THE SAN DIEGO AND IMPERIAL COUNTIES CHAPTER OF THE AMERICAN PUBLIC WORKS ASSOCIATION (APWA) ANNOUNCE A SEMINAR DEMONSTRATING The BMP Sizing

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1 THE SAN DIEGO AND IMPERIAL COUNTIES CHAPTER OF THE AMERICAN PUBLIC WORKS ASSOCIATION (APWA) ANNOUNCE A SEMINAR DEMONSTRATING The BMP Sizing Spreadsheeet A Tool to Comply with Hydromodification Management Requirements (2007 & 2013 MS4 Permits for San Diego Region) The BMP Sizing Spreadsheet replaces the former on-line San Diego BMP Sizing Calculator November 18, 2014

2 Seminar Logistic Background & Introduction Example Project to Compare Online Calculator & Spreadsheet Question & Answer Break Example Problem with 2007 MS4 Permit and 2013 MS4 Permit Requirements Question & Answer Future of Sizing Factor Method 2013 MS4 Permit Compliance Question & Answer Closing AGENDA Jayne Janda Timba René Vidales Nobu Murakami Brendan Hastie Laura Henry

3 Seminar Logistics Housekeeping Please turn cell phones off Sponsors Thank You! (County of SD, City of SD & APWA) Handouts Speaker Profile Bios Acronyms PowerPoint Presentation Sizing Factors Matrix Example Problem Handouts 3

4 Seminar Logistics Survey the audience. Design Engineer Environmental Community Development Community Municipality Regulators PowerPoint available on Project Clean Water Website: 4

5 SPEAKERS PROFILE René A. Vidales P.E, QSD, LEED GA, ENV SP Program Director County of San Diego Watershed Protection Program Department of Public Works 5510 Overland Avenue, Suite 410 San Diego, CA Phone: (858) Nobu Murakami P.E Assistant Project Engineer Rick Engineering Company Water Resources Division 5620 Friars Road San Diego, CA Phone: (619) Fax: (619) Brendan Hastie, P.E., LEED AP Associate Rick Engineering Company Water Resources Division Laura Henry, M.S., P.E. Project Engineer Rick Engineering Company Water Resources Division 5620 Friars Road San Diego, CA Phone: (619) Fax: (619) Friars Road San Diego, CA Phone: (619) Fax: (619) Jayne M. Janda-Timba, P.E., TOR, QSD, QSP Associate Rick Engineering Company Water Resources Division 5620 Friars Road San Diego, CA Phone: (619) Fax: (619) Cell: (619)

6 The BMP Sizing Spreadsheet A Tool to Comply with Hydromodification Management Requirements Background & Introduction René Vidales, PE, QSD, LEED GA, ENV SP Program Coordinator, Watershed Protection Program County of San Diego November 18, 2014

7 Background MS4 Permits Trainings Introduction History and Intent What it is and Purpose Components Mechanics Overview 2

8 Background 3

9 MS4 Permits 2007 MS4 Permit (R ) Required PDPs to implement Interim Hydromodification requirements Interim requirements started January, 2008 Required Copermittees to develop Final Hydromodification requirements Final HMP released January,

10 MS4 Permits 2013 MS4 Permit (R ) Will be implemented December, 2015 Will continue to require PDPs to implement Hydromodification requirements 5

11 Trainings Hydrologic Simulation Program Fortran (HSPF) June 2009 Training 6

12 Trainings Online BMP Sizing Calculator December 2010 Training 7

13 Trainings Online BMP Sizing Calculator March 2011 Training 8

14 Trainings San Diego Hydrology Model (SDHM) January 2012 Training 9

15 Trainings SCCWRP Hydromodification Screening Tool June 2012 Training 10

16 Why this Training? Online BMP Sizing Calculator Expired June 30,

17 Why this Training? Online BMP Sizing Calculator Expired June 30, 2014 Replaced by the BMP Sizing Spreadsheet 12

18 This Training BMP Sizing Spreadsheet November 18, 2014 Training 13

19 Introduction 14

20 History Final Regional HMP includes a table of sizing factors for various BMPs Online sizing calculator developed based on sizing factors in HMP Online sizing calculator taken down and replaced with spreadsheet. July 1,

