How to create a clean water alley, Part 5

While the concrete cured, the crew focused on several elements as illustrated in the following photographs

Refining grade elevations for the bio-swale.
Refining grade elevations for the bio-swale.
Prepping the wall for paint.
Using a roller prevents overspray into adjacent properties
Using a roller prevents overspray into adjacent properties

At the end of November, rain was predicted, and with an incomplee bio-swale, the crew protected the project site from sediment carried in runoff. Construction was halted for several days.

Preparing for rain

Preparing for rain

Rain delayed construction

Rain delayed construction

The storm was an opportunity to see how run-off would flow through the bio-swale.

When it was dry enough to work, the crew focused on completing the forebay and the weir apron.

Placing cobble in the forebay.
Placing cobble in the forebay.
Cobble in forebay almost complete.
Cobble in forebay almost complete.

If you’ve ever wondered, bollards” are structural elements – often posts – that allow pedestrians access but block vehicles from entry. Bollards at the entries of the Paseo make it easier for pedestrians, strollers, and carts to acces the Paseo.

Placing the bollards
Placing the bollards
Making sure the bollard is level.
Making sure the bollard is level.

During the final days of construction, the crew installed the green screen, refined the eleveation points for the bio-swale, and planted more than 10,000 plants native to southern California.

A green screen provides a structure for native vines to grow and adds an element of interest to the length of the Paseo.

Installing the green screen.
Installing the green screen.
Final bio-swale elevation points.
Final bio-swale elevation points.
Placed, spaced, and ready for planting.
Native plants placed, spaced, and ready for planting.
Bio-swale planted…
…and mulched.

A resident appreciated the opportunity to test the “strollability” of the almost complete Paseo.

Testing the ‘strollability’.

The Paseo, ready for pedestrians and rain.

Paseo north entry

The Council for Watershed Health would like to express our appreciation to the residents adjacent to the Paseo and in the neighborhood for their patience with the various construction activities.

We also thank our project funders:

Urban Greening Proposition 84, Strategic Growth Councill, State of California

Santa Monica Mountains Conservancy

Proposition O, Bureau of Sanitation, City of Los Angeles

Department of Water & Power, City of Los Angeles

How to create a clean water alley, Part 3

Now that the infiltration trench and bio-swale have been constructed, it is time to lay the sidewalk, which goes on top of the infiltration trench. How’s that, you say? Putting a sidewalk on top of the place where water is supposed to soak in? For the Paseo, we installed pervious concrete but even if we had used regular cement, it still would have worked as the system is designed to receive water from the bio-swale underground.

The Pervious Concrete Pathway winds its way from one end of the Paseo to the other, providing a pleasant and safe path. Pervious concrete has ‘voids’ or gaps that are created when the fines are removed from mix thereby allowing water to flow through the concrete. Water falling on or over the pervious concrete will flows through these spaces to the infiltration trench below it. To begin construction of the Pervious Concrete Pathway, a course of gravel was spread out over the infiltration trench and areas of the exposed impervious liner.

DSCN2844

Unlike Portland cement concrete, pervious concrete sets up quickly. Many hands were needed to pour, spread, smooth, and score the concrete. The choreography of material and work was impressive that day and kudos to Rudy and his crew at J&M Contractors for a pathway many will enjoy.

To aide in the curing process and protect from errant soil or debris, the completed pathway was covered with plastic sheeting. Below you see the completed pervious pathway along with one of the landscape boulders.

Next up is construction of the Forebay, an important element of the design to protect the bio-swale from erosion and clogged soil.

To be continued

Is Your Garden a Working Landscape?

Gardens on Elmer Avenue in Sun Valley hold rainwater and recharge the aquifer, replacing what they use…and they are pretty, too. I’ll be talking more about Elmer Avenue in the next few weeks, telling the story of the street from research and conception to implementation.

Bioswale in the Rain