Saving Stuff

My hobby is graffiti. I like finding cool and interesting places to paint. Part of an outdoor reservoir was just emptied, and it really is a perfect spot. I was wondering how closely you think the area would be monitored. See I live in in a quiet neighborhood with yards and a bunch of parks, but the area is surrounded by barbed wire (although it has fallen off in one spot). I also live in Washington DC (which is anti terrorist ville), and I feel like people tampering with our water system would really blow. However, like I said, it is a really perfect spot and the water there hasn’t been treated yet and isn’t kept kept clean or anything.

I don’t know opinions on the risk factor? I just don’t want to be in the middle of painting and have H.L.S. come attack me.
Thanks a lot