How much to withhold for damage from cat?

[Dave Bopp]

Hello all,

I'm writing to get some advice on withholding money from a tenants' security deposit because of damage caused by his cat. He just moved out yesterday and upon getting the unit ready for turn over I discovered mounds of cat feces that he had dumped and left in the basement next to the laundry area. I cleaned up the mess, but of course the basement still reeks of cat urine/feces. I plan to withhold money from his security deposit, but am unsure how to quantify what should be with withheld. He had been paying pet rent and paid a $200 non-refundable pet deposit up front, but I know this smell is going to linger and will be an issue for the tenants who just moved in.

Any input would be appreciated!