Section 5 Permanent BMPs A permanent BMP strategy

Section 5 – Permanent BMPs A permanent BMP strategy should: Ø Maximize infiltration Ø Prioritize Treatment BMPs Ø Provide detailed documentation of treatment Permanent BMPs include: Ø Design Pollution Prevention (DPP) BMPs Ø Permanent soil stabilization and concentrated flow controls Ø Treatment BMPs Ø Permanent treatment devices and facilities Ø DPP BMP consideration required for all projects with DSA. Ø Treatment BMP consideration required per EDF. Brown and Caldwell 1

Section 5 - Overview This section will cover: ØDeveloping a permanent BMP strategy ØSite design principles ØDPP BMPs ØDPP infiltration for treatment ØInfiltration Tool ØChecklist T-1, Part 1 Review ØWQV and WQF ØTreatment prioritization ØDocumenting treatment Brown and Caldwell 2

Section 5 – Developing a Permanent BMP Strategy Consider: • Site design principles • DPP BMPs • Treatment BMPs Site design principles include: Vegetated strips and swales Pervious areas receive runoff from impervious Minimize impervious footprint Conserve natural areas, minimize disturbance to natural drainagesarea Design for soil conditions and slope! Brown and Caldwell 3

Section 5 – DPP BMPs DPP BMP Consideration Form Checklist DPP-1, Part 1. If any Checklist DPP-1, Part 1 question is answered Yes, DPP BMPs are required. Document in Section 6 of the SWDR. Brown and Caldwell 4

Section 5 – DPP BMPs that provide infiltration can be documented as treatment, including vegetated and non-vegetated areas. Which of these DPP BMPs could provide infiltration for treatment credit? • Worst one? • Best one? Brown and Caldwell Note: If any DPP BMP creates concentrated flows, refer to HDM Chapter 860. Consider channel lining when appropriate. 5

Section 5 – DPP Infiltration Areas: Ø Vegetated and non-vegetated areas Ø Sized to capture WQV Ø New, modified, or existing areas Ø Areas must be stabilized to prevent erosion Ø Areas can be amended Ø Areas do not necessarily meet the design requirements of Biostrips or Bioswales Ø Use Checklist T-1, Part 11 Brown and Caldwell 6

Section 5 – DPP Infiltration Areas as Treatment BMPs DPP Infiltration Areas are evaluated and tracked as Treatment BMPs Brown and Caldwell 7

Section 5 – Infiltration Tool Strip and Swale Infiltration Tool (SSIT) Basin Infiltration Tool (BIT) Brown and Caldwell 8

Section 5 – Infiltration Tool – SSIT Input Brown and Caldwell 9

Section 5 – Infiltration Tool – SSIT Input Brown and Caldwell 10

Section 5 – Infiltration Tool – Output If < 100%, consider amending soil Brown and Caldwell 11

Section 5 – Infiltration Tool – Amendments Brown and Caldwell 12

Section 5 – Infiltration Tool – Amendments Use for Checklist T-1, Part 1 Question 2 and document in Table E-2. Brown and Caldwell 13

Section 5 – Infiltration Tool The SSIT Results tab produces a design summary report. Brown and Caldwell 14

Section 5 – Treatment Tracking, include all BMPs Track all areas treated by DPP BMPs using Table E-2 If additional treated area required, consider other Treatment BMPs Brown and Caldwell 15

Section 5 –Treatment BMPs Use the EDF to determine if Treatment BMPs are required then use Checklist T-1, Part 1 to evaluate Treatment BMPs. Use to support narrative of Section 6 in the SWDR. Ø Infiltration Rules! Ø Biofiltration encouraged Ø TDCs simply 4 Matrices If approved Treatment BMPs are not feasible, consult with SW Coordinator. May be able to use non-approved Brown and Caldwell 16

Section 5 – T-1, Part 1 Consider Treatment BMPs How do we calculate WQV and WQF for use in T-1, Part 1? Brown and Caldwell 17

Section 5 – Identify Potential Treatment Areas Potential BMP Area Brown and Caldwell 18

