Florida Department of Transportation – Aviation Office Statewide Airport Stormwater Best Management Practices Manual Clean Water – Safe Airports April 27, 2013 Revision (Updates March 6, 2013 Revision altering Table 502-1 to reflect updated FDEP data) FLORIDA STATEWIDE AIRPORT STORMWATER STUDY BEST MANAGEMENT PRACTICES MANUAL CONTENTS Page SECTION 1 – INTRODUCTION 101. Purpose and Intent................................................................................................ 1 102. Introduction to the Airport Environment ............................................................. 1 103. Limitations ........................................................................................................... 5 104. Additional Permit Information ............................................................................. 6 SECTION 2 – AIRPORT STORMWATER QUALITY CHARACTERISTICS 201. Pollutants.............................................................................................................. 7 202. Event Mean Concentration .................................................................................. 7 SECTION 3 – SITE CHARACTERISTICS AND PROPERTIES 301. General ................................................................................................................. 8 302. Soil Properties ...................................................................................................... 8 303. Infiltration Rates .................................................................................................. 8 304. Permeability/Hydraulic Conductivity .................................................................. 9 305. Porosity ................................................................................................................ 10 306. Soil Suction .......................................................................................................... 11 307. Ground Water....................................................................................................... 11 308. Topography .......................................................................................................... 13 309. Slopes and Grading .............................................................................................. 13 SECTION 4 - RAINFALL AND RUNOFF RELATIONS 401. Event vs. Continuous Simulation ......................................................................... 15 402. Hyetographs ......................................................................................................... 17 403. Evaporation and Evapotranspiration .................................................................... 18 404. C vs. CN vs. Green-Ampt .................................................................................... 19 SECTION 5 - STORMWATER QUALITY CALCULATIONS 501. Runoff Load and Concentration........................................................................... 21 502. Groundwater Contributions ................................................................................. 21 503. BMP Efficiencies ................................................................................................. 23 504. Pre and Post Development Load Calculations ..................................................... 24 FLORIDA STATEWIDE AIRPORT STORMWATER STUDY BEST MANAGEMENT PRACTICES MANUAL SECTION 6 – BEST MANAGEMENT PRACTICES 601. Overview .............................................................................................................. 27 602. Minimum Level of Stormwater Treatment .......................................................... 27 603. Flood Control Requirements ................................................................................ 27 604. Required Site Information.................................................................................... 28 605. Structural Best Management Practices ................................................................ 28 a. Overland Flow ................................................................................................. 29 b. Dry Retention Basin ........................................................................................ 32 c. Swales ............................................................................................................. 36 d. Wet Detention Systems (Ponds) ..................................................................... 38 e. Other Retention Treatment Methods ............................................................... 38 f. Off-site Equivalent Treatment ......................................................................... 39 606. Procedural Best Management Practices ............................................................... 41 a. Aircraft Fuel Sumping Control ....................................................................... 41 b. Turf Management............................................................................................ 42 c. Sweeping ......................................................................................................... 42 d. System Maintenance. ...................................................................................... 44 APPENDICIES: APPENDIX A References APPENDIX B Glossary APPENDIX C Site Evaluation Checklist APPENDIX D Formulas for Permeability Field Tests APPENDIX E Typical Green Ampt Parameters Based on Grain Size Analysis APPENDIX F Methodologies, Recovery Analysis and Soil Testing for Retention Systems (Modified from Reference 10) APPENDIX G Annual Rainfall Data (from Reference 10) APPENDIX H Airline Safety and Wildlife Protection Act of Florida APPENDIX I Draft FAC 62-330.449 APPENDIX J Jurisdictional Agencies APPENDIX K Federal Agencies Memorandum of Agreement on Aircraft-Wildlife Strikes APPENDIX L Wildlife Hazards and Airport Safety FLORIDA STATEWIDE AIRPORT STORMWATER STUDY BEST MANAGEMENT PRACTICES MANUAL LIST OF TABLES Table 202-1 Airside and Nutrient Event Mean Concentration (antilog mean log) mg/L ............ 