Residential on West Marigold Street

Drainage plans and hydrology report for an Altadena fire rebuild on West Marigold Street. The site slopes 11 feet from the street down to the rear, with a proposed ADU in the back and widening of the existing driveway to connect to a proposed attached garage.

We designed 5% slope grading 10 feet away from the main house structure with a flowline around the sideyards that sheets flow to the natural drainage pattern. For the ADU, we created flowlines at 5% slope 10 feet away, sloping down at maximum 20% to connect with the rear house patio, and tying into the rear pre-fire drainage pattern.

A 1-foot curb was introduced on the East side to help flatten out the ADU sideyard. Plastic lined rain gardens were placed on both the West and East property lines to slow and store stormwater without triggering LID requirements.

The hydrology report showed pre-fire impervious surface was greater than the proposed construction, which is common on fire rebuilds where the previous structure had more footprint than what is being proposed in the rebuild.