Storm Water Permanent Best Management Practices Manual

1 Hawaii State Department of Transportation Highways Division Storm Water Management Program NPDES Permit No. HI S000001 April 2015 Storm Water Permanent best Management Practices Manual This page intentionally left blank. Storm Water Permanent best Management Practices Manual State of Hawaii Department of Transportation Highways Division April 2015 Effective: October 27, 2015 Permanent best Management Practices Manual State of Hawaii Department of Transportation, Highways Division April 2015 i This page intentionally left blank. Permanent best Management Practices Manual State of Hawaii Department of Transportation, Highways Division April 2015 ii TABLE OF CONTENTS LIST OF APPENDICES .. v LIST OF TABLES .. vi ACRONYMS AND ABBREVIATIONS ..vii DEFINITIONS OF KEY TERMS .. viii RFERENCES .. xi 1. ENVIRONMENTAL BACKGROUND AND INTRODUCTION.

2 1-1 Environmental Background .. 1-1 Introduction to this Manual .. 1-1 2. APPLICABILITY .. 2-1 Scope .. 2-1 Criteria .. 2-1 Unified Criteria .. 2-1 Redevelopment .. 2-2 Applicable Projects (Statewide) .. 2-2 Projects within DOT-HWYS s Rights-of-way .. 2-2 New Projects Requiring a Connection (to DOT s MS4) 2-2 Specific Projects with Potential to Discharge Pollutants to the MS4 .. 2-2 Storm Water Control Design Checklist Tool .. 2-2 3. EXEMPTIONS AND VARIANCES .. 3-1 Exemptions .. 3-1 Projects that are not Eligible for Exemptions .. 3-1 Exemptions .. 3-1 Variances from LID .. 3-2 4. Permanent BMP CONSIDERATION IN PROJECT PLANNING AND DESIGN PHASE .. 4-1 Introduction .. 4-1 Storm Water Permanent BMP Concepts in Project Planning Phase .. 4-1 Permanent best Management Practices Manual State of Hawaii Department of Transportation, Highways Division April 2015 iii Purpose.

3 4-1 When to Develop Concept .. 4-1 Concept Development .. 4-1 Content of Permanent BMP Planning Concept Report .. 4-2 Review and Approval .. 4-3 Storm Water Permanent BMP in Project Design Phase .. 4-3 Permanent BMP Conceptual Design Process .. 4-3 Content of PermanenExtt BMP Design Report .. 4-4 Future Maintenance and Cost Considerations .. 4-5 Review and Approval .. 4-5 5. SELECTION OF THE QUANTITATIVE CRITERIA .. 5-1 DOT-HWYS Hydraulic Design Criteria .. 5-1 The Quantitative Criteria .. 5-1 6. Storm Water QUALITY BMP DESIGN .. 6-1 Water Quality Design Volume Criteria .. 6-1 Objectives of Water Quality Design Volume .. 6-1 Management Practices to Meet Criteria .. 6-1 Additional Requirements and Consideration of Performance .. 6-1 Detention Based Water Quality Control .. 6-2 Design Volume .. 6-2 Runoff Coefficient.

4 6-2 Detention Time .. 6-3 Short-circuiting .. 6-3 Outlet sizing .. 6-3 Flow-Through Based Water Quality .. 6-3 Runoff coefficient .. 6-4 Design Storm Size (Hourly Rainfall Intensity) .. 6-4 Flow Calculation .. 6-4 Water Quality Design Standards .. 6-4 Detention Based Storm Water Quality Control Facilities .. 6-4 LID Treatment Upstream of Detention or Flow-Through Treatment .. 6-4 Permanent best Management Practices Manual State of Hawaii Department of Transportation, Highways Division April 2015 iv 7. Storm Water Permanent BMP OPTIONS .. 7-1 LID Methods Covered in this Manual .. 7-3 Pretreatment .. 7-3 Preserving Existing Vegetation .. 7-3 Non-LID Management Methods .. 7-45 Trash Management Practices .. 7-61 8. INSPECTION, MAINTENANCE, AND RECORD KEEPING .. 8-1 Site Inspection During Construction.

5 8-1 As-Built Certification & Acceptance of Permanent BMPs .. 8-2 BMP Inspections After Construction .. 8-2 BMP Operations and Maintenance .. 8-2 Record Keeping .. 8-3 Permanent best Management Practices Manual State of Hawaii Department of Transportation, Highways Division April 2015 v LIST OF APPENDICES Appendix Title A. Rain Stations Analyzed for Quantitative Criteria B. Storm Water Flow Control and Erosion Techniques Permanent best Management Practices Manual State of Hawaii Department of Transportation, Highways Division April 2015 vi LIST OF TABLES Table Title Page Table 3-1. Hydrogeological Constraints ..3-3 Table 3-2. Physical Constraints ..3-3 Table 3-3. Operational Constraints ..3-4 Table 3-4. Other Constraints/Non-Applicability ..3-4 Table 5-1. Summary of Statewide 85th Percentile Storm Averages ..5-1 Table 6-1. Values of Runoff Coefficients, C, for use in the Rational Table 6-2.

