The Meaning of Hahamongna

The original settlers of the region were sometimes called the Hahamongna Indians. The word means "Flowing Waters, Fruitful Valley" in the native Tongva language.

Hahamongna News


FYI: Massive Post-Station Fire Excavation in Hahamongna Watershed Park





Lori Paul


Arroyo Seco News


Thanks to Mary Barrie for the report below about the County's massive sediment removal project planned for Hahamongna Watershed Park (HWP).

For those of you who drive across Devil's Gate Dam on the way to JPL and La Canada, that means that all the large trees you see beyond the dam forming a dense canopy in the basin will be destroyed, along with the recovering wildlife populations that live, forage and nest among those large trees and shrubs... from tiny frogs and coveys of California quail to great blue herons and white egrets. 300 to 400 trucks will operate every weekday (Monday through Friday) to remove 1,671,000 cubic yards of sediment from where the trees now stand, extending southward to the dam itself. 50 acres will be permanently cleared, including 15 acres of native black willows (Salix gooddingii) and a variety of shrubs. Hundreds of trucks will will enter and exit onto Oak Grove Drive via a new 2-lane paved road into HWP that will cross a popular trail near the Flint Wash Bridge. La Canada High, the upper oak grove picnic area of the park, and JPL will be impacted by the truck traffic, noise of the earth moving operation, and particulates in the air for 3 - 4 years at a projected cost of $35 million dollars.

In addition to the disruption of traffic, destruction of the environment, and loss of tranquility in the park, the question comes to mind: Is $35 million dollars an accurate estimate for such a protracted project or will this intensive sediment removal cost a lot more? If one works out the math based on a 3 - 4 year project duration, the result is an implausibly low cost per truckload of ~$92 - $121 (thanks to Marietta K. for her calculations). It costs more than that to drive each of those big trucks from their yard to the work site and back without a load. And this estimate does not include any cost for labor, excavation of sediment and loading, or other related expenses, including required mitigation for the loss of trees and habitat. 400 truck trips per weekday = 96,000 truck trips per year moving in and out of the park and to remote dump sites 20 miles away on local roads and the 210 Freeway.

Ironically, this "emergency" sediment removal will not commence until September of 2011. Heavy rains this winter might result in a repeat of the 2009 fire-related floods, because over 100% of the watershed above HWP burned. If that happens, additional sediment deposited this season may imperil operation of the dam and endanger downstream neighborhoods. It's interesting that the DPW has filed for exemption from environmental regulations (notably CEQA) for this project based on its urgency; however, the "emergency" removal of sediment will not actually begin until ~2 years after the Station Fire and will not be completed for 3-4 years. On that time scale, is this really an emergency? The opportunity to act immediately after the fire in preparation for this winter is long gone; therefore, exemption from environmental review and public input is no longer justified and this project should be more comprehensively evaluated, including the exploration of more economical and and less environmentally destructive alternatives. Regarding this winter, we can only keep our collective fingers crossed.

When the dam was "re-engineered" in the 1990s one wonders why it was designed with a much lower capacity than when the dam was built in 1920? Why were potential post fire flood levels not taken into consideration? Fires burn above the Arroyo Seco in the Angeles Forest from time to time. Wildfire-generated floods and debris flows should have been factored into planning along with 50 and 100 year flood levels. Perhaps compromises for budgetary reasons were "penny-wise" at the time of the retrofit, but are now "pound foolish" to the tune of $35 million dollars plus all the pollution caused by thousands of trucks going back and forth 20 miles from HWP to dump sites? The County DPW intends to make 50 acres in the basin of Hahamongna Watershed Park a permanently blighted excavation site devoid of trees. DPW will establish a permanent access road and staging area for contractors hired to remove sediment from that location on a regular basis in the future. Is this necessary? Would it be more economical and environmentally responsible in the long term to modify the dam so that some of its original capacity is restored? Or to redesign its features in some way to be less vulnerable to sediment blocking critical water outflow?

There may still be be time before next September to find creative ways to clear sufficient sediment and/or assure that Devil's Gate Dam functions as needed while preserving the native black willow trees and associated riparian habitat in HWP. Large trees and understory vegetation actually helps slow flood waters and enhance capture of runoff into the Raymond Basin aquifer. Trees also attract migratory waterfowl, provide nest sites and protective cover for numerous bird species and habitat for wildlife; sequester carbon, and enhance the beauty of the park for visitors. It is time to consider innovative ideas that might preserve the 15 acres of willows while reducing flood hazard. I and others urge the County to reconsider the current destructive and costly plan, or to at least require a full EIR to determine all options and actual risks.

For the nonce, those living along the Arroyo Seco below the dam might want to consider flood insurance.