Come to Hahamongna

Before the County Destroys It!

Most environmental treasures like this in Southern California have been destroyed.

The bulldozers and trucks are lined up ready to destroy the most precious habitat and wildlife corridor in the west San Gabriel Valley. Los Angeles County Flood Control District has allowed sediment to build up in the flood basin at the base of the San Gabriel Mountains in the Arroyo Seco for more than 24 years. Now they want to excavate a massive amount for the next five years. 425 diesel-spewing trucks per day, hauling the habitat and sediment to distant landfills.

Hahamongna is that rare spot in the Arroyo Seco at the foot of the San Gabriel Mountains where the mountainous watershed meets the urban plain. Periodically floods roar into this basin. Bounded on the north by the mountains and Jet Propulsion Laboratory and on the south by Devil's Gate Dam, Hahamongna contains five unique habitat zones that only exist in alluvial canyons near the mountains.

The devastation to this precious environmental treasure will be permanent since the Flood Control District, when they finish scraping up the rare riparian habitat, will leave a massive fifty-acre pit in the middle of the Arroyo Seco streamzone, stripping it of vegetation each year, destroying the precious habitat and wildlife corridor forever.

The Big Dig will leave the Big Pit.

Bring your friends and family. Take a walk around the basin and discover its magic.

Don't let Hahamongna go the way of other lost environmental treasures in Southern California


The History of
Hahamongna Watershed Park

Get Ready for the Big Pit

The County Flood Control District keeps changing their schedule for their Big Dig in Hahamongna, but here's the latest:

  • November 26th — Road building and habitat removal
  • April, 2019 — Soil and sediment mining and trucking - 425 diesel-spewing trucks per day
  • Eternity — Denuded streamzone due to the County's bulldozers and permanent weed patch

Find out how you can get involved in protecting and enhancing the Arroyo Seco, Southern California's most celebrated canyon.

Arroyo Seco Foundation
570 W. Avenue 26 #450
Los Angeles, CA 90065
PO Box 91622
Pasadena, CA 91109-1622
(323) 405-7326