Meet your Chicagoland Stormwater Storage Requirements with a rain garden!

How to Build a Rain Garden

BuildLike with most landscape installations, how a rain garden is constructed will vary greatly from contractor to contractor and from site to site.

So in this section I will cover the following general information that I have learned from constructing rain gardens over the years:

My favorite rain garden tools.
How to build a water level; a $20 tool that will allow you to find grade changes with the accuracy of a $500 laser level.
How to locate utilities safely in your work area.
A step-by-step example of a native rain garden installation.

My Favorite Rain Gardens Tools

(From Left to Right)

Soil Probe

Roughly $115. Will allow you to quickly see what soil exists 18” below the surface in multiple locations. Not necessary for a homeowner to purchase, but if you are interested in doing rain garden work as a contractor, this is a must have.

Tape Measure

Measures short distances and heights.

Surveyors Wheel

Measures long distances, not necessary for a homeowner.

Short Handle Flat-Headed Spade

In the hands of a skilled laborer this tool can get a drain tile laid faster than any trenching machine, a la John Henry. Digs trench sides straight while chopping roots cleanly, a filed edge helps here. Great at removing small sections of sod as well. Can do minimal work of other shovels if needed.

Manual Sod Cutter

A great tool for contractors who find themselves cutting small to medium areas of sod often. Low-cost alternative to engine driven sod-cutter machine. No gas, very low maintenance, and is great at slicing an even inch or two of soil from the bottom of the rain garden basin for a level final grade, which can then be steel raked away.

Bulb Planter (Red Handle)

Great for installing plants and is handy in utility locating.

Pick Mattock (Yellow Handle)

When used in combination with the Steel Rake is my preferred method to excavate and grade rain gardens. The wide flattened end of the pick breaks up even the driest clay soils that can then be moved around with the rake. Will slice through tree roots with ease. The flattened end can also be used to create a level bottom of a trench after a flat-headed spade removes top sod section. The beak end of this tool is perfect for getting out rocks stuck in the soil, breaking up compacted gravel, and locating a utility without damaging it, something I go into further detail below.

Steel Rake

Used to grade rain garden area, breaks up soil clumps nicely. Spreads gravel and mulch easily.

How to Build Your Own Water Level

There is one more tool that accompanies those listed above to every rain garden I install.

But this one can’t be bought in the stores, you need to make it yourself.

This tool, known as a water level, utilizes water’s inherent property to seek-its-own-level to create a very inexpensive tool that gives even the beginner the ability to figure out elevation changes in and around your rain garden without the purchase of an expensive laser level.

You can build one for under $20 in about one hour, including the 30 minute round-trip to the hardware store.

To do this, you will need:

1 20’ Clear Tube 3/8” ID 1/2” OD
2 Snow Markers (Stick)
2 Meter Rulers (Metal)*
6 6” Zip Ties
2 1/2” Rubber Stoppers

* The metal meter rulers are preferred. If they do not come with three holes drilled in them, you will need to drill them yourself; one at the top, one in the middle, and one at the bottom.

Step 1

Run the zip ties through the openings in the meter stick and close each one slightly, allowing plenty of room for the snow marker and tubing.

Step 2

Slide the snow marker through the zip ties on the backside of the meter sticks, allowing about 3-4” of the snow marker stake below the meter stick.

Step 3

Pull the tubing up through the zip ties on the front side of the meter sticks

Step 4

Tighten the zip ties so that the tubing and snow marker are secured, but do not over tighten. You want the snow marker to be able to move up and down slightly, this will allow some adjustment depending on how firm or soft the soils you are trying to stake the marker into are.

Step 5

Fill up with water until both meters read about 18” when held exactly even with each other, being sure to remove all the air from the tubing.

Step 6

Cap with rubber stopper for storage and transportation of water level when not in use.

Finding Utilities

Sometimes there will be utilities located in the area you want to work.

It is just fine to build your rain garden over these, but you will want to know which ones are there and where they are located so that you can work around them.

To do this, you will first need to contact your Utility Locating Service.

Here in Illinois you can call 811, or you can also fill out a form at JULIE.

Your Utility Locating Service will come to the property and spray paint a line in which the utility should be found below within about 18” of either side of the line.

If a utility is running through your work area, take note of what utility it is.

Phone/Cable/Internet – Very Common. Usually found in top 0-4 inches. Dig them up, move them aside.

Gas/Electricity/Water Line – Use Extreme Caution. Are supposed to be buried more than a foot deep, but is not guaranteed.

Next you will want to either find your utility or make sure that it is easily below the depth that you will be excavating.

To do this without damaging the utility, start by lightly scratching the pointy beak end of your Pick Mattock across the surface, starting at least 18” on either side of the spray paint.

The beak will slowly work down through the soil, stopping on small obstructions without damaging them.

I then use my bulb planter to move the dirt aside to see what I have hit upon before removing it, sometimes I lightly scratch the bulb planter steel against the thin strands in the ground to see if they are roots or plastic wire coating.

Eventually I will either get below a depth that I need to be concerned about, or I will find the utility.

If I find the utility, I will use my spade to carefully dig down around the utility and remove the soil around it so that the utility is free and easily moved or avoided during construction.

Native Rain Garden Installation

Each rain garden installation is different and I hope to post more case studies in the future, but for now, here is an example of what you might expect from a typical rain garden installation.

Contact local utilities locating company to mark out utilities before any excavation work.
Temporarily divert water (if applicable)

Outline rain garden location with paint or hose
Herbicide Turf (optional)
Scalp Sod (optional)

Excavate to find Utilities (if applicable)
Create edge for rain garden
Cut sod, or clear land of other plant matter
Minimize compaction during construction of rain garden basin
Flip sod over to build containing outer berm
Cut and fill your basin so that no/minimal soil needs to be removed

Install plantings

1st Year

2nd Year

And that concludes the Build Section of my Installation Series.

But you are not done yet!

Constructing a garden is just the beginning of a garden’s life, now you need to maintain it.

Maintenance is the most overlooked aspect of rain gardens; the lack of which, in my opinion, is the #1 reason why rain gardens get a bad rap.

To help with this, I have created a maintenance schedule for rain gardens that can help you to anticipate what is needed for your rain garden post-installation, and what are some things you might expect to see in the first couple of years.

You can check all this out on my next post, Rain Garden Maintenance Schedule!

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