The landowner said issues on his Faversham site started in June, when he said his locks were changed to a combination lock for which he did not have the code.
He said dumping on the site had continued ever since, with mattresses, gas bottles and a caravan left on the land.
A private company has quoted him £20,000 to clear the site, which would include fees to test the waste for contaminants such as asbestos.
On top of the cost of replacing locks on the site, concrete blocks would need to be be installed at the entrances to the site in a bid to block fly-tippers from entering.
The owner added that, despite reporting the matter to the police, he had been told that issues of trespass were a civil matter.