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Drainage Issue

Posted by OnAHillside Alabama (My Page) on
Mon, Jan 21, 13 at 14:37

Good afternoon. I came across you guys while I was googling solutions for a drainage issue in my back yard. You all seemed knowledgable, so I am here asking for your help.

Basics of the issue - My house (built in 2006) is a split level home (basement & Main Level) built into a hillside. The backyard is situated at the base of a large hill, and it is holding water. There is a keystone retaining wall separating the back yard and the hill. The water is puddling up at the base of the wall and throughout the yard towards the house. There is no standing surface water next to the house. I've provided a make shift graphic to help explain the issue. I can provide any and all necessary information needed to help identify the best solution to my drainage issue.

I am looking for the best solution or combination of solutions to keep the water away from my basement (poured concrete walls; no prior issues of water intrusion), and to prevent my backyard from holding water.

Note: The red text reads, from left to right of the image, "10' Tall Retaining Wall" and "3' Tall Keystone Wall"


Follow-Up Postings:

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RE: Drainage Issue

Here is a view from the bottom driveway. This picture is taken from the entrance of the basement looking towards the "10' tall retaining wall" noted in the original image. The backyard is located at the top of this wall within the wooden fence.


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RE: Drainage Issue

Here is a view from the edge of the keystone retaining wall (the blue "spray paint" is showing where the water is sitting). You can use the corner of the swing set as a reference point (the previous image of the bottom driveway is located to the right of this image). I hope this image will give you an idea of what the keystone retaining wall looks like and an idea of what the problem is. Again the water is sitting at the base of the keystone wall and saturating the entire yard. I can take more pictures of the yard to provide more information, just let me know what you need. Thanks in advance for your help!!

Note: Ignore the red arrows. This picture was taken from a homeowners inspection report, and they do not pertain to the drainage problem.


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RE: Drainage Issue

The recent picture alludes to the problem but it does not show it. Keep in mind that anyone seeing this doesn't have the advantage of also being able to see it in real life and reference objects in the photo from memory. If the photo is fuzzy, it's difficult to be certain about details. (It took a while to find a swingset and then understand what part of it I was looking at. And there is a structure in your first photo, at the termination of the side drive, next to house, that I am thoroughly baffled by.) I would suggest using better quality and somewhat larger photos and include a portion of the house for reference. I'd suggest adding photos that represent something along the lines of these, with what's inside the pink rectangle generally representing the desired view :


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RE: Drainage Issue

Looking again at my picture I think it might be unclear. I'm not necessarily trying to get you to show the ENDS of your house. I didn't want to take the time to draw a perspective view. If you show enough of the BACK SIDE of the house, that's probably sufficient.


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RE: Drainage Issue

Thanks for the response Yardvaark. I will try to get some additional pictures this evening. I understand what you are asking for in your graphic. I was going off of google maps and old photos that I had available at the office. In the above pictures, I highlighted the problem areas blue.

The structure you are baffled by is an arbor sitting on a concrete pad. The concrete pad extends into the yard and can be seen on the aerial photo above.

Hopefully this picture will help me tell the story for the time being. This picture is taken from the edge of the concrete pad looking over the entire troubled area. The water is pooling in the entirety of the yard pictured. The pooling is worse at the edge of the keystone retaining wall (right hand side of the picture), and lessens the closer you get to the house (house is at the left hand side of the picture).


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RE: Drainage Issue

This picture is taken from the edge of the concrete pad looking towards the arbor and driveway. Again, the water is pooling all along the base of the keystone wall (left side of the picture).

The concrete pad itself is graded appropriately leading away from the yard and the house. It flows around the corner of the house (right hand side of picture) where the is an existing drain that carries water away from the house to the front yard.


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RE: Drainage Issue

Those are better pictures for understanding the yard. That the water pools less toward the house and greater away from it is at least a clue that grading near the house is probably going in the right general direction. With a problem as large and complex as grading and drainage, we can discuss the general concepts that help you understand it, but the discussion can't be interpreted as actual planning work. Though such work could be done remotely, it would require an amount of site information more immense than you are willing or able to collect and more time than anyone here would be willing to provide. Depending on what's actually needed, the planning work may need to be done by a designated professional in order to comply with government regulations. This would likely not be in opposition to your goals since you want the final solution to actually work and solve the problem. Don't be too surprised if you don't like hearing what it takes to fix the issue. Rarely does anyone like hearing that they they need to tear into their finished yard in order to make it work correctly, but that's often what's required to fix a drainage issue.

Can we figure that there is no issue with drainage of water that falls or runs across the concrete slab in the last photo? And what is the light green circular object on the ground near the shrubs in the next to last photo?


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Thanks for the quick response. Understood and agreed on the legalese paragraph. This is part of my due diligence to understand the problem, and to determine what it takes to fix it. Whether that is done by me or a professional is a decision I'll make after I understand better what we are dealing with.

Also, I fully expect to dig into the finished yard. We purchased the house in September, and i have full intentions or re-working the landscape. My number 1 goal is to fix the drainage issue, and the work on the aesthetics and usefulness of the yard.

I am imagining a combination of re-grading, surface drains and french drains to tackle the surface and subsurface water. However, I would like to discuss the specifics with you guys as long as you are willing to shoot the bull with me.

There is no issue with runoff from the concrete slab or connected driveway. The concrete is graded along a course that flows through the middle of the slab,through the gate on the right, and into a concrete spillway (for lack of a better term) that leads to an existing drain. The driveway also drains directly to the concrete spillway and drain. So the source of the accumulated water is runoff and ground water from the hill above the retaining wall.

I believe the green object is a dog bowl. This picture was taken by the previous owners.


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RE: Drainage Issue

Ha! I thought the green "dog bowl" looked like it might be some cheesy drainage structure. It's ruled out as anything pertinent. That the number one landscape priority is drainage indicates a proper perspective about it. Very good then. Tomorrow, you won't hear much from me. I'll be busy most of AM and then travelling. Hopefully others will jump in on this.


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Ok, let's see if we can get some others to offer up ideas.

First, I am operating under the assumption that my house was built appropriately. In other words, I'm assuming the poured concrete basement walls are covered with a impermeable water proof barrier, and that the foundation has as 4" french drain along the base. Other than a major excavation, I don't know how to prove this to be true. So I will assume everything was inspected and built to code. I am not aware of any water intrusion issues since construction was completed, 2006.

With that assumption, my concern is moving the water from the back yard northwest and then west to drain to the already existing storm drain culvert. So I will run the water through the swing set and left around the driveway retaining wall. This will follow the natural lay of the land. See the aerial picture above for reference.

I have two ideas that I'm tossing around right now. I will correct/enhance the grading from the house no matter which option. Option 1, a french drain system with multiple surface drains through out the yard. I'm thinking a french drain along the base of the keystone wall, and a french drain run closer to the house. I will have surface drains connected in order to catch the surface water.

Second idea is a dry well system with sump pump to pump the water to the far side of the driveway and down the hill. I would have drains leading to a buried drum that is outfitted with a sump pump. The drum would have holes in the bottom to allow sub surface water to be captured and pumped away. I'm adding the sump pump because i don't want the dry wells to simply perc the water behind my basement wall. I need the water out of the backyard all together.

Note, my soil is heave clay. So does anybody have any thoughts on these ideas? Pros, cons, and alternatives are all welcome.


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You've given us a good general look to the property and the solution sought. But as Yardvaark idicated, for development of a plan, the devil is in the details.

On what I see now, I would avoid drywells, pumps, or the use of any perferated pipe in a french drain. Surface drains to solid pipe can be used for small isolated areas. Just don't expect surface drains to handle the water coming down the hill in a major storm event.

I suggest you make a detailed assessment of the keystone retaining wall for construction that complies with the specs for that type block.

Things that will help us to help you:

Copy of survey plat of the property.

County in Alabama? Online resources and maps to quantitate the slope and contours.

Distance from the keystone wall to your back property line.


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RE: Drainage Issue

Here is a copy of the survey. We are in Shelby County AL. The only topographic detail I have been able to find is on google maps. I'm not sure this is detailed enough for what you are asking. Is there another resource you are aware of? I looked at the shelby county GIS, but topography is not included.

I am estimating the distance from the keystone wall to the back property line (from left to right on the survey) between 120' and 190'. I can put a tape measure to it later. The back property line is located at the top of the hill (running away from the house). The house is located about 1/2 way down the hillside.

I don't understand exactly what you are asking for in regards to the assessment of the keystone wall.


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"I don't understand exactly what you are asking for in regards to the assessment of the keystone wall."

It would be a shame to spend a lot of money on this project and have a wall failure require another re-do a few years from now. It is the wall stability that concerns me.

Photos are sometimes missleading, but here is what I think I see. Looking at the line formed by the front edge of the top row of blocks, the wall seems to have an irratic alignment unlike what a professional would build. Or perhaps there has already been movement indicating a slow failure is underway.

You say the wall is three feet high and I think I can see 7 or more courses suggesting that each block is 4 inches tall. There is no maximum on how high a SRW wall can be built, but the limit of most of the light weight block found at the big box stores has a limit of around 2 feet.

I don't know of any block made that would be suitable to build the wall in the photo having a steep upgrade behind it without geogrid being installed. To use geogrid,the bank would have to have been dug back some 5 feet behind the wall location. Trees close to the wall tell me it didn't happen.

Find out what type blocks you have. Then check to see how they can be used.


