BP's own modelling shows Great Australian Bight oil spill could reach NSW

An uncontrolled oil spill from BP’s planned wells in the Great Australian Bight could affect the coastline as far away as New South Wales, according to previously secret oil-spill modelling uploaded to the company’s website this week.

Within 24 hours of the modelling being uploaded to BP’s website, the regulator, the National Offshore Petroleum Safety and Environmental Management Authority (Nopsema) announced it would take a further 10 days to assess BP’s plans to drill in the area.

Nopsema’s assessment of BP’s environmental plan would now be completed on 29 September, it said on Friday.

In 2015, frustrated by a lack of published modelling, the Wilderness Society had commissioned its own modelling, which suggested a spill would have a major impact on most of the southern coast of Australia and Tasmania.

But the summary of official BP modelling showing what it considers a worst-case scenario appears to suggest a much more severe impact over a much larger area.

According to BP’s results, the NSW coast would have a 41% chance of being hit with “moderate shoreline contact” within as little as 48 days of a spill in winter months.

In some months, Adelaide would have a 97% chance of being hit with the same sort of contact, possibly within 36 days.

Several areas were assessed as having a 100% chance of moderate shoreline contact in some months, including Port Lincoln, Kangaroo Island and the area between Elliston and Coffin Bay.

BP has said it could completely cap blow-out within 35 days, but its modelling reveals many coastal areas could be hit before that happened.

A spokeswoman for BP told Guardian Australia: “As part of our commitment to transparency, we have made these results available publicly.

“It’s important to remember that the modelling assumes that a worst credible discharge has taken place with no measures designed to prevent this from happening being considered. It also assumes that no attempts to control, contain, disperse or recover the oil are attempted – whereas in reality all these measures would be employed,” she said.

“We will be able to move oil spill response equipment anywhere in that area within two days.”

Wilderness Society campaigner Peter Owen told Guardian Australia the modelling justified the concerns the organisation had been raising.

“It took 87 days to cap a blow-out in the Gulf of Mexico, which is one of the most developed oil fields in the world,” Owen said. “There’s nothing nearby in the Great Australian Bight.”

“Moderate shoreline contact” means water with 100 grams per square metre of oil on it. That is 10 times the amount needed for a “metallic sheen” to be visible on the water. BP says when there is a metallic sheen there would already be mortality among seabirds and other marine wildlife.

That level of spill would move further than the areas likely to be affected by “moderate shoreline contact” and would affect fisheries. In the US, fisheries shut down with a concentration of just 0.01 grams per square metre.

A spokesman for the Wilderness Society said: “BP’s latest spill modelling summary also finally admits to the unacceptable impact that a spill in the Bight could have on critically important ecological systems and marine species that Australia has clear international obligations to protect.”

This week the Guardian revealed that BP could drill in the Great Australian Bight using potentially faulty equipment, which the US regulator has said could cause a major disaster.

A leading international expert on oil disasters, Bob Bea, said BP’s response to the concerns was totally inadequate, and an “early warning sign” of problems that could lead to a disaster.

On Thursday the Senate agreed to launch fresh scrutiny of BP’s plans, with two public hearings.

BP has been contacted for comment.