Unscrupulous operators have set their eyes on Wollondilly as a great place to offload illegal fill.
Many property owners in the shire have had fill delivered with false promises that it is clean and harmless, only to discover later that it is contaminated with building and demolition waste, heavy metals or even asbestos.
Wollondilly Council manager of compliance Robyn Cooper said operators from out of the area were seeking to offload large quantities of illegal fill.
"Moving fill is big business," she said.
"Property owners should ask themselves 'what is in this for the operator?'
"Even if material looks clean, it may not be clean."
Ms Cooper said the council's message to land owners was to contact the council's duty planner to confirm whether consent was required before accepting fill.
"There needs to be a tangible reason for bringing soil onto your property and there are many laws and regulations which apply, with significant fines attached for doing the wrong thing," she said.
"Residents also need to ask, am I improving my property by bringing in this material?
"As well as facing significant legal costs, you could actually be devaluing your property if it is deemed a contaminated site."
The maximum amount of excavated material that can legally be brought onto a rural property is only 100 tonnes, or less than four truck and trailer loads.
Any earthworks should not change the flow of water across the land or impact neighbouring properties.
Even virgin material needs to comply with all the exempt standards.
Once advice is sought and approval is granted to receive fill, residents should take down the details of the delivery driver including the name, license number and vehicle registration.
The source of each load should also be confirmed.
This information can be used to track down unscrupulous operators if fill is found to be contaminated.
Owners should always be present at their property when fill is delivered and once the job is complete they should secure the entry to prevent operators coming back with unclean loads.
If you see any filling or dumping that you have concerns about, you can report it to council on 4677 1100 or the NSW Environmental Protection Authority (EPA) on 131 555.