Here is a link that might be useful: Pavestone-limit 2ft high where ground is flat behind wall


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RE: Drainage Issue

The list of things to avoid, mentioned by pls8xx, is something he and I generally seem to concur on. I agree with him here. I would go a little farther and say that I am generally against placing water in an underground drain and pipe system of any kind IF IT CAN BE AVOIDED. Drains and pipes can fail or clog and they pick the worst possible times to prove it. Some rare storms can deliver a tremendous amount water that is too much for the system designed, with unpleasant consequence. And you've got a big hill aimed right at your back door. The worst systems (to handle any great amount of water) are "french" drain systems. They have a limited capacity that can be overcome quickly. IF there is any way to drain the water with surface flow--and I'm speculating there is--it would be the way to go. I give pls8xx credit for pointing out in another thread that it's the only way to protect against surface flooding. It's an important point.

The pictures you've supplied so far don't give a good visual "read" on the grade (as it relates to the problem area) and it is grade information that is needed. One thing you might try is "walking" us through the drainage path with photos taken in the direction of the drainage at 30' or 40'(whatever makes sense on site with your camera) intervals. At the least, it would help give a feel for the lay of the land. You sound like you grasp the concepts involved pretty well so it wouldn't be an impossible thing for you to make a simple plan showing some spot elevations and good enough to help answer some specific grade questions. (If you were inclined to spend a little time on it.)

One other thing, in your Jan 22 12:24 picture it does not appear as though grade is falling as it approaches and passes the swingset (the path of proposed french drainage you've described previously.) In designing a path for the water to exit, it's generally best if you correlate drainage with the natural slope so that there isn't a tremendous amount of earth to move or extreme results to live with. GRADE INFORMATION would dictate (or at least suggest) how water would best leave your property.


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RE: Drainage Issue

I do not have a very high opinion of the wall. It is Home Depot type block from what I can tell. There is a portion of the wall that looks to be original, meaning better constructed, directly behind the house (corner to corner). This section was dug out and back filled. The rest of the wall looks like a DIY project by the previous homeowner (everything outside of the footprint of the house). It looks like he chiseled the hillside and stacked blocks next to it. More of an aesthetic feature than holding the hill back.

I was able to take some grade measurements using a string and a line level. I'm not claiming for them to be exact, but they are precise enough to give us an idea of grade. It turns out the yard has a negative grade all the way to the foundation (keystone wall to the house/10' tall driveway retaining wall). To answer you point about the grade falling towards the swing set ( as i previously suggested for the french drain), it is a "relatively" level grade from the concrete patio out past the swing set. I sketched the measurements in the above picture. I'm no engineer, so the sketch is definitely not blue print quality. Hopefully I've included enough information to tell the story.

I will try and snap some new pictures in the morning before work.


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The above information is helpful for understanding that there's a problem, but it's a bit like looking at a large picture through a peep hole. When this information is plotted on a plan it will be more useful as it will show how all areas relate to other areas. Also, it would be good to get a picture of back of house taken from behind (on the uphill side of) the keystone wall ... so we can get an idea of how the grade runs along the foundation.


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Yardvaark- "When this information is plotted on a plan it will be more useful as it will show how all areas relate to other areas."

I used the survey graphic under a grid to retrace the info into a base map.

With measurements of the lines shown the map can be made more accurate. Add dimensions to other items in the landscape.


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RE: Drainage Issue

If you could set up 3 level string lines (orange) at the same elevation and measure the elevations at each red mark, we'd have a good idea of how your yard is graded relative to the house. If the long runs of string want to sag, support them with additional stakes. Set outside corner stakes first for an easier time of matching elevations. At the wall, you will probably need to set up sections of line to accommodate the wall curvature. Also, sketch the wall on the plan. (Based on the above grade sketches, the back yard grading looks fairly messed up.)


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RE: Drainage Issue

While the elevation measurements suggested by Yardvaark will work, in the real world there are often difficulties, a keystone wall not parallel with the house and shrubs in all the wrong places.

You may find it easier to use features of the house to collect the needed data. With an additional photo of the back of the house maybe I can recommend something.


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RE: Drainage Issue

Thanks again for your input. I snapped some pictures this morning. I'll go ahead and post them, and then work on the plot. That will take me a little time to get the information and measurements.

Note the swing set is no longer there. It is now the garden area.


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Opposite view. From patio.


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View from lowest corner of garden and corner of driveway retaining wall.


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View towards corner of driveway retaining wall. This is where I propose the water will run.


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RE: Drainage Issue

View from bottom of the driveway retaining wall. Note the grade runs towards the retaining wall. I have a large amount of water the comes through the weeping holes in this retaining wall after it rains. It will weep for days up to a week.


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Final picture for this run. This shows the amount of water that is currently being drained through the weeping holes at the base of the retaining wall. It has been 7 days since the rain stopped. Note, we had about 5-7 days of rain before it stopped. So we were saturated last week.


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"While the elevation measurements suggested by Yardvaark will work, in the real world there are often difficulties..." Was trying to make explanation of the concept as simple to understand as possible, but yes, there are those obstacles. Looks like there is one offset in the wall so it'd require two separate lines to measure elevation from. The back of the shrubs can be trimmed off to get them out of the way. (If it was my house, I'd plan to relocate or get rid of them. I don't see much point in building a wall and then completely covering it up with shrubs ... unless it's really ugly and can't or won't be fixed!)

OnaHillside, on completely different subjects, it looks as if there might be a lawyer's dream in the vicinity of the retaining wall at the few feet where there is no longer a protective railing. It's quite a drop. Also, along that retaining wall, there are a couple of trees planted close to it. Seeing what tree roots do to city sidewalks, and seeing what retaining walls do on their own without the help of trees (fail,) I'd be inclined to relocate the trees farther from the wall.

pls8xx, is it beginning to look to you like a broad, shallow swale might take care of this? (Though running it through a garden would not be ideal.)


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RE: Drainage Issue

There are errors in the base map I posted. It would be better to make corrections before appling elevation data.

The distance between the patio and garden area can not be 66ft. The patio appears to be larger than shown on the old survey plat. Please make the measurements indicated in the graphic below.


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RE: Drainage Issue

And another thing... along the long length of the retaining wall, the shrubs at the top are not really protection from someone falling. In fact, they give a false sense of security because if someone fell on them, the person would go right through them and over the drop. it'd be better to move the shrubs over to the property perimeter side line (so they aren't an impediment to viewing the whole yard) and re-scheme the wall protection. Continuing the deck-type rail to a safe point in adjunct with low, possibly draping plants, would be a better solution. This is food for thought when you get to thinking about it.


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RE: Drainage Issue

pls8xx, I agree that the plot is off. So I went ahead and made the measurements before we continue with the grade measurements yaardvark requested.

I obtained all of your question marks, made corrections to the drawing (red x's), and added the keystone retaining wall (brown). Note the retaining wall is measured from the far edge of the patio, to where the wall is offset, and then from the offset to the fence. Then i measured from the fence to the portion of the wall outside the fence.

I will go ahead and tell you this is not to scale. I do not have the software to correct the plot on grid paper. This is all done on microsoft paint.


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I forgot to mention that the concrete patio flares out in the upper right corner. That is what i drew there. It flares all the way to the retaining wall. The distance between the retaining wall and the concrete patio measured 6'.

Yaardvark, we are on the same page when it comes to the bushes and trees. I've already got plans to turn the tress into firewood. The bushes are going to be moved to another side of the property. To put it nicely, the prior owner's landscaping choices are very "spontaneous". There is no rhyme or reason to it.

The safety rail for the retaining wall will have to wait until I solve this drainage issue. I'm going to lose the retaining wall to hydrostatic pressure if I don't get this fixed, so the lawyers will just have to stay away from the driveway for now!


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Good job on the measurements. I'll do a corrected base map.

Now we to make some headway on finding out how big the uphill drainage area is. Contours of the hill are needed. It's a shame the county GIS doesn't have it online, but there are other ways.

In most places for modern subdivisions, developers are required to submit a preliminary plan that almost always includes contours. The final subdivision plat in land records probably won't have the contours. You might check with the county planning department to see what they might have.

You can use a website like mytopo.com to get the contours from USGS topo maps. The problem here is finding where your property is on the map.

You can use Google Earth to draw the contours using the elevations from their database. It's a slow process if you are not skilled at drawing contours. I'm not sure of the accuracy but it should be good enough for your use.


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This morning I want to review the objectives for this property.

1. Discharge excessive water to prevent deep saturation of the soil behind the basement and retaining walls.

2. Using grade and soil permeability, caputure adaquate water to supply grass and plants while discharging all excess to achive objective 1.

3. Mitigate the potential damage from an extraordinary storm event.

Solutions should consider desired land use and esthic values of the landscape.

The need for objective 3 can only be assessed by looking at the size of the drainage area above the back retaining wall along with how steep the slope is. An area of 3000 sf would present little danger, but an area over 100,000 sf could lead to a 16 inch depth of water on the back patio as well as a 12 inch depth on the drive at the west end of the house along with heavy erosion damage in several areas.

Very few people understand the damage common to a 100 year storm event. You see it in the news sometimes. For every life lost in such a storm there often are hundreds of homes that sustain heavy damages not covered by insurance. Flash flooding can occur almost anywhere. Any grading project should consider this. Small changes in design can reduce the risk.

