Devil's Gate Aerial (Photo - arroyoseco.org).

      Devil’s Gate Aerial (Photo – arroyoseco.org).

      When Judge James Chalfant ordered a stay last week on all activities related to LA County Flood Control District’s sediment management program for Devil’s Gate Dam in Hahamongna Watershed Park, some local residents were puzzled. Isn’t this the same program County Flood tried to do in 2010 as an “emergency?”

      By Tim Brick

      Aren’t we faced with a serious flood threat due to the sediment buildup? Who’s holding things up?

      Let’s take a look at how we got here.


      In 1914 there was a serious flood along the Arroyo Seco that had severe consequences in the Los Angeles stretch of the Arroyo. Dozens of homes were washed away, and 45 people perished. Responding to that event, the County established the Flood Control District, which built Devil’s Gate Dam in Pasadena at the foot of the San Gabriel Mountains as its first major project.

      A concrete ditch

      That was before the day of environmental review of major projects, so the flood engineers did not consider all the impacts that would come from a dam like Devil’s Gate. They ignored operational issues like sediment buildup and environmental issues like the devastation of a major tributary of the Los Angeles River and the destruction of steelhead trout and scores of other fish and aquatic species. Through their efforts the Arroyo Seco has been reduced from a flourishing stream ecosystem to what many people today consider just a debris basin and a concrete ditch.

      Devil's Gate Dam (Photo - arroyosecoviews, YouTube).

      Devil’s Gate Dam (Photo – arroyosecoviews, YouTube).


      It was not until the 1970s that state and federal law required consideration of environmental impacts. There has never been a full environmental analysis of Devil’s Gate Dam and the concrete flood channel in the Arroyo Seco, and the flood engineers are not used to people and organizations challenging their authority.


      County Supervisors ordered County Flood to conduct an environmental review (EIR) of their Hahamongna sediment plan in 2011, and a series of community meetings was held that generally reflected the overwhelming consensus that a slow, ongoing removal program was the way to go. Pasadena set up a Sediment Working Group that recommended such a program, and the Pasadena City Council unanimously adopted those recommendations twice in 2014.

      Hahamongna Watershed Park (Photo - arroyosecoviews, YouTube).

      Hahamongna Watershed Park (Photo – arroyosecoviews, YouTube).

      Final EIR and lawsuit

      When County Flood released their final EIR in October 2014, however, it was clear that they had not taken seriously the community consensus or Pasadena’s plan.  Their revised “environmentally superior alternative” was larger and more destructive than their initial plan. The Arroyo Seco Foundation and Pasadena Audubon Society filed a lawsuit challenging the program and the EIR.

      If County Flood
      had proposed
      a slow, ongoing
      sediment removal
      program in 2010,
      they could have
      been done by now.


      On March 23, Judge Chalfant ruled that the County’s EIR was deficient regarding air pollution, necessary mitigation and cumulative impacts. Now the County will have to revise significant portions of the EIR and submit it to the public, County Supervisors and Judge Chalfant for final approval.

      County Flood has not removed any significant amounts of sediment from Hahamongna since 1994, but they now want to haul out 2.4 million cubic yards in 400 double-bedded, diesel-spewing  trucks a day. They have neglected maintenance for decades, but now they want to impose devastating impacts on Hahamongna habitat and neighboring communities. If County Flood had proposed a slow, ongoing sediment removal program in 2010, they could have been done by now.

      So who is responsible for the sediment buildup and for the numerous setbacks that have delayed County Flood’s “emergency” program for seven years?

      You be the judge.

      Tim Brick is the Managing Director of the Arroyo Seco Foundation, which has joined with Pasadena Audubon Society to challenge the Flood Control District’s sediment management program in Arroyo Seco vs. County of Los Angeles.

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      1. Henry says:

        so whats the big deal about the big dig? lts a dam, not a recreational park nor a sightseeing tourist establishment but a flood control district meant to protect lives and property downstream. lt was not meant to be there for peoples enjoyment but to serve a purpose. l wish people would get their head out of their a** and stop stopping progress that is meant for everybodys concern, not just their view of their back yard.

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