21 History Advantages of spreadsheet versus online sizing calculator (tool) Does not require internet hosting Does not require major updates to maintain compatibility with latest versions of internet browsers Can easily be downloaded to an individual computer Easy to use and understand 16

22 Intent One possible tool for use by applicants (SDHM, SWMM, etc. can still also be used) Simple and easy to use Conservative results For use with common conditions (unusual designs will require continuous simulation modeling) Sizes BMPs for treatment of the 85 th percentile event as well as hydromodification management 17

23 What it is and Purpose Spreadsheet to facilitate calculations from Final HMP (Section 7) and Regional Model SUSMP (Chapter 4) Some input parameters are controlled in order to align with the Final HMP and the SUSMP Some input parameters are determined based on project conditions Spreadsheet output confirms adequacy of design Particularly useful during preliminary design 18

24 Why use it? Online BMP Sizing Calculator is no longer online More reports with hand calculations for HMP 19

25 BMP Sizing Spreadsheet Tabs Let s look at the components within the spreadsheet 20

26 Controlled selections BMP Type Low Flow Threshold Soil Group Slope Categorization Rain Gauge Components 21

27 Components Custom User Input DMA name, size, surface type, and runoff factor BMP area and volume Depth of soil matrix Orifice size 22

28 Components Output Minimum area and volume sizing criteria Minimum and maximum allowable depth Drawdown time 23

29 Select a BMP Five (5) BMP Options in the Final HMP - Bioretention Facilities (Table 7-1) - Bioretention Plus Cistern Facilities (Table 7-2) - Bioretention Plus Vault Facilities (Table 7-3) - Flow-Through Planters (Table 7-4) - Infiltration Facilities (Table 7-5) 24

30 Bioretention/Flow-Through Planter Variable surface ponding depth Variable soil matrix depth 30-inch gravel storage layer Orifice 12-inch off bottom 25

31 Bioretention Plus Cistern Variable cistern depth and volume Overflow outlet to bioretention Controlled orifice outlet to bioretention 26

32 Bioretention Plus Vault Variable vault depth and volume Inflow from bioretention Emergency overflow outlet Controlled orifice outlet 27

33 Infiltration Variable depth and volume No orifice discharge 28

34 Low Flow Threshold Determined based on stream susceptibility Per Section 6.2 of the Final HMP High = 0.1Q 2 (default value; no assessment is performed) Medium = 0.3Q 2 Low = 0.5Q 2 29

35 Soil Group NRCS Hydrologic Soil Group County Hydrology Manual, Appendix A NRCS Web Soil Survey 30

36 Average Slope Flat (< 5%) Moderate (5% to 15%) Steep (>15%) Slope 31

37 Rain Gauge Only three (3) options Lindbergh Oceanside Lake Wohlford 32

38 Rain Gauge Rain gauge information: 33

39 Rain Gauge and Soil Type 34

40 Rain Gauge and Soil Type Click next to point 35

41 Rain Gauge and Soil Type 36

42 Minimum Surface Area Per Tables 7-1 to 7-5 of the Final HMP Expressed as a ratio of the contributing area 37

43 Minimum Volume Per Tables 7-1 to 7-5 of HMP Expressed as a ratio of the contributing area 10-inch of surface ponding (for bioretention) 18-inch storage with 40% porosity (for bioretention) 38

44 Outlet Orifice Sized to discharge at the same rate as the low flow threshold Calculated drawdown time must be less than 96 hours Vector Control Plan required if more than 96 hours County of San Diego Guidelines for Determining Significance County of San Diego Guidelines for Report Format and Content Requirements 39

45 Mechanics Project Info TAB 40

46 Mechanics BMP #1 TAB 41

47 Mechanics Orifice #1 TAB 42

48 Mechanics Orifice #1 TAB 43

49 Mechanics Orifice #1 TAB 44

50 Mechanics Rain Gauge Map TAB 45

51 Mechanics Sizing Factors TAB 46

52 Example Problem To Compare Online Calculator with Spreadsheet 47

53 Comparison of Online San Diego BMP Sizing Calculator (Retired) and BMP Sizing Spreadsheet (New) Nobu Murakami Rick Engineering Company Water Resources Division November 18,

54 Overview Use an example residential project to compare: 1. Online San Diego BMP Sizing Calculator (Retired) 2. BMP Sizing Spreadsheet (New) 2