The accuracy of the base map is coming along nicely. There is still some uncertainty that can be improved with a few more measurements.

In the graphic above I show the fence at the far side of the garden to be 2 feet from the wall corner. I suspect that it is really just at the outside edge of the wall corner?

Note the red dot on the back wall that is in line with the NW end of the house. Please find this point and then make the measurement west to where the wall starts to curve. Size of the garden is also needed. On the other side of the landscape the decorative part of the patio (shaded) in the photos looks to be square? I need some help understanding the rest of this area.


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Looks great. Yes, the fence is even with the edge of the retaining wall, so bump it 2 feet over. The decorative portion of the patio connects to painted concrete that connects to the driveway. So it is all one continuous area of concrete. I cut the measurements off at the corner of the house(back side of the arbor). The wall actually continues to parallel the side driveway further past the corner of the house/ back of the arbor. I can get these measurements if you think we need them, but any drainage to the driveway is carried away by the existing drain discussed at the beginning of this thread. In the aerial in my first post, I highlighted the retaining wall extending past the corner of the house. We will have to extend the plot map to include this area. I will also get the other measurements.

I am also going to load a few topo maps that might help with the contours and elevation. Let me know what follow up questions you have.

This post was edited by OnAHillside on Sun, Jan 27, 13 at 23:32


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This will show the property boundaries as it relates to the topo map above. I am the corner lot where the red arrow is pointing above.


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Edit: Here is another view.

This post was edited by OnAHillside on Sun, Jan 27, 13 at 20:20


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From the red dot (even with the corner of the house) to the curve of the wall is 37'.

Edit: The garden is 21'.

What is the best way to determine the size and slope of the area that is draining to the back yard? I've attached a graphic to discuss how the uphill drainage works. The measurements are examples only for discussion. The contour of the land above the retaining wall creates a "triangle" type of drainage towards the house. The base of the triangle (which is the retaining wall) is the widest point of the triangle, and the triangle tapers in the further uphill you go. The top of the hill flattens out. So everything within the triangle drains towards our problem area, and everything outside of the triangle drains towards the neighbors property to the west, and towards the road to the east.

Edit: After looking into this some more (google). It looks like I just need to calculate the area of a trapezoid. That is basically the shape I sketched above. I plugged in some estimated numbers based on the lot size and the measurements we have made so far. I'm estimating the area to be somewhere between 15,000 - 20,000 square feet. I'll take actual measurements to confirm this. That should get us in the ball park.

Also, the slope of the hill is fairly constant. Can we estimate this slope by taking a sample measurement with a 2x4 and a level? Then we just project that slope onto the entire the drainage area.

Would this information along with the topo maps give us what we need to determine the 100 year "high water mark"?

This post was edited by OnAHillside on Mon, Jan 28, 13 at 0:06


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There are parts of your last post that are confusing to me ..."and everything outside of the triangle drains towards the neighbors property to the west, and towards the road to the east. "

The contours from your graphics are all from USGS Topo maps and are not exactly what I expected based on the photos, the lot lines, and the street locations. The USGS data may be 70 years old from the technology of the time. I reviewed the area in Google Earth and I believe that data to be better in this case, shown in the graphic below.

The house appears to have been built across a natural drainage area, all of the water flowing to the pipe across the street in front of the house. The amount of water coming through this area hasn't changed because a house was built. The size of this pipe will give some idea about the quantity of water. You should measure the pipe diameter. Drainage pipes under roads are commonly sized to carry the flow from a twenty year storm event. Flows from a 100 year event can be much greater.

Based on the GE contours I have shaded the probable drainage area that looks to be around 40,000 sf. There is the possibility of a pipe across the main road that would add to the drainage. There is a smaller area that flows toward the upper drive and from your texts I assume this flow crosses the drive near the house.

From the graphic, when you get a downpour of 1.5 inches over an hour period, a lot of the rainfall will be in a 20 minute period. About 5 to 10 minutes after the most intense rain, I would expect to see a significant flow over the top of the upper wall at some point and large areas in the back yard with depths of 2 to three inches, maybe even overflowing the brick retaining wall. A 100 year storm is likely to produce flows 10 times greater.

From the info provided by you and the aerial photos I think we have all the data needed to draw an accurate base map. The next move will be to follow Yardvaark's suggestion to add elevation data. I will post some ideas on how you might collect the data.


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That looks great. I am going to defer to you on the drainage and contours. I've added the locations of the pipe, city drainage ditches, and drain that carries the water from the downspout, concrete patio, and side driveway. Also, there is no creek on the property.

The drainage area look fairly accurate. I've included another image in a second post below to show you what i mean by everything "east of the triangle drains towards the road". meaning it drains towards the city drainage ditch and into the pipe going under the side driveway. So i don't think the entire area is draining directly to the back yard, however i don't mind erring on the conservative side in designing the solution. I would rather we design a solution to handle more water than less water.


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RE: Drainage Issue

The water on this side of the hillside drains to the city drainage ditch.

I will begin working on the information that yardvaark requested.


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Here are the grade measurements on our most recent plot map. All measurements are in inches. Point 1 is the base point. So I zeroed out this measurement. All other measurements are based off of this zero point. In other words, point 1 is the highest point in the yard. All measurements are measured down from the level line. For example point 2 is 5" below the level line, point 3 is 15" below the level line, and so on.

Points 4, 5, and 6 are at the edge of the garden. 7,8,and 9 are at the corner of the house. 10,11,12, and 13 are at the edge of the build out. 14,15,and 16 are even with the edge of the concrete patio.

Let me know what other information I can get. Hopefully we are getting close.


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OnAHillside, I transferred your point elevation information to the plan, adding 18" to all points so that we would end up working with positive elevations instead of using negative numbers. It makes it easier to understand and it becomes immediately clear where there are some serious grade issues within the yard. It seems that grading is sloped toward the house ... the exact opposite of what you'd want and some of it is at a frightening level ... between points 12 and 13, for example. It seems that even the concrete slab slopes toward the house. If you posted a photo of the back face of the house, I haven't seen it yet, but the question arises, has soil sunk around the foundation? It would be an asset IF the grade could be raised at the house.Grade must slope away from the house and it can only happen by adding soil at the house or by removing it farther away. The other obvious problem is what you first brought up ... water being trapped between the concrete slab and the garden area. With that I'll pause to see what pls8xx brings up that will interface with this.

Sorry, all. I blew the sketch up to make it readable but GardenWeb insists on shrinking it.


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I noticed point 8 was missing and added it. Again. For some reason it wants to jump out of place.


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Here are a few images of the back of the house. It's a hard picture because of the the thick trees on the hillside.

None of the measurements were taken from the concrete slab, just next to it. The slab is graded with a shallow channel running diagonally across the slab. So the concrete is graded away from the house in order for the water to run towards the drain. See my post on 1/28 at 14:19, it's the white drain I drew on the east corner of the house.

I agree that the grade has to be fixed. I think it is going to involve moving soil from the high sides of the yard to the foundation. It sounds like you guys are leaning towards digging a swale close to the keystone wall, so this soil could be moved to the foundation to increase the grade.


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View towards the garden. I prefer to keep the garden in it's current location as this is the only part of the back yard that gets full sun all day. However, I don't mind re-working it to make the drainage work. Including digging the garden down to lower the overall grade of the yard.


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We need the elevations points of the concrete slab (just its corners.) It's a fixed element and grade would/could/should meet it (even if it doesn't now.)

Do any of the elevations provided represent the fixed wooden retaining wall/curb that divides the lawn area from the garden? As it's fixed, it would be necessary to know these, too

What we're looking for in photo shots of back of house is to see how grade meets the foundation, the view of which is pretty much obliterated by the pine tree. Pics taken from bottom of keystone wall might catch it.

Likely there will be a swale. Need to determine how high can soil be added to foundation. At garden, you would not want lots of fast water moving across exposed soil. It might necessitate a water-carrying structure to span it.


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RE: Drainage Issue

Points 4,5,and 6 were taken on the grass side of the rail road ties next the garden. I didn't measure from the top of the RR ties. I assume I will have to remove these in the project, so I only measured the grade of the ground.

Points 14 and 15 should be an accurate grade for the North corner of the patio. I will have to get the grade for the other corners this evening.

I'll snap some more pictures this evening. However, there is no swale or build up at the foundation. The same negative grade continues all the way to the brick. Also, you can see the build out/bay window is pretty close to on grade in the last two pictures I posted. So there is not much room to build up the grade at that section of the house.


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RE: Drainage Issue

It looks at the bay window that grade cannot be increased. It's elsewhere about what can happen that there is a question.

Presuming you already think the wood retainer at the garden will need moving/adjusting, it's a good bed that it's the case. So we'll go with what we have for now. We might eventually need an elevation for the top of the brick wall near the garden. It's just a "heads up."


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RE: Drainage Issue

Before I move on to the property elevations I have one more question. What is the pipe dia. under the upper driveway near the main road?


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RE: Drainage Issue

pls8xx, 15" diameter for the pipe under the upper driveway. Same diameter as the pipe running under the front yard and lower driveway.

Also, the pipe running under the cul-de-sac should read 35" not 35'. Just want to point out that it's a culvert, not a large drainage bridge.

Yardvark, I'll get the brick retaining wall measurement as well.

This post was edited by OnAHillside on Tue, Jan 29, 13 at 13:16


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RE: Drainage Issue

Just as with the horizontal dimensions for the base map, I think we will need some corrections, refinement, and additions to the elevation data.

