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Hahamongna Watershed Park


Hahamongna Watershed Park Aerial View
Formerly Oak Grove Park, Located near Jet Propulsion Laboratory between La Canada High School and Altadena in Northwest Pasadena. This 1300-acre park in the Arroyo Seco extends from Devil’s Gate Dam north into the San Gabriel Mountains. Facilities include: an athletic field; 24 hole Frisbee golf course; and an extensive network of bridle, bicycle, and hiking trails; a dog park; numerous picnic areas and barbecue pits; restrooms; and drinking fountains.

KCET:  Foraging Hahamongna
Watch this video to learn what is edible and what is not in the Hahamongna area.  Discover what plants are invading the natural habitat.  Cook up a meal using this useful advice on what to eat at the watershed park..

Devil's Gate Dam
Built in 1920 and the first of the Los Angeles County Flood Control District's dams.

Hahamongna Watershed Park Master Plan
The Hahamongna Watershed Park Master Plan illustrates a vision for the 300-acres of open space that extends from Devil’s Gate Dam north and into the Arroyo Seco Canyon, on the northwestern edge of the city. The Hahamongna Watershed Park Master Plan was adopted to establish a visionary framework for recreation, water resources, flood management, habitat restoration and cultural resources in this area.

Current Issues

Pasadena  Council approves Devil's Gate Dam sediment removal recommendations
The working group’s plan proposes that 2.5 million cubic yards of storage space be maintained in the dam, meaning that 1.1 million cubic yards should be removed over the next five year using low emission trucks during limited hours of the day, not including holidays and weekends. The proposal also suggests the county not remove sediment in the western portion of the dam area, which is a part of the park that many recreationists and animals use frequently.  (5/13/2014). Courtesy of the Pasadena Star News.

L.A. County meeting on Hahamongna dredging project draws fire from Pasadena residents
About 75 residents of Pasadena, Altadena and La Canada Flintridge — uneasy about the effects of a massive dredging project behind Devil’s Gate Dam in Hahamongna Watershed Park.  (11/15/2013). Courtesy of the Pasadena Star News.

JPL parking lot, soccer field project to be removed from Hahamonga Park
Jet Propulsion Laboratory is preparing to remove its ecological footprint from neighboring Hahamongna Watershed Park, which also will be freed from a controversial soccer field plan if the state approves a change in grant funding. Both projects are being welcomed by open space advocates who have taken a keen interest in Hahamongna.  (3/28/2013). Courtesy of the Pasadena Star News.

California awards $3.2 million grand for Hahamongna
On October 31st, 2012, he Arroyo Seco Foundation was awarded $3.2 million in state funding to improve water reliability and environmental conditions in Hahamongna.  The $3,217,000 grant, one of a group of projects administered by the Los Angeles County Flood Control District, will be funded by the California Department of Water Resources as part of Proposition 84, which was approved by California voters in 2006.  (10/31/2012). Courtesy of the Pasadena Star News.

Officials rethink Hahamongna plans
On October 20th, 2012 controversial plans for a new soccer field and other changes to the landscape of Hahamongna Watershed Park may be headed back to the drawing board.  Pasadena officials are putting the brakes on an environmental review of Hahamongna projects after abandoning an unpopular proposal to fill in acres of marshy lowlands subject to seasonal flooding.  Pasadena City Council members will decide as early as Oct. 29 whether to start over with a new study of remaining proposals for the 300-acre park above Devil’s Gate Dam.  (10/20/2012). Courtesy of the Pasadena Sun.

Rare, endangered bird spotted in Pasadena, San Gabriel River
On October 1st, 2012, The two least bell's vireos seen at Hahamongna during several weeks in July and August could put a stop to plans by the city to build a second soccer field at the park.  The birds may also play havoc with the Los Angeles County Public Works Department's plans to scoop 2.4 million cubic yards of sediment from behind the nearby Devil's Gate Dam. The sediment removal is needed to make sure there is sufficient space in the dam to hold back water.  (10/1/2012). Courtesy of the San Gabriel Valley Tribune.

Opposition Speaks Out on Park Plan
Soccer field at the watershed park gets thumbs down from public at meeting, citing environmental concerns.  (7/14/2012). Courtesy of the Pasadena Sun.

Pasadena meeting on future of Hahamonga area scheduled
A city-sponsored public meeting to answer questions on plans for the Hahamongna area will be held at 6:30 p.m. today at Pasadena City Yards, 233 W. Mountain Ave.  The first Environmental Impact Report scoping meeting will be held at 6:30 p.m. July 12 at the Salvation Army Fellowship Hall, 960 E. Walnut St., Pasadena; the second meeting will be held at the Fellowship Hall at 10 a.m. on July 14.  (6/27/2012). Courtesy of the Pasadena Star News.

March 2011 County Risk Assessment for Devil's Gate Dam
This report describes the risks associated with the current condition of the dam.  The report states "there is a risk of significant flooding and debris flows below the dam".  Those impacted by failure of the dam include the Rose Bowl, South Pasadena and northeast Los Angeles.  "These impacts and risks will only be mitigated by removing the sediment within the reservoir."

Devil's gate dam delemma
On the northernmost edge of Pasadena lies Devil's Gate Dam, a massive concrete barrier designed to be the last line of defense during massive storms. But now, that dam basin is full of mud with little room for floodwater.  Under a worst-case scenario, torrential rains could send mud, rocks and water over the dam and flooding into the Rose Bowl, South Pasadena and northeast Los Angeles in less than 40 minutes.  (5/1/2011). Courtesy of the Los Angeles Times.


See also:
Mission/Rancho Erra - 1700s
Pioneer Era - 1800s
Railroad History
Transportation History