New Draft Model BMP Design Manual for San Diego Region

Transcription

1 New Draft Model BMP Design Manual for San Diego Region Public Input 2013 Storm Water Permit June 10, 2014 & June 11,

2 Welcome Sign-In Refreshments Sponsor Break Q&A and Input 2

3 Outline of Presentation Introduction Permit Requirements and Concepts Break Proposed Structure of the Model BMP Design Manual Project Development Approaches 3

4 Model BMP Design Manual Introduction Sumer Hasenin, P.E. City of San Diego 4

5 Introduction Permit Requirements and Concepts Overview and changes from 2007 to 2013 MS4 Permit Source Control and Site Design Practices Storm Water Pollutant Control Requirements Hydromodification Management Requirements Structure of the Model BMP Design Manual Project Development Approaches Standard Project PDP with Only Pollutant Control Requirement PDP Integrating Hydromodification Management with Pollutant Control 5

6 Project Team Copermittees Sub-workgroup Sumer Hasenin, P.E., Chair Rick Engineering Company Jayne Janda-Timba, P.E. Laura Henry, P.E. Geosyntec Consultants Trevor Alsop, P.E. Aaron Poresky, P.E. Venkat Gummadi, P.E. 6

7 Purpose of Workshop New Model BMP Design Manual Concepts and approaches Public Participation Input during workshop First Public Review thru June 27 th 7

8 Workshop Limitations Workshop will not address: Policies Local Jurisdictional Procedures Alternative Compliance Program 8

9 Permit Background Pursuant to Clean Water Act Issued by San Diego Regional Water Quality Control Board Regulates Municipal Storm Drain Systems Adopted May

10 BMP Design Manual Development Process Replaces Model SUSMP Update due June 2015 San Diego Copermittees joint effort Formed a sub-workgroup Hired a consultant 10

11 Goals of Sub-workgroup 1) Responsive to permit requirements 2) Leverage available resources 3) Preserve overall approach and format 4) Integrate with local ordinances/technical guidance 5) Provide consistency across Jurisdictions 6) Identify opportunities to streamline manual 11

12 Important Definitions Refer to handout - Acronyms Permit includes complete list Consistent with industry standards 12

13 Model BMP Design Manual Manual will Include: 1. Source Control & Site Design LID for All Projects 2. Storm Water Pollutant Control I. Retention II. Biofiltration III. Flow-thru Treatment Control BMPs 3. Hydromodification Management PDP I. Sediment Supply II. Flow Control 13

14 Development Timeline Public Workshops June, 10 & Comments on Public Workshop June 27, 2014 Draft Manual available Public review February 2015 Final Manual June 2015 Local Adoption Dec

15 Permit Timeline Permit Adoption Date Permit Effective Date BMP Design Manual Update Development Regs. Effective Date R months 180 days R May 8, 2013 June 26, 2015 June 27, 2013 Dec 24,

16 Permit Requirements and Concepts Overview and Changes from 2007 to 2013 MS4 Permit Jayne Janda-Timba, P.E. Rick Engineering Company 16

17 Introduction Permit Requirements and Concepts Overview and changes from 2007 to 2013 MS4 Permit Source Control and Site Design Practices Storm Water Pollutant Control Requirements Hydromodification Management Requirements Structure of the Model BMP Design Manual Project Development Approaches Standard Project PDP with Only Pollutant Control Requirement PDP Integrating Hydromodification Management with Pollutant Control 17

18 Highlights of Changes Who does this apply to? PDP categories Changes for all projects Changes for PDPs Storm water treatment hierarchy Hydromodification management Compliance options 18

19 Development Planning Requirements Applies to the following activities: Development Projects Significant Redevelopment Projects Public and Private Projects 19

20 Standard Project vs. Priority Development Project Standard Project Priority Development Project Standard Source Control Standard Low-Impact Development Site Design & Source Control Pollutant Control BMP Hydromodification Management Analysis/ Report Determine if HMP Applies 20

