Canon Boulevard Grading Plan: Steep Altadena Hillside

We took over this Altadena grading plan from another civil engineer. The goal was to redesign the grading and drainage to be as cost-effective as possible for the homeowner while meeting LA County requirements. This is a large lot near the base of the San Gabriel Mountains with steep topography that required careful analysis to get right.

The existing site has a lot of concrete around it. Some of this the new project can connect into, but other areas will need to be removed and regraded. The original drainage pattern used the driveway to sheet flow stormwater to the street. Our approach was to maintain this pattern where possible and use the existing concrete to our advantage rather than removing and replacing it all.

The hillside on the north side is complex. To keep things simple, we placed new retaining walls on the north side of the house with 2-foot wide swales to collect drainage coming down from the upper mountain drainage pattern. These swales drain into catch basins that connect by pipe to the north side of the proposed deck, where area drains on the deck collect everything. From there, the water gravity-flows down through piping to the front of a new short wall at the property line. We tried to minimize piping as much as possible.

On the south side, we extended the existing house footprint slightly to create a walkway. The drainage here sheet flows using a flowline along the sideyard down to the driveway. We did a slight pad cut behind this sideyard to allow a 2-foot maximum height wall by cutting down slightly. Everything drains to the driveway, which matches the pre-fire drainage pattern exactly.

This is a good example of working with existing conditions rather than against them. By using the natural drainage paths and connecting into existing concrete where possible, we keep construction simple and cost-effective.

If you have an Altadena fire rebuild and need grading plans, contact us. Sometimes taking over from where someone else left off and redesigning for cost effectiveness makes sense.