Tuesday, December 13, 2011
Some more impressive videos of water simply disappearing into the ground
by Larry Geller
I was questioned after breakfast. I had some typos in the article below, and wasn’t “knee-high” water in the parking lot of the Ewa Beach Elementary School a mistake? How could that be true?
Well, it was in the original article in the Star-Bulletin. I do make mistakes, so I checked again.
I wonder if they had “no swimming” rules for the parking lot?
Seriously, that’s a horrible situation.
In a comment on that article, Kolea appreciated the video at the end. It is impressive. A more common use for permeable asphalt is to handle rainwater in parking lots.
Here are two more videos, repeated from an earlier article. There are plenty similar videos out there on YouTube. Just Google for them. Key words: porous asphalt, pervious asphalt, permeable asphalt. Concrete can also somehow be made porous it appears.
The first video could be a simulation of Hawaii’s heavy rainfall. Let me emphasize why I am suggesting this: we don’t have to pay big money to carry polluted water to our oceans. Watch the video to see how well it works.
The second video explains just that. Seattle considers runoff that contains oils and pesticides to be a problem in Puget Sound. So the idea is that they can get rid much of it without dumping it in their waterways.
Apparently there was flooding on the H-1 this morning. I don’t know if porous asphalt shoulders would have helped, but it might have. A lot depends on the height of the water table and the quality of the soil, etc. Could this morning’s frustrating traffic jams have been avoided if different roadway technology were used? Maybe.
Update: Trying to get to a late afternoon meeting today, traffic was hardly moving. So I had plenty of time to get out my cell phone camera and snap this sewer regurgitating stormwater picked up from somewhere else, of course. Perhaps there would be less of this backup if there were less water in the system to begin with.
Porous pavement might have its place, but runoff from roadways contains a lot of nasties including hydrocarbons, heavy metals and particulates. Direct infiltration of this water without treatment is not a good idea.
Actually, the infiltration removes stuff in the water. Here is an arbitrary snip from an article:
Permeable pavement can be very effective at eliminating many pollutants that are of concern in the Charles River watershed:
Total Suspended Solids: 85% – 95%•
Total Phosphorus: 65% – 85%•
Total Nitrogen: 80% – 85%•
Nitrate (as N): 30%•
A study measured the level of pollutants in runoff (water on top) and infiltrate (gathered from the bottom), including measuring copper and zinc, and found pollutants to be reduced.
It certainly better than dumping our runoff in Nuuanu Stream!
We don't treat runoff anyway, as far as I know, we dump it in the ocean.
I may have been the last person to have become aware, but I recently saw a documentary on the water engineering of Machu Pichu. Not only did they capture and divert rainfall for drinking water and irrigation, but also to prevent the undermining of the structures perched precariously on the mountain top. Maybe, some day, we will catch up with them.
Here's a link to a Google search which will lead your readers to good in-depth accounts. Fascinating:
HI Larry! We are using permeable pavement for sidewalks and parking lots in many of our local LEED projects (www.usgbc.org) for the very benefits you state. There can be some maintenance issues with siltation in certain applications so a civil engineer and landscape architect's input are important. We definitely should use this type of pavement more often. Alternatively, for smaller projects with defined boundaries we can channel rainwater on conventional concrete into underground cisterns to use for irrigation -- which is a huge waste of potable water in itself. -karen s
Thanks for your comment.
Yes, cisterns, swales and bio great alternatives.
Sadly, here in Hawaii, still being carried away in pipes at taxpayer expense.