From:Kyle, TX Region: Southwest Topic: Rain Gardens Title: Expanding clay soils near rain garden Answered by: Nan Hampton and Chris Caran
I want to put a rain garden in my yard in central TX (Kyle). My subdivision architectural review committee expressed concerns about the expansive clay soils becoming saturated and possibly shortening the anticipated lifespan of a sidewalk and alleyway near by. How do I find information about setback distances for clay soils? I have found that most rain garden plans recommend 10' from foundations, but no comment or mention about distances form sidewalks and alleyways. I found that in Seattle they have rain gardens in the planting strip between the roadway and sidewalk without concern for damage to road or sidewalk. How or where can I get help with this concern? Thanks
First of all, and I'm sure you know this, Seattle soils are not like Kyle soils. I've thought about your question a great deal and, although I wasn't able to find any exact recommendations for distances from sidewalks or streets, I did get some insights from consulting a geologist friend who knows a lot about the expansive clay soils of Central Texas. This is a summary of what he says about your problem: When the weather has been dry, these expansive clay soils shrink and become permeable with small channels running through them much like the honeycomb limestone of the area. When it rains, the water runs through them vertically until they absorb enough to expand and become impermeable. They expand vertically as well as horizontally. When they absorb enough water to become impermeable, the water runs off the surface. The soil can't expand further at this point. The water you catch in your rain garden pond is going to permeate the clay soils underneath it until they become saturated and almost impermeable. Then, the pond will hold the water until it evaporates or seeps slowly down into the ground. The soils under and perhaps adjacent to the rain garden WILL expand considerably once they are wet, so any structures (e.g., pipelines, walkways, etc.) in the immediate proximity of the garden can be expected to shift. The adjoining clay soil in the yard is also going to expand just from the rain that falls on it and the soils near the sidewalk will expand after a rain regardless of whether there is a rain garden nearby or not. If 10' is the recommendation for foundations, that would seem an adequate distance for sidewalks as well.
More Rain Gardens Questions
Plants for freestanding water in Oklahoma July 28, 2013 - I have an overflowing gutter and the ground below becomes a muddy hole. I'd like to put a basin or pot in/or above the ground with a rain chain. Are there any plants--shrubs or otherwise that flouris... view the full question and answer
Native plants for a bioswale in Indianapolis March 07, 2009 - Dear Mr. Smarty Plants, Can you please recommend the types of plants I should use in a bioswale or rain garden in Indiana?
view the full question and answer
Retention pond from Hendersonville NC April 24, 2012 - We have a retention pond that has recently been cleaned and we would like to plant perennial native plant and grass seeds that will enhance the appearance and contribute to the natural process of filt... view the full question and answer
Plants for difficult site in Jacksonville, TX July 07, 2010 - East Texas (Cherokee County) red clay hillside, hard-packed, difficult to get to, 40' of it slopes 4' down in about 6'! Another 30' of it is flat. Between the hillside and the flat clay area is a... view the full question and answer
Native Texas plants for rain gardens March 07, 2007 - I am looking for native Texas plants that would do well in very shady and partial shade rain gardens. Do you have any suggestions? view the full question and answer