NSW roads minister Duncan Gay has released a preliminary report into the handling of the possible contamination of the Herons Creek section of the Pacific Highway upgrade.
The report concludes there is nothing to indicate any radioactive material was ever buried at the site following the 1980 crash of a truck carrying radioactive isotopes, the pesticide DDT and food products for disposal near the site.
ANSTO, which also conducted an investigation of the site, reported no indication of any abnormal radioactivity in the soil on site and removed from the site.
The report claims that the source of the contamination is remnants of sodium propionate material trapped in clay that exhibits some characteristics similar to naturally occurring acid sulphate soil.
Sodium propionate is used in bakery products as a mould inhibitor.
Mr Gay said a number of other contaminants including pesticides, polyaromatic hydrocarbons, petroleum hydrocarbons, polychlorinated biphenyls or any volatile organic hydrocarbons have been ruled out.
Tests for other possible contaminants are continuing, Mr Gay said.