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First hardscape job, need pointers, please

Discussion in 'Hardscaping' started by LawnMan883, Apr 17, 2007.

  1. LawnMan883

    LawnMan883 LawnSite Member
    Posts: 85

    I have been reading many threads on here about retaining walls, but i want to be sure i am going about this the right way. i have a customer who has a septic tank in front of their house and then there is a large slope down to the street. they want to build a wall on the slope so they can fill in dirt about 8" over the septic tank so they can plant flowers in there. The wall I was prohjecting would at one end be about 3-4 feet tall, and a total of about 16 feet long. It will curve around from an existing timber wall and wrap around to the driveway where it will end pretty much ground level. i have read about drainang and th eneed for a good base, but i am worried digging too deep here for fear i dig up some of the septic field. i can bring in gravel for behind the wall, and also run a drain tile with no problem. The issue i can see is not haveing as deep a base as people say is necessary. Here is a picture of the property. Let me know what you guys might suggest and also i have no idea in terms of what a fair price is for a job like this. Please let me know.

    BTW: The septic tank is marked by the 4 bricks in the large mulched area. it's almost ground level at that point but they want about 8" of dirt on top

    misc 150.jpg
  2. Matt k

    Matt k LawnSite Member
    Posts: 60

    Never dig a footer over a septic field!
  3. Dirt Digger2

    Dirt Digger2 LawnSite Silver Member
    from PA
    Posts: 2,396

    thats a tough one..you definetely don't want to be running your machines over the field or tank...and you need to let your customers know that the lid can't be anymore then 12" below grade (in PA anyway)...what you need to do is take the lid off the tank and look in there to see how far below the surface the tank actually is...it might have 4feet of extension rings on it in which case you might be ok. Septic tanks are not designed to support a whole lot of weight on their lids so if the tank is already 4feet below grade you cant add more dirt because normal tanks are only designed to support 4feet of dirt without requiring a special lid...i can offer any insight you might be looking for regarding the septic tank but you'll need to give me more details on where the walls gonna go and how you plan on building it...hell of a first job to pick up..haha
  4. Mike33

    Mike33 LawnSite Bronze Member
    Posts: 1,649

    That was some good input on septics, i learned a few things from your reply. I think he would be okey with a small bobcat just replacing the existing wall that looks in need of repair. I would nt think the drain fields would be running back that way. If he hit one just replace. I would nt do any thing over the septic it self though.
  5. D Felix

    D Felix LawnSite Bronze Member
    Posts: 1,898

    You need to know where the septic fingers/field is located before you even think about doing anything.

    I'm not fully up on septic fields, but you definately don't want to risk putting a hole into a finger pipe... The house may be new enough that the septic doesn't use pipe- instead it may have the plastic "domes" or whatever they are called. Not sure how much wieght those can withstand, but they can't be any easier (or less costly) to fix than a pipe...

    Find out where the septic field is in relation to your access point and where the work will be performed, then get back to us.
  6. LawnMan883

    LawnMan883 LawnSite Member
    Posts: 85

    the owners just moved in the house last year and had no idea they had a septic tank there...and have no idea where the fingers are. With many of the lawns i used to mow as a kid you could tell where the drain field was by uneven turf and especially green grass in the summer, but their yard has none of those carectoristics. In the above picture the bricks in the soil are the corvers of the tank. There are 2 lids the top of what appears to be th etank is only 2" under the ground they want an additional 4-6" of topsoil over it so I dont; think weight will be an issue. In that picture they want the wall to go from the corner where the timbers are to the driveway. I do not have any heavy equipment and was not sure if i would even need a bobcat or something for this job as i can put my trailer right next to the location to load and offload bricks and materials.
    Thanks fo rth einfo thus far
    I still have no idea on a ballpark price either..any ideas based on the picture above?
  7. shovelracer

    shovelracer LawnSite Silver Member
    Posts: 2,009

    I wont claim to be an expert on this at all, but I can see the potential for future problems if it is installed over the field. The town or local jurisdiction may very well have a problem with doing anything anywhere over the septic system. The tank needs to be accessible and cant be overloaded with weight. The field cant be compacted or covered since the newer approach is that it needs to breathe to function properly. I would say building a wall over any part of the system is a big no-no. And I would definitely check with the towns building/zoning department.
  8. Dirt Digger2

    Dirt Digger2 LawnSite Silver Member
    from PA
    Posts: 2,396

    atleast your even thinking of the tank, we once got a call that deck guys were drilling for footers and drilled right down on top of a tank lid..as far as putting a wall on top of the outlet pipe it depends on the depth..again you have to get your hands dirty, take the lid off and look down to see how deep the outlet pipe is.

    D Felix those black things your talking about are generally used for replacement systems and usually only when nothing else will work. if the system was replaced its possible they used these but if its the original system it either goes to a bed, trenches or pump tank.

    regardless the outlet pipe is 4" and most likely there is a 4-5' peice of sch.40 pipe coming out of the tank to go over the overdig then it turns into either thinwall of SDR35 pipe...DONT go proding around with rebar or something trying to find it because if you poke a hole in the pipe you need to replace it.

    you'll be fine building a wall across the pipe but not across the tank, assuming the pipe is atleast 12" below the wall and you arn't building too high/heavy of a wall.
  9. zedosix

    zedosix LawnSite Silver Member
    Posts: 2,635

    I think you can get away with a wall that ends well short of the driveway and not have to worry about the septic field. It may be wise to call the city and get a detailed drawing of how the septic field is laid out. Design your project after you have all the details.
  10. LawnMan883

    LawnMan883 LawnSite Member
    Posts: 85

    They want the wall to reach to the driveway so they can build up that area over the tank for planting of a flower bed. Am I just asking for trouble even doing this job? I was all for it as a first hardscape job, but I don;t want to get myself in deep $hit if i mess up their septic. As I am just starting out it would be pretty bad to screw up on your first customer. Basically what i gathered is i need drawings of the field, to locate the septic tank outlet pipe and if the outlet pipe is deep enough i should be able to build a short wall over the pipe with no problems? If so this may be the only option i have as i am not going ot dig over the drainage field...i know that can cause a world of issues.

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