21 Changes to PDP Categories Land Use 2007 Permit [Total Project Area] 2013 Permit [Total Impervious Area] Residential 10 dwelling units 10,000 sf Commercial 1 acre 10,000 sf Industrial 1 acre 10,000 sf Public Improvements Parking 1 acre 10,000 sf 5,000 sf OR 15 Parking Spaces 5,000 sf 21

22 New Requirements for All Projects Site Design/LID BMPs applicable to ALL PROJECTS Many requirements previously applicable to PDPs only are now applicable to ALL PROJECTS Small collection strategies and harvesting and using precipitation have been added 22

23 PDP Requirements Formatted Differently 2007 Permit Low Impact Development (LID) BMP Requirements Treatment Control BMP Requirements Hydromodification Management criteria was to be developed 2013 Permit Storm Water Pollutant Control BMP Requirements Hydromodification Management BMP Requirements Optional Alternative Compliance 23

24 Changes to PDP Requirements Significant changes to the hierarchy of treatment (pollutant control) requirements 2007 Permit Treat and release runoff Infiltration or bioretention preferred Filtration and/or extended detention also accepted 24

25 Changed PDP Requirements 2013 Permit Retain onsite 85 th percentile runoff (infiltrate, evaporate, evapotranspire, harvest and use) Biofiltration if infeasible to retain runoff onsite Flow-thru treatment control BMPs AND mitigate (offsite) for the design capture volume that was not retained onsite, if infeasible to retain or use biofiltration 25

26 Hydromodification Management Changes Changes to exemptions Pre-development baseline (not preproject condition) Avoid critical sediment yield areas (to be defined by Copermittees) 26

27 PDP Compliance Options PDP Pollutant Control 2 Options Onsite Offsite Retention BMP INFEASIBLE Biofiltration BMP INFEASIBLE Flow-Thru Treatment Control BMP Onsite AND 27

28 Permit Requirements and Concepts Source Control and Site Design Practices Aaron Poresky, P.E. Geosyntec Consultants 28

29 Introduction Permit Requirements and Concepts Overview and changes from 2007 to 2013 MS4 Permit Source Control and Site Design Practices Storm Water Pollutant Control Requirements Hydromodification Management Requirements Structure of the Model BMP Design Manual Project Development Approaches Standard Project PDP with Only Pollutant Control Requirement PDP Integrating Hydromodification Management with Pollutant Control 29

30 Source Control & Site Design for All Projects General Requirements Onsite BMPs shall be close to the source Structural BMPs must not be constructed within the Waters of the U.S Implement measures for vector control Source Control BMP Requirements Site Design BMP Requirements (also referred to as LID BMPs) 30

31 Source Control BMP Requirements Storm drain system stenciling or signage Prevention of illicit discharges into the MS4 31

32 Protect the following from rainfall, run-on, runoff and wind dispersal Outdoor material storage areas Materials stored in outdoor work areas Trash storage areas Source Control BMP Requirements 32

33 Source Control BMP Requirements Any additional BMPs determined to be necessary by the Copermittee to minimize pollutant generation at each project 33

34 Site Design BMP Requirements Conserve natural areas, soils and vegetation 34

35 Site Design BMP Requirements Maintain natural drainage pathways and hydrologic features 35

36 Site Design BMP Requirements Minimize Impervious Area 36

37 Site Design BMP Requirements Minimize Soil Compaction 37

38 Site Design BMP Requirements Disperse Impervious Areas 38

39 Site Design BMP Requirements Runoff Collection (small collection strategies and permeable material) 39

40 Site Design BMP Requirements Harvesting and using precipitation (City of SD has Rain Barrel Rebates) 40

41 Site Design BMP Requirements Landscaping with native or drought tolerant species 41

42 Site Design Benefits for PDPs Adjust Runoff Factors Reduced Structural BMP 42

43 Site Design Benefits for PDPs Create Opportunities for Retention and Biofiltration Reduce or Eliminate Need for Flow-thru Treatment and Alternative Compliance 43

44 Permit Requirements and Concepts Storm Water Pollutant Control Requirements Aaron Poresky, P.E. Geosyntec Consultants 44

