rainwater catchment in the earth in urban yard, off drain pipe

My question is similar but we are not below the water table.

City regulations say you have to handle all your runoff on your land.  Which is the first helpful thing I've heard yet.  Yes, we have a good City council!

But my housemate says the contractors who did another job here said we need to have a big box stuck in the back yard with holes in it, and water will gradually diffuse out of it into the soil.  5' cube (about 2 m cube).  

In some ways, that's great.  It would mean water retention in the soil--even more than the wood chips have helped to effect.  (We had spontaneous mushrooms this year first time ever!!!)

BUT--cautions!
--do we need people digging up the back yard? with heavy equipment?
--will they back over the nut and fruit saplings, the way the other construction crew that PROMISED not to do but did anyway, to TWO different trees--and that was just with a ladder, not a piece of gas-powered machinery?
--what does the plastic leach into the soil? dyes in the plastic?
--isn't this a very petroleum-heavy solution?
--it's what's on the market--so for me the trust has been broken.  You now need to prove innocence if you're trying to sell me something.

I had the good sense not to play my hand too soon, my housemate gets nervous if I propose solutions too soon, as do most people.  Better to take time to understand all the concerns.  and maybe get mine understood too.

My solution, though, is I will personally HAND DIG a pit back there (as I did a few years ago--it's subsequently filled in with sediment and wood chips) about 125 cubic feet deep, put the fill somewhere, and backfill with wood chips.  And we can run the buried pipe from our drainpipe over the hump and into the part of the land that drains toward the berm that I put in a few years back along the back fence.


to illustrate:

HOUSE| --pipe--/up hump then down other side of hump\______/---berm
                                                                                     \/  
                                             5 foot cube ditch filled with wood chips      


I hope that illustration comes through.

We get about 40 inches (1 meter) rain per year, officially  ( though recently it's been in big bursts with long dry periods between.)

Is this OK? it's far enough away from the house (10' is what I recall as danger zone, from someone with more experience and wisdom on this site).  it can't be worse than letting it drain into the basement when it rains, which it has done a bit before, though I'm not aware of it ever coming in the back wall.  It's wood chips, so reasonably natural.  The pit will need to be re-dug in five years probably, but that's not prohibitive.  It's not going to collapse--I've made other ones not as big but they haven't sunk noticeably at all and have done something to moderate the floody rainstorms.  

Also, our soil is much more infiltratable than it used to be when I moved in here, so I think that it will soak in fine.

In fact, I think it would work fine just to run the pipe over without digging an extra hole, but I like the idea of a bit more soaking in, less time for the mosquitoes to find it or for neighbors to be worried.

Sorry if this is a redundant topic, but I didn't find anything on a search of "drainage house yard"

It seems cheaper than a French drain or a big plastic box and back hoes.  

Am I missing anything?  

Supposing you had to convince people cautious about unusual fixes for problems, what might you say to present this?

Hmmm, I've noticed with my woodchip piles, that they seem to stay dry inside--the water seems to run off. If the pipe is under the top layer of woodchips, it might infiltrate down, but it also might clog.

Here where I live, there's a big push for "rainwater gardens." There's a bunch of demonstration gardens in the city of these rainwater gardens, and the city seems to support them. I haven't made one, myself, but it seems that they are pretty well tested to do what they're supposed to do (catch water and let it slowly trickle down), and you could grow edibles in them, like wapato/duck potato/arrowhead, cattails, lotus, currents, blackberries, watercress, etc. Let me see if I can find more information about rainwater gardens...

Ah, here we go, there's a lot of nice how-to pictures on this site (https://www.familyhandyman.com/garden/how-to-build-a-rain-garden-in-your-yard/view-all/):



And this one (http://www.stormwater.allianceforthebay.org/take-action/installations/rain-gardens). Here's a nice profile picture of one





Here's a link to a Massacusets rainwater garden PDF, with plants that will probably do well for you.

I also have a list of edible wetland plants somewhere. let me see where I put it. Ah, here it is! It's still a work in progress, though! https://permies.com/wiki/76253/Edible-Plants-Shady-Wet-Areas

Joshua Myrvaagnes wrote:

City regulations say you have to handle all your runoff on your land.  Which is the first helpful thing I've heard yet.  Yes, we have a good City council!
But my housemate says the contractors who did another job here said we need to have a big box stuck in the back yard with holes in it, and water will gradually diffuse out of it into the soil.  5' cube (about 2 m cube).  
We get about 40 inches (1 meter) rain per year, officially  ( though recently it's been in big bursts with long dry periods between.)
Is this OK? it's far enough away from the house (10' is what I recall as danger zone, from someone with more experience and wisdom on this site).
Supposing you had to convince people cautious about unusual fixes for problems, what might you say to present this?

Indeed, you have a great City Council! I wish: We have large ag fields, and they run a lot of manure that runs in the ditches and ruin the groundwater!
I don't think that a 2m cube/ 5'cube will be enough to handle just your roof runoff if you get 40"of rain a year. You will need to calculate how much water falls on your roof in a one inch rainstorm and X by 40. You will be amazed at the amount of water! Here is a link to help you calculate accurately:
http://www.friendsoflittlehuntingcreek.org/description/roof.htm
You did not indicate what kind of soil you have, but if you want to keep water nearby, how about using that water for crops? We live in very sandy soil but we wanted blueberries, so I had a 33' X 4'X4' ditch built [yes, we asked for help ]
We mounded the original dirt on the edges and placed several tarps and filled with a mixture of that soil [sand, really] wood chips and sawdust. [The tarp was not water tight: I left it open on both ends]. From the corner of the house, I ran an 8" PVC pipe to the ditch. You'll have to see what you can do to keep the water farther away from the foundations, or you may get even more water if your water table is already high.
I put a hedge of blueberries and we are very happy with the results. You may also look at trees that really absorb a lot of water. Basswoods [Tillias] are very good, so are gooseberries and elderberries. NO to willows!: They do suck a lot of water, but their roots are extremely invasive and will bust concrete!
Something that just contains water that slowly escapes can still overrun its boundaries in a harsh rain, but once you add as much soaking vegetation as you can, whatever hole you can make will really help.
As far as convincing arguments, I'll give you 3: crops, water retention for a good purpose [the material will filter the water], no mosquitoes.

Pages C-50 to C-56 of the following has some plans for infiltration systems that don't use a manufactured tank.  Note your worst case storm may require a different size than this indicates.

https://your.kingcounty.gov/dnrp/library/water-and-land/stormwater/surface-water-design-manual/SWDM%202016%20complete%20document%20FINAL%20first%20errata%206%2015%202016.pdf