How to build a simple rain garden in one hour !

.
You can make a big contribution to safety, lake quality, and neighborhood beauty in only one hour!

Runoff flowing down sidewalk and into the street

Sidewalks are an important link in the health of our lakes. In many places, runoff from storms is channeled down sidewalks, and then into the street. From there, the water washes nutrients and pollution down the stormsewer and into the lakes.

Instead, you can trap the rain and nutrients and use them to grow flowers! By placing a garden next to the sidewalk, you don't have to water your garden.

Gravel gardens that never have to be weeded

.

Today I saw my neighbor, John Lewison, at work on his terrace--at 539 S. Owen Drive.  He was halfway through planting a "gravel garden," when he stopped to show me how.

Gravel gardens were developed in Germany, where studies indicate labor savings of 85% over a conventional garden.

Roy's garden

The  concept was presented by Roy Diblik on WPT:  You lay down 5" of gravel over good soil.  Roy used small quartzite chips, because they don't break down.  Other kinds of rock, especially limestone, break down to create soil, which weeds could then invade.  Edging keeps the gravel from mixing with soil or wood chips in the next garden.

Roy planted drought-tolerant plants: Autumn moor grass, Arkansas mint, and prairie dropseed.

The plants are grown in 5" pots, then transplanted into the gravel, by simply pushing the gravel aside for each plant.  They have to be watered every 1-2 days for 8-12 weeks, while getting their roots into the good soil below the gravel.  After that, you never have to water or weed.  Roy says he's  pulled only six weeds in three years from a large gravel garden. 

Although there's no watering or weeding, some maintenance is required.  Fall leaves have to be removed, and the dead crowns of the plants are cut and removed in spring.  This keeps organic matter out of the gravel, where it might create soil.  The garden should last for 30 years.

John's variation

John is modifying the concept to create a rain garden on his terrace.  John hopes to infiltrate a substantial amount of runoff coming from his wide driveway.  During the winter, runoff here makes an icy puddle at a low spot on the sidewalk.

John, a professional landscaper, rototilled the soil, to make it easy to remove.   His plot is about 5' wide by 12' long.  After shoveling out soil to a depth of one foot, he replaced it with 6" of top-quality topsoil. This was necessary because terrace soil below the top few inches usually isn't very good

Then he shoveled in 5" of rounded stream gravel which-- like quartzite--won't break down.

He needed 3/4 of a cubic yard, costing $100. 

Next come the plants.   Stay tuned.

Why rain gardens fail

.
Rain gardens are supposed to put runoff back into the ground.

But they don't do their job if the runoff never gets into them, if they overflow before the water sinks in, or if their bottoms are impervious.  I'll address the first two issues here.

Many large rain gardens--for example, those taking runoff from parking areas--aren't graded properly.  The runoff never gets into them.  Obviously, no one is checking to see if they really work.  I'll give three examples from parking lots.

Metcalfe's Sentry

In this large lot, there are 3-4 long islands between rows of parking, which are supposed to receive runoff from the gutters through gaps in the curb. 

These gardens fail because the basins aren't much lower than the gutter.  No water flows in.

And, there is nothing to deflect the swift flow in the gutter towards the garden.

Madison Gas & Electric visitor's parking

At this lot, we have--at the center of the lot--a filtration chamber.  It was designed to filter the toxic stuff dripping from vehicles, before the runoff gets to nearby Lake Monona.  The filtration was a cooperative project by MG&E, DNR, and other agencies to see how efficient filtration could be.

The filters reside in an underground concrete bunker--the setup cost $50,000. It basically does the job a larger rain garden could do.

 

While this wasn't a rain garden, they did measure how effective the parking area was at gathering water and feeding it to the filters.  Since the parking area wasn't graded to be an effective catchment basin, it sent 30% of the water to surrounding streets.  Only 70% of the water falling on the pavement actually went to the filters.

The area within the red line drained to the filters. The area between the red and yellow lines drained to the street--wasted.

So a rain garden (or filtration system) is no more effective than the grading and inlets to the garden.  If the grading isn't carefully done, you've wasted a lot of money.

Terrace rain gardens on Eaton Ridge

These were among the first rain gardens on terraces, built by the City.

Rain garden inlets on Eaton Ridge were too small, and quickly became clogged.

 

Terrace gardens built by the City on Adams St had better entrances.

Sequoya Commons

This is a beautiful rain garden, with a large capacity.  For the most part, it is well-graded.  Nevertheless, a small portion of the north end of the parking area drains to the street, via the entrance to the lot.

 

My real purpose for mentioning Sequoya is that you can see this garden does reject some water.  I saw if overflow once in a heavy storm.

On another occasion, when the garden was full of water, a steady stream of clear water seeped from the garden into the storm sewer.  While this escaping water didn't get into the ground, at least it was clean and free from sediment.



The bottom line

Before you build a garden, always watch where the rain goes during a storm. 

Test the grade by pouring water on the pavement.

Don't pay the contractor till you see if the garden actually works.

If necessary, build a berm of earth or asphalt to correct the flow.

Rain gardens in New Zealand

.
New Zealand is an island country with keen environmental awareness.  Perhaps that's because they experienced some environmental disasters after colonization by Europeans.

Sheep and deer overran and denuded the country.  Erosion followed.  Species disappeared at an alarming rate.

So it's not surprising that their capital city--Aukland--has some interesting rain gardens.  Recently, I found the following photos on the internet.

The photos are mostly rain gardens for streets and sidewalks. If we're going to improve the lakes, we have to start dealing with street runoff in a big way! (Click on photos to enlarge.)

Rain gardens bring countries together

Rain garden, corner of Struck St. and Watts Rd.



Recently, I passed one of my favorite rain gardens on the way to Woodman's.   It's a large garden draining a parking lot, at the corner of Struck St. and Watts Rd.  I saw a group of people working on the garden, and decided to stop and find out about the garden.

City requests proposals for planting in existing rain gardens

.
On June 14, bids are due on a project to plant and maintain rain gardens in Madison.  Some of the gardens have already been constructed, while others are in the process of construction.  Glenn Clark is the project manager. Work will start about June 21 and end about Sept. 20. 

Existing gardens to be planted
Starkweather Creek rain garden
Marston Ave. rain gardens 1-5
Bernie's Beach bio-retention basin
Allied Drive bio-retention basin
Prairie planting at Beld St. and Wingra Dr.
Kipp rain garden
Westmorland Park rain garden
Vilas Park bike path
Vilas Beach

Newly constructed rain gardens to be planted
609 Gilmore St
2114 E. Mifflin St.
2106 E. Mifflin St.
Ivy Street rain gardens A and B
1000 Edgewood Ave.

The RFP calls for purchase of 4,896 plants, so you can see that "green infrastructure" is fast becoming part of our economy--a source of jobs.

#          #          #

See the RFP here.  There is a map of the garden locations on p.55, and species lists on p. 45.

From snowbank to sea

Reprinted from my "Save Our Stream" blog.

One warm day in March, years ago, my son Chris and I were walking in Forest Hills cemetery.   Everywhere, snow banks were melting into rivulets, coursing down the asphalt.

Chris asked: "Daddy--Where does the water go?"

As I explained about the water running into the sewer, then into the lake, then into the Mississippi River, suddenly a thought struck: "Why not actually show him where it goes?  Why not?"