Broken bricks, shattered pieces of PVC pipe, ripped shadecloth and remnants of garden hose were among the items visible alongside a kilometre stretch of Mirrabooka Avenue in Landsdale.
A faded child-sized football could also be seen half-buried near the road verge on Wednesday, where local residents claimed mulch had been laid in recent months.
"We noticed they started mulching the bush that they've cleared from the development," Steve Dreher told Radio 6PR.
"After a while I drove past it and saw that it wasn't just mulch, it was actually rubbish."
It appeared that work had been done to clean up the mess, with fresh vehicle tracks at the site on Wednesday afternoon.
Mr Dreher said he reported the issue to the council ranger and was told samples of the rubbish had been taken away, tested and were found to be free of asbestos.
"Just a few days ago, they've taken a lot of it away, put some clean stuff on it and started picking [the rubbish] up by hand," he said.
City of Wanneroo mayor Tracey Roberts confirmed that a Landsdale resident brought the matter to the council's attention and thanked the person "for their vigilance".
"As a result, action is underway to resolve this and we are working with the developer to see what further action can be taken," she said.
Linc Property, the developer of the nearby Northlink Industrial Park, issued a statement which said mulch had been spread by a sub-contractor in consultation with the City of Wanneroo in order to improve the presentation of the verge.
"We were subsequently made aware that a portion of the mulch spread by a sub-contractor inadvertently included some rubbish," the statement read.
"The rubbish was subsequently tested by the City of Wanneroo who have confirmed that mulch containing rubbish can be removed. The removal of this mulch is now underway."
The City of Wanneroo urged residents to report illegal dumping by calling 1300 766 541.