Near the top of this thread there are some string line developed measurements shown in profile. Profile #2 appears to be across the yard in the same location as the latest data for points 7,8 and 9. The two are not compatible.

Elevation data can be collected in a number of different ways. String lines have an advantage because it's simple and you already have the equipment. The disadvantage is that precision drops as the string line lengthens, the level device often lacks accuracy, and it's often hard to get measurements in the places needed.

The objective is to determine the elevation of landscape elements such that the relative height of any element can be compared all other elements.

The process involves a lot of adding and subtraction. For this reason it's much easier to take the measurements in feet, tenths, and hundreds of a foot rather than feet and inches. There are tapes and rulers set up this way. This applies no matter what method is used to collect the data. Below is a combination tape, tenths on top, inches below.

The elevation of some elements in the landscape is more important than others and should have a higher precision. In your case this would be the finished floor elevation of the house, the elevation of the top of the brick retaining wall, the corners of the patio, the base of the upper retaining wall, and the bottom of the lowest horizontal board on the fence at the back of the garden.

There are some tricks to getting accurate data with a string line using stakes. There is nothing gained by having the string system be at ground level at any point. In you graphic, suppose you start with a stake at point #2 with a string attached 1.00 above ground level. Next a stake is set at point #16 at the patio edge. With the level device attached at the mid point the string is stretched tight and adjusted up and down on the stake at 16 until level. Next a stake is set at point #15 and a level string extended from 16 over to 15. With the level again at mid point, the string is run back across the yard to a stake at point 1. The level is then checked between the short distance #1 to #2. The amount of error is an indication of accuracy achieved. More than 0.1 of a foot is probably not acceptable and you need a more accurate string level.

Since the house is brick, you can use the accuracy of the mason's work to your advantage. You will need a couple of boards (2 x4 work nicely) and some tape (masking tape).

As shown above, set one board flat on the floor inside the door at an angle. Put the 2nd board on top, extended out the door to the brick. Assume the floor elevation to be 100.00. Two 2x4s are about 0.25', so add this to get the elevation at the top of the boards. Measure the distance from the board up to the top of the next course of brick and add to find the elevation of that course of bricks. Mark that course with tape in several places along the wall and record the elevation.

In your case the siding interrupts following the brick course to the west. But you can can go up from the brick course to a siding line and follow that around to where the brick starts again and go down to be back on the same brick course.

By knowing the elevation of the brick course, you can measure down at any point around the house to determine the elevation of the ground, patio, or the retaining wall at the house corner. (subtract the measurement from the brick course elevation. You can also extend a level string line from the brick course to a point in the yard for additional measurements.

Note that it is just as important to know the horizontal location as it is to get the elevation right.


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RE: Drainage Issue

pls8xx probably has a better chance of extracting serious accuracy of this than I so until that's developed or sorted out, I'll snooze. Meanwhile, I'll be wondering where is the high point at which runoff water will divide and choose it's course down and out. Where...??


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RE: Drainage Issue

Thanks again to both of you for the help and input. As long as you guys keep asking questions, I'll keep getting answers. This is definitely a more in depth analysis than I had imagined, but that's a good thing. Yardvaark, I believe the divide point to be outside of the fence on the north side of the garden. Diagonal from the corner of the driveway retaining wall.

In regards to the consistency of the measurements. Profile view #2 was taken at points 1,2,3 (bad description on my part of profile #2). Also profile #2 was measured all the way to the brick retaining wall. I couldn't do that with point number 3 of the updated measurements because trees and bushes are in the way of running the line all the way to the patio. So the measurements are consistent in elevation change, just different measuring points. FYI profile #1 was taken at points 10,11,12,13. Again the measurement point varied due to placement of the lines. Profile #3 was points 3-16.

I'll work on the measurements as compared to the elevation of the finished floor. We might have to do some math because i don't have a tenths tape measure. I'll sort out the math if it's going to be a problem.

I believe I understand what you mean by using the bricks as our level line. We will arbitrarily assign the elevation of the finished floor 100, and then report all measurements relative to 100.

Also, I see the wooden fence in the same light as the railroad ties. If it needs to be moved or adjusted, then that is what I am going to do. My #1 priority is getting the water away from my foundation. So digging up the yard, removing fencing/rail road ties, putting a permanent ditch through the middle of the yard, etc, is in play to get the water away from my foundation. That is much cheaper than repairing a cracked/leaking/failed foundation wall.


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"Yardvaark, I believe the divide point to be..." Well, I was thinking out loud. what I meant was not where it is now, but where we need to put it in order to drain the yard in the most efficient way possible. The ideas about it can only be toyed with now. After we see what grade can be at house, then we can determine what it can be elsewhere.


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RE: Drainage Issue

A bit about fences and flood flows. For common rainfall, water may trickle down a slope at a slow speed. But for major storms some areas often have flows of 1 inch or more. Then the velocity increases where leaves and debris are then carried along with the water.

When the flow hits a fence the leaves clog the openings and the fence becomes a dam. Water backs up behind the fence until it breaks through the fence or finds another route around it.

Fences can cause flooding where one would not expect it.


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RE: Drainage Issue

Ok guys, to keep the conversation moving until I obtain the new elevation measurements (might be a day or two). What kind of solution are we looking at for my yard?

We have received a significant amount of rain this morning, and my yard is pooled up again. I believe I understand why there is no standing water next to the foundation, while there is standing water in the rest of the yard. If they back filled with the appropriate washed gravel and installed the 4" corrugated pipe at the base of the foundation, then the entire backyard is being drained to the foundation wall and exiting through the corrugated pipe. In my opinion, this is the worst case scenario for the back yard drainage. The pipe at the foundation is there to get rid of any incidental water that happens to reach the foundation, NOT drain the entire yard!

I've also found a hairline crack in my basement wall that has moisture coming through. This is the first time I've seen any moisture come through that crack, but the ground has been saturated for 2 weeks. I guess the rain today was too much. The crack is located directly beneath the north corner of the bay window. The moisture is only a few wet spots on the concrete wall as of right now, but it is moisture in the basement none the less. I will post some pictures of the yard and the foundation this evening.

So now that I am all worked up about the rain today, what are we looking at as a solution?
Digging out the back yard to create the appropriate slope away from the foundation?
Digging a permanent ditch around the corner of the driveway retaining wall?
Pouring concrete over the entire damn yard to make it waterproof???


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RE: Drainage Issue

"If they back filled with the appropriate washed gravel and installed the 4" corrugated pipe at the base of the foundation, then the entire backyard is being drained to the foundation wall and exiting through the corrugated pipe."

I suspected that to be the case from the photos you posted. And no, that's not good.

Before we look at the drainage fix, one last look at the flooding risk.

As water flows down a slope the velocity is largely dictated by the steepness of the grade. For any point along the slope, the quantity passing the point is the same. If the slope changes grade to a flatter run, to maintain the quantity of the same flow. the slower speed must be offset by a wider or deeper flow.

In your case a steep slope empties on to a flat backyard. Moreover there is no place for the flow to widen, meaning it must be deeper.

I have revised my estimate of the drainage area above the wall downward to around 30,000 sf. But the flow along the main road can't be dismissed. With a major storm the 35" pipe may flow full. Add to that a lot of flow down the NW side of the road. When it gets to the 15" pipe under the driveway there's a problem. A 15" pipe has a capacity about 25% that of a 35" pipe. With the added road flow, probably only 10 to 15% of the water will go through the driveway pipe. The rest will go elsewhere and that would be toward the SE corner of your house.

The situation is not dire, but it does point out the need to slope the backyard to speed up the discharge of water. Since your back door is well above the patio grade, it wont be the end of the world if you have a few inches of water on your patio for a short period of time.

The patio end is all concrete, so the other end must be either raised or lowered to create some slope. Raising the garden grade is probably out because of the brick retaining wall and you already have more water than wanted at the patio end from the road.

Thus the answer looks to be a lowered garden area that can serve as a drain way for major storms across it's entire width with a smaller and slightly deeper channel for ordinary rainfall.


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RE: Drainage Issue

While we're passing time, here are a few questions you can answer as we move into the design phase.

Are you looking for a plan that a contractor can complete or does this need to lean toward DIY? If DIY, can you give us some idea of you resources? Are you 25 and look like you spend half you time in a gym or an old guy like me that a stiff wind would blow over? Have you done DIY projects? Tools? Do you have friends or family that can help.

Do you have a preference for type of grass?

Is the garden a land use you want to keep. Are there other uses you need to find a place for in the landscape.


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RE: Drainage Issue

pls8xx,your drainage map looks spot on, including where the water is headed when the 15" pipe is over capacity. I'm guessing you have done this once or twice.

I can't argue with the logic behind lowering the garden and using that as a spill way. That sounds like it accounts for the worst case scenario of the 15" pipe overflowing straight down the driveway to the backyard.

As far as my stats... haha. I fall into the under 30 category (barely), and I would consider myself a somewhat experienced do it yourselfer. I've renovated and flipped houses, installed irrigation systems, installed drainage systems (clearly not to the extent of this issue), etc. Tools include all the necessities for any kind of yard work/home repair job. I'm also not against renting a bobcat to move the dirt. I have some experience working on construction sites, forming and pouring concrete, and doing light bobcat work. I do have friends and family that will work for beer.

