How to Avoid a Stormwater Sump Pump on Your Altadena Fire Rebuild

Every week someone calls us frustrated. LA County plan check told them they need a stormwater sump pump. The builder gave them a number: $30-50k extra for the pump system. Then they call us to see if there’s another way.

There usually is.

What the county is worried about: After the fire, the land cleared. That changes how water moves across the property during construction. The county wants to make sure your project does not make drainage problems worse for neighbors downhill. Once the lot is landscaped again, water will move differently than it does right now on the cleared lot.

The key question: Does your site drain the same way it did before the fire?

How we approach it: We look at the current survey to understand the existing drainage pattern. We trace a historical Google Earth satellite map to assess what the site looked like before the fire. This gives us a picture of how water moved across the land when it was intact.

We run the numbers comparing post-development Q to what the site handled before. If the numbers show the site drains the same way it always has, we present that with a hydrology report.

We also look at infiltration carefully. Neighboring lots may build on zero lot line in the future, which changes how water infiltrates across properties. To help improve conditions from pre-fire, we often specify plastic lined rain gardens. These retain some stormwater on site and slow down runoff rather than letting it all sheet flow off the property. This can actually improve the drainage pattern compared to before the fire.

What that means for you: No sump pump. No electricity needed. No maintenance. No $30-50k construction cost. Just a drainage plan that works with how water has always moved across your lot.

When it does not work: Some lots have drainage patterns that genuinely require a pump. When that happens, it is not just the pump itself. There are also gravity pipes, catch basins on the property line, and right of way construction that can add significant time and cost. County approvals for street work are separate from your building permit and take additional coordination.

We find about 95% of the Altadena lots we look at can avoid it by showing the site drains the same way it did before the fire.

Frequently Asked Questions

How much does a sump pump add to construction costs? When a sump pump is required, costs can run $30-50k or more. This includes the pump system itself, gravity pipes, catch basins on the property line, and right of way construction. County approvals for street work are separate from your building permit and add coordination time.

How do you show the site drained before the fire? We look at the current survey to understand existing drainage patterns. We trace historical Google Earth satellite imagery to assess what the site looked like before it was cleared. This gives us a picture of how water moved across the land when it was intact.

What is the post-development Q compared to pre-fire Q? Q refers to the peak flow rate of stormwater. We calculate the post-development Q based on the proposed improvements and compare it to what the site handled before the fire. If post-development Q does not exceed pre-fire Q, we can argue the site drains the same way it always has.

Can every Altadena lot avoid a sump pump? No. Some lots have drainage patterns that genuinely require a pump, particularly those in natural drainage pockets or with significant grade changes. We find about 95% of the Altadena lots we look at can avoid it by showing the site drains the same way it did before the fire.

What do I need to get started on avoiding a sump pump requirement? We typically need: a site survey showing existing topography, proposed house location from your architect, and any relevant geotechnical reports. With these documents, we can begin the hydrology analysis and drainage design process.