Friday, July 3, 2009

How to build a Stormwater Planter...

We have successfully installed a stormwater planter in front of Montrose Green. And what exactly is a "stormwater planter", you ask? Well, it's similar to the tree wells that you typically see in the sidewalks running along the city streets, but bigger and constructed much differently. Here is a portion of a previous blog post explaining a bit about stormwater planters and how we were inspired to install one at Montrose Green...

(from June 18, 2008) "The Philadelphia Water Department Office of Watersheds has embarked on an ambitious program to install stormwater planters that are designed to capture and infiltrate street run-off. There was a presentation of this at PHS (Pennsylvania Horticultural Society) recently that Emily and I attended...The concept is pretty simple: basically, instead of having continuous impervious paving along the street (with the occasional tree), we can create small stretches of pervious planting beds (up to 20' long) that will infiltrate sidewalk and street run-off. There is also a scheme to do an island 'bump out' that essentially takes the place of a parking space and replaces it with a lush vegetated area that can capture run-off. Obviously, these also greatly enhance the aesthetic of the street as well as contribute to better air quality."

The basic Stormwater Planter diagram, in section...

Here's a link (click here) to an informative document that describes stormwater planters in greater detail.

So it didn't take much for us to be convinced that installing a stormwater planter at Montrose Green would be a worthwhile venture. When it came time to bust up and re-pour our sidewalk a few weeks ago, we marked off an area along the street roughly 3'-6" wide x 15'-0" long and didn't pour any concrete there. After the sidewalk was set in the remaining area, we began the construction process.
Because neither of us are plant experts, the first thing we did was to team up with a great landscape designer to help us with the planter construction as well as the plant selection. We met Brian Weinrich through our contractor, Merlin, who is also helping Brian renovate his own house in South Philly. Brian actually works for the City Planning Commission, so between his landscape background and involvement with urban issues, he was definitely excited about helping us out with the planter. Below are his initial concept sketches (with planting options) as well as his final colored plan.

The curved stone path running through the middle of the planter represents a dry "riverbed" that will fill up during heavy rains. You can also see that we decided to go with three different trees and various arrangements of ground coverings....all of which need to be wet tolerant, due to the amount of water the planter will take on after a big storm.

One of the most challenging parts of this endeavor was the fact we had to dig the planter well by hand due to the utilities -gas and water lines- underneath. Above you can see me (on the left) and Anastasio (from Merlin's crew) digging away. The recommended planter depth is roughly 3'-0" deep. Ugh! It took us a couple days, but we finally got it all cleared out.

Above is a series of photos showing the steps involved in adding the drainage bed of fabric-wrapped 'clean stone'.
Step 1: the cleared out planter, Step 2: we laid permeable landscape fabric down, leaving a few feet of extra material in all sides, Step 3: fill the well with 18" of clean stone, Step 4: wrap the extra fabric up and over the top of the stone, essentially fully encasing the the stone as to prevent any dirt from getting into the drainage bed, compromising its effectiveness. This portion of the planter allows large amounts of water to infiltrate and recharge the ground water system below.

When it came time to select the plants and the soil mixture, we utilized two sources: One was a large nursery out in Lancaster County (where we got the trees and a few of the larger plants) and the other was our favorite local nursery,
Greensgrow Farms, up in the Fishtown area of Philly. We have been going to Greensgrow for years, enjoying their nursery and farmstand, and have also been proud members of their unique CSA. Above, you can see the various bags of material we used for the soil mixture. Brian felt a nice variety of compost (mushroom and leaf), shredded woods, soil conditioner, and sand would make for a rich, well-drained mix for the plants. You can also see a few of the native annuals & ground coverings we purchased. For the trees, we selected a Sweetbay Magnolia, a White Fringe, and a Serviceberry (or Juneberry) which all have different qualities.

Here's a great little clip of the truck (from Cava Building Supplies) delivering over 3 tons of clean stone. I will be honest in saying I was pretty nervous when I saw how much stone dumped out of the back of that truck. I felt we had way too much. In the end, we only needed about 2-1/2 tons but were able to utilize the rest in the back yard rain garden.

So after a long weekend of planting, our stormwater planter came to life...Above you can see Brian (top center image) knee deep into the planting process. And to make extra sure we were planting the correct species - the trees, along with almost all of the other plantings, came from PHS's list of plant species recommended for stormwater planters.
It's not published on their website yet, but we have our sources. The recommended species list includes native plants that are hydrophillic (water-loving), as well as hardy & salt-tolerant due to their proximity to the harsh conditions of street life.

Above are some detail shots of the planter. Hard to believe this is front of a Philly rowhome, huh? We are very pleased with the outcome. Thanks so much to Brian for all his expertise and hard work. In fact we were so excited about our planter that we entered it (along with the green roof and the rear yard rain garden) into the PHS "City Gardens Contest". Wish us luck!

1 comment:

Chad Ludeman said...

Fantastic concept and execution Christopher. One question. Did you guys need to get a special permit from the streets department to implement and if so, was there any push back at all?