Grass type isn't a priority. Bermuda is what I have everywhere else on the property. I do want to keep the garden, if possible. However, fixing the drainage takes precedent over the garden. There are no other specific uses that I can think of.


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RE: Drainage Issue

"Do you have a preference for type of grass? Maui Wowie, but it's so hard to get! :O

It looks like that all this is leading toward running a swale through the back yard and garden area. Water coming off the patio could drain in the opposite direction (if we're sure that the patio is draining away from the house) which would put the "continental divide" at the left edge of the patio ("left" as in the plan views we've seen.) Lots of fast moving water is not a good fit for a garden. It might be worth it to channel water to the back side of the garden and put it in a lined channel of some kind. (If the wall was rebuilt so that it penetrated further into the ground, it would be easier to minimize the amount of space required for channeling water. (With a little time, I could snap a picture of a reasonably nearby example of this that would help explain it.)

Bummer on the yard draining through foundation drain. Not good. But you will fix.


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Glad they handled it, and gave some great ideas. I have been on a zoysia thing in the south lately as it seems to be more hardy in the worst part of summer for most cultivars.

I also just wanted to say I love the woods behind but would cut down those Pines nearest the house in a heartbeat. One day they will be 80 feet, towering above your home, on a hill pointed right at your home. You could go with some dogwoods or redbuds to give it a natural look back there and it would be truly pretty in spring, even magnolias such as little gem or Ann, Felix Jury, or any little girl/tulip/saucer magnolias would look really good. Another idea would be a couple of American Hollies. Personally with it facing south "just a guess from satilite", you could tier it so that the tops of the layers get light. I am an edible nut so I would have blackberries, blueberries, peaches, and pecans front to back layered among the ornamental trees then the larger pines in the back. Food certainly won't be getting any cheaper and the pines will give you free mulch every fall, you might just want to put down Lime to make your soil more alkaline with all the pine needles over time if you find it to be acidic "actually with all the pine needles all I can think of right now is fresh blueberries".

Its hard to tell but do you have the soil of chilton county? The Alabama black belt~

Here is my peach list for our new home in progress zn8tx
3 Chilton County Peaches 18-20 foot wide, Gulf King 57 days before, Southern Pearl 22 days before elberta, Winblo 15 days before Elberta, and fairtime 30 days after Elberta.

7 peaches =
quintessentially extends the peach season to 87 days nearly 3 months! "all freestone"

You defiantly need to take out those pines that are closest or look like they could one day lean. They are also pretty densely crowded. It will be 10x harder 5 years from now. I was in T-town during Katrina and we had roughly 60MPH winds. With the high winds with all these tornadoes/hurricanes I would be a little freaked out when those pines get about 20 years down the road if let alone from a home damage standpoint.

Also it will allow for less cleanup in the fall.


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Another idea I just had and think would be a really cool one is if you have a spot and a bunch of soil left over would be to find a way to try and drain a quantity of water into underground containers for home use or for watering. Yall probably get a decent rain every other week like most of Alabama and with the drought summers that would be a pretty cool idea.

After all you probably only need some beer, a bobcat and if you have a way to divert all you need is the pump, some basic pluming, the and the container. I imagine you could do it in a fraction of the cost if you will be doing an area where you could easily bury it.


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haha, I think there are other forums for growing that grass yardvaark.

I was thinking the same thing as far as channeling the water so the garden doesn't interfere, at least for typical rainfall. If a massive flood comes, then that garden will just have to hang on as best it can. I'll have to see that picture you are talking about, I don't follow.

Oceandweller, I've got all kind of grand plans for what to do with the hillside and the landscaping on the rest of the property. Fruit trees and blackberries are definitely in the design. Our neighborhood has a large deer population, so I have to plant the blackberries in secure locations. Pine tress will be coming down once I am ready to replace them. I don't want to create an erosion problem by cutting them down before I'm ready to plant the hillside.

The soil is a little more clay and rock than Chilton County, but that's not going to stop me from growing peaches. 87 days = a lot of peaches! Good idea with the catch basin. Once i get this water moving in the right direction, I'll take a closer look at catching it.

Still working on getting the elevation measurements for the plot map. Work is getting in the way.


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RE: Drainage Issue

"I've got all kind of grand plans for what to do with the hillside"

You will want to insure that the current project is compatible with any future goals. Will you want steps to access the hillside from your back yard? Where? Will you need a ramp to use a wheelbarrow or mower?

"The soil is a little more clay and rock than Chilton County"

I saw in the photos what appears be some stone in the undeveloped areas. Is it a type that might be used some way?

You may think it strange but I see real clay as a valuable resource for growing things. I prefer it to topsoil gardening.


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"If a massive flood comes, then that garden will just have to hang on as best it can." I once had an entire dump truck load of crusher run "disappear", carried away by rain water and that's how I paid a couple hundred bucks to have a storm teach me a lesson. With 5 minutes of the gravel being dumped, a storm struck up out of nowhere. In another couple of minutes, water was guided around the street's outside corner where it was released in a torrent to flow directly at my precious load of gravel. Unfortunately, the holding area was located just beyond where the street curb ended so water washed unrestrained over the land. While I stood and watched from my front porch, the ENTIRE pile disappeared from view in 20 minutes. There wasn't enough left to scrape up. But there are rainbows. When the rain subsided and after wiping away all my tears, I noticed the gravel came to good use for my "road widening" project just down the hill from my house. :)

(Later, in this same area, I learned how to use stormwater to fill in eroded areas. So its evil power can do good, too.)


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RE: Drainage Issue

Good call pls8xx. I want to install a staircase from the backyard to the top of the hill. The staircase would ideally be located across from the bay window. I plan on landscaping and using the hillside. So the staircase is going to provide the access we need. A ramp won't be necessary. It's hard enough to walk up the grade, so pushing a wheelbarrow doesn't interest me.

There are a lot of natural rocks and boulders on the property. They are used in the landscaping around the side of the house and front yard, so I wouldn't mind putting them to use elsewhere. Do you have any ideas?

Do you amend the clay before you plant? I've had good luck burying leaves and compost several months before I plant. It makes the clay easy to grow in.


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RE: Drainage Issue

Progress seems to gave slowed somewhat. In preparation for design and the addition of detail, I have completed a base map derived from the survey map, photos, field measurements. and aerial photos with the scale bumped up to 1" equals 10' (5 by 5 grid, each small square = 2ft). The drawing is now so large I'll post a link at the bottom.

If the regrading is done to minimize flooding risk, the critical point in design occurs across the yard from the point at the house/brick wall to the base of the upper wall. While we do not yet know the relative elevation of the three critical elements (patio, top of brick wall, and base of upper wall, there are some things that can be noted.

1. The new grade at this point should be a minimum of 0.7 below the patio grade to establish a slope to move water across the yard.

2. The new grade should be a minimum of 0.2 below the brick wall so that some flood flow is across the garden area before spilling over the brick wall.

3. The regrading should not disturb soil closer than 3 ft of the upper wall.

4. Just past this point there will need to be a slightly lower channel to carry normal rainfall through the garden area as Yardvaark noted. The channel can be located along the brick wall, on the other side 3 ft from the upper wall. or through the middle of the garden.

Here is a link that might be useful: Base Map


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RE: Drainage Issue

Ok, here are the measurements. Let me know if we need more, but hopefully this will give us what we need. I went ahead and converted the inches to tenths (measurement in inches/12).

Again, I plan on removing the fence during the dig, and I will adjust it accordingly once the project is done. I made the fence measurement off of the retaining wall. The fence is buried as it extends towards the keystone wall. It will probably help to remove the fence from consideration in the final solution.


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RE: Drainage Issue

Nice work!

I have another request. Working from the top of the brick wall, elevation 98.29, can you string line to confirm the elevation at the base of the upper wall at the three points marked with a red dot. Also needed is the distance from the corner of the brick wall over to the upper wall where marked with a "?"


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RE: Drainage Issue

Sounds good. I'll get those measurements within the next couple of days.

In regards to the smaller ditch to carry away normal rain water. Is that within the 3 feet of undisturbed dirt next to the keystone wall, or within the swale?

"The new grade at this point should be a minimum of 0.7 below the patio grade to establish a slope to move water across the yard."
Where is the .7 measured, edge of the fence, edge of the patio, etc?


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RE: Drainage Issue

Here's the picture of the swale at the wall. (Sorry it took long to get it.) It requires the wall to go deeper into the earth but means that the swale does not need to take up so much width as it passes through a space. Lining the channel with erosion-proof material and making it deeper would be a way for the channel to be even less wide.


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RE: Drainage Issue

I have some general comments on this thread.

Before spending a lot of money on surface structures and plants, homeowners should always consider any needed regrading and drainage improvements. The ground work comes first or you will often destroy the surface improvements to correct the grades.

I hope this tread highlights the difference in a free garden plan from a nursery and that of a professional landscape firm with a large design fee. There is a huge difference in the service provided.

Over the years some of the pros here have expressed reservations on the possibility of remote design, mostly from a lack of ability of the homeowner to adequately define the existing landscape. My feeling is that in this case that has been overcome and the resulting base map has a similar precision to that which most could use in combination with the many photos. I have a completed map but I'll wait to post it until the after last couple of vertical measurements are made.

An economical regrading dictates the dirt removed from one place be balanced with the quantity of dirt placed elsewhere in the landscape resulting in an improvement to both areas and avoiding the expense of bringing in or hauling off dirt. This project has identified an area where a significant amount of dirt will need to be removed. It's time to consider where that dirt will go.