45 Introduction Permit Requirements and Concepts Overview and changes from 2007 to 2013 MS4 Permit Source Control and Site Design Practices Storm Water Pollutant Control Requirements Hydromodification Management Requirements Structure of the Model BMP Design Manual Project Development Approaches Standard Project PDP with Only Pollutant Control Requirement PDP Integrating Hydromodification Management with Pollutant Control 45

46 Pollutant Control Permit Requirements Permit Hierarchy for Onsite BMPs Technical Feasibility BMPs for PDPs BMP Selection Flow Chart Storm Water Pollutant Control BMPs 46

47 Onsite Pollutant Control BMPs Retention BMPs Implement technically feasible retention BMPs Biofiltration BMPs Implement technically feasible Biofiltration BMPs for remaining volume. Flow-thru Treatment Control BMPs Treat remaining volume AND participate in alternative compliance program 47

48 Pollutant Control Requirement The New Standard Evapotranspiration Infiltration 48

49 Technical Feasibility Physical Limitations Risk of Impacts Site Constraints 49

50 Technical Feasibility Physical Limitations Soil infiltration rate Limiting soil horizons High, mounded groundwater 50

51 Technical Feasibility Risk of Impacts Groundwater and/or soil contamination Groundwater source protection Groundwater mounding Geotechnical, setbacks Sanitary sewer onflow & infiltration Ephemeral streams 51

52 Technical Feasibility Site Constraints Elevation Utility conflicts Physical Constrains 52

53 Technical Feasibility Retention Feasibility Feasibility Screening for Harvest and Use BMPs Is there a demand onsite? Feasibility Screening for Infiltration BMPs Is infiltration potentially feasible and desirable? If so, what quantity? Biofiltration Feasibility Can it be designed for remaining DCV onsite? 53

54 Project Planning and Design Assess the site for opportunities and constraints Document site planning and opportunity assessment activities Select Source Controls and Site Design BMPs Develop the site layout 54

55 Priority Development Projects Evaluate at Drainage Management Area (DMA) Scale BMP Selection Estimate Design Capture Volume (DCV) Is DMA Self-retaining? YES NO Adjust runoff factor to account for site design BMPs and update DCV A Compliant with Pollutant Control BMP Sizing Requirements 55

56 A BMP Selection NO Is Harvest and Use Feasible? YES Is remaining DCV retained? Implement Harvest and Use BMPs* NO B YES Compliant with Pollutant Control BMP Sizing Requirements * Project applicant has an option to choose between infiltration and harvest and use BMPs if both feasible 56

57 BMP Selection B Is Infiltration Feasible? Full Infiltration Implement Infiltration BMPs Partial Infiltration Implement Bioinfiltration BMPs No Infiltration Implement Biofiltration BMPs Compute Sizing Requirements Compute Sizing Requirements Compute Sizing Requirements C More on this later Compliant with Pollutant Control BMP Sizing Requirements 57

58 BMP Selection C Implement BMP using maximum feasible footprint and document why the remaining BMP size could not fit on site* NO Can the BMP be designed for the remaining DCV? YES Implement Flow-thru Treatment Control BMPs Participate in alternative compliance program to mitigate for the pollutant load not retained onsite Design BMP for the required size, per design criteria and considerations listed in the fact sheets Compliant with Pollutant Control BMP Sizing Requirements * Project approval at the discretion of agency/jurisdiction 58

59 Site Design / Project Type Site Characteristics Watershed Characteristics Site planning principles incorporated, as applicable, and potential BMP locations identified; conduct feasibility screening for each DMA Infiltration Feasibility Would infiltration of the full design volume be feasible from a physical perspective without any undesirable consequences that cannot be reasonably mitigated? Yes Full Infiltration Category Infiltration Basin Bioretention with No Underdrain (or plugged underdrain) Permeable Pavement No Would infiltration of water in any appreciable amount be physically feasible without any negative consequences that cannot be reasonably mitigated? Yes No Partial Infiltration Category No Infiltration Category Bioinfiltration (i.e., bioretention with elevated underdrains) Harvest and Use if feasible, then Biofiltration if feasible, then Flow-thru Treatment Control BMPs 59

