informativebitching t1_j5tmrk8 wrote on January 25, 2023 at 2:14 PM

Reply to comment by Fluxmuster in The Key to California’s Survival Is Hidden Underground The state is ping-ponging between severe drought and catastrophic flooding. The solution to both? Making the landscape spongier. by Sariel007

What is the 85th percentile equal to for recurrence interval? What makes it infeasible? Subsurface conditions only or combination of the site being hemmed in and subsurface conditions? Ever discover a new fault while investigating the subsurface?

Fluxmuster t1_j5vfjd9 wrote on January 25, 2023 at 9:00 PM

Usually infeasibility is proven based on the underlying soil's conductivity . We have to do infiltration tests as part of the geotechnical investigation for the site prior to design. If the volume of water from the 85th percentile storm can't be infiltrated within a 36 hour period it's infeasible. There are other criteria like nearby utilities, steep slope, contaminated soil etc that can preclude infiltration as well. 85th percentile is based off long term (80 years) local rain gauge data. Never encountered a new fault being discovered, but most geotech investigations don't go deep enough for that.

informativebitching t1_j5vnqt9 wrote on January 25, 2023 at 9:50 PM

Fun. I’m a civil but never had the pleasure of working on storm water or subsurface anything