Urban heat islands

I was wondering if anyone here has any knowledge of using porous pavements to acquire LEEDs credits for reducing urban heat islands. This is something my firm wants to get more familiar with, and I thought this was the perfect place to ask.

Thanks in advance,

ktulu

First, my disclaimer: I know nothing about LEED, and am not an environmental/regulatory person.

Here my thoughts on it (might not answer question, but help spark discussion), just a brainstorm on it.

That would seem to be adding quite a bit on non-point source polution (eg antifreeze, oil, cleaning chemicals and gas/diesel) to the ground water supplies. I know some cities in CA have developed stormwater treatment plants to take point source (ie before it enters the ocean) pollutants out of the water.

It seems like soil type should be taken into account (eg, hardpan would absorb much less water than gravely sand).

what about heaving in frost prone areas?

I wouldn't think porous asphalt or concrete would be any different from the non-porous varieties in terms of heat absorption/radation. If you use something like grass pavers, then that's different. But you would only want to use grass pavers for some sort of overflow parking, for a couple of reasons: One, the grass won't grow if people are parking or driving on top of it every day. Two, nonpoint source pollution, like Desert Water says. In a heavy use parking lot, it's just better overall to use regular pavement and direct the runoff to a treatment BMP (sand fitler, bioretention, etc.) prior to any infiltration.

On the other hand, I think the biggest use for permeable asphalt and concrete pavement is sidewalks and other pedestrian areas. I still don't think it helps with the heat island issues (plant some trees....), but it certainly helps in reducing the overall runoff volume that you have to treat and dispose of.

Everyone in my neck of the woods is going nuts over this porous paving stuff. All our landscaping guys and planner types want to use it everywhere for everything. Like it's going to make your strip mall parking lot hold onto water like a forest.

Some of my big concerns are:

1. What kind of soils do you have underneath and where is the seasonal high groundwater? You need to be sure the water will actually drain.

2. Frost action. Not a concern everywhrere but a big deal here. If you get water trapped in the pores and it freezes/thaws over and over again it will screw up your road.

3. How do you go about modeling it? I do a lot of stormwater modeling and need some guidance before I'd feel comfortable about plugging that into HydroCad.

I agree with DLeg here. Pave it with the normal stuff, then put a BMP in somewhere. I think porous pavement can help make your site greener, but it's not a be all end all in stormwater management. I also don't think it's proven well enough yet.

^^The guidance I got from our stormwater design contractors was just to treat it as an area with a lower C if using the Rational method, or a lower curve number for TR-55 based models like Hydrocad. Good engineering judgment is required - if designing a BMP I'd base it on the underlying soil's hydrologic group and treat it as lawn/turf, perhaps, but if I was designing anything critical like detention/overflow structures or culverts, I would probably just assume that it becomes clogged over time and treat it like pavement.

But, the original post was about heat island effects and whether or nor porous pavement (****, you don't know how many times I inadvertently typed "porpous pavement") would reduce it, to which I again say no, not at all. Not if you're talking about porous asphalt or concrete pavement.

Also, another disadvantage to porous pavements is clogging - although I know they have vacuum machines that can supposedly suck it clean, I still wouldn't spec porous pavement for anything other than a pedestrian area or some VERY lightly used traffic/parking area. All it takes is one rainy day or a nearby construction site and your pavement would get clogged right up with tracked mud.

I agree in that most porous pavements are designed and used for water drainage, etc. but they have also been shown to reduce the UHI effect (UHI = Urban Heat Island). They do this by absorbing and storing less heat, they reduce the heat buildup and heat radiation produced by conventional asphalt and concrete pavements.

Research has been conducted at Arizona State University. ASU

What I an trying to find is a project that has successfully used porous pavements for obtaining LEED credits for reducing UHI. I am beginning to think that none exist right now.

ktulu

I stand corrected! Nothing like some good data to kick one's assumptions in the butt.

ktulu said:

What I an trying to find is a project that has successfully used porous pavements for obtaining LEED credits for reducing UHI. I am beginning to think that none exist right now.

Click to expand...

Have you considered searching LEED Project Certified Search List or contacting the US Green Building Council (USGBC) at [email protected]

Good luck!!

JR

For REAL information related to Porous Pavement Technologies, please go to the University of New Hampshire's Stormwater Center Website. What you will find is that Porous Pavements not only work EXTREMELY well for stormwater peak rates, they work even better as a BMP for stormwater quality. I would without a doubt spec porous concrete or asphalt before I spec'd an underground storage system. I don't care about cold weather climates, heaving, frost, expansion, poor soils below, seasonal high water. If you know what you are doing, you can design a system that will work as a driving surface and at the same time act as a drainage detaining structure. With every single concern you may have, I have a research proven remedy. If you need any help with modeling, designing, or installation advice, please feel free to contact me at [email protected]. I am a busy professional but I will do what I can to answer any questions you may have.

As the Federal Government starts handing out fines for polluting impaired water bodies, you will see more and more local governments mandating these porous technologies. They work no matter where you install them as long as you install them correctly.

A porous concrete pavement system that looks like it may be clogged, still functions usually at a minimum of 22 inches per minute. UNH's porous asphalt install does not get vacuumed yet it still has absolutely no run-off even when a 55 gallon drum of water is dumped on it.

