Preliminary Report:

Hydrological Analysis Report

Generated: 2025-06-04T10:29:45.529538 File: 1350275466_184231742_taft_airfield.kml

Executive Summary

Location: Taft, Kern County, California Flood Zone: X - Low Risk (minimal flood hazard) Site Area: 30.6 acres (0.05 sq mi)

Site Information

Geographic Data

  • Center Coordinates: 35.142525, -119.440025
  • Bounding Box:
    • North: 35.143654
    • South: 35.141396
    • East: -119.437307
    • West: -119.442743
  • Dimensions: 0.31 mi × 0.16 mi

Flood Zone Analysis

Primary Flood Zone: X

Risk Level: Low Risk (minimal flood hazard) DFIRM Panel: 06029C

Flood Zone Implications

  • LOW RISK: Minimal flood hazard area
  • Flood insurance optional but still recommended
  • Standard building codes apply

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=35.1425&lon=-119.4400

Location: 35.14252466329534°, -119.44002524815869° Region: Western US Data Source: NOAA Atlas 14 - Actual Data

Design Storm Summary

  • Water Quality Volume (WQv) - 1-year, 24-hour storm
    • Depth: 0.763 inches
    • Use: BMP sizing for water quality treatment
  • Channel Protection Volume (CPv) - 2-year, 24-hour storm
    • Depth: 1.1 inches
    • Use: Extended detention for channel erosion prevention
  • Overbank Flood Protection - 10-year, 24-hour storm
    • Depth: 1.98 inches
    • Use: Detention sizing for flood mitigation
  • Extreme Flood Protection - 100-year, 24-hour storm
    • Depth: 3.48 inches
    • Use: Emergency spillway and freeboard design

Precipitation Frequency Estimates

Return Period 5-min 15-min 60-min 24-hr
1-yr 0.07 in 0.12 in 0.233 in 0.763 in
2-yr 0.091 in 0.159 in 0.307 in 1.1 in
10-yr 0.152 in 0.263 in 0.509 in 1.98 in
25-yr 0.195 in 0.338 in 0.654 in 2.54 in
100-yr 0.273 in 0.473 in 0.914 in 3.48 in

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

Rainfall Intensity (for Rational Method)

  • 10 yr, 5 min: 1.82 inches/hr
  • 25 yr, 5 min: 2.34 inches/hr
  • 100 yr, 5 min: 3.28 inches/hr

Regulatory Requirements

Jurisdiction

  • Federal: FEMA, USACE (if wetlands present)
  • State: California
  • County: Kern
  • City: Taft

Permits Required

  • Standard building permits
  • NPDES Construction General Permit (>1 acre disturbance)

Studies Required

  • Basic stormwater management plan
  • Stormwater Pollution Prevention Plan (SWPPP)

Local Permit Research

Research conducted: 2025-06-04T10:29:45.529588

Jurisdiction Analysis

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

  1. STATE-LEVEL REGULATORY AGENCIES
  • The primary state environmental agency is the California Environmental Protection Agency (CalEPA).
  • The State Water Resources Control Board (SWRCB) oversees stormwater management.
  • Construction projects disturbing 1+ acres require a state Construction General Permit.
  • The state has its own erosion and sediment control requirements in the Construction General Permit.
  • California has a state wetland protection program in addition to federal requirements.
  • The state sets its own water quality standards and TMDL requirements.
  1. STATE REGULATORY REQUIREMENTS
  • Construction projects disturbing 1+ acres require a state Construction General Permit.
  • The state has its own BMP design standards in the Construction General Permit.
  • California requires additional freeboard beyond FEMA minimums in certain areas.
  • The state mandates post-construction stormwater controls for applicable projects.
  • California requires professional engineering certifications for certain documents.
  1. COUNTY/LOCAL REGULATORY STRUCTURE
  • The Kern County Public Works Department handles floodplain permits.
  • The Kern County Engineering, Surveying and Permit Services Department oversees stormwater.
  • Bakersfield and other cities have additional stormwater requirements beyond the county.
  • Key ordinances include the Kern County Code of Ordinances Chapter 17.32 Flood Damage Prevention.
  1. UNIQUE LOCAL REQUIREMENTS
  • Kern County requires 1-2 feet of freeboard in floodplains beyond FEMA minimums.
  • The county specifies acceptable stormwater calculation methods and modeling software.
  • Kern County has its own Standards for Drainage Design manual with local requirements.
  1. STATE-LOCAL INTERACTION
  • Projects must obtain applicable state permits before local permits can be issued.
  • There are no joint application processes between state and local agencies.
  • Kern County's requirements generally meet or exceed state minimums.
  1. TECHNICAL STANDARDS
  • Kern County requires analysis of the 100-year, 24-hour storm event for most projects.
  • The county specifies acceptable runoff coefficients and curve numbers by soil type.
  • Detention basins must limit post-development runoff to pre-development levels.
  • Kern County has additional water quality requirements beyond state and federal minimums.
  1. KEY REFERENCE DOCUMENTS
  • SWRCB Construction General Permit
  • California Stormwater Quality Association (CASQA) BMP Handbooks
  • Kern County Code of Ordinances Chapter 17.32
  • Kern County Standards for Drainage Design
  • Kern County grading permit application and checklist
  • Kern County development services fee schedule