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RE: Drainage Issue

Alright, here are the next set of measurements. Work really got in the way this week. Let me know what other measurements I can get.

All of these were measured based on the 98.29' measurement taken from the top of the retaining wall.


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RE: Drainage Issue

I have corrected the small misalignment I had of the wall in the base map.

The elevations for the positions 'C' and 'D' are somewhat higher than I expected. The higher grades there will have a significant impact to possible solutions to the grading. Since it is very easy to make a one foot error in the measurement and math, I suggest you check these two elevations.


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RE: Drainage Issue

Those are the measurements. I checked it twice when i took the measurements and when I did the math. That is the highest point in the yard.


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RE: Drainage Issue

The existing contours indicate the flow that is causing a problem and clearly show the difficulty in pushing the water to flow against the natural slope and around the corner of the retaining wall.

Below are a couple of graphics for discussion.

The most difficult slope for regrading is at the back of the garden area (profile 'A' in the plan view). It would appear the homeowner built part of the block wall was laid on a slant resulting in the base of the wall being 1.4 ft higher at this location. To achieve a flat garden area that would serve as an emergency floodway for major storms, creates a grade differential of about 2.4 ft. While this could be overcome with a 2.4' wall, lack of access to the area for a concrete truck leads me to believe for a DIY project a terraced approach with two 16" walls would easier for homeowner construction.


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RE: Drainage Issue

ps8xx, what are the contour intervals in the plan views?


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RE: Drainage Issue

Contours: Note lines between EL 100 & 99; 0.2 interval.


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Quite an investment you've got in effort, pls8xx. I confess I am not keeping up with all the details since it was established that the existing grade is out of whack. Could you please confirm that the violet colored lines are the terraced walls of which you speak and what sort of drainage structure is represented by the turquoise blue lines?

It seems like this project boils down to making the yard whole (like it was supposed to be but never was) or making it work in spite of the fact that some things are not ideal. Doing either of those things weighs against whatever resources there are to accomplish them and it sounds like the OP has not only experience and other resources (equipment and labor) but quite a bit of ingenuity and a good grasp of the issues as well. If the yard were to be made whole, the vision I have of it is that it is graded to contain a swale that begins not far from the concrete pad and passes through the garden, around the corner of the driveway retaining wall and down the chute, still in a swale. Certain portions of that may be reinforced or protected by special surfaces, as needed. It would require regrading and rebuilding of the keystone wall from the vicinity of its portion which juts outward. So it wouldn't exactly be an inexpensive project. But accomplishing it maximizes the usable yard space and drains water away from the house without using underground drainage structures.


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RE: Drainage Issue

Wow, the graphics look great. I want to thank you again for the time and expertise you are sharing with me. I'm impressed with how you were able to put the entire issue together based on the snip-its of information I was able to provide.

As far as the tiered wall, what kind of wall are you thinking? Is this going to be additional layers of keystone, or is it just a terraced area of the yard (as in no wall support needed)?

I'm also wondering the same thing as yardvaark in regards to the swale design. In profile C it looks like the yard is flat except for the turquoise ditch to carry the rain water. Would we not need a shallow swale spanning the area between the driveway retaining wall to the base of the keystone wall to carry away the water from a large storm?


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RE: Drainage Issue

"Quite an investment you've got in effort, pls8xx."

Some people like to work crossword puzzles. I'm no good with crosswords.

Like Yardvaark, I'm tempted to think of the possibilities that a generous budget would allow. In some areas of this country this house would appraise at more than a million dollars, the existing landscape would devalue the property, and a $50,000 project would be appropriate. The badly built block wall could be totally removed and new appropriate walls built to enlarge the usable backyard and better aesthetics.

In this location a $50k project would probably not increase the value more than 10 to 15 thousand; a bad investment. It comes down to as Yardvaark put it "making it work in spite of the fact that some things are not ideal."

The turquoise lines do represent one possibility to move common rain flow through the garden area. Yardvaark earlier pointed out that a swale or channel can be wide and shallow or narrow and deep. And there is also the choice of location across the garden. Design should consider how the channel will impact gardening the area as well as aesthetics.

I'm thinking a channel of about 3 feet wide provides access to the garden and reduces the foot traffic across the grow area without taking up much space and probably need not be overly deep. Tall vining crops such as pole beans could be grown along the side on an arch over the walk for easy harvest.

For aesthetics, the principal view is from the patio and maybe the bay window. I like the idea of a channel centered in the view. Maybe the fence at the back can be relocated to the front and some sort of entrance arch placed at the channel. The channel can be grass, but if it is Bermuda, there will be a continuous battle against encroachment in the garden. Since the owner has experience with concrete I would suggest a concrete walk as a channel with side curbs 4 to 6 inches tall.

The other lines denote a possible location for low terrace walls. The grade close to the block wall should not be disturbed less the wall be destabilized. I suggest about a 3 foot strip. The climate does not produce frozen soil, so deep footers are not needed. Poured concrete walls up to 16 inches tall are easy for any homeowner to do. A 3.5 inch wall thickness is suitable and reduces the concrete needed, which is important where a concrete truck can't get to the site and quantity needed dictates a on-site mix. And if that block wall should ever fail and the whole area is to be improved in a future project, 3.5 inch walls are easy to take out with a sledge.


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RE: Drainage Issue

A $50,000 backyard upgrade is slightly outside of the scope of this project.... I can appreciate big thoughts, but they will have to stay as thoughts for the time being.

I was thinking of lining the swale through the garden with rocks. Similar to the picture. I like this look better than the idea of adding more concrete to the back yard area.

Also, is there any reason that I can't create a steep slope downward from the 3' mark beneath the wall. Instead of creating terraced steps from the base of the wall, couldn't i just slope it downwards to create one side of the swale? In other words, the swale will be located near the keystone wall.


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RE: Drainage Issue

Could you make the grade transition with a slope? Yes, but even at a 4 to 1 slope (too steep for a garden) the slope would take up most of the garden area; 3 ft from the wall plus 10 ft (2.4 x 4 =9.6), leaving too little width to discharge major storm flow. An additional strip for the channel leaves little for a garden (3+10+3=16 ft from a total of around 20 ft for the area.

I would expect material cost for the wall to be a bit over $200, with one day building forms and 1 to 2 days for the pour with help from your buddies.

Stone could be used for the channel, but I would want a very flat stone since you will be walking across it a lot.


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If we concede the keystone wall side of the garden to the slope and swale (no gardening on the slope), then could we use a slope of 2:1 or even 1.5:1. This results in 3 feet of undisturbed ground, 4.8 (2x2.4) feet of slope, and 3 feet of swale= 10.8 feet. This leaves about half of the total 20' area for gardening. I could elongate the garden into the yard for more growing space if necessary. Would that setup work as an alternative to building the terraced walls?


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RE: Drainage Issue

If the subsoil has a high clay content the answer is yes in the short term. It wont be pretty. In the long term you will have to leave the bank dry, no watering the upper level around the block wall. Expect any plants there to dry up and die. And whether water comes over the block wall in this location will determine what level of erosion occurs. At some point the walls will probably become necessary.


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RE: Drainage Issue

There is also the option of ignoring the risk of a major storm event and building a channel along the brick wall to handle ordinary rains. It should probably be concrete to protect against water getting to the backfill behind the wall. This would require little excavation that could be done by hand. Not everyone wants to design for flash floods. And your garden area would still be on a slope.


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RE: Drainage Issue

That's good info on the slope. I actually went ahead and hand dug a ditch through the yard last weekend. We've been getting a lot of rain, and I had to do something to address the water that is currently pooling in the yard (control issues on my part...). The ditch is actually moving the water away form the backyard fairly well, but it does not address the overall issue of the yard having the wrong grade. In order to execute the ditch option properly, i still have to solve the grade. In order to solve the grade, i have to remove a significant amount of dirt. Removing the dirt will still leave us with the same terracing issue near the retaining wall. I guess what I'm getting at is I'm not super excited about adding 16" walls in the back yard. Not that I won't do that if necessary, but I'm trying to think around that right now.

I guess another option is to take down the retaining wall near the garden, dig to the appropriate elevation, and then rebuild the wall with a few additional rows of block.


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RE: Drainage Issue

Don't even think about rebuilding that wall at a lower elevation with added height. The wall is already higher than the block is rated for. You would almost be sure to have a wall failure.

There are other types of block that can be used to build a 4.5 ft wall. They are much more expensive. To do the job right requires tools and skills a homeowner doesn't have. In a warm climate a poured wall is cheaper and stronger and can be veneered with stone or other material to look much better.


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RE: Drainage Issue

Onahillside, regarding the drainage channel through the garden, you could make it like the picture of stone you show, or a dished out concrete walk with stone (width as needed) lining the sides at a sloped angle. If you can't use concrete for the center of the channel, then--agreed with pls8xx--flat surface stones would be much better.

Good move on digging your temporary drainage channel.

It could cost much less than $50K, depending on your skills and resources, so explore all options. If you're willing and able to DIY much of it, the cost could come down significantly.


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RE: Drainage Issue

Ok, so to review the key points on what we determined. The yard needs to be regraded to move water away from the house. We have to dig out the yard because the bay window will not allow us to add more dirt against the building.

Profile C is the key point of the project. The elevation will need to be .7' below the patio elevation in order to have the proper slope in the yard. Question #1: What is the proper slope that I should maintain from the patio to the garden?

