Can I expense rental condo special assessment?

I own a condo that I rent. I paid $4500 for a special assessment to improve the drainage properties of the crawl spaces. The board determined the work done was a capital improvement with a 30 year life. Can I expense this rather than depreciate? If I depreciate, what method should I use?  Any new laws that allow for quick depreciation?  This is the only property I own.  Thought I saw something that allowed me to expense this if the amount was less than 6% of the value of the property.