Can Pervious Concrete Work in Clay Soils?

11/2/2015
Can Pervious Concrete Work in
Clay Soils?
Protecting our water resources
© Copyright Estes Design Inc. 2013
for
The NPCPA San Diego
Conference
August 6, 2014
1

11/2/2015 © 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
2

WATER SUPPLY
CN = 55 ??
3

DEVELOPMENT
 CN = 92 ??
11/2/2015 © Copyright Estes Design Inc. 2013 4

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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”
Charlotte
NOAA 24 hr ARI
© Copyright Estes Design Inc. 2013 6

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
7

11/2/2015
Mecklenburg County Soils, NC
Approximately 64% of
Mecklenburg County is HSG B.
Dominant series Cecil 59%
95th percentile storm 1.8”

11/2/2015
Case Studies
Estes 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
Field infiltration rate helps
determine probable outcome
and initial design parameters
14

11/2/2015
1.10 in/hr 1.50 in/hr
Test Results
1.125”/hr
1.5”/hr

11/2/2015
7.4
acres
Reduced
Detention
Infiltration
Wetland
Bio-retention
Gardens
Bio-
retention
Garden
Bio-
Infiltration
Garden

11/2/2015
Reduced
Detention
Basin
Bio-
Retention
Gardens
Bio-
Retention
Garden
Bio-
Infiltration
Garden
Infiltration
Wetland

11/2/2015
LID Modeling
Jetton Street, Town of Davidson
Reduction of 10 yr peak storage
volume by 45%
18

11/2/2015
Rain Garden 2
Redundant Treatment
Sub-drains to Bio-
infiltration Garden 1

11/2/2015
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

11/2/2015
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

11/2/2015
Infiltration Wetland 5
Designed to
infiltrate the 2yr
storm

11/2/2015
Rain Garden
5 is being
monitored
utilizing water
level data
loggers

11/2/2015

11/2/2015
Monitoring
infiltration
rates with
water level
data loggers

11/2/2015
Infiltration Pond 5
February
2008 –
April 2009
Avg.
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
28

11/2/2015
Wilmore Walk LID
Site

11/2/2015
Wilmore Walk
 2.8 acre Multi-Family Urban
Redevelopment
 Over 90% of site runoff is treated

11/2/2015
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

11/2/2015
Plan
Bio-
Retention
Porous
Concrete
Bio-
Retention

Bio-Retention
Drain
System

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.

11/2/2015
Preliminary Soils Survey

Site-Specific
Infiltration Testing:
0.24 – 3.15 in/hr
Avg. 0.9 in/hr
Infiltration in Sandy Clay Loam
Field infiltration rate helps
determine probable outcome
and initial design parameters

11/2/2015
Design
Stone Infiltration
Reservoir sized for
the 2yr storm for
respective watershed
Watershed includes
surrounding rooflines
and any off site
contributions.
Seasonal ground
water fluctuations
important

Understanding soil
components and structure
required in predicting design
outcome
43

Sub-grade Prep
Clay soils are highly susceptible to inadvertent compaction

Stone
Reservoir

11/2/2015
Porous Concrete Installation
May 10, 2005

Porous
Concrete
Pavement

Finished
Porous
Concrete

11/2/2015
Monitoring
Infinities USA
Pressure Water
Level Data
Logger

11/2/2015
Monitoring Data
Aug-Sept 06
Average infiltration
rate of 0.09 in/hr
(0.23 cm/hr)
13” in 6 days
in semi-dry
conditions
Rawls, Brakensiek and Saxton 1982 : Clay Loam = K of 0.23 cm/hr

11/2/2015
Testing
New Standard Test Method
for Infiltration Rate of In Place
Pervious Concrete being
developed
by ASTM committee C09/49
4 years later rates of 1040 –
1430 in/hr

11/2/2015
Preliminary Monitoring Data
Saturated 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
53

UNCC 2 Year Monitoring Study
Wilmore 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.
54

Frankfort Kentucky
Building to be
demolished
A cooperative
effort
between the
City of
Frankfort and
KRMCA
55

Frankfort Kentucky

Frankfort Kentucky
 City of Frankfort
Storm Water
11/2/2015
Working with UK and KRMCA on
the Monitoring

CRMCA, Charlotte NC

CRMCA, Charlotte NC
Sandy clay loam
61

CRMCA, Charlotte NC
• Over 6
month period
72 rain
events.
• Rate of
infiltration
into sub-
grade 0.25”-
0.40 “ /hr
62

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
63

11/2/2015
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 Gray
Department of Geography & Earth Science
University of North Carolina Charlotte
66

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©
11/2/2015 67© Copyright Estes Design Inc. 2013

METHODS - STORMWATER MODELING
SCS 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 Conditions
Land-use Cover
70

“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
72

“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 Scale
Results 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

11/2/2015
END
 Thanks for listening!

Can Pervious Concrete Work in Clay Soils?

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