The elevation at profile C will also need to be .2' below the brick retaining wall. The change in elevations requires the construction of 2 16" x 3.5" walls in order to keep the integrity of the block retaining wall.

Question #2; In order to have the proper grade at the house, what slope do I need to have running away from the house towards the middle of the yard (Profile A)? It seems like this is going to create the swale shape for the entire yard. In other words, the swale to handle flash flood waters is going to be created as a by product of correcting the grade from the house.

The other key point of the solution is to build a channel through the yard to carry away normal rain waters. This channel should be 3' wide. Question #3; how deep should the channel be?

Question #4; What size does the channel need to be once it turns the corner and is running down hill? The slope increases significantly at this point. Do I need a deeper channel, or should I maintain the same size channel?


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RE: Drainage Issue

Profile C is the key point of the project. The elevation will need to be .7' below the patio elevation in order to have the proper slope in the yard. Question #1: What is the proper slope that I should maintain from the patio to the garden?

The elevation at profile C will also need to be .2' below the brick retaining wall. The change in elevations requires the construction of 2 16" x 3.5" walls in order to keep the integrity of the block retaining wall.

While Profile C is that area most adverse to the desired water flow, it is the elevation of the brick wall where it joins the house midway between profile A & B that is a critical grade point 0.7' below the patio (0.2' below top of wall). From that point the grade must continue downward through the garden channel. The garden area can have less slope to the back. A standard for minimum slope for grass is 2%. From the patio to the brick wall is about 30', so the 0.7' drop is satisfactory.

Question #2; In order to have the proper grade at the house, what slope do I need to have running away from the house towards the middle of the yard (Profile A)? It seems like this is going to create the swale shape for the entire yard. In other words, the swale to handle flash flood waters is going to be created as a by product of correcting the grade from the house.

A flow directly away from the house is not very feasible in this case, but a mostly lateral flow slightly away from the house can be made to remove all of the water.

The other key point of the solution is to build a channel through the yard to carry away normal rain waters. This channel should be 3' wide. Question #3; how deep should the channel be?

I don't think I would do a defined channel through the yard area, better to keep the flow spread as wide as possible. Below is a rough drawing of what the new grading might look like.


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RE: Drainage Issue

I would lean toward carving out the swale slightly nearer to the beginning of yard drainage in order to direct water away from the house face (as opposed to lateral to it.) Onahillside, I would not think of the through-the-garden-drainage channel as a separate structure, but more of a LINING to the swale that is going through the yard. If fast moving water passes over loose earth, which a garden pretty much always is, then it can easily grab that loose dirt and pull lots of it with the water. The lining prevents that or, at least, minimizes it in a major flow.


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RE: Drainage Issue

Breakthrough!!! I've finally fixed a key piece of the puzzle! Until this morning, I have not been able to find the end of the foundation drain. As I noted previously, my driveway will stay wet for weeks after a rain. Well I finally found the drain, and it is now flowing without a problem.

I was digging off of the end of the retaining wall (right at the base of the column in the picture), and I knocked a hole in the pipe. I had water bubling out of the ground like a hose pipe. I kept digging and realized it was the foundation drain. So i uncovered a section of the pipe and pulled open one of the joints. When i did that, it shot out like a fire hose. It has been draining for about 2 hours now.

Apparently the foundation drain is crimped or clogged somewhere beyond the joint i un-did. As soon as I opened up that pipe, my driveway immediately began to dry out. No more weeping from the base of the retaining wall!! I can only assume that water has been sitting at the base of the foundation and retaining wall for years. Finally I have a functioning drainage system. I think we are on our way to fixing this problem now. We are diverting the water away from the house with the ditch in the back yard AND we are effetively draining away any water that makes its way down to the base of the foundation.

I'll tell you, i've never been so excited to see flowing water. I finally feel like I've turned the corner on this water issue.


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RE: Drainage Issue

Congratulations on your important discovery. Your thread serves to illustrate just how troublesome underground drainage can be, especially if one is not the original installer. Things get forgotten about, lost, covered and can be very difficult for a new owner to find and figure out. Usually, a small taste of these difficulties is enough to persuade one that keeping drainage above ground, if possible, is a preferable solution. It's probably a wonder that your retaining wall is still in good condition, in spite of the lack of drainage. It sounds like you'll be able to get things in shape with less grief than originally thought. Good luck!


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RE: Drainage Issue

Back again. I'm making good progress on the back yard. I've got a large portion of the sod removed, and I'm working on moving the dirt out of the yard. I've been going at this project with a wheel barrow and shovel so far. I don't have the free time from work this time of year to rent the necessary equipment. It is working out well because I am filling in around the foundation and other areas of the yard with the loads of dirt I'm moving.

My question today is concerning the drainage channel that begins at the garden. The deeper I can make this channel means the greater the slope of the swale between the patio and the garden. The problem with going deeper is that i will have a substatial ditch after a while. A substantail ditch is not only unsightly, but it is also a safety hazard.

My idea I'm tossing around now is digging the substantial ditch and back filling it with gravel. The back filled gravel will basically allow the ditch to drain, but not create a safety hazard. What are the cons of backfilling a ditch with gravel?


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RE: Drainage Issue

Now that I am thinking about this ditch, what are the cons of installing a french drain at the bottom of the ditch? This will allow me to dig as deep as I want, will cath all of the run off water, and the overall grade and swale will still catch all of the water from a flood event.

I can dig this ditch down several feet, install a PVC pipe with drain holes, landscape fabric, and backfill with gravel. This will serve the purpose of the channel. If there is a large rainfall event that overwhelms the pipe, then it will just run through the swale just like the pipe wasn't there.

I know you guys are not fans of underground drainage, but what is the down side if this is done in conjunction with all of the other measures we have discussed previously? The grade will still be correct, the yard will be swaled to act as an overflow for a 100 year event, and the normal rain water will still be carried away through the french drain.
It seems like this would only enhance the design as a whole. Even in the event of a complte failure during a severe rainfall, the swale will still carry away the water. I highlighted the location of the drain in red. Thoughts?


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RE: Drainage Issue

Do you mean that the red lines represent a gravel surface water collection channel? Having a gravel channel run through the yard seems like the main negative point for a system that may clog at some point (though it could last several years.) Other drawbacks would be its cost or effort required to install. What would be the objective or main benefit of installing such a system?


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RE: Drainage Issue

I strongly advise against a french drain anywhere in your backyard. While a french drain can dry the soil at the surface, it also causes the soil below the pipe elevation to become wetter. In your case, over a few years there is the potential to completely saturate the clay subsoil. If the clay expands it can place a huge load on the house foundation and retaining wall. The wall drainage system does not protect against this hazard. Considering the expected volume of water, a couple of 4 inch pipes wont make that much difference in the surface flow anyway. In short, a french drain would be a lot of work and expense with little benefit and the potential for great harm.

As for using gravel for the surface on the channel through garden, I don't think that is a good idea. Suppose you get a 2 inch storm with a 1.5 inch runoff from 36,000 sq ft, with a 1 inch runoff peak over 20 minutes. That yields 3,000 cu ft of water (23,000 gal) that has to flow through the garden in a 20 minute period, or 150 cu ft per minute, 2.5 cu ft per second. For a 3 ft wide channel with a 2 inch depth of flow, you get 0.5 cu ft of discharge for every foot of velocity. Thus the volume of water handled requires a flow speed of 5 ft per second at a 2 inch depth. Most gravel wont stay put under those conditions. If you elect to go with gravel, I suggest you widen the channel to 6 feet.


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RE: Drainage Issue

The main benefit is to maintain the usefullness of the yard. A gravel filled ditch can be walked on, a wheelbarrow can be rolled over it, etc.

How would a french drain saturate the soil below the drain anymore than an open air ditch? Both systems would be sloping downhill. It would seem like evaporation would be the only difference.

It's not the flow rate that I am worried about. It is the functionality of the yard on a daily basis. The flow will be handled with or without a pipe. An overwhelmed french drain would make no difference since it would be located at the bottom of the swale. It is all headed down hill whether it's through the pipe or over the top of the pipe.

Instead of a french drain, would placing steel grates over the ditch be a better solution for maintaining functionality? They would keep large debris out of the ditch, allow full drainage flow, and maintain the functionality of the yard.


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RE: Drainage Issue

The mention of "ditch" is confusing me. I'm not envisioning such a thing in your back yard, but only a gentle swale. A french drain "sucks" water into the ground. A planted swale has most water running off.


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RE: Drainage Issue

"How would a french drain saturate the soil below the drain anymore than an open air ditch?"

French drains have a functional lifespan that usually ends when silt builds up in the trench bottom to obstruct the holes in the pipe. The pipe is usually laid on a bed of gravel and the voids in the gravel below the pipe give a place for silt to collect for a long time before the pipe holes are blocked. Every time you get a little rain the voids below the pipe fill with water that never exits through the pipe. This water sits there until it is absorbed by the clay subsoil. Theoretically, you might think it will flow along the trench in the gravel outside the pipe; it wont. Thus the french drain in your case will serve to quickly move water deep into the clay subsoil. Over a period of months or years the clay will become totally saturated below the pipe elevation. That's why drain systems around basements are put below footer height.

