Can Pervious Concrete Work in Clay Soils?
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Transcript of Can Pervious Concrete Work in Clay Soils?
05/03/2023
Can Pervious Concrete Work in Clay Soils?
Protecting our water resources
© Copyright Estes Design Inc. 2013
forThe NPCPA San Diego
Conference
August 6, 2014
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• 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
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WATER SUPPLY
CN = 55 ??
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DEVELOPMENT
CN = 92 ??
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RUNOFF
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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
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Clay Soils
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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
Site
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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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Soils
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Preliminary Soils Survey
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Site Specific Infiltration Testing
RG-1
RG-5
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Field infiltration rate helps determine probable outcome and initial design parameters
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05/03/20231.10 in/hr 1.50 in/hr
Test Results
1.125”/hr
1.5”/hr
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Jetton Street Condominiums
7.4 acres
Reduced Detention
Infiltration Wetland
Bio-retention Gardens
Bio-retention Garden
Bio-Infiltration Garden
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Jetton Street Condominiums
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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Bio-infiltration Garden 1
Soil conveyor reduces compaction and eases access.
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Bio-infiltration Garden 1
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
Infiltration Wetland 5
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Infiltration Wetland 5
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Infiltration Wetland 5
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
Site
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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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Plan
Bio-Retention
Porous Concrete
Bio-Retention
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Bio-Retention Drain System
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Bio-Retention DrainSystem
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Finished Bio-retention as landscape areas
Rapid infiltration rate to start. Eventually stabilized in 6 mos.
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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
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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
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Understanding soil components and structure required in predicting design outcome
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Sub-grade Prep
Clay soils are highly susceptible to inadvertent compaction
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Stone Reservoir
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Porous Concrete Installation May 10, 2005
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Porous Concrete Installation May 10, 2005
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Porous ConcretePavement
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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
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UNCC 2 Year Monitoring StudyWilmore Walk
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• 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.
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Frankfort Kentucky
Building to be demolished
A cooperative effort between the City of Frankfort and KRMCA
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Frankfort Kentucky
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Frankfort Kentucky
City of Frankfort Storm Water
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Working with UK and KRMCA on the Monitoring
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CRMCA, Charlotte NC
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CRMCA, Charlotte NC
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Sandy clay loam
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CRMCA, Charlotte NC
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• Over 6 month period 72 rain events.
• Rate of
infiltration into sub-grade 0.25”- 0.40 “ /hr
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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
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Pervious Concrete Pavement Testing
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END Thanks for listening!
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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?
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THE WATERSHED EFFECT
GIS modeling study of watershed retrofit
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Capstone research project by Megan GrayDepartment of Geography & Earth Science
University of North Carolina Charlotte
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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?
Applied SCS CN TR-55 runoff model to predict effect of PP on watershed by using;1. ArcGIS© 2. HydroCAD©
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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)
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Watershed Scale
Digital Elevation Model for seven precipitation maps (P maps) ranging from 1.25 to 100-year storm events
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Watershed Scale
Hyperspatial image of Irwin Watershed was used to create land use maps
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Existing ConditionsLand-use Cover
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“S” Maps
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Watershed Scale
Hyperspatial image & SSURGO soil survey map was used in combination to create the CN maps
Impervious = CN 98
Pervious = CN 61
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Existing Conditions
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“CN” Maps
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Watershed Scale CN Map for
Scenario 2, Driveways Sidewalks & Parking lots are pervious
75% of impervious area
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Watershed Scale
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Scenario 2 – Parking Lots, Driveways and Sidewalks account for 75% of area where permeable pavement might be installed and are typically privately owned.
-9.97
IECA Environmental Connection 2014
Runoff “Q” Maps
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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
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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!
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