At its April 26 meeting the Hahamongna Watershed Park Advisory Committee received an update from Los Angeles County Flood Control concerning the interim measures to be taken to clean out sediment in Hahamongna behind Devil's Gate Dam. The most important update was a clarification of the haul routes to be used to remove the sediment.
According to the presentation, 25,000 cubic yards of sediment will be removed from the area immediately behind the dam. The work will proceed on an emergency basis under a CEQA exemption which will require that no further environmental work will have to be done.
Preparatory work began March 31, 2011. Actual sediment removal is anticipated to take 16 to 20 days with the removal of 1600 cubic yards of dirt per day. Clean out is scheduled to begin June 17 and to continue until August 15, 2011. Other measures to improve dam safety are scheduled to be completed between August 15 and October 15, 2011. These include heightening the sluice gate, replacing the damaged ladder system, installing a new catwalk and log booms, and modifying the Altadena West Storm Drain.
The County anticipates having to do a similar clean out effort each year until the environmental impact report for the final sediment removal project is completed.
The haul route as illustrated in the presentation will go north along an access road on the east side of the park to just below the east JPL parking lot where the trucks will turn south and go down Windsor Avenue to the 210 Freeway. The bulk of the sediment, over 90%, will then be trucked east to pits in Irwindale. The organic material comprising the rest of the sediment will be taken via the 210 Freeway to Scholl Canyon landfill in Glendale.
There were a number of questions concerning why the County had chosen the haul route which would cause the most neighborhood disruption as well as the most environmental impact within the park. The Committee and the public both asked about other alternatives. One mentioned was the road at the southwest corner of the park which has been used for prior debris clean outs. Another was the possibility of exiting the park from the southeast in a way which would not impact the neighborhood. The County assured the Committee that this alternatives had been considered.
The Advisory Committee passed a motion to request the Pasadena City Council to examine the County's transportation plan to identify areas to be impacted, to ask the County to consider alternative routes which would reduce environmental impacts, and to notify areas to be impacted.
If you would like to read County Flood Control's presentation, it can be found at
http://dpw.lacounty.gov/wrd/Removal/DevilGate/HWPAC Interim Measures 200110426.pdf