Clay soil

Asked December 19, 2019, 4:51 PM EST

When we moved in there was a lawn in my front yard that would never drain. I've decided to get rid of the lawn and make a path and make berms to plant in. So in the fall we rented an bob cat and excavated the path down about 6 in. We installed a french drain and tied that into the downspout. We then we build up the berms added our irrigation. So then the rains came and we have a river of water on top of this clay. I had my workers dig a foot down and a foot wide trench down the center of the path. We put in landscape cloth and filled it with small round river rock. This trench flows and intersects with the french drain pipe. We still have puddles of water that do not drain in to this trench. I know that I want to put a base layer of basalt but am wondering if these basalt will sink to the bottom of the clay. The clay layer is about 12" deep. I'm thinking about putting a woven permeable landscape cloth down first. My plan was to put the decomposed grante on top of the basalt base layer. My question is... Am I on the right ideas to create a dry path? Should I put down that landscape cloth first? Should I have a taller base layer? I have photos to share but would like a reply before I upload the photos.

Yamhill County Oregon horticulture landscape plans

1 Response

Drainage in clay soil is always a challenge. And you certainly do not want water draining towards your home.

There might be several reasons why the soil isn’t draining in your front yard. It could be that the water table is high in your area, so that it doesn’t take much rain before the water table is just below the soil surface. Thus any rain water will pool. There might be springs in the area that add to the rain water and thus to surface pooling. Does water drain from elsewhere to your front yard? As you are well aware, it takes a long time for water to percolate through clay soil. This is exacerbated if the soil has been compacted, as it often is, during home construction.

The purpose of the geo-textile fabric lining drainage areas is to prevent soil from doing what it does naturally, filling in the cracks and crevices between rocks and hindering quick drainage. So, yes, put down the fabric first, fill with larger rocks, cover the top of the rocks with the fabric, then put the decomposed granite on top of that or more larger rocks then the decomposed granite.

Keep in mind that you need to get below the clay band so the water has someplace to go. It could be that you can redirect the water so that it makes it to the French drain without pooling.

A publication from Washington State University Extension, Improving Drainage, will help guide you through the frustrating project to reduce standing water.

Another thought for you might be to create a rain garden, a sunken area that collects the water and allows it to slowly soak into the soil. This guide from University of California Master Gardeners, How to Build a Rain Garden, will give you an idea on how it works.

Have courage, there are answers to this challenge.