The cost of excavating the latest stage of Blaxland tip has skyrocketed by $373,000.
This is approximately 80 per cent more than the amount approved just five months ago.
In June, council awarded the tender for the work to J. K. Williams Contracting Pty Ltd for $467,000.
The company has now sought more money (which has been approved) because it needs to use a rock hammer to a section of “very hard sandstone that was unidentified at time of tender and was unusual for the area”.
This is despite information in the tender documents which specifically stated that “excavation works will be through typical Hawkesbury sandstone which includes bands of hard ironstone which is common in the Lower Blue Mountains area”.
The tender documents continued: “The contract does not include a separate rate for excavation in rock and [the tenderer] is required to provide plant and equipment which is capable of the excavation work required.”
But the extra money approved by council includes $52,000 for detailed rock excavation.
The other main overrun was due to “the number of seams and deficiencies in the sandstone surface” exposed during excavation.
A report presented to the last council meeting called these “latent conditions” that existed at the time but were hidden.
J. K. Williams was awarded the tender in part because it was ranked No 1 in terms of cost. It also rated highest in overall value for money.
That was when its price was $467,000. The total cost is now $840,000 but it is unclear if that would still leave J. K. Williams as the best value for money. Council said the additional works would have applied to all tenderers.
A report to council on the matter urged the money to be paid because the risk of not completing the project within the scheduled time frame could mean there was no room at the tip and council would have to transport wasteout of the area at “an extremely high cost”.
The Gazette asked council what geological or geotechnical information was provided in the tender.
A spokeswoman responded: “Geotechnical information for the project was originally determined by information from previous excavation works at the site. This had shown the sandstone was easily ripped and therefore classed as bulk excavation. A separate rate for rock excavation was therefore not included in the tender, for this reason.”