In summary, Kern County has a complex framework of both state and local hydrological requirements. The state Construction General Permit has detailed stormwater and erosion control standards. Locally, Kern County mandates strict floodplain and stormwater detention requirements beyond state minimums. Careful coordination between state and local agencies is essential.

Specific Requirements

Here is the detailed information you requested for a 30.6-acre site in flood zone X in Kern County, California:

  1. STATE-LEVEL PERMIT REQUIREMENTS
  • State environmental agency: California Environmental Protection Agency (CalEPA)
  • Construction General Permit (CGP): Required for projects disturbing 1+ acres. Permit No. CAS000002.
  • Stormwater permit: Included in CGP, no separate permit. Notice of Intent (NOI) required.
  • Erosion/sediment control: Included in CGP. Stormwater Pollution Prevention Plan (SWPPP) required.
  • Wetland permits: U.S. Army Corps 404 permit and state 401 Water Quality Certification may be required if wetlands are impacted. Consult site-specific wetland delineation.
  • Professional certifications: CGP requires Qualified SWPPP Developer (QSD) and Qualified SWPPP Practitioner (QSP). California-licensed civil engineer required for hydrology/hydraulic calculations.
  • State permit fees (FY 2022/23): $1,016 for NOI fee, $7,860 for annual fee. Additional fees may apply.
  • Permit applications: CGP and NOI available at https://www.waterboards.ca.gov/water_issues/programs/stormwater/construction.html
  1. LOCAL PERMIT REQUIREMENTS
  • Local permits required:
    • Kern County Floodplain Development Permit: Required for all development in flood zones.
    • Kern County Grading Permit: Required for projects disturbing 1+ acres or 50+ cubic yards.
    • Kern County NPDES Applicability Form: To determine if project requires local stormwater permit.
  • Form numbers and download links:
  • Submittal requirements:
    • Floodplain permit: 2 hard copies (1 original, 1 copy), 1 electronic copy (PDF), plans at 1"=40' scale
    • Grading permit: 3 hard copies (1 original, 2 copies), 1 electronic copy (PDF), plans at 1"=30' scale
    • NPDES form: 1 hard copy
  • Current fees (FY 2022/23):
    • Floodplain permit: $1,654
    • Grading permit: $1,489 for 20-50 acres
    • NPDES form: No fee
  • Review timelines:
    • Floodplain permit: 4 weeks for initial review, 2 weeks for resubmittals
    • Grading permit: 30 days for initial review, 2 weeks for resubmittals
    • NPDES form: 1 week
  1. PERMIT SEQUENCING AND COORDINATION
  • Sequence: Submit local permits first, then state CGP NOI at least 30 days before construction.
  • No combined application process between state and local permits.
  • Local agencies (Kern County) review for compliance with local codes. State focuses on CGP requirements.
  • Estimated timeline for complete permit package: 2-3 months (1 month for local, 1-2 months for state)
  1. TECHNICAL CALCULATIONS
  • State methodology: Follow 2009-0009-DWQ CGP Attachment D for SWPPP requirements.
  • Local methodology: Kern County Standards for Drainage Design (Hydrology Manual).
  • Software: No specific software mandated. HEC-HMS, XPSWMM, and StormCAD are commonly used.
  • Required storm events:
    • State CGP: 2-year 24-hour and 10-year 24-hour for temporary BMPs, 100-year 24-hour for flood protection
    • Kern County: 2-year 24-hour for stormwater quality, 10-year 24-hour for conveyance, 100-year 24-hour for detention
  • NOAA Atlas 14 precipitation values: Accepted by both state and Kern County without adjustment.
  • Storm distribution: SCS Type II for state, SCS 24-hour for Kern County
  • Time of concentration: Follow Kern County Hydrology Manual methods (Kirpich, FAA, Upland, etc.)