60 Harvest and Use BMP Roof Downspout Irrigation valve for landscape use First Flush System Roof washer Building Access Hatches Filter Optional discharge to infiltration Storage discharged to infiltration Cistern Storage reserved for irrigation Pump system for reuse BMP manual will have a Fact Sheet for: Cistern Sizing BMPs shall be sized to retain the Design Capture Volume (DCV; runoff from 85 th percentile 24-hr rainfall depth) 60

61

62

63 Biofiltration Standards MS4 Permit requires the Copermittee's to provide guidance for hydraulic loading rates and other biofiltration design criteria necessary to maximize storm water retention and pollutant removal Standards and Checklist to be included in an Appendix of Manual Facilitates consistent review and approval of Biofiltration BMPs 63

64 Concentrations Influent Speciation Flowrates/ Volumes Bypass Sizing Media filtration rate Clogging Removal Mechanisms/ Conversions Volume Reduction Infiltration rates Underdrain placement Evapotranspiration Sources/ Conversions Effluent Concentrations Speciation Flowrates/ Volumes 64

65 Biofiltration Standard 1)BMP selection process based on documented feasibility analysis 2)Sized using acceptable sizing methods described in the Model BMP Design Manual 3)Sited and designed to achieve maximum feasible infiltration and evapotranspiration 65

66 Biofiltration Standard 4) Designed with a hydraulic loading rate to maximize pollutant retention, preserve pollutant control/sequestration processes, and minimize potential for pollutant washout 5) Designed to promote appropriate biological activity to support and maintain treatment processes 66

67 Biofiltration Standard 5) Designed to prevent erosion, scour, and channeling within the BMP 6) Include O&M design features to provide for continued effectiveness of pollutant and flow control functions Design features and criteria to meet these goals will be described in BMP Fact Sheets 67

68 68

69 Flow-thru Treatment Control BMPs Energy Dissipater Inlet Side Slope: 3H:1V or milder Outlet Check dam if bottom slope exceeds 2.5% Flow Spreader Proprietary BMPs can be used as Flow-thru treatment control BMPs Bottom Slope: 1.5-6% BMP manual will have Fact Sheets for Vegetated Swales Media Filters Sand Filters Dry Extended Detention Basin 69

70 Permit Requirements and Concepts Hydromodification Management Requirements Laura Henry, P.E. Rick Engineering Company 70

71 Introduction Permit Requirements and Concepts Overview and changes from 2007 to 2013 MS4 Permit Source Control and Site Design Practices Storm Water Pollutant Control Requirements Hydromodification Management Requirements Structure of the Model BMP Design Manual Project Development Approaches Standard Project PDP with Only Pollutant Control Requirement PDP Integrating Hydromodification Management with Pollutant Control 71

72 Hydromodification Background Information What is hydromodification? Hydromodification means changes in a watershed s runoff characteristics resulting from development, together with associated morphological changes to channels receiving the runoff Hydromodification Management Plan (HMP) for San Diego County Final HMP dated March

73 Hydromodification Background Information Strategies for hydromodification flow control LID Devices Flow control ponds Sizing based on continuous simulation modeling Methods San Diego BMP Sizing Calculator Project-specific continuous simulation modeling 73

74 Hydromodification Management Requirements Background information What is new under the 2013 MS4 Permit What is not changing at this time Logistics of implementing new/updated standards Future of San Diego BMP Sizing Calculator 74

75 Hydromodification Management Applicability Hydromodification management applies to PDPs when runoff from the project site will drain to systems susceptible to erosion Does not apply to projects discharging runoff to exempt water bodies Detailed applicability requirements will be addressed later in this workshop 75

76 What is new in the 2013 MS4 Permit? Changes to applicability / exemption criteria Requirement to control to pre-development condition instead of pre-project condition New requirement to protect coarse sediment yield areas 76

77 Lane s Diagram From Rosgen (1996), from Lane, Proceedings, Published with the permission of American Society of Civil Engineers 77

78 What is NOT Changing Flow control performance standard (range of flow rates to be controlled) 0.1, 0.3, or 0.5Q 2 to Q 10 Methods to determine lower flow threshold SCCWRP Channel Screening Tools Critical Flow Calculation 78