7 Table 304-1 Typical Range of Permeability of Natural Soil........................................................ 9 Table 305-1 Typical Values of Porosity and Effective Porosity expressed as a Decimal Ratio .........................................................................................................................10 Table 306-1 Typical Values of Soil Suction ................................................................................11 Table 401-1 Daily Rainfall Characteristics at Select Florida Airports with Published Design Storm Events ............................................................................................................16 Table 402-1 Comparison of Time Step Effect on Calculated Runoff ..........................................17 Table 502-1 Median Nutrient Concentrations in Ground Water by County ................................21 Table 605-1 Accepted Methodologies for Recovery Analyses ....................................................35 Table 605-2 Erosion Velocity Limits ...........................................................................................38 Table 606-1 Expected Concentration Reduction from Sweeping with Collecting Vacuum and Broom Sweepers ......................................................................................................44 FLORIDA STATEWIDE AIRPORT STORMWATER STUDY BEST MANAGEMENT PRACTICES MANUAL LIST OF FIGURES Figure 102-1 Typical Airport Airside and Transitional Facilities ............................................. 3 Figure 102-2 Illustration of Airside and Landside Areas .......................................................... 4 Figure 305-1 Soil Components Block Diagram ........................................................................ 10 Figure 309-1 Peak Runoff Sensitivity Results for Impervious Areas ....................................... 14 Figure 402-1 Recorded 5-minute Rainfall Record for Orlando International Airport .............. 18 Figure 403-1 Plot of Daily Evapotranspiration Measured in Central Florida ........................... 19 Figure 404-1 Comparison of Actual and Green-Ampt Predicted Runoff .................................. 20 Figure 605-1 Recommended Placement of Ditch Bottom Inlets ............................................... 31 Figure 605-2 Recommended Placement of Underdrain Systems .............................................. 31 Figure 605-3 Retention/Swale Placement ................................................................................. 33 Figure 605-4 Interevent Time at Selected Florida Weather Stations ........................................ 35 Figure 605-5a Underdrain for Groundwater Control .................................................................. 37 Figure 605-5b Retention Underdrains ......................................................................................... 37 Figure 605-6 Hazard Zones for Wildlife Attractants Around Airports ..................................... 40 Figure 606-1 Mowing Buffer Around Inlets ............................................................................. 43 FLORIDA AIRPORTS STORMWATER BEST MANAGEMENT PRACTICES MANUAL Section 1 INTRODUCTION 101. PURPOSE AND INTENT The Florida Airports Stormwater Best Management Practices Manual is intended for use by consultants, regulators and airport sponsors charged with design, permitting and operation of airside stormwater management facilities. The document is directly referenced in the General Permit for Construction, Operation, Maintenance, Alteration. Abandonment or Removal of Airport Airside Surface Water Management Systems, Chapter 62-330.449, F.A.C., and focuses primarily on airport stormwater quality. It sets forth the procedures and criteria for those facilities eligible for the general permit. It is applicable to most, but not all airside facilities, and its use must consider the site specific conditions. This BMP manual is a stand alone document. However, companion documents, the Technical Report for the Florida Statewide Airport Stormwater Study and the Application Assessment for the Florida Statewide Airport Stormwater Study provide additional reference material that may be consulted. Also, Federal Aviation Administration (FAA) Advisory Circular (AC) 150/5320-5C must be consulted for airside specific drainage design and stormwater quantity guidance. These documents can be accessed at http://www.dot.state.fl.us/aviation/stormwater.shtm and http://www.faa.gov/regulations_policies/advisory_circulars/ The goals of airside stormwater management are two-fold. From a regulatory perspective, the stormwater management system must meet statutory and rule requirements intended to protect water quality, limit or prevent flooding, and preserve or maintain healthy ecosystems. From a public transportation perspective, the stormwater management system must be consistent with safe and efficient air transportation. Ultimately, from all perspectives, the public is the intended beneficiary of both stormwater management and transportation system efforts. This manual was assembled because aircraft and airport operations differ significantly from other regulated development. Airport safety may be directly affected by the choice of stormwater management system. Surface water or wetlands in proximity to the airside can and sometimes do become safety hazards, particularly if they are wildlife attractants. Also, the airside operating environment and procedures result in lower pollutant loadings than most other urban land uses. Temporary flooding in extreme events is allowable on the airside. These issues dictate targeted stormwater management practices. Information on the airport environment is included in the following subsection for familiarization purposes. Information in this manual is intended for design of individual airside facilities or master planning airport airside stormwater management systems. References in Appendix A should be consulted for further information on airside stormwater management. 102. INTRODUCTION TO THE AIRPORT ENVIRONMENT In its basic configuration an airport consists of airside and landside areas. Airside includes all areas commonly allocated for aircraft operations or servicing. They are often separated by a fence or other barrier from landside areas to limit access. Ground vehicle traffic does occur on the airside. It is normally associated with servicing aircraft and routine inspections, and it is generally confined to aprons/ramps. Page 1 FLORIDA AIRPORTS STORMWATER BEST MANAGEMENT PRACTICES MANUAL Typically the airside includes significant open space/grass areas serving to separate runways and taxiways from each other. Elements of the airport airside are:  One or more runways for aircraft landing and takeoff operations. These are usually paved, but may be turf for facilities serving light airplanes.  