The north pier of the Grafton bridge that is lagging behind the others pictured in the background.
The north pier of the Grafton bridge that is lagging behind the others pictured in the background. Adam Hourigan

Concern Grafton bridge substance leaked into Clarence River

POTENTIALLY thousands of litres of a "non-toxic" substance leaked into the environment when construction of the northern end of the Grafton bridge went awry.

Rumours have circled the Grafton bridge construction site, with the southern end looking close to completion but the northern side lagging far behind.

Roads and Maritime Services said up to 8000 litres of non-toxic diluted polymer was used in construction in June 2017 at the northernmost pier on the bank of the Clarence River.

During construction of the pier, polymer - a jelly-like substance - was poured into the pile and rather than set as it should, the polymer reacted with soil and an unknown amount entered groundwater near the river.

A NSW Environmental Protection Agency spokesperson said a report was made by the RMS of a "higher than expected" amount of polymer used in the construction.

"It is standard for polymer to be used in setting bridge pylons," the spokesperson said.

The EPA "did not identify any environmental impacts resulting from this issue" and has worked with the RMS and its contractors to "improve their practices with polymer use at the site".

The EPA said an officer undertook "regular on-site inspections" as well as an independent environmental representative who ensured adherence to conditions set by the Department of Planning and Environment.

However, an industry insider has alleged the issue occurred multiple times.

"Some chemical in the soil has reacted with the polymer, not allowing it to set," he said.

"The polymer they used didn't work and they've poured thousands and thousands of litres into the groundwater.

"They just kept pumping it in, expecting it to set, and it just kept washing away - potentially into the river."

An RMS spokesperson said the bridge was a fixed-price project and costs associated with changes to the piles were the responsibility of the contractor.

"All piers at the Grafton bridge have been completed and quality tested, and the project has moved onto the next stage of construction," the spokesperson said.

"The contractor is responsible for quality assurance outcomes and covers all costs associated with required changes to the piles."

RMS has opted for a new technique to finish the last piles, which will involve using steel casings filled with concrete.

In April last year, the RMS said it had identified "issues" within the two northernmost piles, which "may have reduced their overall durability and strength".

RMS has maintained the issue was related to the quality of concrete and was not related to the polymer issues.

Despite community concern, the northern end of the bridge looks far from completion, however the RMS maintains the project will be completed on time.