79 What is NOT Changing San Diego 2011 Final HMP is not being updated 2011 HMP components are being incorporated into the Model BMP Design Manual with modifications as necessary 79

80 Implementation of Updated Standards Where criteria has changed, the Model BMP Design Manual will supersede the Final HMP Applicability / exemption criteria Pre-development condition New requirements will be addressed in the Model BMP Design Manual Management of critical coarse sediment yield areas 80

81 Implementation of Updated Standards Model BMP Design Manual will compile guidance and parameters for continuous simulation modeling 81

82 BMP Sizing Calculator Accessing the tool Use of BMP Sizing Calculator and sizing factors under the 2013 MS4 Permit 82

83 BMP Sizing Calculator June 30, 2014 end of support for web-based application LID Sizer Tool replaced with spreadsheet tool available now on Sizing factors are still valid for sizing LID facilities under the 2007 MS4 Permit Pond Sizer Tool will not be replaced Critical Flow Calculator 83

84 BMP Sizing Calculator Under the 2013 Permit: Do not use impervious surface coefficients when determining pre-development Q 2 for outlet orifice sizing Sizing Factors for some facilities will be removed due to inconsistency with new retention requirements Treatment-Only sizing will not be available use procedures presented in the Model BMP Design Manual 84

85 BREAK 10 Minutes 85

86 Structure of the Model BMP Design Manual Trevor Alsop, P.E. Geosyntec Consultants 86

87 Introduction Permit Requirements and Concepts Overview and changes from 2007 to 2013 MS4 Permit Source Control and Site Design Practices Storm Water Pollutant Control Requirements Hydromodification Management Requirements Structure of the Model BMP Design Manual Project Development Approaches Standard Project PDP with Only Pollutant Control Requirement PDP Integrating Hydromodification Management with Pollutant Control 87

88 Organization Chapter 1 Policies and Procedural Requirements Performance Standards and Concepts Chapter 2 Chapter 3 Planning and Design of a Project BMP Requirements Chapter 7 Long Term Operation & Maintenance Chapter 8 Submittal Requirements Chapter 4 Source Control and Site Design Practices for all Projects Chapter 5 Storm Water Pollutant Control BMPs for PDPs Chapter 6 Hydromodification Management BMPs for PDPs 88

89 Model SUSMP Chapter 1. Policies and Procedures Chapter 2. Concepts and Criteria Chapter 3. Preparing your Project Submittal Model BMP Design Manual Chapter 1. Policies and Procedural Requirements Chapter 2. Performance Standards and Concepts Chapter 3. Planning and Design of a Project Chapter 4. Source Control and Site Design Practices for all Projects Chapter 4. Low Impact Development Design Guide Chapter 5. Storm Water Pollutant Control BMPs for PDPs Chapter 6. Hydromodification Management BMPs for PDPs. Chapter 5. Operation & Maintenance of Stormwater Facilities Chapter 7. Long term Operation & Maintenance Chapter 8. Submittal Requirements 89

90 Organization Chapter 4: Source Control and Site Design Practices for All Projects Chapter 5: Storm Water Pollutant Control BMPs for PDPs Chapter 6: Hydromodification Management BMPs for PDPs Chapter 8: Submittal Requirements Appendix A: Source Control BMP Requirements Appendix B: Hydrologic Calculations and Sizing Methods Appendix C: Geotechnical and Groundwater Investigation Requirements Appendix D: Approved Infiltration Rate Assessment Methods for Selection and Design of Storm Water BMPs Appendix E: BMP Design Fact Sheets Appendix F: Biofiltration Standard and Checklist Appendix B: Hydrologic Calculations and Sizing Methods Appendix G: Guidance for Continuous Simulation Appendix H: Regional Watershed Management Area Analysis Appendix I: Forms and Checklists 90

91 Chapter 1 Model BMP Design Manual NO Is Project a Priority Development Project (PDP)? YES Is Hydromodification Management Applicable? YES NO Standard Project PDP with Only Pollutant Control Requirement PDP with Pollutant Control and Hydromodification Management Requirements Section 2.1 & Chapter 3 Section 2.1; 2.2 & Chapter 3 Chapters 2 & 3 91

