I was caching with my daughter Enchanted Fox today. We were mainly picking up puzzles - but I noticed a few challenges like this one that I had qualified for so we included those on our list too.
We continued on up the track. A robin came and sat on a branch nearby just before we reached this one. Another good hint so the cache was a quick find - the first one of the day for Enchanted Fox. The sewage farm seems to be pretty hot on security doesn't it - I'm not sure that many people would want to break in anyway.
I qualify for this challenge as can be seen from my profile, but I'm also attaching a screenshot of the challenge checker as proof.