T-1 Infiltration Tools, v3.01 Presented to Caltrans and RWQCB Staff May 10, 2013 Prepared by Caltrans and Office of Water Programs 1 Presented by Sean Penders (Caltrans) Eric Berntsen (SWRCB) Brian Currier (CSUS-OWP)

Overview  Background  Prioritizing soil-based BMPs in the Caltrans BMP Selection Process  Conceptual infiltration model review  Example: strip/swale and detention basin treatment train  Q&A 2

Background  Sustainable BMP goals from EPA, FHWA, SWRCB, RWQCB, & Caltrans  District Design needs  Performance-based ranking for target design constituents using statewide studies confirmed that infiltration was a key variable for load reduction 3

Consistency with Water Board Goals  Board resolution on sustainability  Caltrans MS4 NPDES permit  Based on the CGP Post Construction “Soil Quality” credit in the CGP Water Balance Calculator  Phase I & II MS4 4 Background

Caltrans Conditions and Applicability  Not for flood Analysis Analyzing small storm sizes Only for water quality BMP sizing  Tailored to Caltrans Compacted fill Motorist safety Useful statewide 5 Background

Caltrans Design Process: Project Planning and Design Guidance (PPDG)  1-acre net new impervious post- construction BMP threshold Hwy  5000 sf non-hwy  PPDG, T-1 Checklist: Treatment BMP Selection Performance-based ranking of BMPs Requires infiltration calculation 6 Background

T-1 Checklist Process 7 > 90 % strip/swales infiltration no > 90% treatment train infiltration yes Identify special-cases Add special BMPs Add strips/swales Add basin yes Potential BMPs Add Tier 1 BMPs Estimate infiltration Ranking Algorithm Select pollutant Two- tiered list no Need Infiltration Prioritizing Soil-based BMPs Prioritizing soil- based BMPs MEP BMP Selection

T-1 Selection: Performance-Based Ranking Across Caltrans Studies Performance-Based Ranking of Treatment BMPs. CTSW-RT February 26, Prioritizing Soil-based BMPs

Performance-Based Ranking Across Caltrans Studies 9 Prioritizing Soil-based BMPs Performance-Based Ranking of Treatment BMPs. CTSW-RT February 26, 2010

Conceptual Infiltration Model Review  No surface storage Strips Swales Natural and amended conditions Infiltration Trenches  With surface storage Detention Basins Infiltration Basins 10

No Surface Storage: Strips and Swales Infiltration Tool (SSIT) 11 Native Soil Amended Soil Native Soil Conceptual Model

With Surface Storage: Basin Infiltration Tool (BIT) 12 Conceptual Model

Example Project: New Highway  10 acres of new impervious surface  Limited area for a strip/swale and detention basin  Type B soil  ½ acre of pervious shoulder 13

Strip/swale and Detention 14 Example

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Native Soil, Rate-Based Estimate 16

Amendment Input 17 Example

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Adjust Soil Amendment  Use 9 inches instead of 4 to meet surface loading design requirements 19 Example

SSIT Results Page 20  Substantial benefits from amendment Example

Adding a Downstream Basin 21 Example

Basin Size Reduced Based on Maximum Upstream Losses 22 Example

Basin Inputs  Enter available area (100 ft x 50 ft)  Verify soil infiltration rate 23 Example

BIT Results  56% total treatment train infiltration!  42% upstream infiltration + 58% basin treatment = 100% treatment! 24 Example

Consistency with Water Board Standards and Goals  Consistent with State Water Board resolution on sustainability (Resolution No )  Caltrans MS4 NPDES permit  Based on the “Soil Quality” credit in the CGP Water Balance Calculator 25

Links  Basin Sizer  WQPT  Infiltration Tool  PPDG   SWRCB 08/rs2008_0030.pdf  Caltrans NPDES MS4 permit 26

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