Santa Monica’s Green Street Explored

July 31, 2009 § 3 Comments

The Bicknell Avenue Green Street, looking south toward the Santa Monica Bay

Santa Monica's Bicknell Avenue Green Street, looking southwest toward the Santa Monica Bay

Los Angeles Creek Freak headed west today for an all-bloggers lunch with Siel (Green L.A. Girl) and Damien (L.A. StreetsBlog.) I took the opportunity to go and visit the city of Santa Monica’s new green street project. Creek Freak mentioned this project briefly in an earlier entry, referring readers to Heal the Bay’s Mark Gold’s account of the street’s opening festivities. There’s also coverage of its July 14th 2009 opening at L.A. Frog, LAist, the Santa Monica Mirror, and video footage posted by Global Green. The project was funded by state water bond Proposition 50, the state Water Resources Control Board, the local Regional Water Quality Control Board, the Santa Monica Bay Restoration Commission, and the city’s water quality parcel tax Measure V.

The green street features are located on both sides of the 100 block of Bicknell Avenue, extending from Ocean Avenue to Neilson Way – just a block from the beach, not far from the Santa Monica Pier:

The overall design is pretty smart! It’s reminiscent of some simpler curb-cut water harvesting tree wells (click link for excellent photo worth easily a thousand words) that Brad Lancaster has done in Tucson. The concept is the same: street runoff in the gutter flows into the parkway (landscaped area between the sidewalk and the curb) and soaks into the ground there, watering trees and other plants. In large storms, excess water overflows back into the gutter.

I actually prefer Lancaster’s design, which is simpler and perhaps more elegant; it merely subtracts some concrete, and utilizes the same gap for inflow and outflow of water. The Santa Monica green street is a little more engineered. It has rainwater flowing in a gap inlet, then through a depressed area (a swale), and then any excess that hasn’t soaked in will flow out a second opening (outlet) at the downstream end.

There are many reasons that is all really really good. (Regular readers who have already read L.A. Creek Freak’s multi-benefit watershed management tirade can skip ahead to the next paragraph.) Our local waterways have big problems with pollution (water quality) and flooding (water quantity.) Additionally, we don’t have enough local water (water supply) so we import plenty of it at great monetary and environmental cost. We’ve designed most of our urbanized basin to usher rainwater out to the ocean as quickly as possible. Rain hits a roof, heads down a pipe onto a concrete driveway into a concrete gutter, into a concrete pipe (a storm drain,) into a concrete-lined creek, and into the ocean. We flush that rainwater out as fast as possible, in order to prevent flooding. Another approach, which this street represents, is to (in the words of Brad Lancaster) treat rainwater as a welcome guest: invite her to not be in such a hurry, to slow down and hang out with us for a while. When we slow rainwater down, pollutants it’s carrying settle out. When it runs across earth, the water soaks in and micro-organisms break down the pollutants. This results in cleaner water, less severe peak flooding, and more water stored underground… not to mention greener neighborhoods, more habitat, less air pollution, and lots more good stuff.

Here’s a detailed explanation showing step-wise how the street works: (I’ve shown only one swale area here – there are about ten of these in the whole project.)

Water Inlet

Curb-Cut Water Inlet

Water in the gutter flows in this inlet. The inlet is a gap in the curb that has been covered with a metal lid forming a little tunnel.

Depressed Landscaped Parkway

Depressed Landscaped Parkway

From there the water flows through the parkway in what we creek freaks call a “bio-swale.” It’s basically a mini-creekbed – a depressed, landscaped area between the sidewalk and the curb. The inlet above is shown at the bottom of this photo. The water flows in there and upward (photo-wise) toward the outlet in the upper right.

Curb-cut Outlet

Curb-Cut Water Outlet

Much of the water that enters the parkway soaks into the ground. In a large storm, water will reach the end of the bio-swale and will overflow back out into the gutter.

Porous Pavement Parking

Porous Pavement Parking

In addition to the curbside bio-swales, the parking lane has been paved with porous (or permeable) concrete. In the above photo, the regular black asphalt shows on the right, and the porous pavement beneath the car is slightly lighter in color. In working with the city of Los Angeles on a shared street project in my neighborhood, neighbors pushed for permeable pavement in our street, but the city hadn’t used permeable pavement enough to be familiar with it. They expressed concern that it wouldn’t be strong enough to support the weight of large vehicles, so they only used it for the sidewalk on our street project. Santa Monica has used conventional asphalt for the center of the road, which needs to bear the most weight, and has put the porous pavement in the parking lane, which bears less weight.

Explanatory sign

Explanatory sign

There are signs at each end that explain how and why the street does what it does. Oddly, they’re posted so high that even our 6’3″ tall L.A. Creek Freak correspondent had a hard time viewing and reading them. For a little more detail, there’s a decent almost-readable photo of one of these signs posted online by L.A. Frog. Perhaps the city of Santa Monica could lower these? and perhaps post one of them online somewhere?

