Wide-eyed looks and a mea culpa at LA County's Hahamongna presentation

A Los Angeles County representative admitted on Monday evening that the Department of Water and Power should have worked harder during past years to keep sediment levels in the Hahamongna Basin low. At a Pasadena City Council meeting the assistant deputy director of the LADWP Water Resources Division, Chris Stone, said: "We were a little bit negligent in maintaining our projects."

The City had invited Stone and the principal engineer for the Water Resources Division, Keith Lilley, to the meeting so that they could present their department's updated plan for removing sediment from the basin. It calls for hauling away 2.4 million cubic yards of dirt from the area behind the Devil's Gate Dam over the course of three to five years and would result in up to 400 truck trips a day, i.e. 50 trips per hour or almost one trip per minute.

Local residents and activists stood up on Monday evening to urge the City to intervene for a more sustainable solution. The main concerns include truck emissions, traffic congestion and dust as well as the destruction of wildlife habitat and the loss of recreational areas. Lilley's assurance that the traffic from trucks would not significantly impact the road intersections in the area elicited wide-eyed looks from many residents and an "Are you kidding me?" from Councilwoman Margaret McAustin.

The sediment level in the Hahamongna basin is currently high for two reasons: No dirt has been removed since 1994 (hence Stone's admission of negligence) and the Station Fire in 2009 resulted in a thick layer of additional mud and debris. The County, the City, local residents and environmental activists agree that the heavy build-up could cause flooding further downstream during a period of heavy rainfall. But while no one wants to see communities along the Arroyo in danger, opinions about what to do and how fast to do it differ.

Timothy Brick, the Managing Director of the Arroyo Seco Foundation, pointed out that the revised project plan would remove sediment down to a level not seen since 1935. He pleaded for the County to remove less dirt and to then maintain that level, and for the City to protect its citizens and natural resources. "This is not some waste area that we can destroy willy-nilly," he said.

The LA County Board of Supervisors will discuss the DWP's plan on November 12. If it is approved, sediment removal could begin in the spring of 2016. The County's original project would have removed 2.95 million cubic yards of dirt. A citizens working group convened by the City of Pasadena suggested that a total of 1.1 million cubic yards of sediment should be hauled away over the course of five years. The City adopted the working group's recommendations in May.