Wildlife

Thursday, 1/28, was a beautiful day in Southern California.  Apparantly the blue skies and fresh air attracted a lot of wildlife, including some birds that we don't often see at the Nature Center.   Here is a Green Heron enjoying the sun. 

   Below is a Double Crested Cormorant scanning the water for a morning snack.  Just after the photo was taken, this cormorant snapped up a fish that looked to be about 4" long.

This juvenile Least Bittern didn't seem bothered by the heavy equipment moving boulders on the streambank about 30 feet away.  The sun and the wealth of pollywogs in the water more than made up for the noise.

The Nature Center turtles have been hibernating in the mud around the lakes for the past couple of months and the warmer weather brought them out in droves.  Dozens of turtles were floating happily in the lakes, with just their faces above the water, soaking up sun and air.  Below is a River Cooter showing off the pretty yellow markings under his/her chin.

Fungus are sort of the bridge between flora and fauna and, of course, the rains have been great for the fungus population.  Below is a photo that I really like, showing a very clear image of gills.

Rain of Epic Proportions

Willow poles will be planted along the stream banks to prevent erosion. The half-mile long stream has a mile of banks and that means we need a lot of willow cuttings. Willows grow literally like weeds and need to be removed from waterways that serve as flood control channels.  Mike Bubalo Construction has another project constructing spreading basins for the Santa Ana River, and the site is thick with willows.  So they are removing willows from there and bringing them to the Nature Center to use in our bioengineering treatments.  It's really a win-win situation.

Looking at the pond built to hold the willows last week, we wondered how we would keep it from drying out.

Dry willows turned out to be the least of our concerns this week as torrential rains drenched Southern California. The lakes in El Dorado Regional Park are connected, with overflow from the first lake south of Carson flowing to the lake north of Wardlow, then under Wardlow to the lake south of Wardlow, then to Horseshoe Lake, finally flowing into the north lake at the Nature Center.  The photo above shows the overflowing Horseshoe Lake just north of Spring Street in the Regional Park.  The photo below shows the overflow draining towards the culvert under Spring Street, on its way to the Nature Center.

The north lake quickly overtopped the dam above the weir and water flowed into the streambed. The dam at the south lake was intentionally breached to allow storm water to drain from the stream and into the south lake. Overflow from the south lake drains into Coyote Creek and then into the San Gabriel River and on to the Pacific Ocean.

While the rains will delay the project a little bit, they also give us the opportunity to check where bank erosion is the most severe.  Next week we'll be making sure that our bank treatments are focused on the places that most need protection.

3 Abutments Down, 2 to Go

The foundations for the bridge abutments were poured last Friday (1/8).  Above is a photo of the foundation for the east abutment for Bridge 2.  On Wednesday, 1/13, the abutments were poured for Bridges 1, 3, and 4.  The abutments for Bridges 2 and 5 are scheduled for later this morning.  The photo below shows the pour of the west abutment for Bridge 3.

After the concrete is poured and vibrated, it has to be smoothed and finished.  This work looks really easy, but the material is heavy and it takes a skilled hand and eye to do a good job quickly.

Once the concrete has set enough, the forms are removed.  In about 2 weeks, the concrete will be fully set.  The pre-fabricated bridges will arrive and will be placed atop these abutments.  The area around the abutment will be back-filled and boulders will be placed aesthetically around the abutment and streambank for erosion protection.  The path will be graded to provide a smooth transition between path and bridge.  Above is the east abutment for Bridge 1.  I thought it looked like an upright piano, so I gathered up wood chips for the black keys and asked Terry to play us a little tune.  The sound from this thing is awful, but how often do you get to play a concrete piano while standing in a dry streambed?

Pouring the Foundations

On Friday, 1/8, the foundations for the bridge abutments were poured.  Access to the location of the 1st bridge was the most difficult and concrete had to be brought in with a skip loader.  But even the skip loader could only get to the abutment on the east side of the stream.