55 Example Residential Project Area Reserved for LID BMP Total DMA = 1.22 AC DMA to LID (w/o self-treating area) = 1.14 AC 3

56 Example Residential Project Additional Information / Assumptions: The POC will be at the point where the runoff leaves the project No channel assessment performed use low flow threshold of 0.1Q 2 Design goal is to size a LID BMP using a Cistern to Bioretention tool 4

57 Online San Diego BMP Sizing Calculator (Retired) Basin Manager Tool: Start Tab (Introduction/Overview for Basin Manger) Project Tab (Define Project Information) Basin Tab (Define Basin Properties) POC Tab (Low-flow Threshold Calculation) Export Tab (Export/Import Project Information files) LID Sizer Tool: Start Tab - (Introduction/Overview for LID Sizing) DMA Tab - (Define/Manage DMA Properties) LID Tab - (LID BMP Sizing Calculation) Report Tab - (Provides a summary of the project / LID Sizing) Export Tab - (Export/Import DMA/LID files) Basin Manager Tool and LID Sizer Tool 5

58 Online San Diego BMP Sizing Calculator (Retired) Project TAB (Basin Manager Tool) Online San Diego BMP Sizing Calculator 6

59 Online San Diego BMP Sizing Calculator (Retired) Basin TAB (Basin Manager Tool) Online San Diego BMP Sizing Calculator 7

60 Online San Diego BMP Sizing Calculator (Retired) POC TAB (Basin Manager Tool) Online San Diego BMP Sizing Calculator 8

61 Online San Diego BMP Sizing Calculator (Retired) DMA TAB (LID Sizer Tool) Online San Diego BMP Sizing Calculator 9

62 Online San Diego BMP Sizing Calculator (Retired) Note: All of the DMAs have been defined, including the self-treating areas. However, the Online Calculator would not consider the self-treating DMA in sizing the LID BMP since the DMA did not contribute to the LID BMP. DMA TAB (LID Sizer Tool) Online San Diego BMP Sizing Calculator 10

63 Online San Diego BMP Sizing Calculator (Retired) Minimum Bioretention Area = sf. Minimum Cistern Volume (V1) = cf. Flow Threshold 0.1Q 2 = cfs Orifice Size = 0.6 in. LID TAB (LID Sizer Tool) Online San Diego BMP Sizing Calculator 11

64 BMP Sizing Spreadsheet (New) Available Tabs within the BMP Sizing Spreadsheet Project Info (Project Information) BMP #1 (BMP Sizing Calculation) Orifice #1 (Orifice Sizing Calculation) Rain Gauge Map (for reference) Sizing Factors (Lookup Tables from the 2011 Final HMP) 12

65 BMP Sizing Spreadsheet (New) Project Info TAB BMP Sizing Spreadsheet 13

66 BMP Sizing Spreadsheet (New) Project Info TAB BMP Sizing Spreadsheet 14

67 BMP Sizing Spreadsheet (New) Project Info TAB BMP Sizing Spreadsheet 15

68 BMP Sizing Spreadsheet (New) Project, Basin and POC tabs from the San Diego BMP Sizing Calculator have been consolidated into this Project Info Tab in the BMP Sizing Spreadsheet. Project Info TAB BMP Sizing Spreadsheet 16

69 BMP Sizing Spreadsheet (New) BMP #1 TAB BMP Sizing Spreadsheet 17

70 BMP Sizing Spreadsheet (New) BMP #1 TAB BMP Sizing Spreadsheet 18

71 BMP Sizing Spreadsheet (New) BMP #1 TAB BMP Sizing Spreadsheet 19

72 BMP Sizing Spreadsheet (New) BMP #1 TAB BMP Sizing Spreadsheet 20

73 BMP Sizing Spreadsheet (New) BMP #1 TAB BMP Sizing Spreadsheet 21

74 BMP Sizing Spreadsheet (New) BMP #1 TAB BMP Sizing Spreadsheet 22

75 BMP Sizing Spreadsheet (New) BMP #1 TAB BMP Sizing Spreadsheet 23

76 BMP Sizing Spreadsheet (New) BMP Area = sf * (1.0) * (0.02) = 166 s.f. Cistern Vol. = sf * (1.0) * (0.2) = 1655 c.f. BMP #1 TAB BMP Sizing Spreadsheet 24

