I'm getting started on prepping the yard for my son's new play structure. It will have an irregular footprint, but for the purposes of this discussion, let's assume it to be 25' x 25'. My yard is sloped (about 8 feet from the house to the creek in the back over about 60'. The last 15 20 feet or so only drop about a foot, maybe 18". My plan is to cut and fill to get the area I need, then install the structure and add 9" of cedar chips. Now to the question. My soil is heavy clay and doesn't drain well. In the wetter months (I live in Portland, OR, so that's 8 months of the year) we'll see water running down the surface of the slope and leaving the bottom of the yard mucky for long periods of time. So, will 9" of cedar chips be sufficient to avoid puddles around the play structure (and premature death of the posts and supports) or should I look into running some kind of drainage under the play structure area - and if so, what do you suggest?