The unwanted "donations" included everything from rusty chairs to broken sofas.
However, the charity appreciated the genuine donations it did receive and didn't like to throw anything away, she said.
Salvation Army spokeswoman Major Christina Tyson said junk left outside was a seasonal problem, which peaked around Christmas and died back as people returned to work. Although $600,000 was spent last year on disposing of rubbish, the cost was spread over 125 stores, meaning an average disposal cost of $4800, she said.
"It is the nature of what we've always had to do.
"We're not wanting to sound mean-spirited about it, we accept that it is a cost of doing business."
Ms Tyson said the stores had worked on their signage to ensure would-be donors knew it was better to drop off goods when stores were open.
"Then there's the security of knowing things will make it inside the store and they're not exposed to the elements."
Salvation Army family store consultant Fraser Kearse said while the quality of the donated goods varied, the vast majority were usable. Goods that were not sellable in the family stores could be used for other means.
"We go through a recycling process and in terms of clothing that includes things like ragging, where that material is turned into rags that we can then sell."
Other clothes not suitable for the family stores were packed into bales and sent to poorer countries, he said.
"Occasionally you might get an actual rubbish bag [filled with] someone's household refuse, but that's so few and far between that if that happens it just gets popped into the skip bin."
Mr Kearse said the number of donations varied widely store to store. While some donors knew what they were dropping off was of a very low quality, they were a minority, he said.
No one should be discouraged from donating goods, Mr Kearse said.
"At the end of the day, without our donors, our Salvation Army stores wouldn't exist."