77 BMP Sizing Spreadsheet (New) Sizing Factors TAB BMP Sizing Spreadsheet 25

78 BMP Sizing Spreadsheet (New) Note: All of the DMAs have been defined except the area for self-treating DMA has been purposefully left blank since this DMA does not drain to the LID BMP AC. Minimum Bioretention Area = s.f. OK Minimum Cistern Volume (V1) = 6011 c.f. OK BMP #1 TAB BMP Sizing Spreadsheet 26

79 BMP Sizing Spreadsheet (New) BMP #1 TAB BMP Sizing Spreadsheet 27

80 BMP Sizing Spreadsheet (New) Orifice #1 TAB BMP Sizing Spreadsheet 28

81 BMP Sizing Spreadsheet (New) Orifice #1 TAB BMP Sizing Spreadsheet 29

82 BMP Sizing Spreadsheet (New) Existing Condition Cover: Scrub refers to a natural (pervious) cover Urban refers to a landscaping area with irrigation N/A applies only when Impervious is selected as the Soil Type Orifice #1 TAB BMP Sizing Spreadsheet 30

83 BMP Sizing Spreadsheet (New) Orifice #1 TAB BMP Sizing Spreadsheet 31

84 BMP Sizing Spreadsheet (New) Orifice #1 TAB BMP Sizing Spreadsheet 32

85 BMP Sizing Spreadsheet (New) Orifice #1 TAB BMP Sizing Spreadsheet 33

86 BMP Sizing Spreadsheet (New) Orifice #1 TAB BMP Sizing Spreadsheet 34

87 BMP Sizing Spreadsheet (New) User s Input Orifice #1 TAB BMP Sizing Spreadsheet 35

88 Q & A 36

89 Break 37

90 Example Problem 2007 MS4 Permit and 2013 MS4 Permit Requirements Brendan Hastie Rick Engineering Company Water Resources Division November 18, 2014

91 Purpose Compare the BMP Sizing Spreadsheet results for the example problem by inputting data based on 2007 MS4 and 2013 MS4 Permit Requirements 2

92 Presentation Overview Goals of Example Problem Example Problem Information/Assumption Example Problem 2007 MS4 Permit Example Problem 2013 MS4 Permit Summary of the results based on the permit changes that affect structural BMP design 3

93 Goals of Example Problem Identify and describe the required data (2007 MS4 vs MS4) Describe the data entry procedures Demonstrate how to operate the BMP Sizing Spreadsheet by entering data for example problem 4

94 Example Problem Information/Assumption Redevelopment Project Goals: We will examine one Basin draining to a storm drain system. The POC will be at the point where the runoff leaves the project. Design goal is Treatment + Flow Control. No channel assessment performed use low flow threshold of 0.1Q2 (High Susceptibility). Rainfall Basin, Soil Type, Pre-Project Cover (2007 MS4 Permit), Pre-Project Slope, and DMA Surface Types are shown on the Example Problem-Redevelopment Project. Pre-Development Cover used for the 2013 MS4 Permit. Design a Flow Through Planter 5

95 Example Problem Information/Assumption (Sheet 1 of 2) 6

96 Example Problem Information/Assumption (Sheet 2 of 2) 7

97 Example Problem Information/Assumption (BMP Sizing Spreadsheet) Available Tabs within the BMP Sizing Spreadsheet Project Info BMP #1 Orifice #1 Rain Gauge Sizing Factors 8

98 Example Problem 2007 MS4 Permit In the BMP Sizing Szpreadsheet, select the Project Info tab Enter information in highlighted section Note: Rain Gauge has dropdown menu to select either Lindbergh, Oceanside, or Lake Wohlford. Channel Susceptibility has a dropdown menu to select either High, Medium or Low. Project Info Tab 9

99 Example Problem 2007 MS4 Permit The Project info tab is completed. Next step is to select the BMP #1 tab in the Spreadsheet Project Info Tab 10

100 Example Problem 2007 MS4 Permit Start Sizing BMP Footprint The BMP #1 Tab in the Spreadsheet has been selected Note: The highlighted fields have been automatically populated from the previously entered information in the Project Info tab BMP #1 Tab 11

