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Interesting Brian! Also, "Jack the Sparrow Hawk" might be better known as "Jack the American Kestrel." These beautiful birds are the most common found falcons in North America.


Tanner Springs Park is a “small pocket” indeed. Unfortunately, it is too small to be much of a wildlife habitat. It is too bad the city and developers backed-off their plans to daylight the entire Tanner Creek. It would have been a nice natural break from all the glass and concrete, would have supported a much broader range of wildlife, and would have helped Portland ”become an innovator for nature in the city.”

As for ecoroofs is there any long-term cost / benefit analysis that take into account long-term maintenance?

Did you ask Mike Houck to comment on ecoroofs? Are ecoroofs good habitat for anything besides plants?

I understand that ecoroofs slow and filter run-off, but I imagine it would be more beneficial, if not as exciting, if the money were instead spent to divide our combined sewer system.


interesting. Looking forward to more dialogue on this topic.



I think the goal would be better to not even need to split the combined sewer system. If a site just simply uses it's own storm run-off, through harvesting for non-potable uses and percolating the rest, you wouldn't need to uproot the whole sewer system in the process. Let's stop investing so much in a storm sewer system that doesn't solve the real problem. Sure, likely there will need to be some overflow into the combined system but the attempt should be made to make this minimal. In Portland, we benefit from a very predictable stormwater season.



Gardens as graphics on the roofscape of our buildings gives something back to not only the city, affording pleasant views rather than rooftop HVAC, but also provides habitat which supports attributes of biophilia. Habitat for birds could work on roofs, and we might even design them to promote it, BUT we will have to take care with the glass that is adjacent. That is the killer to the birds. Especially when they see a tree on the inside. Nice horizontal grill, or pattern on the glass surrounding these eco-roofs could prove to be a nice amenity to any city or building.


I like the look of ecoroofs, but I want to be sure that they are as green as they look.

Of the water that falls on an ecoroof in Portland, what percent is actually evaporated back into the atmosphere, and what percent is just slowed on its eventual path to the sewer? Given that Portland’s predicable storm water season has little sunshine, my guess is a large percent is just slowed on the way to the sewer.

There will always be storm water run-off from sidewalks and streets and from parking lots and roofs for years to come. Treating storm water and sewage the same is inefficient (not green) and so I think Portland will eventually divide the systems. It is too bad we are spending $1.4 billion on a “big pipe” to simply move storm water and sewage to North Portland instead of, as we will eventually have to do, dividing our sanitary sewer and storm water lines.


See here for one cost/benefit analysis: http://www.portlandonline.com/bes/index.cfm?c=50818&a=261053

And don't forget about transpiration - evaporation isn't the only mechanism vegetated systems provide to get water out of the system. It's not wholly sun-dependent.




True green strategies strive to de-centralize as much as possible. Why depend on the electrical grid if you can make enough power on-site. Why pipe drinking water from Mt Hood when you can harvest it locally. Green roofs are the first step in de-centralizing our stormwater systems. Rather than spending a ton of money to provide a new stormwater sewer grid throughout the city, why not use that money to stimulate more robust green roof systems, rooftop planters and other common strategies at grade so that a site can truly be self-sustaining when it comes to rainwater?


Thanks for posting Brian. The event this weekend is described in detail at www.portlandonline.com/bes/ecoroofpdx , and Friday's sessions would be especially relevant to this discussion.


Dreiseitl's park in the Pearl has very little to do with ecology. It is nothing more than an energy intensive recirculating water feature and unusable open space that does nothing but put further pressure on other areas for open space and recreation. Dreiseitl sold the residence in that area a bill of goods with his fancy video presentation and blue jump suits. The park isn't even a very comfortable place to hang out, much less a thing of beauty.

Brian Libby

Aneeda, appreciate your opinion but I don't completely agree. I like the idea that not every open space is about recreation and tons of people spending time there. Given how solidly nearby Jamison Square Park fills that role, with kids frolicking and such, I appreciate that Tanner Springs Park is its opposite.

The ecology at Tanner is admittedly far more symbolic than literal. But symbolism isn't wholly without value either. Whenever I'm in this neck of the Pearl, I enjoy spending time sitting on the steps of Tanner and getting a little Zen moment in the center of the city.


Mudd , good thoughts ! I might go one step further and require all new buildings to have water storage tanks built in , to capture 90 % - ish of all rainwater for re-use. Dream Big !


Your note about Tanner Springs Park above, could have been written by me. I'm glad that Jamison Park is popular but I really appreciate the tranquilty of Tanner Springs Park.


Mudd, I am in favor of decentralized treatment, which is one reason spending a ton of money on the the "big pipe" seems like a bad idea.