One or more taxiways allowing aircraft to move between the runway(s) and parking areas  One or more aprons (also called “ramps”) for aircraft to park. Figure 102-1, excerpted from the Airport Facilities Directory, illustrates a Florida airport serving both light general aviation and commercial jet operations. Landside areas are those where aircraft do not operate. In the most basic form, the landside area is a roadway for access and an automobile parking lot adjacent to the airside. However, the landside may include a number of alternate uses. Airports often own large tracts of land that are not used for aviation purposes. A goal and requirement for airports is that they be as self- supporting as possible. Consequently, commercial and industrial parks are often constructed on non-aeronautical, airport owned land. Some airports also have shopping centers, recreation areas, and professional sports facilities located on their property. These have characteristics typical of other, similar development in Florida. However, they are subject to the same hazard controls that apply to aviation use areas owned by the airport. The rents they pay help support airport operation, maintenance and capital improvement programs. Figure 102-2 shows an Airport Layout Plan (ALP) illustrating various airside and landside land use, and the relations to each other at a Florida general aviation/limited commercial service airport. Expansion and improvement projects undertaken by airports that typically require stormwater management permits include the following:  Runways, including new runways and runway extensions  Taxiways, including new taxiways, taxiway extensions and taxiway widening  Aprons/Ramps  New Hangar Buildings  Terminals, including new terminals and terminal expansions  Perimeter Access/Safety Roads  Automobile parking lots  Access Roads The above list is not all-inclusive, but is meant to outline primary categories of projects done by airports. Fuel farms and aircraft wash-racks may require stormwater management permits, but are more commonly regulated through industrial wastewater permits. Private developers and corporations often do other landside development. Landside development is outside the stormwater management scope of this manual, but noted safety considerations may still apply. Page 2 FLORIDA AIRPORTS STORMWATER BEST MANAGEMENT PRACTICES MANUAL Figure 102-1 Typical Airport Airside and Transitional Facilities Page 3 FLORIDA AIRPORTS STORMWATER BEST MANAGEMENT PRACTICES MANUAL A final item of importance in the general airport discussion is access control. Airport security is continually tightening in the wake of the events September 11, 2001. The Transportation Security Administration (TSA) now regulates airside security and access. TSA briefings indicate aviation remains a weapon and target of choice for terror attack. Consequently, airside access is being made “harder” by design. This directly impacts permit conditions regarding observation and inspection of facilities, particularly at commercial service airports. It may also impact design of some stormwater management facilities to preclude these becoming a “soft” entry to the airside. 103. LIMITATIONS The Florida Airports Stormwater Best Management Practices Manual and the General Permit for Construction, Operation, Maintenance, Alteration. Abandonment or Removal of Airport Airside Surface Water Management Systems, address only the airport airside stormwater management. They are concerned with runoff from runways, taxiways and aprons. Also, until further research is completed, the manual addresses only infiltration BMPs such as overland flow, swales, and/or dry retention as the primary stormwater quality treatment methods. Wet detention ponds, including those with features recommended by the FAA and the United States Department of Agriculture (USDA) to make them less attractive to wildlife are outside the scope of this document. Landside stormwater management is not included, and must be addressed using other applicable FAA, FDOT, FDEP, and/or Water Management District regulations. However, it is important to consider that the twin needs for safety and stormwater management do not end at the airside when doing landside design and permitting. Land use compatibility around airports is addressed in FAA Advisories Circulars and in Chapter 333, Florida Statutes, both of which should be consulted prior to selecting a stormwater management system – airside or landside. The Best Management Practices (BMPs) in this Manual must be evaluated and applied with sound engineering judgment. Knowledge of the Conditions of Issuance for an Environmental Resource Permit is a pre-requisite. The manual presumes use by registered professionals and technical professionals with a background that includes hydrology, hydraulics, water quality, geotechnical, transportation and environmental subjects. Of course, applicability of any procedure is specific to the particular airport and its site and operating characteristics. Use of these tools is at the sole discretion and responsibility of the users. Wildlife management and control are not elements of this document, although reducing standing water attractants is a goal of the stormwater management strategies presented. Users should refer to the Advisory Circulars 150/5200-18, 150/5200-33, 150/4200-36, FAA Rule 49 CFR 139. and to the USDA/FAA Wildlife Hazard Management at Airports Manual for that guidance. Appendices H, K and L present additional information on wildlife hazards. The importance of considering wildlife hazards and attractants when selecting airport stormwater management strategies to the safety of the travelling public is emphasized in the documents in these appendices. The airport airside stormwater data presented is from the Florida Statewide Airport Stormwater Study, jointly funded by the Federal Aviation Administration (FAA) and the Florida Department of Transportation (FDOT). This project included stormwater monitoring at 13 airports in Florida Page 5