101 Example Problem 2007 MS4 Permit Sizing BMP Footprint Populate BMP Name, BMP Native Soil Type, and BMP Type fields The selected soil type presents the soil type that the BMP will be located on. The soil type will be used to determine the BMP Infiltration Rate of the BMP. Note: Field BMP Infiltration Rate field has been automatically populated as the user enters BMP Native Soil Type field. The example problem is to design Flow-Through Planter ; therefore, impervious liner has been selected that results in N/A BMP Infiltration Rate. BMP #1 Tab 12

102 Example Problem 2007 MS4 Permit Sizing BMP Footprint HMP Sizing Factors and Minimum BMP Size fields will be automatically populated/calculated as the user enters information in the highlighted/blue fields for each DMA The goal is to obtain the BMP Sizes for Surface Area, Surface Volume, and Subsurface Volume BMP #1 Tab 13

103 Example Problem 2007 MS4 Permit Sizing BMP Footprint Populate the selected blue fields for each DMA BMP #1 Tab 14

104 Example Problem 2007 MS4 Permit Sizing BMP Footprint The first DMA has been entered. Continue the same exercise and enter information for the second DMA. BMP #1 Tab 15

105 Example Problem 2007 MS4 Permit Sizing BMP Footprint The second DMA has been entered. Continue the same exercise and enter information for the third DMA. BMP #1 Tab 16

106 Example Problem 2007 MS4 Permit Sizing BMP Footprint The third DMA has been entered. Continue the same exercise and enter information for the fourth DMA. BMP #1 Tab 17

107 Example Problem 2007 MS4 Permit Sizing BMP Footprint The fourth DMA 4 has been entered. Continue the same exercise and enter information for the fifth DMA. BMP #1 Tab 18

108 Example Problem 2007 MS4 Permit Sizing BMP Footprint Now all five DMAs has been entered. The final results for the BMP Size are summarized within the box to the right. -The minimum surface area is s.f. -The minimum surface volume is 675 c.f. -The minimum subsurface volume is 468 c.f. BMP #1 Tab 19

109 Example Problem 2007 MS4 Permit Sizing BMP Footprint Enter the proposed BMP Size equal or close to the to the minimum BMP Size for start Note: To model for 2007 MS4 Permit, all DMAs with impervious area in the pre project condition shall be left empty in runoff factor field BMP #1 Tab 20

110 Example Problem 2007 MS4 Permit Sizing BMP Footprint Enter the Soil Matrix Depth Note: This is only needed for bioretention or flow-through planter designs; 18 inches is the minimum depth) BMP #1 Tab 21

111 Example Problem 2007 MS4 Permit Sizing BMP Footprint Complete Enter the Selected Ponding Depth Note: Assumed 10 inches for start BMP #1 Tab 22

112 Example Problem 2007 MS4 Permit Start Sizing Orifice The Orifice #1 Tab in the Spreadsheet has been selected Q2 Sizing Factor, Orifice Flow - %Q2, and Orifice Area will be automatically generated as the user enters data in the highlighted fields Note: DMA Name, Rain Gauge and DMA Area columns have been automatically populated from the previously entered information in the BMP #1 Tab. Orifice #1 Tab 23

113 Example Problem 2007 MS4 Permit Sizing Orifice Soil Type, Cover, and Slope information for the first DMA has been entered. Continue the same exercise and enter the Example Problem information for the second DMA Orifice #1 Tab 24

114 Example Problem 2007 MS4 Permit Sizing Orifice Soil Type, Cover, and Slope information for the second DMA has been entered. Continue the same exercise and enter the Example Problem information for the third DMA Orifice #1 Tab 25

115 Example Problem 2007 MS4 Permit Sizing Orifice Soil Type, Cover, and Slope information for the third DMA has been entered. Continue the same exercise and enter the Example Problem information for the fourth DMA Orifice #1 Tab 26

116 Example Problem 2007 MS4 Permit Sizing Orifice Soil Type, Cover, and Slope information for the fourth DMA has been entered. Continue the same exercise and enter the Example Problem information for the fifth DMA Orifice #1 Tab 27

