I would look for heavy plastic crate or even a light metal coated grate for outdoor use. Put in the french drain, cover with slight pebble along sides, then put grate on top, then more pebble, then some decorative rock and call it a day :). Hope that helps.

Your pictures are too close up and don't show how one piece of the back yard fits with another. The main question I had after reviewing your post is, where is all the water supposed to go? In that hole? Is that going to be a french drain? I don't have enough information to summarize the project, but my suspicion is that this project is not well thought out and you're on a path to overkill... making the project bigger (and more expensive) than it could otherwise be. With a drainage issue, what must be understood is the PATH that the water will take which clearly shows that it can exit your property without obstruction. I'm guessing that instead of solving the problem, you're making a "bowl" further away from the house to put the water in. For most rain events it will probably work (but not necessarily without problems.) But when that torrential, freak downpour occurs, the water will fill up the bowl and come back to you. Once the path of the water flow is identified and a strategy is created to direct the water, it may turn out that you can do it without a wall, or with a very low wall.

Please put some photos (not close up) on the thread that clearly illustrate the path of water flow until it exits your property. Since it looks like water is entering at the back of the lot, I'm guessing it's leaving at the front. That's where photos should start. Take pictures that illustrate the grade.

Thanks, Oceandweller! Good ideas and I appreciate you taking the time to think about it. :)

Yardvaark, I took the pics from inside the house out the back window, about as far away as I can get. There isn't really a good vantage point for that sort of panoramic shot as the yard is surrounded by woods, a fence, part of the house, etc. I think I'll get a professional in to scope it out and give 2 cents on the matter. Just need to look into who/what/where and give them a call. Thanks for your help.

You definitely require a professional consultation.
It will be money well spent and you can build upon that information with peace of mind.

We are professionals w/ 25 yrs of landscape construction experience and we seek engineering ( geo-technical, civil and structural) all the time, as a matter of fact we usually cannot even start building a project , especially a retaining wall, without engineering.

The cost is minimal once you consider the full scope of the job along with the liability potential.