The “Cost Benefit Evaluation” to which Stephen linked (thank you Stephen) seems to indicate more data is needed. Under the “Certainty of Information” section, the evaluation states, “Many reports describe costs and benefits qualitatively or without documentation. Furthermore, limited information exists on Portland-specific performance, cost or benefits.”

Given that is evaluation represents a possible rosy scenario, so to speak, the report states that an ecoroof can reduce run-off by 56% in the summer and 47% in the winter. A larger percent than I would think, but that still leave half the water needing further treatment.


Most of the cost saving in the Cost Benefit Evaluation comes from an assumed longer life span of an ecoroof (40 years) over a conventional roof (20 years). The evaluation states, “Not needing to replace or significantly improve the conventional roof twice would provide an avoided cost of $600,000.” Wouldn’t the ecoroof only save one replacement, as at the end of the 40 years the ecoroof would also need to be replaced? Am I missing something?

The evaluation does not indicate how much more an ecoroof would be to replace on an occupied building or repair compared to a conventional roof. The evaluation seems to only take into account the original new installation cost of the ecoroof.

Furthermore, under “Ecoroof Construction Costs” the evaluation states, “Ecoroofs vary greatly in cost.” and “For the purposes this evaluation {sic}, a simple ecoroof that represents the bare minimum components that will function effectively in Portland’s climate”.


Yeah, yeah. Sure, Linder, sometimes the math doesn't add up perfectly. Luckily, the design world isn't made up of mathematicians making all of the decisions.

Green design cannot exist without beauty.

However, since you keep it up with the math, that other half of the stormwater could easily be consumed via additional synergistic strategies related to water. The only way we will ever get truly green buildings and sites is by looking at everything as inter-related. In this case, consume the other 50% of your stormwater thru rainwater harvesting for the occupants' non-potable needs as well as for productive gardens or other things that people can enjoy. Definitely, don't just put it in an expensive pipe in the ground.


I agree that more data is always a good thing, and the report I linked to is only one story. But if you're focusing on the separation of the sanitary and storm systems, which according to you we will "eventually have to do", some corrections are in order. The report states that the 56% reduction is average annual volume reduction, not the summer reduction as you described. The actual number stated for summer volume reduction is 86%. But perhaps most importantly, the peak flow reduction - or the reduction of flow at the highest flush of a storm - is 96%. As far as the combined sewer system is concerned, this is a very important number that bears mentioning.


Stephen, you are right to point out that the peak water flow reduction is one of the most important environmental benefits of an ecoroof, and sorry about misquoting the summer water data.

However, the implication of this post is that ecoroofs provide some type of improved habitat for wildlife, and help "to re-introduce nature and wildlife into the city" but to date I don't think that is the case. I would like to see ecoroofs that actually focus on creating habitat with native plantings, perhaps attempting to recreate an oak savanna.

So much habitat restoration work needs to be done in Portland's existing opens spaces, work with a proven record of accomplishment. I feel money spent on existing habitat restoration will yield wildlife that is more diverse if that is the goal.

As a birder in Portland for the last 18 years, I know we have been losing habitat and wildlife diversity in the city, though there are a few bright spots of restoration work.


Urban Habitats has a relevant report “Space for Urban Wildlife: Designing Green Roofs as Habitats in Switzerland,” by Stephan Brenneisen here:


The report outlines the importance of increased and varied substrate depth and natural substrate composition in support diverse pant, insect and bird life.

The paper quotes studies that “clearly showed the limitations of the roofs for supporting certain species” that could do reach the roof or could not survive the harsh dry summer conditions on a roof. In addition, “The size of the replacement habitat provided by green roofs is also a limiting factor. In the recent study (Brenneisen & Hänggi, 2006), the shunting yards cover several hectares and are thus in a different order of magnitude to a typical green roof”.

Given the increased requirements of a diverse habitat supporting ecoroof and the relative abundance of natural habitat in Portland in comparison to Basel or London, I am convinced that investing limited money in restoring our existing natural habitats would have a much greater impact on wildlife for years beyond the limited life of an ecoroof. In addition, the best opportunities for ecoroofs would appear to be on very large roofs on the outskirts of the city, such as the Swiss rail “shunting yard” or the Stucki Shopping Center in Basel, which is “roughly half the size of all the greenroofs in Portland.”

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Don't you envy the freedom of birds, that they can fly without mechanical assistance? And no ticket needed!

[name removed - spam]

I need information on Eco roofs like the cost and everything?
If u have a normal roof (slanted at points) can you still have an eco roof and can you plant vegetables or flowers on it? How much would the whole thing cost? You would have to get the plants changed in winter right? How much would that cost?

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