117 Example Problem 2007 MS4 Permit Sizing Orifice Completed Soil Type, Cover, and Slope information for the Existing Condition (Pre-Project Condition) for all DMAs has been entered Calculated Max Orifice Diameter is 0.54 inches. The size of 0.54 inches shall be entered. Based on the entered 0.54 inches in the Orifice #1 tab, the BMP Sizing Spreadsheet will calculate the Drawdown Time. Ignore the drawdown time on this tab Orifice #1 Tab 28

118 Example Problem 2007 MS4 Permit Computing Drawdown TIme The size of 0.54 inches is entered in the Orifice #1 tab. The calculated Drawdown Time is 20.1 hours. Note 1: Check BMP #1 tab if the entered Selected Ponding Depth is between the required Minimum and Maximum depths. Note 2: If the minimum ponding depth is more than the maximum ponding depth, adjust the BMP size, soil matrix depth and/or the selected ponding depth. Orifice #1 Tab 29

119 Example Problem 2007 MS4 Permit BMP footprint size and ponding depth check The initially assumed Selected Ponding Depth of 10 inches is between the required minimum and maximum ponding depth; therefore sizing of the BMP footprint, Orifice Size, and Drawdown Time is completed. BMP #1 Tab 30

120 Example Problem 2013 MS4 Permit In the BMP sizing spreadsheet, select the Project Info tab Enter information in highlighted section Note: Rain Gauge has dropdown menu to select either Lindbergh, Oceanside, or Lake Wohlford. Channel Susceptibility has a dropdown menu to select either High, Medium or Low. Project Info Tab 31

121 Example Problem 2013 MS4 Permit The Project info tab is completed. Next step is to select the BMP #1 tab in the Spreadsheet Project Info Tab 32

122 Example Problem 2013 MS4 Permit Start Sizing BMP footprint The BMP #1 Tab in the Spreadsheet has been selected Note: The highlighted fields have been automatically populated from the previously entered information in the Project Info tab BMP #1 Tab 33

123 Example Problem 2013 MS4 Permit Sizing BMP footprint Populate BMP Name, BMP Native Soil Type, and BMP Type fields. The selected soil type presents the soil type that the BMP will be located on. Since the example problem is for Flow-Through Planter we selected Impervious Liner instead of soil type. BMP #1 Tab 34

124 Example Problem 2013 MS4 Permit Sizing BPM footprint HMP Sizing Factors and Minimum BMP Size fields will be automatically populated/calculated as the user enters information in the highlighted/blue fields in each DMA The goal is to obtain the BMP Sizes for Surface Area, Surface Volume, and Subsurface Volume BMP #1 Tab 35

125 Example Problem 2013 MS4 Permit Sizing BMP footprint Populate the selected blue fields for each DMA BMP #1 Tab 36

126 Example Problem 2013 MS4 Permit Sizing BMP footprint The first DMA has been entered. Continue the same exercise and enter information for the second DMA BMP #1 Tab 37

127 Example Problem 2013 MS4 Permit Sizing BMP footprint The second DMA has been entered. Continue the same exercise and enter information for the third DMA BMP #1 Tab 38

128 Example Problem 2013 MS4 Permit Sizing BMP footprint The third DMA has been entered. Continue the same exercise and enter information for the fourth DMA BMP #1 Tab 39

129 Example Problem 2013 MS4 Permit Sizing BMP footprint The fourth DMA has been entered. Continue the same exercise and enter information for the fifth DMA BMP #1 Tab 40

130 Example Problem 2013 MS4 Permit Sizing BMP footprint Now all of the DMAs has been entered. The final results for the BMP Size are summarized within the box to the right. -The minimum surface area is s.f. -The minimum surface volume is 1910 c.f. -The minimum subsurface volume is 1375 c.f. BMP #1 Tab 41

131 Example Problem 2013 MS4 Permit Sizing BMP footprint Enter the proposed BMP Size equal to the minimum BMP size for start. Enter the soil matrix depth and the ponding depth fields BMP #1 Tab 42

132 Example Problem 2013 MS4 Permit Start Sizing Orifice The Orifice #1 Tab in the Spreadsheet has been selected Soil Type, Cover, and Slope information for the Existing Condition (Pre-Project Condition) for the first DMA has been entered Q2 Sizing Factor, Orifice Flow - %Q2, and Orifice Area will be automatically generated as the user enters data in the highlighted fields Note: DMA Name, Rain Gauge and DMA Area columns have been automatically populated from the previously entered information in the BMP #1 Tab Orifice #1 Tab 43

