Wednesday, June 18, 2008

Water management

One of the biggest challenges in sustainable design is how to properly manage the water that falls from the sky onto your building and your site. There are a few different schools of thought on this topic. These range from 100% on-site management to channeling all of your run-off into the city's storm water system.

There is also an interesting dialogue happening now between the various governing entities within the city that seems to have conflicts of interest and can be quite confusing to the rest of us. The Department of License & Inspections seems to approach the issue from one end and requires that all storm water be collected and channeled directly into the the City's piping system (with downspout boots and site drains.) I suppose I understand this mode of thought in that they are simply trying to prevent storm water run-off from going places it shouldn't and causing damage and erosion. The PWD - Office of Watersheds, on the other hand, approaches the issue from the other end and is encouraging people NOT to connect to the City's infrastructure by taking measures to manage your storm water 'on-site'. This can be done in basically two ways: harvesting and retention/infiltration. After speaking with a number of landscape architects, green roof designers, and environmental planners, we have decided that the Office of Watersheds' approach is the right way to go. Now it does appear that L&I and PWD are approaching a common ground on some of these issues and PWD actually wants to register all on-site stormwater management projects with L&I.

There's just too much pavement these days. Basically, when it rains, water that falls on impervious surfaces is typically channeled into sewer pipes that travel 'downhill' and eventually lead directly into our rivers, carrying with it many pollutants. By allowing rain to slowly infiltrate directly into the ground, it is able to be naturally 'filtered' by the earth before it makes it's way into the water table and/or rivers. Also, this infiltration allows "groundwater" to recharge naturally, at it's own pace.

Every drop of water that falls onto the earth's surface, falls within what is called a "watershed". A watershed is
an area of land where all of the water that is under it, or drains off of it, goes into the same place. Watersheds cross all boundaries. No matter where you are in the world, you're in a watershed. [From the EPA's website]

The ultimate goal behind PWD's mission here is "to restore our watersheds, by converting our streams, creeks and surrounding green spaces into healthy systems that local residents, along with native fish and wildlife, can use as amenities, sanctuaries and habitats. Stormwater management projects will not only help protect our invaluable drinking water sources, but they will help green the city, restore our waterways and improve quality of life for all residents."

So here's our strategy...

1. Green Roof. We are moving forward with the green roof installation (opposed to the white membrane). We were back and forth for a while as to whether or not we would be able to install a green roof. The only thing holding us back was cost. We always knew it was the right thing to do (and even planned for it structurally) but the choice comes with a considerable fee...especially to do it right. But after many conversations with different folks, we believe that we will most likely be able to recoup the cost in the purchase price of the house, which is all we are really after in regards to this decision. Also, we have decided against going with the 'modular tray' system and are pursuing a more conventional installation. I have had the privilege of speaking with and getting some advice from Charlie Miller with Roofscapes, Inc. Charlie (the 'guru of greenroofs') is responsible for such projects as Chicago City Hall and Life Expression Wellness Center. After speaking with him, I was able to establish the waterproofing and root repellent system, thickness of media, and types of plants best suited for this project. He then pointed me in the direction of JIG. JIG is the construction arm and 'green roof division' of Onion Flats, a design/build/development firm in Philly. I am meeting with them next week to discuss the possibilities of the project. As I have continually admired the work of Onion Flats over the years, the possibility of a collaboration with them on this project is exciting.

Various types of green roofs

Benefits of a green roof:
  • Longer lifespan of the roof membrane
  • Energy savings due to increased insulation
  • Sound insulation
  • Aesthetic amenity (your own little park)
  • Improved air quality and biodiversity
  • Reduces urban heat island effect
  • Storm water: in summer, can retain 70-90% of the water that falls on them; in winter they can retain between 25-40%
Obviously, the last item is the one that directly relates to the topic discussed here.

Green roofs have actually been around for 1000's of years and other countries have been utilizing them much more than the U.S. [From the Greenroofs for Healthy Cities website]: "In North America, the benefits of green roof technologies are poorly understood and the market remains immature, despite the efforts of several industry leaders. In Europe however, these technologies have become very well established. This has been the direct result of government legislative and financial support, at both the state and municipal level. Such support recognizes the many tangible and intangible public benefits of green roofs." Although, I would venture to say that in the last couple of years (and since this statement was written), the green roof industry has exploded in this country, with no end in site. And, with the new administration here in Philly (and soon the U.S. government!!), we are seeing some real exciting changes for the better.

