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HOW TO BUILD A RAIN GARDEN
Location

  1. Location is Critical Proper location is one of the most important components of successful rain garden installation. The first step in planning a rain garden is walking a property during a rainfall event.  Get out in the rain, and watch how runoff moves on the site. You have to locate a rain garden so that runoff moves to it.

    If you have a low spot where water ponds, it might be a good site for a rain garden - but maybe not. If you have a spot that ponds water for an extended period of time (i.e. long enough to kill grass) it does not percolate well enough for a rain garden to work properly.  A rain garden should impound water for about 12 hours (maybe up to 24 hours). You do not want water standing in a rain garden for an extended period of time.
  1. One Call Another key item in locating a rain garden is the presence or absence of utilities. So you should make sure there are no phone lines, gas lines, or other infrastructure in the area you will be digging. Call “Iowa One Call” at 800-292-8989 to request assistance locating utilities. Call at least 48 hours before you want to start installing a rain garden.
  1. Other Considerations
    1. Rain gardens should never be located upslope from a house or closer than 10 feet from a foundation. 30 to 40 feet away from a foundation is recommended if the site allows. Roof water can be directed to a rain garden by extending tile from downspouts to the rain garden, or by creating a swale that will convey runoff to the rain garden.
    2. Avoid locating rain gardens under trees. There will always be some excavation involved with rain garden installation, and excavation under the drip line of a tree canopy will cause damage to a tree’s roots.
    3. Rain gardens should not be installed in areas with high water tables (some sites in central Iowa), or areas with shallow soils over bedrock (some sites in northeast Iowa). There should be at least 4 feet of soil profile between the bottom of a rain garden and the normal high water table or bed rock. Soil survey information from the Soil and Water Conservation District will indicate whether the potential high water tables exist or whether shallow bedrock might exist.
    4. Rain gardens should not be located on steep slopes that can become unstable when saturated.  If excessive slope exists, installing a rain garden will be more of a challenge. Retaining walls are usually needed to create a level depressional area for a rain garden on steep slopes.

    More on Rain Gardens

 

 

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