133 Example Problem 2013 MS4 Permit Sizing Orifice Completed Soil Type, Cover, and Slope information for all DMAs has been entered. Calculated Max Orifice Diameter by the BMP Sizing Spreadsheet is 0.21 inches. Based on the entered 0.21 inches, which is equal to the maximum orifice diameter, the BMP Sizing Spreadsheet calculates the Drawdown Time. Since the drawdown time exceeds 96 hours, return to BMP tab and adjust the initial BMP size, and/or the soil matrix depth and/or the selected ponding depth. Orifice #1 Tab 44

134 Example Problem 2013 MS4 Permit Increase the BMP Footprint and/or Soil Matrix Depth to Reduce DDT Proposed BMP Size and Soil Matrix Depth are iteratively increased until the Minimum Ponding Depth is less than the Maximum Ponding Depth. This indicates that a drawdown time less than 96 hours can be provided. The selected ponding depth has been adjusted to 1.54 inches BMP #1 Tab 45

135 Example Problem 2013 MS4 Permit Check if BMP Adjustments Result in acceptable DDT After adjusting the BMP size, the soil matrix depth, and selected ponding depth, the drawdown time is now less than 96 hours; therefore, sizing of the BMP is complete. Orifice #1 Tab 46

136 Summary of the Results based on the permit changes that affect structural BMP design 47

137 Summary of the Results based on the permit changes that affect structural BMP design The changes from the 2007 MS4 and 2013 MS4 have been implemented in the example problem to size the BMP Surface Area, Surface Volume, Subsurface Volume, and Orifice Size, and to calculate the Drawdown Time using BMP Sizing Spreadsheet 2007 MS4 compares proposed project site surface cover with the Pre- Project surface cover 2013 MS4 compares proposed project site surface cover with the Pre- Development project surface cover Change in the results: 2013 MS4 requires bigger BMP Surface Area, Surface Volume, Subsurface Volume, Soil Matrix Depth, and smaller Orifice Size. Drawdown Time becomes a significant challenge for BMPs with small drainage areas! 48

138 Q & A 49

139 Future of Sizing Factor Method 2013 MS4 Permit Compliance Laura Henry Rick Engineering Company Water Resources Division November 18, 2014

140 Purpose How to apply sizing factors developed based on 2007 standards to meet 2013 standards 2

141 Presentation Overview Background and new terminology 2013 MS4 Permit changes that affect structural BMP design Using sizing factors under the 2013 MS4 Permit 3

142 Background Standard for design of flow control BMPs for hydromodification management requires continuous simulation modeling Project-specific modeling (HSPF, SDHM, SWMM); OR Sizing factor method (developed based on unit-area modeling) 4

143 Background Sizing factor method is static Unit-area modeling prepared one time Not being revised for 2013 MS4 Permit BMP Design Manual will incorporate applicable sizing factors, leave out non-applicable sizing factors 5

144 New Terminology BMP Design Manual (formerly SUSMP) Pollutant control BMP (formerly treatment control BMP) Retain (infiltrate, evaporate, evapotranspire, harvest and use) 6

145 New Terminology Structural BMP encompasses: Single purpose BMP (pollutant control OR hydromodification management flow control) Dual purpose BMP (integrated BMP that combines pollutant control AND flow control) 7

146 New Terminology Bioretention (full retention/infiltration) Bioinfiltration (partial retention/infiltration) Biofiltration (no retention/infiltration) Bioretention: No Underdrain Bioinfiltration: Raised Underdrain Biofiltration: Underdrain at Bottom 8

147 Flow-Thru BMP New Terminology Treatment control BMP that does not incorporate significant biological methods Vegetated swales, media filters, sand filters, dry extended detention basins 9

148 Permit Changes for Structural BMP Design Hydromodification management performance standards Pollutant control performance standards 10

149 Changes to Hydromodification Management Requirements Changes to applicability/exemptions New requirement to protect critical coarse sediment yield areas Requirement to control to pre-development condition instead of pre-project condition 11

150 Changes to Hydromodification Management Requirements Pre-development condition means runoff conditions from the project footprint based on: Infiltration characteristics of the underlying soil Existing grade No impervious area 12

