We have another Altadena drainage plan where the goal was to not use a stormwater sump pump. The way the lot sits the existing stormwater used to drain all from the top of curb at the street to the rear of the property. When we can we try to raise the house so we reverse the drainage towards the street. Whether the rear requires a sump pump or not, if you can get less stormwater into the rear that means less water to handle.
We began by looking at the existing topography which the Altadena excavated lots are a bit different than usual for surveys. The contours go all over the place, so the main places to look are at the property lines. If we come up 1% minimum from the street we can easily gravity sheet flow to the street. This sets the garage finished floor. Stepping through the outer structure we then tie into the existing, raising 8″ above the existing and that sets that house finished floor. From there we make our way around how to get as much stormwater to the front as possible. After asking the Architect if we can shift downspouts around we now have a good drainage pattern for what LA County is looking for.
Once we get the house elevation set, we can move onto the rear trying to use as much gravity sheet flow around the house as we can to reduce piping and area drains. This property has a basement which happened to daylight very well with how the Architect tied the rear deck into the existing slope. A few minor tweaks and we have a lot that drains much better than prefire. The driveway is slightly raised from existing, the house sits in a similar position, and we handle the remaining stormwater without using a stormwater sump pump. If you have drainage plan comments for a fire rebuild in Altadena, contact us, we possibly can save a lot of money in construction costs with our approach.