Multi-Unit Residential on Ganesha Avenue

Multi-unit residential fire rebuild in Altadena following the Eaton Fire. This sideways lot has the entrance on the West side with topography sloping North to South. There is about a 6-foot drop North to South over a 75-foot run, creating enough slope to work with for gravity drainage. The structure is longer than a typical house, requiring careful consideration of how stormwater moves across the site. We used gravity drainage wherever possible with only minor interventions needed at the lowest points. Short walls on the North and South sides balance the building in the middle and provide just enough elevation to get gravity drainage from the rear to the front. A unique challenge was the driveway apron design, which required adjusting the flowline to work around a concrete slab acting like a little bridge over the street flowline. We created a flowline that blended into the apron at 1% minimum while maintaining standard curb and gutter crossslope. The drainage ultimately flows into a plastic-lined rain garden at the rear corner of the lot. A hydrology report demonstrates post-development flows match pre-fire conditions, avoiding the need for a stormwater sump pump.