151 Changes for Sizing Factor Method What pre-development condition requirement means for sizing factor method: Unit runoff ratios for urban and impervious cover types may not be used to determine pre-development Q 2 for low flow orifice sizing under 2013 MS4 Permit Assume a natural pervious cover ( scrub ) for the predevelopment condition 13

152 Changes to Pollutant Control Requirements 2013 Permit Pollutant Control Hierarchy: Retain onsite 85 th percentile runoff (infiltrate, evaporate, evapotranspire, harvest and use) Volume-based sizing Design Capture Volume (DCV) Biofiltration if infeasible to retain runoff onsite Flow-thru treatment BMPs AND mitigate (off-site) for the DCV that was not retained onsite, if infeasible to retain or use biofiltration 14

153 Changes for Sizing Factor Method How/why do changes to pollutant control requirements relate to the sizing factors? The change to DCV-based sizing and emphasis on retention makes it impractical to apply some of the sizing factors that included a flow-based treatment component Names of sizing factor BMPs are not consistent with updated pollutant control terminology 15

154 Changes for Sizing Factor Method Sizing factor compatibility issues Bioretention area sizing factor from Cistern Plus Bioretention BMP Bioretention area sizing factor from Bioretention Plus Vault BMP 16

155 Changes for Sizing Factor Method Mapping of BMP names for integrated pollutant control and flow control BMPs BMP Sizing Spreadsheet BMP Name Infiltration 2013 Compatible BMPs Full retention category Infiltration basins Permeable pavement (without underdrain) Bioretention without underdrain 17

156 Changes for Sizing Factor Method Mapping of BMP names for integrated pollutant control and flow control BMPs BMP Sizing Spreadsheet BMP Name Bioretention 2013 Compatible BMPs A or B soils: Full retention category Bioretention without underdrain C or D soils: with dead storage layer: Partial retention category Bioinfiltration C or D soils: without dead storage layer: No retention category Biofiltration 18

157 Changes for Sizing Factor Method Mapping of BMP names for integrated pollutant control and flow control BMPs BMP Sizing Spreadsheet BMP Name Flow-Through Planter 2013 Compatible BMPs No retention category Biofiltration 19

158 Changes for Sizing Factor Method Mapping of BMP names for integrated pollutant control and flow control BMPs BMP Sizing Spreadsheet BMP Name Bioretention plus Vault Cistern plus Bioretention 2013 Compatible BMPs Not applicable Not applicable* * Cistern is still useful for hydromodification management flow control volume sizing, but the treatment element of the BMP downstream of the cistern should be designed based on 2013 standards instead of sizing factors 20

159 Evaluate feasibility to retain runoff for pollutant control, determine pollutant control category Full, Partial, or No retention Select a structural BMP How to Size the structural BMP for hydromodification management For integrated BMPs, verify pollutant control performance (check drawdown time for DCV) 21

160 Sizing Factors Applicable to Types of Pollutant Control Facilities Full retention Sizing factors for infiltration Sizing factors for bioretention in A or B soils 22

161 Sizing Factors Applicable to Types of Pollutant Control Facilities Partial retention Sizing factors for bioretention in C or D soils* *retention storage must be provided below the underdrain, sizing factors will not provide credit for the retention storage 23

162 Sizing Factors Applicable to Types of Pollutant Control Facilities No retention Sizing factors for bioretention in C or D soils, when there is no retention storage provided below the underdrain Sizing factors for flow-through planter Sizing factors for cistern 24

163 Sizing Factors Applicable to Types of Pollutant Control Facilities Full Retention BMP Partial Retention BMP No Retention BMP 2013 BMP Infiltration Sizing Factor Basin Permeable Pavement Bioretention Bioinfiltration Biofiltration Infiltration (A or B soils) X X Bioretention (A or B soils) X Bioretention (C or D soils) Flow-Through Planter (C or D soils) Cistern X (with dead storage layer below underdrain) X (without dead storage layer below underdrain) X X 25

164 Drawdown Time Why is drawdown different for pollutant control sizing vs. hydromodification management? 26

165 Limitations on use of sizing factors Sizing factor method is intended for simple projects No diversion No off-site area Use project-specific continuous simulation model for more complex projects Guidance and parameters will be provided in the BMP Design Manual 27

166 Q & A 28