Get on board now. Learn it now before it is forced on you.

ktulu said:

I agree in that most porous pavements are designed and used for water drainage, etc. but they have also been shown to reduce the UHI effect (UHI = Urban Heat Island). They do this by absorbing and storing less heat, they reduce the heat buildup and heat radiation produced by conventional asphalt and concrete pavements.
Research has been conducted at Arizona State University. ASU

What I an trying to find is a project that has successfully used porous pavements for obtaining LEED credits for reducing UHI. I am beginning to think that none exist right now.

ktulu

Click to expand...

Here in NH I have one in construction, and a handful at the Planning Board. All are looking for LEED Cert. We are getting our LEED Certification as Professionals in the near term future.

Desert Water said:

First, my disclaimer: I know nothing about LEED, and am not an environmental/regulatory person.
Here my thoughts on it (might not answer question, but help spark discussion), just a brainstorm on it.

That would seem to be adding quite a bit on non-point source polution (eg antifreeze, oil, cleaning chemicals and gas/diesel) to the ground water supplies. I know some cities in CA have developed stormwater treatment plants to take point source (ie before it enters the ocean) pollutants out of the water.

It seems like soil type should be taken into account (eg, hardpan would absorb much less water than gravely sand).

what about heaving in frost prone areas?

Click to expand...

Porous concrete and asphalt both develop a microbial like system within the gravels. The amazing thing is this microbial system actually enjoys snacking on oils, kerosene, gases and so on. Porous technologies are the best BMP for stormwater quality.

VTEnviro said:

Everyone in my neck of the woods is going nuts over this porous paving stuff. All our landscaping guys and planner types want to use it everywhere for everything. Like it's going to make your strip mall parking lot hold onto water like a forest.
Some of my big concerns are:

1. What kind of soils do you have underneath and where is the seasonal high groundwater? You need to be sure the water will actually drain.

2. Frost action. Not a concern everywhrere but a big deal here. If you get water trapped in the pores and it freezes/thaws over and over again it will screw up your road.

3. How do you go about modeling it? I do a lot of stormwater modeling and need some guidance before I'd feel comfortable about plugging that into HydroCad.

I agree with DLeg here. Pave it with the normal stuff, then put a BMP in somewhere. I think porous pavement can help make your site greener, but it's not a be all end all in stormwater management. I also don't think it's proven well enough yet.

Click to expand...

Actually it is proven and is now becoming a staple in our EPA letters when we exceed 10,000 sf of wetland fill. Ask you client if he wants to install a 1 acre pond or would he prefer to add another 20,000 sf of retail space.

^ Let me guess. You work for UNH?

I was going to attend one of your workshops at the field lab site but got sick that day. I would like to get to one in the spring. Most engineers I know are very skeptical of the stuff.

This is a fairly hot topic these days though. I got me an idea for an after dinner topic for an ASCE meeting sometime...

danbalfour said:

... Porous technologies are the best BMP for stormwater quality.

Click to expand...

That's a pretty big claim there....

Why don't you provide the link to the university website you referenced, so others can find it more easily? I'm interested, but not entirely sold.

^^^ x2 +1

JR

VTEnviro said:

^ Let me guess. You work for UNH?
I was going to attend one of your workshops at the field lab site but got sick that day. I would like to get to one in the spring. Most engineers I know are very skeptical of the stuff.

This is a fairly hot topic these days though. I got me an idea for an after dinner topic for an ASCE meeting sometime...

Click to expand...

No I actually do not work at UNH.

for others that asked for the link

http://www.unh.edu/erg/cstev/

Yes I agree it is a very bold statement but if you have the time to be on this board, you have time to research it. Look at the numbers in regard to stormwater quality. No net gain in TMDL will be the catch phrase in 2009 and porous technologies actually provide the solution.

jregieng said:

^^^ x2 +1
JR

Click to expand...

Here is a nice little link for a packet of info regarding Porous Technology!!

http://www.cement.org/bookstore/profile.asp?itemid=EB303

^^^ Thanks for the links!!

I have been home sick - this will give me something to read over while I wait for my death sentence to be commuted. :hung-037:

JR

danbalfour said:

Yes I agree it is a very bold statement but if you have the time to be on this board, you have time to research it.

Click to expand...

Dan,

you need to cut back on the red bulls, we're all friends here... YOU made the claim, YOU provide the proof...

There are other things than "no net gain" in stormwter management to worry about. Groundwater contamination comes to mind. That's my main problem with porous pavement technologies, if the clogging issues get worked out. Like I said before, I think it is a good choice for certian uses, but for "hotspots" where contaminants to groundwater are a concern, I don't think I could ever agree that porous pavement is the "best" BMP.

In the interest of maintaining professionalism here, I think I speak for many of us when I ask if you could disclose, if you're not a representative of UNH, just who do you represent? Do you represent a company that installs porous pavement technology? I don't know if it's ever been stated in the rules here at this forum, but at most other forums, statements from vendors are usually required to be identified as such.

No offense, it's just that I've been in stormwater for a while and I've never heard anyone make those types of claims about ANY BMP, unless they were advertising one that they personally sell. So far, I've seen absolutely nothing in the literature to suggest that porous pavement, or ANY other BMP is the "best" in all situations.