  • Runoff coefficients/curve numbers: Use values from Kern County Hydrology Manual based on soil type/land use.
  1. DESIGN STANDARDS
  • State BMP design: Follow 2009-0009-DWQ CGP Attachment D and California Stormwater BMP Handbook
  • Local design standards:
    • Kern County Code of Ordinances Chapter 17.32 Flood Damage Prevention
    • Kern County Standards for Drainage Design
  • CRITICAL FREEBOARD VERIFICATION:
    • State freeboard requirement: No state-specific requirement, defer to FEMA/local
    • Kern County freeboard requirement: 2 feet above BFE per Code 17.32.130(A)(3)
    • For Zone X specifically: 1 foot above adjacent grade or highest adjacent BFE per Code 17.32.130(A)(3)
    • Is local requirement GREATER than FEMA's 1-foot minimum? YES
    • Source ordinance for freeboard: Kern County Code of Ordinances 17.32.130(A)(3)
  • Detention requirements: Detain 100-year 24-hour storm with max release rate equal to undeveloped conditions
  • Water quality volume: 85th percentile 24-hour storm depth (0.65 inches in Kern County)
  • Post-construction requirements: Treat WQV, implement source control measures, include O&M plan
  • Elevation certificates: Required for structures in floodplain, must be by licensed surveyor or engineer
  1. SUBMITTAL DETAILS
  • State CGP submittal:
    • NOI and SWPPP uploaded electronically to SMARTS system
    • SWPPP must be certified by QSD
  • Local plan sheets:
    • Kern County grading plans: Title sheet, existing conditions, grading/drainage plan, erosion control plan, details
    • Floodplain permit: Site plan, grading plan, building elevations, floodproofing details
  • Required certifications:
    • State CGP: SWPPP by QSD, NOI by Legally Responsible Person (LRP)
    • Kern County grading permit: Plans and calcs by CA professional engineer
    • Floodplain permit: Elevation certificate by licensed surveyor or engineer
  • Digital submittal formats:
    • State CGP: PDFs uploaded to SMARTS
    • Kern County: PDF plans, hydrology calcs in PDF or native software file
  • Review timelines:
    • State CGP: 30 days from NOI submittal to pre-construction meeting
    • Kern County grading permit: 30 days initial review, 2 weeks resubmittal
    • Kern County floodplain permit: 4 weeks initial review, 2 weeks resubmittal
  1. STATE AGENCY CONTACTS
  • CalEPA main office: 916-323-2514, calepacomm@calepa.ca.gov
  • Regional office: Central Valley Regional Water Quality Control Board, Fresno office, 559-445-5116
  • Stormwater program: State Water Resources Control Board, Stormwater Section, 916-341-5536
  • Erosion control: CGP program, 916-341-5537, stormwater@waterboards.ca.gov
  • State floodplain coordinator: California DWR, Floodplain Management Branch, 916-574-1475
  1. LOCAL CONTACTS AND RESOURCES

In summary, a 30.6-acre site in Zone X in Kern County will require a state Construction General Permit, Kern County Floodplain Development Permit, and Kern County Grading Permit at a minimum. The local freeboard requirement of 1 foot above adjacent grade or BFE is the controlling factor. Detention must be provided for the 100-year storm, and water quality treatment is required. Careful coordination between state and local permitting is essential to avoid delays. All technical calculations must be performed by a licensed civil engineer.

Recommended Next Steps

  1. Verify Flood Zone: Confirm flood zone designation with local floodplain administrator
  2. Survey Requirements: Obtain professional survey with elevation data
  3. Preliminary Consultation: Meet with local planning/permitting department
  4. Engineering Analysis: Engage qualified engineer for required studies
  5. 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 10:31:33

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