2. Rain Barrels and Rain Gardens. The remaining amount of water that does not get absorbed by the green roof will travel down a downspout and into a Rain Barrel where it will be stored and used for watering the plants in the backyard. A pipe will also be connected to the bottom of the rain barrel which will slowly feed water into a Rain Garden, located under the kitchen windows.

Rain Gardens and a Rain Barrell

In addition to helping recharge groundwater as well as preventing pollutants from traveling into rivers, rain barrels also help lower water costs when the stored water is recycled for landscape irrigation. Keep in mind..."Whether you buy or build a rain barrel, the most important thing to remember is that they are only effective at stormwater management when the stored water is emptied in between storms, making room in the barrel for the next storm." (from Philadelphia Stormwater Management Guidance Manual)

To read more about rain barrels, rain gardens, and many other things you can do as a homeowner to help successfully manage stormwater, check out "Appendices K-L: Voluntary Small Sites Checklist" at

3. Pervious paving. So I know we have mentioned in the past that we intend on paving the backyard with the salvaged bricks from the demolition. Outside of the sustainable strategy of using reclaimed material, this feature will also be beneficial to our water management. Now I realize that this is not "pervious paving" in the true sense of the term as the actual brick pavers are not pervious (which they do make and and which work beautifully) but it's more the surface as a whole system that will allow water to opposed to pouring a solid concrete slab which is the usual strategy. You see, these bricks will be 'sand set' (not grouted) and laid on bed of compacted gravel about 8" thick. This will allow the water that does fall onto the back patio to infiltrate into the ground. Another option that we are pursuing is having a raised wood deck as the central surface with gravel and pervious 'landscape fabric' beneath. We would then find another use for the salvaged bricks...maybe pave the path of the alley running along side the house. Both systems would allow water to percolate into the ground, and in the end, its mostly an aesthetic decision. Also, we are planning on creating a continuous planting bed (no bricks), that will have an increased absorption capacity, around the perimeter of the back yard in order to catch any overflow during heavy rains .

4. Storm Water Planters.
The Philadelphia Water Department Office of Watersheds has embarked on an ambitious program to install storm water planters that are designed to capture and infiltrate street run-off. There was actually a presentation of this at PHS ( Pennsylvania Horticultural Society) on Monday night that Emily and I (and Nicholas) attended. It was a very nice event with a great turnout. 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.

We are tearing up our sidewalk very soon. I approached a couple of PWD representatives and told them about what we are doing here at Montrose and how we are trying to successfully capture all of our own storm water. They were enthusiastic about the benefits that this system could provide for our project. I hope to meet with them soon to continue discussing the concept of storm water planters.

So... from the storm water planters at the street, up the facade, across the green roof, down the spouts to the rain barrel and rain garden, along the pervious paving at the patio, and all the way back to the planting beds along the fence, we are doing our best to properly manage all of the storm water (or at least the "first inch of rain", which I hear is the most important) on our site.


Anonymous said...

You put a lot of thought into water management on the exterior of the house. Has there been any thought on the use of a 'grey water system'? If this has been researched, how cost effective is it, and how long will it take to pay for itself?

I have seen this company advertised a lot on the web and tv:

Southern Liberties, LLC - Phila, PA said...

Thanks, "anonymous", for your continued interest in the project. This is a great question. So far we have addressed water conservation 'inside' the house by specifying low-fixtures, including dual-flush toilets, water-saving shower heads and low-flow faucet aerators. As far as Grey Water Recycling goes, I have looked into it and the cost is fairly reasonable but one concern I have is it's "legality". Grey water is almost always a legal issue for permitted new construction and remodeling (unless you're in a visionary state such as Arizona or New Mexico.) I am still researching this and will definitely let you know what I find. If we can do it on 'the up and up', the Brac system looks like a great way to go. On a smaller scale, I am looking into a product called Sloan Graywater System that is installed under the bathroom sink. It stores and sanitizes the water from the sink drain and then uses is to flush the toilets. I will go into more detail about this and other features in an upcoming blog entry. Thanks again for the great suggestion.

Chad Ludeman said...

I've perused a lot of residential green building projects in the past few years, and I have to say that you guys have done the best job with water management I've seen. Taking it all the way onto the sidewalk with the stormwater planters is going above and beyond, as you're now assisting with your neighboring homes and sidewalk water runoff. Keep it up!