Can Pervious Concrete Work in Clay Soils?

05/03/2023

Protecting our water resources

forThe NPCPA San Diego

Conference

August 6, 2014

05/03/2023 © Copyright Estes Design Inc. 2013

• By the year 2030 it is estimated 47% of the world's population will face severe water shortages. Organization for Economic Co-operation and Development 2008

• 82% of the U.S. population reside in urban areas

• 50-75% of the U.S population rely on undeveloped forested watersheds to produce adequate water supplies. Forest Ecology and Management 258 (2009) 2269–2281

• The key hydrological function of forested watersheds is infiltration

• Impervious area in U.S. is projected to increase by over 36% by 2030 compared to 2000. JOURNAL OF HYDROLOGIC ENGINEERING © ASCE / APRIL 2009

• 6 of the 20 fastest developing metro areas in the U.S. are located in the Piedmont plateau. USDA, Natural Resource Inventory (NRI) database

• Dominant soils of the Piedmont are clay like. The Center for Environmental Informatics (CEI)

• The dominant soils series of the Piedmont is Cecil

INTRODUCTION - STATISTICS

WATER SUPPLY

CN = 55 ??

DEVELOPMENT

CN = 92 ??

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RUNOFF

5© Copyright Estes Design Inc. 2013

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Precipitation

1 yr – 2.79”

2 yr - 3.36”

10 yr – 4.89”

100 yr – 7.28”

CharlotteNOAA 24 hr ARI

Clay Soils

Clay soils are widely misunderstood Clay soils are not equal. There are

different types of clay Infiltration rates and shrink-swell vary

greatly. Piedmont soils are typically well drained and low to moderate shrink swell potential

The majority of Piedmont soils are ideal for infiltration

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Mecklenburg County Soils, NC

Approximately 64% of Mecklenburg County is HSG B. Dominant series Cecil 59%95th percentile storm 1.8”

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Case StudiesEstes Design Inc.

Davidson, NC - Built 2007 monitored 3.5 years

Charlotte, NC - Built 2005 monitored 3 years

Both projects infiltrated 95% of their annual rain events

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Jetton Street Condominiums

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Technology

Infiltration BMP’s - 2 1 bio-Infiltration &1 infiltration wetland Detains & infiltrates designed volume.

Bio-retention - 3 Captures & treats first 1” Replaces standard planting beds Can be used in areas of high clay

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Preliminary Soils Survey

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Site Specific Infiltration Testing

Field infiltration rate helps determine probable outcome and initial design parameters

05/03/20231.10 in/hr 1.50 in/hr

Test Results

1.125”/hr

1.5”/hr

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7.4 acres

Reduced Detention

Infiltration Wetland

Bio-retention Gardens

Bio-retention Garden

Bio-Infiltration Garden

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Reduced Detention Basin

Bio-Retention Gardens

Bio-Retention Garden

Bio-Infiltration Garden

Infiltration Wetland

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LID ModelingJetton Street, Town of Davidson

Reduction of 10 yr peak storage volume by 45%

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Rain Garden 2

Redundant Treatment

Sub-drains to Bio-infiltration Garden 1

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Bio-infiltration Garden 1

Filter Fabric impedes infiltration??

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Soil conveyor reduces compaction and eases access.

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Rain Garden 1 is being monitored utilizing water level data loggers

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Bio-Infiltration Garden 1

February 2008 – April 2009

Avg. 0.26”/hr (0.66 cm/hr)

6.35”/day(16.13 cm/hr)

Rawls, Brakensiek and Saxton 1982 : Sandy Clay Loam = K of 0.43 cm/hr

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Infiltration Wetland 5

Designed to infiltrate the 2yr storm

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Rain Garden 5 is being monitored utilizing water level data loggers

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Monitoring infiltration rates with water level data loggers

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Infiltration Pond 5

February 2008 – April 2009Avg. infiltration rate 0.14 “/hr(0.36 cm/hr)

3.2”/day(8.13 cm/day)

July Aug Sept OctJuneMayAprMarFeb Nov Dec Jan Feb Mar Apr

Rawls, Brakensiek and Saxton 1982 : Sandy Clay Loam = K of 0.43 cm/hr

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Wilmore Walk LID

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Wilmore Walk

2.8 acre Multi-Family Urban Redevelopment

Over 90% of site runoff is treated

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Wilmore Walk

BMPs were retrofitted into an existing site design, including 6,355 sf of pervious concrete with 3,800 cf available storage in a gravel base

All water quality permit requirements were satisfied using “Bio-Retention” BMPs

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Bio-Retention

Porous Concrete

Bio-Retention

Bio-Retention Drain System

Bio-Retention DrainSystem

Finished Bio-retention as landscape areas

Rapid infiltration rate to start. Eventually stabilized in 6 mos.

Bio-retention as landscape areas

Overflow weir

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Porous Concrete

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Wilmore Walk

Existing soils were investigated Green-Ampt equations for infiltration were

used for design of basin beneath the pervious concrete area

Bio-retention areas were located with grading plans adjusted accordingly.