Access is so limited on the west side that the only thing small enough is a Bobcat.  The Bobcat scooped concrete from the skip loader and took it to the other side of the streambed.  Doesn't it look like a baby bird being fed by its mommy or daddy?

And here is the Bobcat putting concrete into the form for the west abutment for the 1st pedestrian bridge.

The other bridges are MUCH more accessible, and the cement mixer was able to drive down the stream corridor and pour straight into the forms.  The photo above shows concrete being poured into the form for the east abutment for bridge #5.  The crew member on the right is vibrating the concrete so it will fill the form evenly and bond strongly to the rebar.  The photo below shows the mason getting the concrete smooth and level.

Getting Ready to Pour

The pits have been dug and the rebar placed for the footings for all the bridge abutments.  The inspector from the City's Department of Development Services was out on Thursday to check it all out, and the concrete is scheduled to be poured later today.  The photos above are at the location of the 1st pedestrian bridge -- where the stream flows out of the north lake and over the weir.

The 2 photos above show the locations of the 2nd and 4th bridges. You can see the rebar sticking up out of the holes, ready for concrete to be poured around it.  The bridges are being manufactured in Alabama and trucked to Long Beach ready to be secured to the abutments.  The only bridge construction that has to be done on-site is attaching the hand rails.  The weathering steel of the bridges will add a beautiful rustic flair, while proving secure crossings and clear views of the stream--a big improvement over the crumbling, slippery, and wobbly original bridges.

The Hard Stuff

The bridges are being manufactured and the poured-in-place concrete abutments for the 5 new bridges have been approved by the City.  The longer the concrete allowed to sit, the stronger the abutment will be.  So the contractor is taking advantage of the holiday lull to get ready to pour concrete.  The photo above shows crew members marking out where the abutments will go.

The point bar is starting to take shape as cobbles are brought in and placed.

There are a few places along the stream where we want to let visitors get right up to the water, but we also need to provide some extra-strong protection for the bank.  In those places, the contractor has placed large, angular boulders that lock together to form a solid structure.  There is no grout or concrete holding the boulders together, just gravity and friction--two things that will outlast the strongest grout.

Bioengineering 101

On Friday (12/18/09), Drew Goetting, Principal designer at Restoration Design Group, came down from Berkeley to give us all a lesson in bioengineering.  First, dig a 3-4" deep trench at the toe of the bank slope.  Toss the dirt from the trench upslope to make it easier to fill the wattle.

Next, lay out the coir fabric so the edge extends a few inches upslope past the lip of the trench.  Secure the fabric to the soil with biodegradable staples (in this case, Bio-Stakes made from corn).

Shovel some of the soil from the trench over the coir fabric, then place willow pieces (branches, twigs, and leaves) over the soil.  Add more willows and more soil, making sure that the willows are generally oriented along the streambank and no branches are sticking out perpendicular to the direction of the water flow.  More willows and more soil, until the whole thing is the right height (see below for what "right" means).

Next, imagine that you are making a giant California roll, using the coir fabric as your sushi mat and the willows and dirt as your rice, crab (or krab), and avocado.  Kick and push the mixture into place--it is pretty rugged and will withstand some rough treatment.  The goal is an evenly compacted roll whose top is fairly level.  The finished top of the willow wattle should be above the water surface when the stream is flowing.

Pull the coir fabric fairly tightly over the soil and willows.  Secure the edge of the coir fabric with more biodegradable staples.

Pound some willow stakes straight through the entire thing.  The stakes should go at least a couple of feet into the ground under the wattle. 

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The result is a willow wattle.  The fabric will hold the soil and protect the bank on a temporary basis.  Meanwhile, some of the willows inside the wattle and some of the willow stakes will sprout and their roots will grow to hold the streambank.   After a while, the coir fabric and the staples will biodegrade and all that will be left will be willows, creating a sustainable streambank and a vegetative screen of riparian habitat.