Drainage/Holding Basin Questions
I have a property has some drainage problems in heavy rains, large ponds tend to form during the wettest weather but most of the time it is just muddy. I love the look of dry creeks, but since the property is flat I don't think that will work for us.
The plot is 110 ft x 205 ft, there is a storm drain near the south-eastern corner and the largest pond forms in the back of the backyard on the western end of the property. There is a septic tank and a grey water disposal system, so there are a lot of leech lines running the length of the back yard. I learned this winter that ours is the only property in the neighborhood that that doesn't drain any water to the street side where the storm drains are, all of ours goes into the back where the septic/grey water systems are. On top of that the neighbors on the south side raised their places so that the water drains off onto our property, as a result we get some pretty big ponds in the winter.
There are a few factors that make the drainage problems in our backyard difficult to solve. Our property is flat - there are some higher spots and lower spots but there is no grade to speak of, we have leech lines that we can't dig trenches through, and we have oak trees whose roots I don't want to disturb.
I would like to install one or more 'holding basin' water gardens to deal with the rain water and to be a landscape feature in the relatively featureless backyard. I was thinking it might be best to have a smaller holding basin closer to the house where there is a smaller pond, and a larger detention pool with a spillway into a dry well that has a pump to move water to the front yard farther back where the largest pond forms. There is a small slope towards the storm drain in the south-eastern corner, would it be possible pump the water to a little dry creek that runs to the storm drain? Can the holding basins sit above the leech lines or should they be kept away, if so how far away?
I have the plans for the septic and grey water systems, but the sketches are a little sketchy so I'm not sure as to the exact location of the leech lines, so in my plans I just drew them larger than I think they actually are. I will consult with a professional before doing anything back there, but I wanted to get a better idea of my options and plans first.
I want the backyard design theme to be 'Woodland Meadow' and I think a couple of water gardens with a lot of stone will go with that.
Here are some plans I drew as well as a pic of the backyard taken from outside the back door.