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Preliminary Soils Survey

Site-Specific Infiltration Testing:0.24 – 3.15 in/hrAvg. 0.9 in/hr

Infiltration in Sandy Clay Loam

Field infiltration rate helps determine probable outcome and initial design parameters

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Design

Stone Infiltration Reservoir sized for the 2yr storm for respective watershedWatershed includes surrounding rooflines and any off site contributions.Seasonal ground water fluctuations important

Understanding soil components and structure required in predicting design outcome

Sub-grade Prep

Clay soils are highly susceptible to inadvertent compaction

Stone Reservoir

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Porous Concrete Installation May 10, 2005

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Porous Concrete Installation May 10, 2005

Porous ConcretePavement

Finished Porous Concrete

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Monitoring

Infinities USA Pressure Water Level Data Logger

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Monitoring DataAug-Sept 06

Average infiltration rate of 0.09 in/hr

(0.23 cm/hr)

13” in 6 daysin semi-dry conditions

Rawls, Brakensiek and Saxton 1982 : Sandy Clay Loam = K of 0.43 cm/hrRawls, Brakensiek and Saxton 1982 : Clay Loam = K of 0.23 cm/hr

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Testing

New Standard Test Method for Infiltration Rate of In PlacePervious Concrete being developed by ASTM committee C09/494 years later rates of 1040 – 1430 in/hr

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Preliminary Monitoring DataSaturated Soils Feb. 06

Preliminary data suggests average infiltration rate of 0.06 in/hr (0.15 cm/hr)(7.5” in 5.5 days) in saturated soil

Extended research completed by UNCC 2010.

Rawls, Brakensiek and Saxton 1982 : Silty Clay Loam = K of 0.15 cm/hr

UNCC 2 Year Monitoring StudyWilmore Walk

• Monitored for 2 years

• Monitored water levels and precipitation

• Average infiltration rate 0.105”/hr, 2.52” /dy, 12.6” /5dy

• Concluded that rain events greater than the 10 year 24 hr events were retained and infiltrated.

• 10 yr event is 4.8” = 12.6” gravel depth

• 100 yr event is 6.96” = 18.3” gravel depth.

Frankfort Kentucky

Building to be demolished

A cooperative effort between the City of Frankfort and KRMCA

Frankfort Kentucky

City of Frankfort Storm Water

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Working with UK and KRMCA on the Monitoring

CRMCA, Charlotte NC

Sandy clay loam

CRMCA, Charlotte NC

• Over 6 month period 72 rain events.

• Rate of

infiltration into sub-grade 0.25”- 0.40 “ /hr

CRMCA, Charlotte NC

CRMCA1 3720 in/hr First parking space (Older pour)

CRMCA2 5930 in/hr Second parking space (Older pour)

CRMCB1 way too slow for accuracy (impervious strip)

CRMCC1 2600 in/hr (First space new pour)

CRMCC2 3740 in/hr (second space new pour)

MINIMUM OF 2600 IN/HR

Pervious Concrete Pavement Testing

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END Thanks for listening!

Reversing History of Urban Hydrology

What Could Happen On A watershed Scale?

What if we modeled a watershed in the piedmont based on where an infiltration project is already established, monitored and validated over multiple years.

How could a real urban watershed be retrofitted?

How would this scenario effect watershed hydrology?

THE WATERSHED EFFECT

GIS modeling study of watershed retrofit

Capstone research project by Megan GrayDepartment of Geography & Earth Science

University of North Carolina Charlotte

PROJECT OBJECTIVES

Expanded Wilmore Walk research to explore watershed implication of PP on runoff using GIS and HydroCAD

How would PP affect runoff within a watershed?

METHODS - STORMWATER MODELINGSCS CN RUNOFF MODEL

Four CN Maps represent four scenarios: 1 – Present, real-time data. Impervious surfaces are

impervious 2 - Parking lots, driveways, and sidewalks are pervious 3 - Secondary roads are pervious 4 – Parking lots, driveways, sidewalks, and secondary

roads are pervious CN Values

Impervious = 98 Pervious = 61 (Used Equivalent CN of grass for B

Hydrogroup. Conservative)

Q = (P – 0.2S)2/(P + 0.8S)

Watershed Scale

Digital Elevation Model for seven precipitation maps (P maps) ranging from 1.25 to 100-year storm events

Watershed Scale

Hyperspatial image of Irwin Watershed was used to create land use maps

Existing ConditionsLand-use Cover

“S” Maps

Watershed Scale

Hyperspatial image & SSURGO soil survey map was used in combination to create the CN maps

Impervious = CN 98

Pervious = CN 61

Existing Conditions

“CN” Maps

Watershed Scale CN Map for

Scenario 2, Driveways Sidewalks & Parking lots are pervious

75% of impervious area

Watershed Scale

Scenario 2 – Parking Lots, Driveways and Sidewalks account for 75% of area where permeable pavement might be installed and are typically privately owned.

IECA Environmental Connection 2014

Runoff “Q” Maps

Watershed ScaleResults Scenario 2 - HydroCAD approximately 55%

reduction in peak flow for the 1.25 year 24 hr rain event

approximately 37% reduction in peak flow for the 100 year 24 hr event

approximately 30 minute delay in peak compared to scenario 1 & 3

infrastructure not modeled

WATERSHED EFFECT CN = [1000/[10 + 5P + 10Qa– 10(Qa2+ 1.25QaP)1/2] where:

P = rainfall (in) Qa = Runoff Volume

Pervious Concrete with 6” stone base Stone base retains 2.4” = CN 45.5 Include real time Ir 0.10” /hr (2.4”) = CN 29.4 Pervious concrete pavement 6” retains 1.2” = CN 25

A watershed that is 75% CN 30 and 25% 98 = CN 47

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END Thanks for listening!

Can Pervious Concrete Work in Clay Soils?

Engineering

Transcript of Can Pervious Concrete Work in Clay Soils?

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