Section 5 – Delineate CDA Contributing Drainage Area Brown and Caldwell 19

Section 5 – WQV, Volume-Based Runoff Coefficient (RV) Brown and Caldwell 20

Section 5 – WQV, Volume-Based Runoff Coefficient (RV) When 50% o more of impervious surfaces drain from impervious to pervious, use Table 5 -2 or calculate coefficient directly using Urbonas (1999) equation Three scenarios where a composite VR calculation is required: 1. CDAs with hydraulically separated pervious and impervious areas 2. CDAs where impervious surfaces are less than 50% of the drainage area 3. CDAs where pervious area drains to impervious Where: VR 1 = WQV impervious VR 2 = WQV pervious Brown and Caldwell 21

Section 5 – WQV, Volume-Based Runoff Coefficient (RV) Brown and Caldwell 22

Section 5 – WQV, Volume-Based Runoff Coefficient (RV) Brown and Caldwell 23

Section 5 – WQV Example Given: • Sacramento County • Potential drainage (shown), is 0. 3 mile (1, 633 ft) long with 2 new lanes, a shoulder, and an embankment • Average overland slope of the flow path is 1%. • 85 th percentile, 24 -hour rainfall depth is 0. 62 inch • Potential BMP requires volumebased sizing. Brown and Caldwell 24

Section 5 – WQV Example Solution: Step 1: Calculate Areas The CDA consists of 2 travel lanes, a shoulder, and the embankment: The percent impervious for the CDA is calculated: Brown and Caldwell 25

Section 5 – WQV Example Solution: Step 2: Volumetric Runoff Coefficients Because the CDA drains impervious to pervious and the impervious is 50%, use Table 5 -2 to determine RV for the CDA. RV = 0. 34 Brown and Caldwell 26

Section 5 – WQV Example Solution: Step 3: Water Quality Volume Where, RV = 0. 34 (from Step 2) P = 0. 62 in (from problem statement) A = 2 acres (from Step 1) Brown and Caldwell 27

Section 5 – WQF, Flow-Based Runoff Coefficient NOTE: Continue to use runoff coefficients from HDM Chapter 831 to develop Design Storm flows. Brown and Caldwell 28

Section 5 – WQF Example Given: • Sacramento County • Potential drainage (shown), is 0. 3 mile (1, 633 ft) long with 2 new lanes, a shoulder, and an embankment • Rainfall intensity from Basin Sizer is 0. 16 in/hr • Potential BMP requires flow-based sizing. Brown and Caldwell 29

Section 5 – WQV Example Solution: Step 1: Calculate Areas The pervious area is: The impervious area is: Brown and Caldwell 30

Section 5 – WQF Example Solution: Step 2: Flow-Based Runoff Coefficients Using Table 5 -3 coefficients: Composite runoff coefficient: Brown and Caldwell 31

Section 5 – WQF Example Solution: Step 3: Calculate WQF Where, Use the WQV/WQFs calculated for potential BMPs to continue T-1, Part 1 Brown and Caldwell 32

Section 5 –Checklist T-1, Part 1 Continue through Checklist T-1, Part 1 to consider Treatment BMPs to meet TMDL requirements. Brown and Caldwell 33

Section 5 –Checklist T-1, Part 1 Brown and Caldwell 34

Section 5 – T-1, Part 1 Brown and Caldwell 35

Section 5 – T-1, Part 1 Brown and Caldwell 36

Section 5 – T-1, Part 1 Brown and Caldwell 37

Section 5 – T-1, Part 1 Brown and Caldwell 38

Section 5 – T-1, Part 1 Brown and Caldwell 39

Section 5 – T-1, Part 1 Brown and Caldwell 40

Section 5 – T-1, Part 1 Brown and Caldwell 41

Section 5 – T-1, Part 1 Treatment Tracking Brown and Caldwell 42

Section 5 – Project Treatment Summary Use Table E-1 to summarize all impervious areas treated project BMPs. Document in Section 1 of the SWDR. Don’t forget to include DPP BMPs that infiltrate. Brown and Caldwell If PCTA Balance < 0 and additional treatment cannot be provided, document Alternative Compliance strategy in 43