This was dumped sometime during the day.  We left at 9:00 AM and it was not there.  When we returned home around 5:45 PM, it was. 

We suspect from the marks on the far side of the pile that someone might be storing this here temporarily and coming back for loads.  But we aren't experts on piles of stuff so that's just speculation. 

Regardless, our neighborhood is not a warehouse for construction materials.