T-1 Infiltration Tools, v3.01

Presented to Caltrans and RWQCB StaffMay 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

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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

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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

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Background

http://www.waterboards.ca.gov/board_decisions/adopted_orders/resolutions/2008/rs2008_0030.pdf

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

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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

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Background

T-1 Checklist Process

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> 90 % strip/swales infiltration

no

no> 90%

treatment train infiltration

yes

Identify special-cases Add special BMPs

Add strips/swales

Add basinyes

Potential BMPs

Add Tier 1 BMPs

Estimate infiltrationRanking

Algorithm

 

Select pollutant

 

Two-tiered

list

no

 

Need Infiltration

Prioritizing Soil-based BMPs

Prioritizing soil-based BM

Ps

MEP BMP Selection

T-1 Selection: Performance-Based Ranking Across Caltrans Studies

Performance-Based Ranking of Treatment BMPs. CTSW-RT-10-239.01. February 26, 2010 8

0%

20%

40%

60%

80%

100%

0% 20% 40% 60% 80% 100%

% L

oad

Redu

ction

% Infiltration

Dissolved Zn

EDB

EDBL

Delaware

Austin

Austin Earthen

MCTT

Wet Basin

Swales

Retrofit As/Ad > 0.2

Retrofit As/Ad < 0.1

RVTS As/Ad > 0.2

RVTS 0.1≤As/Ad≤0.2

RVTS As/Ad < 0.1

Prioritizing Soil-based BMPs

Performance-Based Ranking Across Caltrans Studies

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Prioritizing Soil-based BMPs

Performance-Based Ranking of Treatment BMPs. CTSW-RT-10-239.01. 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

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No Surface Storage:Strips and Swales Infiltration Tool

(SSIT)

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Native Soil

Amended Soil

Native Soil

Conceptual Model

With Surface Storage:Basin Infiltration Tool (BIT)

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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

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Strip/swale and Detention

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Example

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Native Soil, Rate-Based Estimate

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Amendment Input

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Example

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Example

Adjust Soil Amendment

Use 9 inches instead of 4 to meet surface loading design requirements

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Example

SSIT Results Page

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Substantial benefits from amendment

Example

Adding a Downstream Basin

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Example

Basin Size Reduced Based on Maximum Upstream Losses

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Example

Basin Inputs Enter available area (100 ft x 50 ft)

Verify soil infiltration rate

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Example

BIT Results

56% total treatment train infiltration!

42% upstream infiltration + 58% basin treatment = 100% treatment!

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Example

Consistency with Water Board Standards and Goals

Consistent with State Water Board resolution on sustainability (Resolution No. 2008-0030)

Caltrans MS4 NPDES permit

Based on the “Soil Quality” credit in the CGP Water Balance Calculator

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Links Basin Sizer

http://svctenvims.dot.ca.gov/wqpt/basinsizer.aspx

WQPT

http://svctenvims.dot.ca.gov/wqpt/wqpt.aspx

Infiltration Tool

http://www.dot.ca.gov/hq/oppd/stormwtr/t1.htm

PPDG

http://www.dot.ca.gov/hq/oppd/stormwtr/ppdg.htm

SWRCB

http://www.waterboards.ca.gov/board_decisions/adopted_orders/resolutions/2008/rs2008_0030.pdf

Caltrans NPDES MS4 permit

http://www.swrcb.ca.gov/water_issues/programs/stormwater/caltrans.shtml26

Questions and Comments

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