Altadena Fire Rebuild Sheet Flow

Q: How does simplifying drainage design reduce construction costs on Altadena fire rebuilds?

Simplifying drainage design cuts costs in several ways. Using sheet flow instead of piped systems means fewer area drains, catch basins, and underground pipes to purchase and install. Avoiding retaining walls eliminates significant engineering and construction costs. When stormwater can drain naturally across the property using gravity and existing grades, you do not need to engineer and build mechanical drainage systems. Sometimes the previous drainage design worked but added complexity that was not necessary. Taking over a project and finding a simpler approach that achieves the same result can mean the difference between a six-figure drainage system and one that costs a fraction of that. The goal is the same stormwater management outcome, but without building infrastructure that is not actually required.

We are taking over for another Civil Engineer to bring construction costs down on some Altadena fire rebuild drainage plans. This particular lot we were able to sheet flow the entire property. Besides the typical downwards sloping lot, the reverse out of the garage driveway we had to clear some items on the property. Other than that as we do more of these drainage plans, they become more straightforward.

3D topographical wireframe site plan showing terrain and elevation contours for the Altadena Pine Street lot

The existing lot was cleared, that’s clearly excavated out with a small pile of soil where the house used to sit near the front. The 3d model of the site shows this in more detail, along with a short wall at the rear where the garage used to sit. The surveyors are all over the place on some of these projects, as the excavation make existing contours hard to follow sometimes, but this particular one is pretty good to tie into the existing propertly lines.

Topographic drainage plan for an Altadena property showing terrain contour lines and site boundaries

For the proposed, we are trying to keep the Architect’s finished floor when they give them to us, but sometimes we need to raise that finished floor to keep a 10ft 5% grade from the highest point on the building corner. We then gently regrade the front yard that’s sloping down towards the house and start matching the driveway into the neighboring property line. The goal here is to not use any short retaining walls if possible. The other goal on this site was to see if we could not use area drains and pipe, and create different paths to sheet flow on grade, which we were able to accomplish. You can see how the driveway grade is about 6% and then flattens out as it gets closer to the rear and garage. Not much can be done with the rear yard between the house deck and the garage, but its flat enough to walk on or setup a picnic without rolling down the yard.

Driveway grade detail showing 6% slope flattening toward rear garage for Altadena fire rebuild drainage

If you have LA County plancheck comments requesting drainage plans, or asking for sump pumps, give us a call. There is a method to save money here. Pine Street Sheet Flow - View the full drainage plan design with sheet flow to driveway.

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