6 Values of Runoff Coefficients, C, for alternate conditions ..6-3 Table 7-1. LID BMP Selection - Storm Water Treatment Table 8-1. Inspection Events during Construction of Permanent BMPs ..8-1 Permanent best Management Practices Manual State of Hawaii Department of Transportation, Highways Division April 2015 vii ACRONYMS AND ABBREVIATIONS BMPs best Management Practices DOT-HWYS State of Hawaii Department of Transportation, Highways Division EA Environmental Assessment EIS Environmental Impact Statement EPA Environmental Protection Agency HAR Hawaii Administrative Rules HDOH State of Hawaii Department of Health HDOT State of Hawaii Department of Transportation HWY-DE DOT-HWYS Division, Design Branch, Environmental Permitting and Compliance Section HWY-DH DOT-HWYS Division, Design Branch.

7 Hydraulic Design Section HWY-P DOT-HWYS Division, Planning Branch LID Low Impact Development LOS Lines of Study MEP Maximum Extent Practicable MS4 Municipal Separate Storm Sewer System NPDES National Pollutant Discharge Elimination System PS&E Plan, Specifications, and Estimate Documents for a Plan Submittal SWMP DOT-HWYS Storm Water Management Plan Tm Recurrence Interval TMDL Total Maximum Daily Load USGS United States Geological Survey WLAs Waste Load Allocations WQDV Water Quality Design Volume WQFR Water Quality Flow Rate WQLS Water Quality Limited Segments Permanent best Management Practices Manual State of Hawaii Department of Transportation, Highways Division April 2015 viii DEFINITIONS OF KEY TERMS 303(d) LIST Under section 303(d) of the Clean Water Act, States are required to compile a list of impaired waters that fail to meet any of their applicable Water quality standards or cannot support their designated or existing uses.

8 This list, called a 303(d) list , is submitted to Congress every two years. States are required to develop a Total Maximum Daily Load (TMDL) for each pollutant causing impairment for Water bodies on the list. best Management PRACTICE (BMP) According to CFR , schedules of activities, prohibitions of Practices , maintenance procedures, and other Management Practices to prevent or reduce the pollution of 'waters of the Unites States'. A Permanent BMP shall be maintained in its perpetuity unless the original purpose of the project no longer exists. CONTRACT PROJECT A construction project, which is designed either by DOT-HWYS personnel or by an engineering consultant firm and is constructed by a private contractor. DETENTION VOLUME The volume of runoff that is held and treated in a BMP structure. DISCHARGE RATE The rate at which Water is discharged out of the BMP after being stored and treated. DISTURBED AREA / DISTURBANCE OF LAND The penetration, turning, or moving of soil or resurfacing of pavement with exposure of the base course or the exposure of bare soil or ground surface; including the land surface exposed by construction roads, baseyards, staging areas, demolition, headquarters, and parking areas.

9 It includes grubbing in its normal meaning of the use of equipment to knock down and push vegetation out of the way, typically uprooting vegetation and disturbing the ground surface. It does not include grass or weed cutting, bush or tree trimming or felling that leaves soil or ground intact. DRAINAGE AREA The specific land area that drains Water into a river system or other body of Water . Drainage area also refers to the drainage basin or watershed. ENCROACHMENT PROJECT A construction project undertaken by a non-DOT-HWYS entity ( third party) within the DOT-HWYS right-of-way and requires the issuance by DOT-HWYS of a Permit to Perform Work Upon State Highways. FREEBOARD The vertical distance between the Water surface of the design discharge and a point of interest such as a low chord of a bridge or top of a channel bank. GEOMORPHIC BALANCE The balance of changes in hydrology and hydraulics that affect stream shape, planform, slope, and sediment transport.

10 GROUNDWATER RECHARGE The process of Water soaking into the ground to become groundwater. GRUBBING The use of equipment to knock down and push vegetation out of the way, typically uprooting vegetation and disturbing the ground surface. HYDROLOGIC CYCLE The cycle of Water movement from the atmosphere to the earth and returning to the atmosphere through various stages or processes such as precipitation, interception, runoff, infiltration, percolation, storage, evaporation, and transportation. Permanent best Management Practices Manual State of Hawaii Department of Transportation, Highways Division April 2015 ix HYDRAULIC GRADE LINE A line characterized by a plotted ordinate position, which represents the sum of pressure head plus elevation head for the various positions along a given fluid flow path such as a pipeline or groundwater stream line. HYDRAULIC GRADIENT The slope of the Water surface. The gradient or slope of a Water table or piezometric surface in the direction of the greatest slope, generally expressed in feet per mile or feet per feet.