I am a student looking for methods to estimate repair costs when trees damage public works structures such as sidewalks, roads, power lines, street lights, water, sewer & gas lines, etc. My project's focus is the valuation of an urban forest. Most trees in the dataset are an asset and I'll apply the CTLA method, but some trees are considered a liability because they have damaged infrastucture. How can I derive this "public works cost of repair" factor for liability trees? Any ideas?