Saturday, January 16, 2016

When Good Intentions Create Hazards - Storm Drain Flooding

Subtitle:  City Officials Plug Storm Drains - Puzzled by Flooding

Recent rains in the Los Angeles (California) area made the news because of street flooding, cars stranded, and people in peril from the flood waters.   What did not make the news, though, is a decision that was made some time ago that stops up the storm drains at the streets.  The streets flood because the water has no place to go.   See photo at right.
Street curb storm drain inlet with hinged debris barrier
in Los Angeles, CA photo by Roger Sowell

The debris barrier is a perforated, horizontal metal plate that is hinged at the top, and spring-loaded to remain closed.   The plate is to swing inward from the bottom when water pushes against the plate.   Debris is to be caught by the barrier and removed so that the storm drain piping system underground is not blocked.   At least, that is the theory.  In practice, the debris barrier shown in the photo was frozen shut.   The hinges did not allow the plate to move.   Only after a few strong kicks was a worker able to make the debris barrier move.  Even then, the spring tension was quite high for the intended purpose.  It is doubtful that the force from a few inches of water would overcome the spring tension and hold open the grate.   (I personally pushed the debris barrier to determine for myself how strong was the spring tension.)

So, in effect, Los Angeles has installed drain stoppers in thousands of locations.   This, just in time for the El Niño rains.   A recent news article (see link) describes the flooding in an area of Los Angeles, the San Fernando Valley (aka The Valley).  

Sometimes one has to stop and wonder at the actions of government.  Surely, there were good intentions behind the installation of thousands of debris barriers.  After all, it is a good idea to prevent sticks and trash from entering the storm drains since those can block or partially block the flow.   Ideally, only the rain goes down the drains.  However, one must also wonder if the city's decision-makers talked to any engineers about the negative effects of the debris barriers.   These are mechanical devices, relying on a plate that rotates about a hinge.  They are in an outdoor location, subject to the elements.   Even if they don't rust, they still will have dust, grit, grime, moisture, collect on the hinged areas.  The grit will grow in layer upon layer, until the force required to swing open the barrier is just too great for any water flow.  

There was substantial flooding in some areas in the last round of rains, about one week ago (January 5 and 6, 2016).   One news story showed a city worker in water up to his waist, using his feet to clear a clogged storm drain in the suburb of Sun Valley.   One can only imagine the difficulty in kicking open that debris barrier while standing in 3 feet of water.   

I also witnessed a few flooded intersections where I drive in my daily routines, on the same dates.  Having lived in the area for 30 years, I can say that those intersections never flooded before.   I did not stop to feel around on the storm drains in the rain, but it is quite apparent now that the rains have stopped that those intersections also have the drain plugs - excuse me, the debris barriers.  

Roger E. Sowell, Esq.
Marina del Rey, California
copyright (c) 2016 by Roger Sowell, all rights reserved

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