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onahillside

Drainage Issue

onahillside
11 years ago

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"

Comments (115)

  • pls8xx
    11 years ago
    last modified: 9 years ago

    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.

    {{gwi:7655}}

    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: {{gwi:7633}}

  • onahillside
    Original Author
    11 years ago
    last modified: 9 years ago

    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.

  • pls8xx
    11 years ago
    last modified: 9 years ago

    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 "?"

    {{gwi:7656}}

  • onahillside
    Original Author
    11 years ago
    last modified: 9 years ago

    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?

  • PRO
    Yardvaark
    11 years ago
    last modified: 9 years ago

    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.

  • pls8xx
    11 years ago
    last modified: 9 years ago

    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.

  • onahillside
    Original Author
    11 years ago
    last modified: 9 years ago

    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.

  • pls8xx
    11 years ago
    last modified: 9 years ago

    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.

  • onahillside
    Original Author
    11 years ago
    last modified: 9 years ago

    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.

  • pls8xx
    11 years ago
    last modified: 9 years ago

    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.

    {{gwi:7657}}

    Below are a couple of graphics for discussion.

    {{gwi:7658}}

    {{gwi:7659}}

    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.

  • PRO
    Yardvaark
    11 years ago
    last modified: 9 years ago

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

  • pls8xx
    11 years ago
    last modified: 9 years ago

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

  • PRO
    Yardvaark
    11 years ago
    last modified: 9 years ago

    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.

  • onahillside
    Original Author
    11 years ago
    last modified: 9 years ago

    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?

  • pls8xx
    11 years ago
    last modified: 9 years ago

    "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.

  • onahillside
    Original Author
    11 years ago
    last modified: 9 years ago

    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.

  • pls8xx
    11 years ago
    last modified: 9 years ago

    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.

  • onahillside
    Original Author
    11 years ago
    last modified: 9 years ago

    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?

  • pls8xx
    11 years ago
    last modified: 9 years ago

    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.

  • pls8xx
    11 years ago
    last modified: 9 years ago

    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.

  • onahillside
    Original Author
    11 years ago
    last modified: 9 years ago

    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.

  • pls8xx
    11 years ago
    last modified: 9 years ago

    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.

  • PRO
    Yardvaark
    11 years ago
    last modified: 9 years ago

    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.

  • onahillside
    Original Author
    11 years ago
    last modified: 9 years ago

    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?

  • pls8xx
    11 years ago
    last modified: 9 years ago

    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.

    {{gwi:7660}}

  • PRO
    Yardvaark
    11 years ago
    last modified: 9 years ago

    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.

  • onahillside
    Original Author
    11 years ago
    last modified: 9 years ago

    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.

  • PRO
    Yardvaark
    11 years ago
    last modified: 9 years ago

    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!

  • onahillside
    Original Author
    11 years ago
    last modified: 9 years ago

    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?

  • onahillside
    Original Author
    11 years ago
    last modified: 9 years ago

    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?

  • PRO
    Yardvaark
    11 years ago
    last modified: 9 years ago

    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?

  • pls8xx
    11 years ago
    last modified: 9 years ago

    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.

  • onahillside
    Original Author
    11 years ago
    last modified: 9 years ago

    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.

  • PRO
    Yardvaark
    11 years ago
    last modified: 9 years ago

    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.

  • pls8xx
    11 years ago
    last modified: 9 years ago

    "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.

  • lyfia
    11 years ago
    last modified: 9 years ago

    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.

  • onahillside
    Original Author
    11 years ago
    last modified: 9 years ago

    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.

  • PRO
    Yardvaark
    11 years ago
    last modified: 9 years ago

    "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.

  • pls8xx
    11 years ago
    last modified: 9 years ago

    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.

    {{gwi:7661}}

    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.

    {{gwi:7663}}


    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.

  • onahillside
    Original Author
    10 years ago
    last modified: 9 years ago

    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?

  • pls8xx
    10 years ago
    last modified: 9 years ago

    "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.

  • onahillside
    Original Author
    10 years ago
    last modified: 9 years ago

    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.

  • onahillside
    Original Author
    10 years ago
    last modified: 9 years ago

    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.

  • onahillside
    Original Author
    10 years ago
    last modified: 9 years ago

    Another view.

  • onahillside
    Original Author
    10 years ago
    last modified: 9 years ago

    Another

  • onahillside
    Original Author
    10 years ago
    last modified: 9 years ago

    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.

  • pls8xx
    10 years ago
    last modified: 9 years ago

    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.

  • onahillside
    Original Author
    10 years ago
    last modified: 9 years ago

    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?

  • PRO
    Yardvaark
    10 years ago
    last modified: 9 years ago

    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!

  • PRO
    Yardvaark
    10 years ago
    last modified: 9 years ago

    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!