92 Chapter 3 Model BMP Design Manual Step 1 Coordinating Between Disciplines Step 2 Gathering Information About the Site Step 3 Site Planning and Assessing Opportunities & Constraints Chapter 4, 5 & 6 Step 5 Preparing a Project Storm Water Submittal Chapter 8 Step 4 Developing Final Site Layout and Storm Water Design Chapter 4, 5, 6 & 7 92

93 Standard Project Chapter 3: Planning and Design of a Project Chapter 4: Source Control and Site Design Practices for all Projects Chapter 8: Submittal Requirements 93

94 PDP With Pollutant Control Chapter 3: Planning and Design of a Project BMP Requirements Chapter 7: Long Term Operation & Maintenance Chapter 8: Submittal Requirements Chapter 4: Source Control and Site Design Practices for all Projects Chapter 5: Storm Water Pollutant Control BMPs for PDPs 94

95 PDP With Pollutant Control & Hydromodification Mgt. Chapter 3: Planning and Design of a Project BMP Requirements Chapter 7: Long Term Operation & Maintenance Chapter 8: Submittal Requirements Chapter 4: Source Control and Site Design Practices for all Projects Chapter 5: Storm Water Pollutant Control BMPs for PDPs Chapter 6: Hydromodification Management BMPs for PDPs 95

96 Project Development Approaches Standard Project Venkat Gummadi, P.E. Geosyntec Consultants 96

97 Introduction Permit Requirements and Concepts Overview and changes from 2007 to 2013 MS4 Permit Source Control and Site Design Practices Storm Water Pollutant Control Requirements Hydromodification Management Requirements Structure of the Model BMP Design Manual Project Development Approaches Standard Project PDP with Only Pollutant Control Requirement PDP Integrating Hydromodification Management with Pollutant Control 97

98 Standard Project Implement most of the same measures as before Protect Outdoor Storage Areas Source Control Buffer Zones Prevent Illicit Discharges Project Site Minimize Impervious Areas Protect Trash storage Areas Site Design Impervious Area Dispersion 98

99 Standard Project Must Now Implement Landscaping with native or drought tolerant species Minimize disturbance to natural drainages PDPs in 2007 Conserve natural areas, soils and vegetation Project Site New Small collection strategies Harvesting and using precipitation Minimize soil compaction and use of permeable material 99

100 Documenting Design Use Checklists to document design Priority Development Project determination Checklist Source Control & Site Design Checklist Prepare and submit a Storm Water Management Plan 100

101 Project Development Approaches PDP with Only Pollutant Control Requirement Venkat Gummadi, P.E. Geosyntec Consultants 101

102 Introduction Permit Requirements and Concepts Overview and changes from 2007 to 2013 MS4 Permit Source Control and Site Design Practices Storm Water Pollutant Control Requirements Hydromodification Management Requirements Structure of the Model BMP Design Manual Project Development Approaches Standard Project PDP with Only Pollutant Control Requirement PDP Integrating Hydromodification Management with Pollutant Control 102

103 PDP with Only Pollutant Control Requirement Retention BMPs Biofiltration BMPs Flow-thru Treatment Control BMPs + Alternative Compliance 103

104 Infiltration Feasibility Infiltration Feasibility Screening Would infiltration of the full design volume be feasible? 104

105 Categorization of Infiltration Feasibility Condition Part 1 - Full Infiltration Feasibility Screening Criteria Is infiltration rate below proposed facility > 0.5 in/hr.? Can infiltration of the full DCV be allowed without: increasing risk of geotechnical hazards increasing risk of groundwater contamination causing potential water balance issues 105

106 Infiltration Feasibility Infiltration Feasibility Screening Would infiltration of the full design volume be feasible? Yes Full Infiltration Category No Would infiltration of water in any appreciable amount be physically feasible? 106

