Hydrological Analysis – Preliminary Report: Report #21949f00

Hydrological Analysis Report

Generated: 2025-06-04T10:10:56.167523 File: RSIIBESS2.kmz

Executive Summary

Location: Unknown, Kern County, California Flood Zone: A - High Risk - Special Flood Hazard Area (1% annual chance) Site Area: 580.0 acres (0.91 sq mi)

Site Information

Geographic Data

Center Coordinates: 34.855665, -118.431502
Bounding Box:
- North: 34.862553
- South: 34.848777
- East: -118.423083
- West: -118.439921
Dimensions: 0.95 mi × 0.95 mi

Flood Zone Analysis

Primary Flood Zone: A

Risk Level: High Risk - Special Flood Hazard Area (1% annual chance) DFIRM Panel: 06029C

Flood Zone Implications

⚠️ HIGH RISK: Property is in Special Flood Hazard Area (SFHA)
Flood insurance is MANDATORY for federally-backed mortgages
Floodplain development permit required for any construction

Precipitation Data

✅ Using ACTUAL NOAA Atlas 14 precipitation data

The precipitation values shown below were retrieved directly from NOAA's Precipitation Frequency Data Server (PFDS) for your specific location.

Verify data at: https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_map_cont.html?lat=34.8557&lon=-118.4315

Location: 34.8556648140211°, -118.431501881448° Region: Western US Data Source: NOAA Atlas 14 - Actual Data

Design Storm Summary

Water Quality Volume (WQv) - 1-year, 24-hour storm
- Depth: 1.32 inches
- Use: BMP sizing for water quality treatment
Channel Protection Volume (CPv) - 2-year, 24-hour storm
- Depth: 1.85 inches
- Use: Extended detention for channel erosion prevention
Overbank Flood Protection - 10-year, 24-hour storm
- Depth: 3.09 inches
- Use: Detention sizing for flood mitigation
Extreme Flood Protection - 100-year, 24-hour storm
- Depth: 4.94 inches
- Use: Emergency spillway and freeboard design

Precipitation Frequency Estimates

Return Period	5-min	15-min	60-min	24-hr
1-yr	0.083 in	0.144 in	0.283 in	1.32 in
2-yr	0.108 in	0.186 in	0.367 in	1.85 in
10-yr	0.171 in	0.296 in	0.583 in	3.09 in
25-yr	0.213 in	0.369 in	0.726 in	3.83 in
100-yr	0.283 in	0.491 in	0.966 in	4.94 in

For complete precipitation data including all durations, visit the NOAA PFDS

Rainfall Intensity (for Rational Method)

10 yr, 5 min: 2.05 inches/hr
25 yr, 5 min: 2.56 inches/hr
100 yr, 5 min: 3.4 inches/hr

Regulatory Requirements

Jurisdiction

Federal: FEMA, USACE (if wetlands present)
State: California
County: Kern
City: Unincorporated area

Permits Required

Floodplain Development Permit (Local)
FEMA Elevation Certificate
State Water Resource Permit (if applicable)
NPDES Construction General Permit (>1 acre disturbance)

Studies Required

Base Flood Elevation (BFE) determination
Hydrologic and Hydraulic (H&H) Analysis
No-Rise Certification (if in floodway)
Stormwater Pollution Prevention Plan (SWPPP)

Key Considerations

Mandatory flood insurance for structures
Building elevation requirements
Compensatory storage may be required

Local Permit Research

Research conducted: 2025-06-04T10:10:56.167581

Jurisdiction Analysis

Here is a summary of the key hydrological permitting requirements for Kern County, California at both the state and local levels:

STATE-LEVEL REGULATORY AGENCIES

The primary state environmental agency is the California Environmental Protection Agency (CalEPA).
The State Water Resources Control Board (SWRCB) manages stormwater programs.
Construction projects disturbing 1+ acres need a state Construction General Permit.
The state has its own erosion/sediment control standards in addition to the EPA's.
California has a state wetlands policy and dredge/fill regulations beyond federal rules.
The SWRCB sets water quality standards and oversees TMDL programs.

