Hydrology Study

The content of this page will provide guidance through the Hydrology Study approval process for subdivisions, Conditional Use Permits (CUP), or any other project where Public Storm Drain System is proposed to be ultimately transferred and maintained by LA County Flood Control District (LACFCD).



 


HYDROLOGY STUDY APPROVAL PROCESS


HYDROLOGY STUDY PREPARATION


TYPICAL HYDROLOGY STUDY
Information Lookup:
Blease note, Hydrology Study can only be prepared by a California Registered Civil Engineers.



REFERENCE LINKS

Below are links to useful references if you have detailed questions regarding Hydrology Study.




CONTACT US

If you have additional questions or concerns, please contact our Drainage Unit at (626) 458-4930, or email us at LDD-Drainage@pw.lacounty.gov. To discuss your project with us, you can make an appointment for an online meeting between the hours of 7:00 am and 5:00 pm, M-Th by using the following link: https://pw.lacounty.gov/landing/onlineappointments.cfm

HYDROLOGY STUDY SUBMITTAL


In order to properly process your submittal and to facilitate your plan review, please submit all of the applicable items below. It is our policy to review only completed submittals. Submittals that are not complete or do not contain the necessary references, documents, or supporting calculations may be delayed or rejected. All documents should be submitted electronically, using PDF form, to EPIC-LA. If you have already formally submitted a plan check package in the past and you wish to upload revised documents, you must resubmit to EPIC-LA under the existing plan case. For questions regarding this checklist, please contact the appropriate plan checking unit at (626) 458-4930.

APPLICATION

To submit your hydrology study for review, upload your report and supporting information online (link below). Once you've signed into your account, apply for a Plan case, and choose "Hydrology Study." Follow the on-screen instructions to complete your submittal.

Submit my report


Fees

You can pay the plan check review fees in person or online using e-check / credit card (for charges less than $50,000.00). After you have submitted your plans for review, your plan checker will create a fee invoice where you can pay the fee online.

For your convenience, our fee schedule is available below. Please note that the plan check fee covers up to 3 reviews of the Hydrology Study plan submittal. Additional fees will be required after the 3rd submittal.

LDD Fee Schedule


Paperless Submittals

We've been processing paperless plan review since 2013! Accordingly, you can submit all of your reports and supporting documents online at the link provided above. To see a typical list of all supporting documents that are required for obtaining Hydrology Study approval, here is a Hydrology Submittal Check List.


Submittal Procedure

Step by step on completing the application


Resubmittals will be required to address any corrections needed on the Hydrology Study. Make sure to submit annotated response to plan checker comments on the report and correction list or your resubmittal may be rejected.




CONTACT US

If you have additional questions or concerns, please contact our Drainage Unit at (626) 458-4930, or email us at LDD-Drainage@pw.lacounty.gov. To discuss your project with us, you can make an appointment for an online meeting between the hours of 7:00 am and 5:00 pm, M-Th by using the following link: https://pw.lacounty.gov/landing/onlineappointments.cfm

HYDROLOGY STUDY PLAN REVIEW & APPROVAL


REVIEW PROCESS
For each submittal, a check print showing plan check comments and a corrections list will be generated and sent to the applicant who submitted the report. These documents will address deficiencies in the report and inform you of supporting documents that needed in order to obtain Hydrology Study approval. The following links to resubmit your plans and to some documents that you should find useful during the sewer improvement plan review:

Resubmit my report

Hydrology Study Review List

Infiltration Test Approval

Infiltration Test Approval is required prior to approval of Low Impact Development (LID) or any proposed Retention/Detention. Submit a soils report confirming assumed infiltration rates throughout the site. This report must address areas where it is infeasible to infiltrate and must be approved prior to hydrology approval. The infiltration test must be performed according to GMED Policy GS 200.2 (https://pw.lacounty.gov/gmed/permits/docs/policies/GS200.2.pdf).


What happens after a Hydrology Study Approval?

Depending on which entitlement you're trying to get approval for, the approved hydrology study will determine if there will be further improvements and mitigation needed. You may need to submit a storm drain plan as part of your development or connections to existing storm facilities. The findings on the approved report will be the basis on proper design of the storm drain system.
The approved Hydrology Study shall be revised should there be an increase of impervious surfaces, change in proposed storm drain alignment, an increase in the tributary watershed, a change in storm drain connection points or a revision to the current plan.




CONTACT US

If you have additional questions or concerns, please contact our Drainage Unit at (626) 458-4930, or email us at LDD-Drainage@pw.lacounty.gov. To discuss your project with us, you can make an appointment for an online meeting between the hours of 7:00 am and 5:00 pm, M-Th by using the following link: https://pw.lacounty.gov/landing/onlineappointments.cfm



FREQUENTY ASKED QUESTIONS

A hydrology study is an analysis of the existing and proposed conditions of a development to determine the impact to stormwater runoff generated and leaving the site.
An approved hydrology study is needed to confirm the stormwater runoff generated from the analysis does not increase from the existing to the proposed condition.
An approved hydrology study is required when a development alters the drainage pattern of a site. Improvements from the existing to proposed condition may also indicate that a hydrology study is required.
For unincorporated area, the hydrology study approval process is conducted by Land Development Division. Review files are to be submitted electronically through EPIC-LA.
All hydrology studies must be prepared, stamped, and signed by a State of California registered Civil Engineer.
An approved hydrology study runs with the life of the entitlement. The approved hydrology study must be revised as needed if there are changes to the tentative map.