107 Categorization of Infiltration Feasibility Condition Part 2 - Partial Infiltration vs. No Infiltration Feasibility Screening Criteria Do soil and geologic conditions allow for any infiltration in any appreciable rate or volume? Can Infiltration in any appreciable quantity be allowed without increasing risk of geotechnical hazards posing significant risk for groundwater related concerns violating downstream water rights 107

108 Infiltration Feasibility Infiltration Feasibility Screening Would infiltration of the full design volume be feasible? Yes Full Infiltration Category No Would infiltration of water in any appreciable amount be physically feasible? Yes No Partial Infiltration Category No Infiltration Category 108

109 PDP with Only Pollutant Control Requirement Full Infiltration Retain Partial Infiltration Bioinfiltrate; Retain as feasible, then biofilter No Infiltration Biofilter Bioretention Permeable Pavement Bioinfiltration Or equivalent Biofiltration Or equivalent Infiltration Gallery Or equivalent 109

110 Documenting Design Document feasibility and selection Criteria, checklists Reference supporting documents Use BMP Fact Sheets to design selected BMPs Prepare a Storm Water Submittal Prepare storm water management report Worksheets/checklists to document design O&M Plan 110

111 Project Development Approaches PDP Integrating Hydromodification Management with Pollutant Control Laura Henry, P.E. Rick Engineering Company 111

112 Introduction Permit Requirements and Concepts Overview and changes from 2007 to 2013 MS4 Permit Source Control and Site Design Practices Storm Water Pollutant Control Requirements Hydromodification Management Requirements Structure of the Model BMP Design Manual Project Development Approaches Standard Project PDP with Only Pollutant Control Requirement PDP Integrating Hydromodification Management with Pollutant Control 112

113 PDP Hydromodification Mgt. & Pollutant Control Applicability / exemptions Designing for pre-development condition Protection of coarse sediment yield areas Integrating hydromodification management with pollutant control Using San Diego BMP Sizing Calculator LID facilities under the 2013 MS4 Permit 113

114 Applicability / Exemptions Review of March 2011 Final HMP Applicability Requirements Language Section 6.1 HMP Applicability Requirements Figure 6.1 HMP Applicability Determination 114

115 HMP Applicability Checklist Exemption 2007 Permit 2013 Permit Not a Priority Development Project No increase to impervious area or peak flows Exempt Exempt Exempt Invalidated due to requirement to control to pre-development condition 115

116 HMP Applicability Checklist Exemption 2007 Permit 2013 Permit Direct discharge to exempt receiving water Exempt receiving waters: Pacific Ocean San Diego Bay Exempt river reach Exempt reservoir Tidally influenced area Still exempt receiving waters: Pacific Ocean San Diego Bay Exempt reservoir Must be re-approved through WMAA/WQIP: Exempt river reach Tidally influenced area 116

117 HMP Applicability Checklist Exemption 2007 Permit 2013 Permit Discharge to exempt receiving water via stabilized conveyance system Stabilized conveyance system includes: Existing storm drain systems Concrete channels Stable engineered unlined channels Still includes: Existing storm drain systems Concrete channels Must be re-approved through WMAA/WQIP: Stable engineered unlined channels 117

118 HMP Applicability Checklist Exemption 2007 Permit 2013 Permit Project in highly impervious watershed (>70% impervious) Exempt Must be re-approved through WMAA/WQIP Urban infill project Exempt Must be re-approved through WMAA/WQIP 118

119 Designing for Pre-Development Pre-development condition runoff means runoff conditions from the project footprint based on: Infiltration characteristics of the underlying soil Existing grade No impervious area 119

120 Protection of Critical Coarse Sediment Yield Areas Each PDP must: Avoid critical sediment yield areas known to the Copermittee or identified by the optional Watershed Management Area Analysis, or Implement measures that allow critical coarse sediment to be discharged to the receiving water, such that there is no net impact to the receiving water 120

121 Protection of Critical Coarse Sediment Yield Areas How will critical coarse sediment yield areas be protected? Identify locations Provide management measures for onsite areas and off-site areas draining through the site 121

122 Identifying Critical Coarse Sediment Yield Areas Regional mapping of critical coarse sediment yield areas will be available Procedures will be included to define Geomorphic Landscape Units (GLUs) Procedures will be presented to identify GLUs expected to be critical coarse sediment yield areas 122