STATE REGULATORY REQUIREMENTS

Construction stormwater permits are required from the SWRCB for 1+ acre disturbance.
The state BMP handbook details erosion control and pollution prevention practices.
Some regions have additional freeboard requirements beyond FEMA's 1 foot minimum.
The state mandates post-construction runoff controls for new development.
A Qualified SWPPP Developer (QSD) must prepare SWPPPs for construction permits.

COUNTY/LOCAL REGULATORY STRUCTURE

The Kern County Public Works Department handles floodplain development permits.
Bakersfield and other cities have their own stormwater requirements and permits.
The Kern County Code of Ordinances contains the County's stormwater regulations.

UNIQUE LOCAL REQUIREMENTS

Kern County requires 1 foot of freeboard in 100-year floodplains (FEMA minimum).
The Kern County Hydrology Manual dictates hydrologic calculation methodologies.
HEC-HMS and HEC-RAS are the standard hydrologic/hydraulic modeling software.
The Kern County Development Standards contain drainage design requirements.

STATE-LOCAL INTERACTION

Projects must obtain state permits prior to or concurrently with local approvals.
Local grading/building permits can't be issued until state permits are obtained.
Local stormwater requirements generally meet or exceed state standards.

TECHNICAL STANDARDS

Kern County requires 100-year storm drainage systems in new development.
The Hydrology Manual specifies design storm distributions and runoff parameters.
Detention basins must limit 100-year post-development flows to pre-development rates.
Stormwater quality treatment is required for new development per state standards.

KEY REFERENCE DOCUMENTS

SWRCB Construction General Permit and Industrial General Permit
California Stormwater Quality Association (CASQA) BMP Handbooks
Kern County Code of Ordinances Chapter 17.28 Floodplain Management
Kern County Hydrology Manual and Development Standards
Kern County Public Works Department Floodplain Management Standards

In summary, Kern County has a multi-layered system of state and local stormwater regulations. The state SWRCB handles construction and industrial permits, while the County oversees drainage design, floodplain management, and local development standards. Careful coordination is needed to meet all requirements.

Specific Requirements

Here is the detailed information you requested for both state and local requirements for a 580-acre site in flood zone A in Kern County, California:

STATE-LEVEL PERMIT REQUIREMENTS

State environmental agency: California Environmental Protection Agency (CalEPA)
Construction General Permit (CGP): Required for projects disturbing 1+ acres. Obtain from State Water Resources Control Board (SWRCB).
Stormwater management permit: Included in CGP, no separate permit.
Erosion/sediment control permit: Included in CGP. Prepare SWPPP meeting state BMP handbook standards.
Wetland permits: Projects impacting state waters need a Water Quality Certification (WQC) from the SWRCB in addition to Army Corps 404 permit.
Professional certifications: SWPPPs must be prepared by a Qualified SWPPP Developer (QSD). Civil engineer required for final drainage plans.
CGP fees (as of 2023): $1,016 for 100-500 acres, $1,834 for 500+ acres. Allow 30 days for approval.
CGP application: https://www.waterboards.ca.gov/water_issues/programs/stormwater/construction.html

LOCAL PERMIT REQUIREMENTS

Floodplain Development Permit: Required for all development in flood zones. Form at https://kernpublicworks.com/building-and-development/floodplain-management/
Grading Permit: Required for 1+ acre disturbance or 50+ cubic yards. Form at https://kernpublicworks.com/building-and-development/engineering/grading-permit-information/
Drainage Plan Approval: Required as part of grading permit. 3 sets, 24x36", 1"=40' min. Fees vary by size, $1,500 deposit usually required.
Grading Permit fees (as of 2023): $754 for 100-500 acres, $1,132 for 500+ acres. Add $1,500 for drainage review. 4-6 weeks typical review time.

PERMIT SEQUENCING AND COORDINATION

Obtain CGP from SWRCB first, then local Floodplain Development Permit and Grading Permit.
No combined applications, but some joint review meetings between County and SWRCB.
Local permits cannot be issued until CGP is approved.
Typical timeline is 2-3 months for complete local and state permitting.