Water moves differently in clay than in silt or sand. In silt and sand the movement is down, or if blocked it will move latterly. In clay, water moves from an area of greater wetness to areas of less wetness in all directions, down, up, and sidewise. Clay is saturated with only small amounts of water but many clays will then take on more water by swelling. The effect is not unlike the force generated when water freezes. Swelling clay can cause big problems for basement and retaining walls.

I suggest you go back and read what Yardvaark said on January 24 at 18:32.

I'm confused about your comment about a ditch of any kind too. It's important to work from a plan when doing regrading. Nothing in the drawings posted shows a ditch. If you have completed another grading plan you are now following, I would be interested to see it.


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RE: Drainage Issue

Be careful to fill in around the house. You should have at least 4" to the base of your siding or ledger board from the ground.


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RE: Drainage Issue

I'm still working from the same plan. The ditch is the blue channel that was included in the garden in the original plan. The ditch has to get deeper as it progresses in order to carry the water downhill. My concern is having the channel/ditch interrupt the functionality of the yard. So I am trying to figure out solutions that maintain functionality, but still drain the yard appropriately.


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RE: Drainage Issue

"The ditch has to get deeper as it progresses in order to carry the water downhill."

This is true, but if kept broad through the majority of the yard, then it could seem nearly flat and not like a ditch. Where it is forced to become narrow because of the limited room, then it could be deeper and narrower, but could also be more like a passageway. The overall portion of the yard does not need to have a "ditch" in it. Where it passes through the garden the soil needs some kind of protection as loose garden soil would be quickly washed away. Earlier, I recommended lining with something durable, like a dished out concrete walk. Or, I think we talked about stones embedded like a cobblestone paving. It could also be a grass path. Going around the corner beyond the garden it would need to be the narrowest place, and durable, but the most of the yard should seem like a yard, not a ditch.


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RE: Drainage Issue

I should have never used the term 'channel' for the feature running through the garden. If this project were completed a homeowner would call it a walkway, one that happens to be slightly lower than the surrounding grades and carries the water when it rains.

To clarify matters I'll blow up the plan of the garden area and put some numbers on it for elevations consistent with the grading plan.

In the profiles I have posted I have used an exaggerated scale where 1 inch horizontal equaled 10 ft, but 1 inch vertical equaled 1 ft in elevation; a 10 to 1 ratio. This could be confusing to those not used to it. In the graphic below I use a 1 to 1 scale for a profile in the location near where the lawn meets the garden.


As can be seen, there a 4 inch drop from the retaining wall to the garden grade and then a little over 3 inch drop to the walk/channel. Note if this area is excavated from the existing grades (about a foot) it might have the appearance of a ditch until the garden grade is lowered to plan. Depending on the surface of the walk, it might need to be lowered another inch for a rough hardscape such flagstone, or two inched lower for a grass surface.


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RE: Drainage Issue

Ok, I see what you are saying now. I guess i was picturing something different than what you were describing. I could see that working.

In regards to the 4" drop from the retaining wall to the edge of the curb. What wouldn't I slope this area towards the curb to encourage runoff into the channel? It seems like I would want a slope rather than a flat surface .

Also, in regards to the two walls/terraces that will need to be constructed in the garden. Would rail road ties work instead of pouring concrete?


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RE: Drainage Issue

"In regards to the 4" drop from the retaining wall to the edge of the curb. What wouldn't I slope this area towards the curb to encourage runoff into the channel? It seems like I would want a slope rather than a flat surface ."

You could slope the garden area towards the walk/channel. I thought it might be better to make a slight slope to the rear of the garden.

"Also, in regards to the two walls/terraces that will need to be constructed in the garden. Would rail road ties work instead of pouring concrete?"

RR ties could be used, but they are not permanent like concrete. And concrete can be made to look much better. Cost will be about the same.

Do the concrete and you will learn a skill that can be used elsewhere in your landscape. I can show you how to build simple bolt together reusable forms.


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RE: Drainage Issue

Sounds good. That is what I was thinking as well.

I mention the cross ties because I am removing about 6 of them from the garden as I am re-grading. The previous homeowner built up the garden area using cross ties, dirt and mulch. It was previously a kid's playground.

I would prefer to use the cross ties to save a few dollars for the time being. I would most likely replace them with concrete in the future. Although, I'm leaning towards replacing the block wall all together with a permanent and professional retaining wall in the distant future. That is years down the road however.


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RE: Drainage Issue - Update

I want to update you all on the drainage project behind my house. I hired a bobcat operator to remove the dirt for me. He removed approximately 12-15 dump truck loads from my backyard. I now have a substantial swale in the backyard to say the least. I believe we removed more dirt than what we had to planned to remove in our plan above. I'm please with it because the water will undoubtedly flow away from my house and around the corner of the retaining wall. I will post a few pictures from this weekend.


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RE: Drainage Issue

Another view.


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RE: Drainage Issue

Another


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RE: Drainage Issue

Last one. There is a ditch on the left between the wall and the concrete patio. This is to catch water the that had been pooling at the base of the wall. You cannot see it very well in this picture. I will take another photo this evening.


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RE: Drainage Issue

First off, I would like to thank you for returning to the forum with the construction details. It's seldom we get to see the results of a discussion.

You say that you probably removed more dirt than indicated in the plan (12 - 15 truck loads). Looking back on the thread and my files, I don't see where I posted cross sections or did the dirt calculations to determine the quantity that would need to be removed. Considering your cooperation, I wish I had done that for you. Anyway, looking at the plan, my eyeball estimate would be somewhere around 60 to 80 cy. If the truck was a five yard dump, 12 to 15 loads seems about right.

The plan had an elevation of 98.29 for the top of the retaining and a grade of 97.4 at the center of the swale at the wall corner. The difference of 0.89 ( 10.5 inches) looks to be about what your photos show was constructed. In other words the grading seems to be very close to what Yardvaak and I suggested.

The ditch between the patio and upper wall looks to be a little overdone. All that is needed there is a very shallow swale below the patio grade and extra depth will make maintenance more trouble.


Have you had enough rain to confirm that the new grading has eliminated water getting to the deep drainage protecting your house foundation and brick retaining wall?

I'm curious what your plans are for the old garden area and the slope between the swale and the upper retaining wall. There is also the issue of soil preparation for new grass.


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RE: Drainage Issue

Not a problem. You guys shared your time and knowledge, so I'm happy to provide updates.

I'd be interested to see what the elevation is where the swale turns the corner. I'll have to take a measurement to see how close we came in the drawings.

The ditch could be a little overdone, but most of it was necessary. If you remember the edge of the patio represents the "continental divide". The patio is graded in the opposite direction, draining to the other corner of the house. So I was digging the swale grade opposite of the patio grade. This resulted in more of a ditch rather than a swale, but I'm fine with it. I'll deal with the maintenance issues.

We have not received a drop of rain, so I put a water hose at the highest point of the patio ditch. The water ran down hill and around the corner all the way. I call that success as compared to where I was this winter!

I have some ideas for the space, but I would like to hear what others have to say. It might be easier to start a new thread, but I am going to ask the board their thoughts on the space. I still want the garden area as we discussed, but I am open to ideas if anyone wants to share them.

In regards to the drainage, would it be overkill to pour the concrete swale/pathway from the patio ditch all the way through the yard and around the corner?


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RE: Drainage Issue

I share pls8xx's sentiments that it is good of you to post the results of the thread discussion. Thanks for that.

The yard may not look its prettiest today, but to my eye there is a great peace of mind in that swale you have created. I know you're pleased now, but I'm sure you will be really pleased when you finally get a monster deluge (so long as the planting is finished!) For this phase, I think it looks very good. Not that long from now, all the scarring will be healed and it WILL look handsome again. Probably better, actually, since you are obviously willing to put some effort into it.

"In regards to the drainage, would it be overkill to pour the concrete swale/pathway from the patio ditch all the way through the yard and around the corner?" My gut reaction is that it would be overkill. There might be some need to protect, with surfaces, areas where concentrated flow moves through an area ... like through the garden, or as water makes the turn to the left. But it's unlikely you'd need it in a lawn area near the patio, if that's what you end up having. I'd let the needs and solutions evolve with the design process.

Since this thread is getting long and a new one would be easier to review, it seems like a good idea to start one for the planting. (A thread will be automatically cut off / filled up after 150 posts unless the GW rules have changed.) You might link to this thread in the opening salvo.

Congratulations on your work!


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RE: Drainage Issue

I share pls8xx's sentiments that it is good of you to post the results of the thread discussion. Thanks for that.

The yard may not look its prettiest today, but to my eye there is a great peace of mind in that swale you have created. I know you're pleased now, but I'm sure you will be really pleased when you finally get a monster deluge (so long as the planting is finished!) For this phase, I think it looks very good. Not that long from now, all the scarring will be healed and it WILL look handsome again. Probably better, actually, since you are obviously willing to put some effort into it.

"In regards to the drainage, would it be overkill to pour the concrete swale/pathway from the patio ditch all the way through the yard and around the corner?" My gut reaction is that it would be overkill. There might be some need to protect, with surfaces, areas where concentrated flow moves through an area ... like through the garden, or as water makes the turn to the left. But it's unlikely you'd need it in a lawn area near the patio, if that's what you end up having. I'd let the needs and solutions evolve with the design process.

Since this thread is getting long and a new one would be easier to review, it seems like a good idea to start one for the planting. (A thread will be automatically cut off / filled up after 150 posts unless the GW rules have changed.) You might link to this thread in the opening salvo.

Congratulations on your work!


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