123 Identifying Critical Coarse Sediment Yield Areas What is a Geomorphic Landscape Unit (GLU)? Combination of slope, geology, and land cover What kind of GLU will be defined as a critical coarse sediment yield area? Open (undeveloped) land cover Areas of high relative sediment production based on normalized RUSLE Analysis Coarse-grained geologic material - material that is expected to produce greater than 50% sand when weathered 123

124 Identifying Critical Coarse Sediment Yield Areas Delineate drainage boundaries for the project Intersect project-level topographic mapping, land cover, and geologic information to create GLUs For on-site areas use project-level topographic mapping, verify the existing land cover, and use best available geologic information For off-site areas ok to use regional mapping 124

125 Identifying Critical Coarse Sediment Yield Areas Determine whether any critical coarse sediment yield GLUs exist within the drainage boundaries Provide optional additional analysis to determine if areas are not producing sediment that is critical to receiving streams This could refine/reduce the area to be avoided/protected Provide management measures for critical coarse sediment yield areas 125

126 Management Measures Critical Coarse Sediment Yield Area On-site areas Preserve natural drainage systems Avoid disturbing critical coarse sediment yield areas Do not process drainage from these areas through basins that will trap sediment Property Boundary 126

127 On-Site Areas Critical Coarse Sediment Yield Area Preserve natural stream Avoid disturbing this area Do not process runoff from this area through a basin Property Boundary Avoid disturbing this area Do not process runoff from this area through a basin 127

128 Management Measures Off-site areas draining through the site Preserve natural conveyance systems Allow coarse sediment from off-site areas to be conveyed through the project site Do not process drainage from these areas through basins that will trap sediment Property Boundary Critical Coarse Sediment Yield Area 128

129 Off-Site Areas Critical Coarse Sediment Yield Area Allow coarse sediment from offsite areas to be conveyed through the project site Do not process runoff from this area through a basin Preserve natural stream on-site Property Boundary 129

130 Hydromodification Mgt. with Pollutant Control Onsite Peak Flood WSL Hydromod Capture WSL Pollutant Control Capture WSL 130

131 Hydromodification Mgt. with Pollutant Control Onsite 1) Evaluate feasibility to retain runoff for pollutant control 2) Determine pollutant control category Full Infiltration Partial Infiltration No Infiltration 3) Initiate design based on the pollutant control category 131

132 Hydromodification Mgt. with Pollutant Control Onsite Full Infiltration Design retention area to meet pollutant control standards Check flow control Increase volume as needed to meet flow control performance standards Increase retention if feasible Employ outflow control for runoff to be discharged from the facility as needed to meet flow control performance standards 132

133 Hydromodification Mgt. Partial Infiltration with Pollutant Control Onsite Design retention area to maximize retention Design additional runoff storage area with outflow control to meet flow control performance standards Use biofiltration if feasible If not biofiltration, use a flow control basin Address pollutant control requirements for the portion of the design capture volume that could not be retained on-site Design biofiltration area to pollutant control performance standards if feasible If not biofiltration, use flow-thru treatment control and participate in alternative compliance program 133

134 Hydromodification Mgt. with Pollutant Control Onsite No Infiltration Biofiltration Design a biofiltration facility to meet flow control performance standards Check pollutant control by biofiltration Increase volume as needed to address pollutant control Alternative Compliance Design a flow control basin to meet flow control performance standards Use flow-thru treatment control and participate in alternative compliance program 134

135 Hydromodification Mgt. with Pollutant Control 1) Evaluate feasibility to retain runoff for pollutant control 2) Determine pollutant control category 3) Initiate design based on pollutant control category 4) Adjust design to meet the second standard 5) Check drawdown time Onsite 6) Demonstrate each standard separately 135

136 Questions & Feedback 136

137 Thank you for your input! Resources: Regional MS4 Permit: /water_issues/programs/stormwater/ Contact Information Sumer Hasenin, P.E. City of San Diego tel: (858) Jayne Janda-Timba, P.E. Rick Engineering Company tel: (619)