Because that dark gray surface behind him is the side of a 2500 gallon rainwater storage tank that is finally where it belongs, on a platform of rocks and concrete with its opening right under the end of the gutter on the north side of the house (west corner.) Deciding how to reposition the tank (which used to sit out from the house and have a downspout extension that was either knocked down by squirrels, possums, and raccoons, or blown down by storms) and then hauling rocks and sand for the platform, was a months' long process.
When asked to pose and look triumphant, he not only did that, but also did a Happy Dance of Tank Completion:
Now all we need is rain. Though there's been a little rain in Central Texas in the past eight weeks, we haven't had any--and we were short before that. We'd really like some water in that tank, now. All our storage tanks are going dry.