-start of construction council says access to the popular springs would not be affected during this time, "however alternate routes will need to be taken".

"Council requests the community's cooperation and understanding during this time and request that all alternative access signage is adhered to," the spokeswoman said.

"Katherine Town Council acknowledges that this project's duration has been much longer than expected and we appreciate the patience of the Katherine community.

"We look forward to making the final touches on this magnificent community asset."

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