Why is Hahamongna So Special?

Hahamongna is that rare spot in the Arroyo Seco at the foot of the San Gabriel Mountains where the mountainous watershed meets the urban plain. Periodically floods roar into this basin. Bounded on the north by the mountains and Jet Propulsion Laboratory and on the south by Devil's Gate Dam, Hahamongna contains five unique habitat zones that only exist in alluvial canyons near the mountains. Most sites like this in Southern California have been destroyed.

Don't let Hahamongna go the way of other lost environmental treasures in Southern California.

What Is A Spreading Basin?

A spreading basin is an engineered zone intended to allow diverted water to percolate into the groundwater beneath.

But is this the best way to conserve water for the future? We believe that in an alluvial canyon like the Arroyo Seco a natural stream zone — a living river — would be a more efficient and environmentally appropriate way to conserve water.

This nature-based solution would also be better for fish and birds and habitat and people.

View PWP's Draft EIR