Thanks everyone for the good information. To answer a few questions. The truckload of stone that I put in the spillway I toted by hand in a wheelbarrow. It took most weekends for one spring and summer. All of my pond spillways & dams are inaccessible by any vehicle. I look on the positive side, it's good exercise. One very dry summer I rented a TerraMite, (small backhoe) and had some earth moving work done but as my property is wetlands, unless it's very dry, any heavy machinery just sinks into the mire.
As I mentioned in my first post, Big Pond has what appears to be the remnants of the original streambed flowing out of one side. I tamed that area a few years back and hemmed in the stream with these same wall blocks. And tho' that area becomes a torrent is rainy times, these wall blocks have held up and only tilted slightly. The spillway where I put the load of stone and eventually built my wall was caused by erosion. So, once the wall was completed and back filled with pond goo, it staunched the flow of water and the small side stream took over as the outlet. However, water being what it is, found a way to flow under my massive rock pile and under the right side of the wall. Still the wall held but strangely it was the left side, where there was no active flow of water, which began to tip forward.
I did cover the pond goo backfill with topsoil and planted grass seed and some ground hugging shrubbery. It did not grow so well as the area is very shaded. I had not considered the idea of building the earth up higher than the wall to encourage the rain water to flow over the top of the blocks as opposed to under. I will add that to my arsenal of knowledge.
Regarding how to proceed, I wondered if concrete was needed as a base. Unless we have a drought, it would be near impossible for me to dig a trench and lay concrete -- there is simply too much water. And I don't have any way to lower the level of Mystery Pond. So, the idea of putting in a layer of stone and then concrete bags on top of that as the foundation of the wall might be my best bet.
I must do something. My property is unique in that my house sits directly on the water, being only a few feet from the water's edge in some places. So my crumbling wall is very visible from my deck and it has become an eyesore. Yesterday Punxsutawney Phil declared it will be an early spring. So I, hopefully, will don my waders and begin my rebuilding in April.
Again, thanks for all the great info. I will be visiting this site frequently because I have a slew of other questions.
