Wednesday, November 07, 2012


Your Honolulu taxes at work: carrying private storm water to the ocean

by Larry Geller

I’ve written about stormwater and methods of getting rid of it before, but looking at some of the pictures of devastation caused by Hurricane Sandy prompts me to go over this issue again. It’s an area where Honolulu appears to lag the rest of the country, and of course we pay for it. This is not an area where I have any expertise, but heck, I’m paying for this infrastructure and want to speak my mind on it. Perhaps some new legislation would actually save us taxpayers some money. To get there, someone will have to speak up first (sigh).

You’ve seen those little stencils or medallions on the sidewalk saying not to throw stuff in the storm drain because it goes to the ocean. Indeed, there is a system of drains and pipes which do just that—take the runoff and whatever is in it and dump it into the ocean. It’s part of our municipal infrastructure.

There’s a neat web app that shows where each drain, catch basin, manhole cover and pipe is located. The system is quite extensive.

When you go to the web page, for some reason it opens centered on Mililani:

Stormwater main window

That’s quite a network of pipes, and obviously benefited the developers and now the residents of the area.

Moving it around, we can see that indeed city water is dumped into the ocean:

Goes to ocean

The view above shows several outfalls into Honolulu Harbor (the little green diamond icons).

Of course, every city needs to get rid of its street water, and our tax money goes to support the sewer system that takes this water off our hands. Sewer maintenance (even if the City and County were good at it) costs money.

Honolulu even picks up private water and carries it to the ocean—at public expense. Several other states do not allow this. They require developments (for example, shopping malls) to dispose of their own storm water in-place.  In other words, the rain falls and goes into the ground just as it did before the area was developed. Usually, this also feeds the ground-water system, so aquifers are preserved. Why dump perfectly good rainwater into the ocean??

Honolulu is not a member of that club.

Here’s an example. 

Switching the same app to satellite view, we peer down at Zippy’s on Vineyard Blvd. (click for larger). Zippy’s is towards the right. The street going diagonally from upper right to lower left is Maunakea.  Right at the Maunakea driveway is a red dot, with another across the street. Those are catch basins. In other words, spots where water is picked up to enter the drainage system. The water then moves down the street along the colored lines and eventually gets dumped into the ocean.


Let’s check further. Right near one of the red dots we find this channel, leading from the Zippy’s parking lot under the sidewalk and into the street:

Zippys runoff 1b

The camera is located inside the parking lot, looking out towards the street. Zippy’s has built this neat little channel that takes the water out of their parking lot. At the center of the photo is a steel plate covering the channel as it goes across the sidewalk. Where does the water go from there? Into the gutter. And then into the city stormwater system.

Zippys runoff 2

Here’s another channel, this one close to the corner of Maunakea and Vineyard. This picture is taken from the Vineyard Blvd. sidewalk. The channel drains water from the landscaped area in front of the restaurant on the Vineyard side. That’s the neatly cared-for foliage that you see when you drive by. Any pesticides, any weed killers, and of course rainwater travels under the sidewalk and ends up in the gutter.

Now, if there were laws or regulations in effect when the property was developed, it could have been a requirement that the developer install facilities to dispose of the water right on the property. In a parking lot, this can be done with permeable asphalt, for example. It’s a specially-formulated asphalt which allows rain to pass right through and be absorbed back into the soil under the parking lot.

Here’s how it works:

Have you seen anything like that in Honolulu? I haven’t.

The landscape at the front of Zippy’s could similarly dispose of its own rainwater. Probably a great deal does go into the soil anyway.

If you walk down Maunakea through Chinatown, check for all the little pipes dumping water into the street. Those pipes are no doubt ancient. They take water from rooftops (and perhaps elsewhere) and dump it into the street. They pass under the sidewalk and discharge at the curb. Unless you look for them, no one would see them. There’s nothing to be done about these, and I only used Zippy’s as an illustration. I’m not suggesting that these should be removed at this point.

If we want developers to dispose of their own water and not put it into the city stormwater system, we may need laws to make that happen.


Larry, if you had talked to folks in the Department of Health Clean Water Branch or the City's Department of Planning & Permitting Civil Engineering Branch, you would have discovered that the laws of the State and the City do require land owners to hold storm water on their sites and allow percolation and settling out of sediments to reduce non-point pollution discharges reaching the ocean, as required by the EPA. in addition, a new refinement of the program called "Low Impact Development" will add requirements for bio-filtering and capture of storm water for irrigation purposes as a condition of building permit approvals for a wide range of projects which are most likely to have storm water pollution impacts.

You are right to point out the problem, and yes we could do better, but you are way off the mark in saying we don't have laws on this. They have been in place for a number of years and have greatly affected all new construction.

I didn't speak to the DOH or the Civil Engineering Branch, but I did speak to a landscape architect about stormwater. Perhaps I have done a bad job of research, and I will have to check with the sources you suggest. I did not learn that water could not be discharged into the city stormwater system, and I wasn't asking about sediment, which I knew is not supposed to be discharged into the system. I also did not ask about future laws.

It's not only the pollution, but the holding of the water itself. I also learned that permeable pavement was not used here.

Ok, back to the drawing board, and thank you very much for your comment.


The problem is that a lot of the existing buildings were built before the existing non-point pollution laws went into effect. I think with climate change water is going to get more valuable and businesses are going to realize that they are letting money run down the stormsewers.

With the high cost of water already, I am surprised that more use is not made of catchment water when possible. Homes in Manoa are blessed with abundant rainfall but don't make use of it.

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