Drainage with natural rock?

Discussion in 'Landscape Architecture and Design' started by mcclureandson, Dec 29, 2004.

  1. mcclureandson

    mcclureandson LawnSite Member
    Posts: 242

    I've got a large install with several hundred feet of wall. Some will be SRW, some Pa. Fieldstone and a 100', mild slope along the back will just get scraped, the base cut at an angle and filled in with irregular stone (medium to large sized pieces w/no drainage behind). The yard will be landscaped to the base of the irregular stone and what's above it will be left natural. Will I need to install a french drain along the base of this 'wall'? I don't have a great place to send the water...how about a dry well? I've never constructed one before and am wondering if any considerations need to be made with regards to what will eventually be placed over the backfilled well...patio, firepit or just lawn, does it matter? Thanks.
     
  2. D Felix

    D Felix LawnSite Bronze Member
    Posts: 1,898

    I'm trying to imagine this.... So you have two walls that will basically be tied together, one is SRW, the other is natural stone, right? Then you have an area that is basically rip-rapped that is next to the walls?

    You need drain pipe behind the SRW wall. The natural stone wall doesn't need the pipe, but if it's convienient to carry it through behind the stone, it's not going to hurt anything. That drain pipe needs to outlet to daylight.

    The rip-rapped slope should have some sort of barrier fabric down between the ground and the rock. As for drainage, it's hard to tell from here. It really depends on what it's like above the rock. If there is a "swale" of sorts that the rock is going into, or if there is irrigation above, then you will probably want some drainage at the bottom. The drainage could be as simple as a new swale cut to divert the water, or as complex as inground pipes.

    If the soil isn't well drained to begin with, a drywell won't gain you much. You'd still need to allow for overflow out of the top, which gets you back to square one....

    Don't know how much this helped, but hope it did!


    Dan
     
  3. mcclureandson

    mcclureandson LawnSite Member
    Posts: 242

    Thanks DFelix...no the two (actually more than two) walls are NOT tied into one another...I only mentioned that I was installing other types of walls so no one would say "why don't you do an SRW, it looks so much nicer!" Basically, the front of the house has the walls with the nicer finishes and around back/side is where the rip-rap will be. What is the purpose of the fabric underneath the rip-rap? The slope continues ABOVE the rip-rap at a modest degree for sixty or eighty feet, is heavily wooded and shows no sign of past drainage/wash-out problems. The length of the rip-rap 'wall' is closer to 150', it's mostly level and after the grader makes the cut I was planning on trucking in the stone and stacking it using the slope as natural batter (should be +/- 6" for every vertical foot). Thanks.
     
  4. D Felix

    D Felix LawnSite Bronze Member
    Posts: 1,898

    The fabric is to keep the soil separated from the rock, and also act as a weed barrier.

    If there are no springs in the hillside, you may be OK with no drain line at the bottom of the slope. Just make sure that whatever water does come down the slope won't have a chance to sit at the bottom for very long.


    Dan
     
  5. mcclureandson

    mcclureandson LawnSite Member
    Posts: 242

    Thanks again...what concerns me is the area at the base of the rip-rap is flat and heavily shaded AND within 20 feet of the house...I don't want to create a soggy side yard and it will be kept mostly bare (it's designated for a dog-run later on). I suppose plantings at the TOP of the rip-rap will help retain the soil and the thirstier they are the better. I still keep returning to thoughts of a dry well...cost is no object (to a certain point, otherwise this wall would be upgraded to something with a near-vertical face and drainage behind) so a little overkill on the drainage is all right. Anyway, I appreciate your input. You are always willing to offer experienced, well-thought out advice...
     
  6. D Felix

    D Felix LawnSite Bronze Member
    Posts: 1,898

    If you have somewhere to outlet it to daylight at, it might not be a bad idea to install a drain pipe in the rip-rapped section, right as it turns from sloped to flat. Especially if it'll be a dog run, that should help keep it from getting too muddy.


    Dan
     

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