That's a good point Yard. Neither my wife nor I are very happy with how the end of it turned out, so I very well might be re-doing it at some point when I'm not so tired. The cutting of stones was a bit of a learning curve. I ended up redoing quite a few of them my second time round. I was just manually measuring with a straight edge ruler and getting a little creative with my curves to help lock it in. There were sadly a ton of curves to cut. We rented the saw the first day late for 24 hours. So I worked from 4pm or so until 8pm on them. By the end it was going much better. Sure enough the next morning I woke up at 7 am to finish up and it was sprinkling. Started cutting in the rain until about 11am when it started pouring. We realized how slow it was going and that I would have to rent the saw again, so my wife convinced me to stop working in the rain and return it. Sure enough as soon as it was back, the rain stopped. I doubt I would have finished either way though, never expected it to take that long to cut so much. I ended up working a full day from 7am to 8pm to finish the pavestone and capstone.

Look at multi-flow drainage systems on google. You need drainage. It probably should have had a wider footing going back toward the slope (called a cantilever wall - the backfill sits on the footing like a fat guy on a chair so that the back of the char can't tip over). He built what is called a "gravity wall" which relies on the mass of the wall being greater than the force of what is being retained so that it won't move. Any water build up behind that wall causes what is known as hydrostatic pressure which adds to the force being applied to that wall. Weep holes would have been a good idea during construction. Now it is a bit more difficult to make the weep holes. At minimum, put in drain pipe and clear drainage stone behind the wall so that the water can get out. What was built is a typical basement wall built to support something on top of it and with a structure holding the top of the walls apart and a concrete slab holding the bottom of the walls apart. He is essentially asking a vertical slab to hold back 40" of fill without pushing out or toppling over.

@ken - You can kind of see one of the white septic vents in the weeds a few feet in front of the deck and on top of the large retaining wall. It had to be put there (from my understanding) due to the drainage of our land. We put our home on 10 acres in the corner of one of our grain fields. Behind our home is a natural spring pond that eventually creeks off and feeds into a river about a half lv of a mile away from our home. We live in central SD. Our children right now are 2 and 2 months. Don't worry, I don't plan on ever having them unsupervised out there. We also have gates on both entrances of our decks. The plant choice is more for a deterrent/peace of mind since climbing a fence is pretty easy and fun for pour 2 year old. @Select - I appreciate the suggestions! I will look into those. I like the prickly idea. My parents planted prickly bushes in front of my bedroom window, I would assume to keep me in and the boys out, Hah! I doubt there are any codes due to the sparse population of our county, but I will certainly look into it! It is something I've thought of but forgot to research.

I'm not sure if I'm picturing how the wall was built accurately, so... The contractor dug a trench, leveled out the bottom and compacted the soil. At this point best practice would have been to lay down a layer of gravel in a trench wide enough to accomodate both the first layer of timbers and the drainage pipe. Perhaps you have especially gravelly/sandy soil and a mild climate where frost does not penetrate deeply. If so, what the contractor did may be fine. For most soils, though, you're likely to end up with a sump at the base of the wall with water unable to exit. If it also freezes, there will inevitably be shifting of the base layer of timbers and consequently the entire wall. If the wall is quite long, drainage pipe could slope in two directions and empty into dry wells at each end. For a relatively short wall, a single dry well on one end is probably enough. i'd also ask the contractor if the first layer of timbers is anchored to the ground with rebar or something similar. Check also if there are any ties, timber or something else, running at right angles to the wall which extend back into the earth. It is impossible to evaluate the contractor's work without actually being on site, but even for a 2 foot wall it does seem unwise to have placed the crucial first layer of timbers directly on the ground.