Why This Matters Now
LA County reviews Altadena fire rebuild drainage plans differently after the Eaton Fire. When land clears, water moves differently. County plan check wants to see how your project handles post-fire runoff and keeps neighbors downhill safe.
We work through plan check every week. We know what LA County wants to see and how to present your Altadena drainage plans in a way that gets approved.
What We Do
- Altadena drainage plans
- Hydrology reports
- Pre-fire / Post-fire analysis
- Grading plans (when required)
- LID compliance (when required)
- Stormwater Sump Pump Design (when required)
- Street Plans (when required)
How It Works
- 1 Send us your survey and proposed site plan
- 2 We run the hydrology numbers comparing pre-fire and post-development conditions
- 3 You get an approved drainage plan ready for county submittal
Why Not Every Engineer Does This
LA County plan check for Altadena fire rebuilds has been changing weekly since the Eaton Fire. Most engineers are guessing. We've been doing this since 2011, so we're in the thick of it every week. We know what works and what doesn't.
We show your site drains the same way it did before the fire. That keeps you out of sump pump requirements and LID covenants. That's the goal for your Altadena drainage plan.
Frequently Asked Questions
A drainage plan handles water flow and minor grading. A grading plan is full civil engineering for complex sites with large cuts, fills, or retaining walls. Most Altadena fire rebuilds only need a drainage plan.
Once we have your survey and proposed site plan, we typically turnaround a drainage plan in 1-2 weeks. Let us know if you need it faster for your building permit timeline.
LA County does not require hydrology reports, but they use them to justify sump pump requirements. We calculate pre-fire and post-development flow rates. If post-development Q does not exceed pre-fire Q, the pump requirement can often be removed.
LID requirements trigger when post-development impervious surface increases more than 50% compared to pre-fire conditions. This includes driveways, roofs, and concrete. Stay under that threshold and LID generally does not apply.
LA County Code section 22.130.160 is the basis for drainage plan requirements on residential lots. Whether a drainage plan is required depends on the specific topographical and geological conditions of your lot. Lots with significant slope, drainage patterns that cross property lines, or proximity to downstream properties typically require a drainage plan to show how stormwater is managed. Insurance companies have asked this same question when reviewing fire rebuild documentation.
LA County has two options for handling cross-lot drainage per their recovery FAQ. First, any impact to an adjacent property must be mitigated onsite or require an offsite drainage acceptance covenant signed by the adjacent property owner and recorded against their title. Second, if the pre and post construction onsite drainage net effect at the property line is deemed negligible by the architect or engineer of record, findings are reviewed and if accepted, the statement is placed on the plans for permanent record. This means we can often show that your project does not increase drainage to neighboring properties, avoiding the need for a formal covenant.
LA County checks if your impervious surface increases more than 50% compared to pre-fire conditions. If you stay under the threshold and maintain pre-fire sheet flow pattern, LID requirements generally do not apply.
Drainage plans are typically $4,400 and hydrology reports are $2,400. These costs are separate from architect and geotechnical fees. Avoiding a sump pump saves $30-50k in construction costs.
For your specific Altadena project, talk to B+W Engineering.