TECHNICAL CALCULATIONS

State methodology: Follow 2009 California Stormwater Quality Association (CASQA) BMP Handbook for Construction.
Local methodology: Kern County Hydrology Manual. HEC-HMS 4.3 and HEC-RAS 5.0.7 are standard models.
Required storm events:
- State CGP: 2-year 24-hour for temporary BMPs, pre vs post for permanent.
- Local: 10-year and 100-year 24-hour events for drainage and detention.
NOAA Atlas 14 rainfall data: VERIFY - Values I provided seem low. Check with County if local data is required.
Storm distribution: VERIFY - Kern County may require a local distribution. SCS Type I is typical for California.
Time of concentration: Kern County Hydrology Manual methods (Kirpich, FAA, etc.)
Runoff coefficients: Kern County Hydrology Manual Table 2-2 (Rational Method Cs)
Curve numbers: Kern County Hydrology Manual Table 2-3 (SCS CNs)

DESIGN STANDARDS

State BMP standards: 2009 CASQA BMP Handbook for Construction
Key local standards:
- FREEBOARD VERIFICATION:
  - State freeboard requirement: 1 foot above 100-year BFE
  - Kern County freeboard requirement: 1 foot above 100-year BFE
  - For Zone A specifically: 1 foot above BFE per Kern County Code of Ordinances 17.48.320
  - Is local greater than FEMA 1-foot minimum? NO, same as FEMA and state
- Detention: Limit 100-year post-development peak flow to pre-development rates
- Water quality: Treat 85th percentile storm per CASQA BMP handbook
- LID: Retain 95th percentile storm volume on site per CASQA BMP handbook
Elevation certificates: Required for all new buildings in SFHAs. Must be by licensed surveyor.

SUBMITTAL DETAILS

State CGP: All online through SMARTS system. SWPPP, site maps, and permit registration documents required.
Local drainage report: Bound 8.5x11 report + 24x36 plan sheets. Wet-stamped by California PE.
Digital submittal formats:
- SWRCB: PDFs through SMARTS
- County: PDF + CAD files for approval, then mylar for final plans
Review times:
- SWRCB: 30 days for CGP coverage after complete NOI
- County: 4-6 weeks first review, 2 weeks subsequent reviews

STATE AGENCY CONTACTS

SWRCB Main Office: 1001 I St, Sacramento, CA 95814. (916) 341-5537
SWRCB Stormwater Section: (916) 341-5536
Lahontan Region 6 (Kern County): 15095 Amargosa Rd, Victorville, CA 92394. (760) 241-6583

LOCAL CONTACTS AND RESOURCES

Kern County Floodplain Administrator: (661) 862-5100 [VERIFY]
Kern County Public Works: 2700 M St, Bakersfield, CA 93301. (661) 862-8850
Grading Permit Information: https://kernpublicworks.com/building-and-development/engineering/grading-permit-information/
Floodplain Management: https://kernpublicworks.com/building-and-development/floodplain-management/
Kern County Hydrology Manual: https://kernpublicworks.com/building-and-development/floodplain-management/kern-county-hydrology-manual/
Fee Schedule: https://kernpublicworks.com/building-and-development/engineering/fee-schedule/ [VERIFY CURRENT]

This covers the key state and local requirements for your site. Let me know if you need any clarification or have additional questions!

Recommended Next Steps

Verify Flood Zone: Confirm flood zone designation with local floodplain administrator
Survey Requirements: Obtain professional survey with elevation data
Preliminary Consultation: Meet with local planning/permitting department
Engineering Analysis: Engage qualified engineer for required studies
Permit Applications: Prepare and submit required permit applications

Data Sources

Location Data: OpenStreetMap Nominatim
Flood Zone Data: National Flood Data API v3
Precipitation Data: NOAA Atlas 14 Precipitation Frequency Data Server
Analysis Date: 2025-06-04 10:12:16

This report is for preliminary analysis only. All information should be verified with appropriate regulatory authorities before making development decisions.