Help evaluate my backyard drainage problem. (diagram attached)

16 years ago

http://mysite.verizon.net/vzet7ek9/diagram.pdf

IÂm thinking of crisscrossing my backyard with a series of French drains and wanted to get your second opinions. After a series of rains (lets say 2-3 inches over a week) my sump pump runs continuously. And itÂs a soggy boggy mess. I know I have clay soil back there so IÂm thinking that the water just lies on top of the clay soil then penetrates enough to the water table then somehow finds my sump pump pit and thatÂs where it goes to be pumped out(theory).

With a fully saturated ground and new rain, IÂve calculated that the pump will run for 3 full days for every 2 inches of rain. (I have a rain gauge to keep track of all rainfall.) In the summer, the mud seems to attract a different looking fly (mudfly?).

Sorry about the crude drawing. Some further explanation: I did a French drain to left (west) of my house that drains almost to the sidewalk. The water used to pool really badly there after rains. The reason I put it there is because after some heavy rainfalls, the left basement well window ended up taking water (the window is half above ground). The water came into my basement when it was higher than the window. That problem seems to be solved as the water pooling there is gone within a few hours (it used to take a full day before).

The places on the top where it says "water pools" means areas where water seems to gather more than others. Not man-made ponds or water enclosures.

Also, the gutter downspouts (G) have been fully extended (about 7-12 feet) except for the one in the bottom right. It drains to a sidewalk right by my house. Unless I crack open the sidewalk, I canÂt extend it further. On the downspout on the top left I buried some corrugated pipe and extended it all the way to the catch basin. I did this due to the earlier well window flooding problem I mentioned above (overabundance of caution). The top right downspout drains into the buried 4" pipe that is fed by the catch basin (I did not do this improvement). I also extended the sump pump outlet about 8 feet via a buried drain pipe (it used to drain via one of those concrete downspout things).

My neighbor to the right has a sump pump and it never comes on. ThereÂs been times when it rains so hard that a little creek can be seen flowing into the city drain in between my house and my neighborÂs. My neighbor marvels about how my pump seems to run all the time.

The grades everywhere a pretty gradual and not steep. Except for the area between my house and my neighbor (to the right). There, itÂs more like a spread out V.

IÂm thinking of doing a series of spider web drainage pipes to get the water away from the backyard quickly all fed to the catch basin. Thus, the sump pump wonÂt be stressed so much later on. Is this project a waste of time? Be happy to answer any questions.

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Comments (3)

lehua49
16 years ago
Hi On n Up,

Just a tad more info. I do like your diagram. It helps quite a bit(photos available?). Are you the original owner of the property? Do you know of any regrading of your lot? How much lower is your backyard compared to your neighbors yards? Are all the yards part of a large subdivision? How old is the subdivisions? Is the parking lot and dirt tree area to the left lower than your yard? Who's property is the parking lot and dirt tree area? It is strange that your neighbor yards in the back all drain to your yard as well as your neighbors yard to the right. Check your percolation rate of your soil by digging a 18"x18"x18" hole in the yard, then fill it full of water, then let it empty out and fill it again, keep track of the time it take to empty again. Till we communicate again, stay dry. Aloha
onward-upward
Original Author
16 years ago
Thanks, lehua. Here are my responses: I'll try to have photos posted tonight. I am not the original owner. I don't know of any regrading of the lot. I think I am at a downslope from A, B, C houses, but my neighbor to the right (D) is about the same. A, B, C are older homes. Myself and D are a newer row of homes (more homes to the right; about 6) that were built in 2000 or so. I would estimate that the ABC homes were built in the 50s.

Parking lot is about the same level as my yard. The parking lot is for a fire station next to us. It may be a while to dig that 18" hole! I am in the DC suburbs. Right now, all the moist soil/water has frozen so it may not be a good time of the year to do a percolation test.

Before this current period of sustained freeze, we had a lot of rain for December (about 7 inches and we average around 3 for Dec.). I did core aerate/reseed the yard this past spring, which I thought could breakdown the clay soil & absorb more rainwater. However, this won't work in December where we have short days and no warming/evaporation of the water. the lawn is probably less thirsty in December.

This may or not matter, but one of the original owners of one of the our generation homes next to us told me that the land where they built our homes used to be a city park. The park was next to the firestation. Also, when I dug out the long french drain, I kept getting my shovel jammed with many rocks. Some as big as fists.
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lehua49
16 years ago
Hi O-U,

Very interesting. It makes sense know. Then it is an historic condition that the drainage of your neighbor's water comes into the ex-park now your yard. If you are lower than your back neighbors, you might want to install a gunite or concrete lined surface ditch that pick ups their flow and takes it to the parking lot or tree area. Who owns the tree and dirt area next to the parking lot and next to your lot? This surface ditch has the best capacity, fastest moving and most maintainable way to keep water from entering your property. You can adjust your yard grades to make the drains work and get the water to the front of your house and away from your house slab. Underground french drains eventually fail and clog and it is very expensive to rehabilitate. If your soil is clay with low percolation, fast surface drainage is even more important. Pictures would be great. You have my warmest sympathy for the freezing weather. Aloha