Before I launch into some critique, I want to emphasize that this is an excellent project! Yaaaayyyy! It should serve as a prototype for how streets should work all over. I really like that it’s actually pretty “readable” – one can look around the site and fairly easily understand how rainwater flows through it. I think it’s very important that we reveal water flows, so that the public can better understand and value our natural water cycles.

I do want to mention a few additional criticisms:

– To me, the project appears somewhat over-built. There’s quite a bit of impermeable concrete – a swath along the curb, and a few concrete pathways leading from the sidewalk to the curb. Could this have been permeable pavement? or maybe stepping stones? (with wheelchair access to the street at the driveways and at the corners)
Also in the over-built category, there seem to be a lot of extraneous drainage systems. At the end of the street there’s already a couple of good-sized storm drain inlets… but the project has included more than half a dozen seemingly-unnecessary additional drains. There are little green ones inside some of the bio-swales:

Some kind of filter?

Some kind of filter?

and some sort of extra storm drain grates (with some kind of filter devices inside?) at some of the outlets:

Extra storm drain inlet?

Extra storm drain inlet?

Perhaps the project designers could explain what additional functionality (capacity? functionality?) these features contribute. They perhaps add some additional capacity for those once-in-a-lifetime hurricane-force storms. Even if this is true, they appear to be unneeded extra expenses. I suspect that they may make the project more prone to high tech failure… How long do you think it will it take for someone to step on and break those green plastic filter hood thingies?
For my preference, I think that it’s better for us to trust nature to do the cleaning here. Nature does a great job on day one, and only gets better more effective as time progresses. This extra gray filter technology works as well as it ever will on day one and gets worse from there (unless we spend plenty of maintenance resources keeping it clear.) My preference would be to install more basic landscaped bio-swale on more streets, than to add excess thingamabobs and get to fewer streets. I am open to an explanation of what these do… I could be wrong. Also, this is a pilot, so it may be a good place to throw in the kitchen sink and monitor what works and what doesn’t… but it feels to me like someone wanted to spend more more money on gizmos, and less on green.

– I didn’t see any trash grates, which I would have expected on the inlets. Grates would help to keep trash out of the bio-swales.

– Overall the project is designed to keep the existing configuration of the street… which favors cars. If we are to achieve real sustainability in our cities, I think that we need to achieve more modal balance in our streets – which is to say that our streets should foster alternative modes of transportation, including bicycles, pedestrians, and transit. A greener design here could have included traffic calming features, such as bulbouts, which make it safer for pedestrians to cross the street, and which can make for even more permeable green space areas to filter and infiltrate rainwater. The city of Santa Monica has done traffic-calming bulbouts in other areas; similar features here could have made this project street even greener.

Despite some aspects that I question, the Bicknell Avenue Street Greening Project is wonderful. As far as I know, it’s the first place in Southern California where we’ve actually broken the curb to allow rainwater to get out of the gutter and into the soil. It was definitely worth my time to bike and bus across town to check it out, and I am looking forward to observing it function during an actual rainstorm. Congratulations to the city of Santa Monica and all the folks involved in funding, designing and implementing the project!

Another Photo of the Green Street!

Another Photo of the Green Street!

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§ 3 Responses to Santa Monica’s Green Street Explored

  • rajahasson says:

    I attended the Bicknell opening in Santa Monica. Just to clarify some mis-understood design ideas:

    *Those “green filters” are directed to overflow perforated pipes which take the excess water underground within the swale. Swales are designed to handle certain volumes of water. With an overflow perforated pipe, you can ensure that your swale will not “flood” during a larger storm than designed for.

    *The “storm drain inlets” at the swale outlets are directed to the underground infiltration trenches running the length of the street on both sides. This is something left out of the story. These trenches take in the water from the porous concrete, and extra flow out of the swales, and infiltrate them underneath the road. These do not go to the stormwater system. Another reason for the high price tag is tearing up the street, digging the hole, and putting in perforated pipes.

    I agree that a lot of this project was over-engineered. However, a bit more of site observation, and better swale design could make this project better.

    The swales need something (like pebbles) at the inlet to disperse the hydraulic energy. When water entered them during the demonstration, the water pooled up at the inlet, stirred up the mulch, and sent the mulch and water back out the inlet. There needs to be a steeper gradient in the depressed areas as well, followed with a check dam, to make sure the water enters the swale and stays there…

    Thanks for covering this story! As greenstreets become more “normalized”, its important to learn from all of these designs, whether they work or not…

  • Shelley Luce says:

    Thanks for the details on the Bicknell green street, I also am thrilled that Santa Monica put this in. Also I wanted to mention that there are very simple curb cuts along Lincoln Blvd. at the Playa Vista development – they simply dug a swale between the sidewalk and the curb, planted it with grasses, and made cuts in the curb for the water to flow into the ditch. Looks pretty and simple and cheap to me. The parking lot of the new Whole Foods market on Lincoln Blvd. at Rose Ave. also has some seriously cheap BMPs – they cut holes in existing curbs around parking lot planters. I can email you some photos if you are interested!

  • Mike says:

    Permapave can be used to retrofit open grates to keep 100% of gross pollutants out of the sewer grates and allow only pure water to filter in, preventing floods and reducing pollution.

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