County ponders second drain for Mullally

With a recent push by city officials and hillside residents, L.A. County Department of Public Works engineers are taking a fresh look at some old ideas for increasing the capacity of the Mullally debris basin.

Located just east of the top of Ocean View Boulevard at the end of Manistee Drive, Mullally was never more noticeable than during the post-Station-fire storms of February 2010. Large rocks and other debris brought down from the hillside by heavy rains clogged the basin’s drainage system and sent a wall of mud into yards and homes.

County officials worked over the summer to expand Mullally’s capacity, and the basin handled December’s storms without incident.

But now engineers are back at work on a more than decade-old idea to help prevent dangerous clogs by running an additional drain westward under Manistee Drive and straight into nearby Pickens Canyon.

“We’re developing the concept, identifying all the constraints of putting it in,” said Chris Stone, assistant deputy director of the county Public Works’ Water Resource Division.

Mullally currently drains southward behind the ends of streets that line the east end of Ocean View Boulevard.

County officials have previously considered expanding that flow-way, but the need to tear up landscaped yards and seek easements to do so makes tunneling under Manistee appear to be much more feasible.

A new storm drain would serve as a sort of overflow valve in the event of a clog.

“With an additional drain in there, if you had [a clog] and the lower drain quit functioning because it was plugged with sediment, you’d have another drain at a higher elevation that would relieve it,” Stone said.

At a workshop last month with L.A. County Supervisor Michael Antonovich, La Cañada Flintridge City Council members expressed growing impatience for a decision about improving the Mullally basin.

“The bottom line is that a decision needs to be made and implemented. They have been far too long for studying; it’s now time to move forward with the long-term solution. Exactly what solution is, that’s where you need the engineers,” said Councilman Greg Brown.

Chamber of Commerce President Pat Anderson, whose Manistee Drive home sustained severe mudflow damage last February, is eager for a solution — but not so eager as to risk the project’s effectiveness.

“The plan has been sitting in study-land for 15 years. It’s frustrating that nothing is happening,” said Anderson. But, she said, “It’s important that they choose the right plan and important they don’t rush and sacrifice the end result.”