Another Rain Garden

I've had a big problem with drainage on my side yard. This isn't a problem for my basement, but after big rains the water has pooled there for some time. Last winter we had a stint of snow, warming to thaw it, followed by several days of a deep freeze, and that section of my yard turned into a skating rink. 

First iteration of rain basin, perking acceptably

Yards on my street tend to be mostly level, little plateaus created by bulldozers. But then there are steep slopes before the ground levels out to the next yard. This side of my yard is deeply shady, and slopes gradually to the fence, after which it drops down a whole story of a house. My ground is level with my next door neighbor's roof. This is great for privacy. It seemed, however, to be a bad idea to solve my drainage problem by sending it all down the slope to the foundation of the house next door - especially when I know they already have problems with water in their basement. Besides, I'm pretty sure water coursing down that steep hill will drive significant erosion in the slope, resulting eventually in my lovely fence toppling over down the hill. Deluges are becoming more frequent, and they drive much more erosion than the same amount of water spread out over a longer time.

Beginning of the trench

After some years of studying the problem, watching the movement of water through my yard, measuring slopes with a laser level, I decided to run french drains along the side to the front, where I have a small space far enough from trees, my house, and the drop-off to put in another rain garden. The natural slope of the land is from back to front so this working with gravity in my favor. I have a downspout off the roof gutters at the back side corner of my house which would feed directly into the drains. I have another downspout along the back of my house, and I would allow that to drain on the surface, where it should run down across my grass to the low ground in the yard where the porous french drains would channel it out of the area.

This was going to be a much bigger project than my front rain garden, because I would be starting from scratch. I don't think I would have had the gumption to tackle it without the boost from challenging myself in my vacations this summer.

First, I dug up and set aside the large stepping stones that made a path along the side from the back to the front. I needed the wheeled dolly to move many of the huge stones. Then, I laid out the drainage basin area in front, and dug it out with a shovel to about 18". I used most of the displaced soil to bank up the sides of the basin, especially towards the down slope. It dug fairly easily, but where I stopped the looser top soil had yielded to some hard clay. I dug down further into that hard-packed area, and mixed with the clay several bags of locally-generated compost, filling the basin partially back up. I filled the basin with water, and watched it drain - it took about an hour to perk through the clay and soil. That seemed promising.

The trench gets deeper

I trenched backwards from the basin along the house to the back yard. The first layer of the trench was done solely by hand, but there were only 2"-4" of topsoil there before I reached clay (I just put it to the side as I went). I have an electric roto-tiller, and so I got into a routine of running through the trench with the rototiller, loosening the clay. Then I would come back with a spade and remove the loosened soil for a couple of inches, tossing stones to the downside and dirt to the upside. There were some roots that required sawing by hand. (I didn't worry too much about damage to any trees, as the trench is about ten feet from the house, so the roots couldn't have traveled much further than where I cut them off.)  

This was a very big undertaking. It took me maybe five or six days of two hour stints of rototilling and digging to get the trench as deep as I was willing to go. This includes one day of rototiller repair, when I got it too close to a metal mesh fence and the blades got stuck in the fence. I had to pretty much disassemble the whole machine to disentangle it from the fence, and then put it back together again. 

During the deluge. See the drain pipe sticking out

Before I was all the way done with the trenching, we had a big rain - about 1.4" of rain in a few hours. I hooked the drain pipes together in advance of the rain, and watched how it worked. The good news is water ran nicely along the system as planned. The bad news is the rain garden basin wasn't nearly big enough, and it overflowed. The water that was collected there took over 18 hours to drain away - I figure that long time was because the ground was saturated and there was no place for it to perk to. So after it had dried out some, I resumed digging and made it bigger in circumference. I also worked on the berm and tried to slope the sides so that overflow would move in the direction of my main front garden, not over the edge.

Finally I declared the trench as deep as it was going to go. I lined it with landscape fabric, put down pond stones in the bottom of the trench, laid in the porous drain pipes, wrapped the landscape fabric around it like a blanket, and covered it over with the displaced dirt. Hooray!

Bixby digging

I set the stepping stones back on the surface. I still need to sink and seat them properly, on the to-do list. But I want to make sure everything has settled in place before I expend too much effort leveling them out. I should note that I have voles actively tunneling around and between the stepping stones. When I dug my trench I apparently cut through a major passageway, and they have been rebuilding. Bixby entertained himself going after them - it seems he can smell and hear them from the surface. So sometimes I would rake an area smooth, only to have to step and smash new vole tunnels, and rake dirt back into the holes Bixby had dug.

Stepping stones and plants in place

 

 

 

I planted white turtleheads into the rain basin, along with transplanting a single existing pink turtlehead that had popped up away from my main patch.  Along the side of the house - very deeply shady - I put in a grand total of about 30 plants - three kinds of ferns and three kinds of sedges. I planted them pretty densely and I have hopes of a green area with contrasting shades, heights and textures, that needs only minimal management. 

In the rest of the back / side yard, a flat open area, I planned to plant grass. I dug up the biggest weeds by hand. Then I rototilled the whole area to loosen the hard packed soil. Then, I distributed compost over the whole area, and rototilled it again to mix it in. Next I raked the whole area smooth, and tamped it down with my feet. Lastly, I spread bags of special "lawn soil" over the top, raking again, and finally, in advance of the first anticipated rain for several days, seeded it by hand. 

Baby grass! (I have to blow the leaves out-no raking yet)

Yay, ten days later, I've got baby grasses coming along! Last fall, when I planted grass inside the fenced yard, I felt I needed to protect it from Rocky's big feet and questing mouth. Now, I'm not too worried about little Bixby dancing across the tender shoots, but I monitor him and don't let him start digging for voles.

Whew! All told, over a month has elapsed. And as I said, it was years in the planning. We haven't had a downpour since the once that overflowed, (before I was finished) so I don't know how well it will do, but I'm fairly confident it will make a substantial difference.