INSTRUCTORS
Curtis Hinman
Senior Scientist
Key project experience: Research
specialist in the performance and
design of LID practices.
CHRIS WEBB, PE
LEED FELLOW
Associate Engineer
Key project experience:
permeable pavement,
bioretention, rainwater
harvesting
introduction
permeable pavement basics
common siting, design and construction
design and construction by pavement type
AGENDA
wrap-up
LOGISTICS
SCHEDULE
8‐hour training
Lunch on your own
60 minute site visit
OTHER LOGISTICS
• Restrooms
• Food
• Turn off cell phones
• Sign in and sign out
LEARNING OBJECTIVES
1. Gain an intermediate level knowledge
necessary for proper entry level design
and implementation of permeable
pavement systems in residential and
commercial settings (new and retrofit).
2. Learn skills necessary for basic site
assessment and locating permeable
pavement areas in residential and
commercial settings.
3. Learn practical skills necessary for
construction of basic permeable
pavement systems.
PROGRAM OVERVIEW
• 2012: Public and private
partners engage state
legislature to fund program
• June 2012: LID Training
Steering Committee convened
• 2012‐2013: Washington State
LID Training Plan developed:
www.wastormwatercenter.org/
lid‐background
• 2014: Training program built
from state LID Training Plan
PROGRAM OVERVIEW
• Implement first phase of
trainings (September 2014
through May 2015)
• 64 trainings offered in first
phase
• Three levels: Introductory,
Intermediate, and Advanced
• Train the Trainer program for
service providers and LID
topic experts
• Future funding unknown.
PROJECT LEAD
ADDITIONAL TRAINING SUPPORT
TEAM
CORE TEAM
Introduction to
LID for Eastern
Washington
INTRODUCTORY
INTERMEDIATE
ADVANCED
TRAIN THE TRAINERS
Service Providers
Introduction to
LID for Inspection &
Maintenance Staff
Introduction to
LID for Developers &
Contractors: Make
Money be Green
Intermediate LID
Design: Rainwater
Collection Systems &
Vegetated Roofs
Intermediate LID –
NPDES Phase I & II
Requirements
Intermediate
LID Design:
Permeable Pavement
Intermediate
LID Design:
Hydrologic Modelling
Advanced Topics in
LID Design:
Bioretention
Advanced Topics in
LID Design:
Permeable Pavement
Advanced Topics in
LID Design:
Hydrologic Modeling
Advanced Topics in
LID Design: Site
Assessment, Planning
& Layout
LID Topic Experts
Advanced Topics in
LID Design: Rainwater
Collection Systems &
Vegetated Roofs
Advanced Topics in
LID Design:
Bioretention Media
TRAINING SEQUENCE
Advanced Topics for
LID Operations:
Bioretention
Intermediate
LID Design:
Bioretention
Advanced Topics for
LID Operations:
Permeable Pavement
Intermediate LID
Design: Site
Assessment, Planning
& Layout
Introduction to
LID for Eastern
Washington
INTRODUCTORY
INTERMEDIATE
ADVANCED
TRAIN THE TRAINERS
Service Providers
Introduction to
LID for Inspection &
Maintenance Staff
Introduction to
LID for Developers &
Contractors: Make
Money be Green
Intermediate LID
Design: Rainwater
Collection Systems &
Vegetated Roofs
Intermediate LID –
NPDES Phase I & II
Requirements
Intermediate
LID Design:
Permeable Pavement
Intermediate
LID Design:
Hydrologic Modelling
Advanced Topics in
LID Design:
Bioretention
Advanced Topics in
LID Design:
Permeable Pavement
Advanced Topics in
LID Design:
Hydrologic Modeling
Advanced Topics in
LID Design: Site
Assessment, Planning
& Layout
LID Topic Experts
Advanced Topics in
LID Design: Rainwater
Collection Systems &
Vegetated Roofs
Advanced Topics in
LID Design:
Bioretention Media
TRAINING SEQUENCE
Advanced Topics for
LID Operations:
Bioretention
Intermediate
LID Design:
Bioretention
Advanced Topics for
LID Operations:
Permeable Pavement
Intermediate LID
Design: Site
Assessment, Planning
& Layout
introduction
AGENDA
• New Permit Requirements for
local governments on 3 levels:
• Building site and subdivision
• Municipal (codes)
• Watershed
• New & Redevelopment
• Site & subdivision ‐ S5.C.4.a.i. & ii.
(S5.C.5 in Phase I)
• Development Codes ‐ S5.C.4.f.
• Watershed Scale ‐ S5C.4.g.
LID REGULATORY STATUS
• Phase I Permittees
• Snohomish, King, Pierce, Clark
Counties
• Seattle, Tacoma
• WSDOT
• Phase II Permittees
• WWA: 80 cities, 5 counties, WSDOT
• EWA: 18 cities, 6 counties
• Secondary Permittees:
• Approximately 45 such as ports and
universities
LID REGULATORY STATUS
LID REGULATORY TIMELINE
Adopt new
site &
subdivision
stormwater
codes
Phase I:
June 30,
2015
Phase II:
December
31, 2016*
Review and
revise
development‐
related codes,
rules &
standards
Phase I:
June 30,
2015
Phase II:
December
31, 2016*
* Or GMA update deadline, whichever is later
LID REGULATORY STATUS: Minimum Requirements
#1 Preparation of
Stormwater Site
Plans
#2 Construction
Stormwater
Pollution
Prevention
#3 Source Control
of Pollution
#4 Preservation of
Natural Drainage
Systems and
Outfalls
#5 On‐site
Stormwater
Management
#6 Runoff
Treatment
#7 Flow Control
#8 Wetlands
Protection
#9 Operation and
Maintenance
LID REGULATORY STATUS: New Development Thresholds
• > 5,000 sq. ft. new and replaced hard surface area, or
• > 3/4 acre vegetation to lawn/landscape, or
• > 2.5 acres native vegetation to pasture
Min. Requirements #1 ‐ # 9:
• > 2,000 sq. ft. new and replaced hard surface area, or
• > 7,000 sq. ft. land disturbance
Min. Requirements #1 ‐ #5:
• All projects (No submittal for projects <2,000 sf new and
replaced hard surface or <7,000 sf land disturbance)
Min. Requirement #2 ‐Erosion control
LID REGULATORY STATUS: Definitions
Pollution‐Generating Hard Surface (PGHS)
• Pollutant‐generating hard surfaces subject to vehicular use,
industrial activities, material storage
• Pollution‐generating impervious surfaces (PGIS) and pollution‐
generating permeable pavement
PG Permeable
Pavement
PGIS
LID REGULATORY STATUS: Infeasibility Criteria
• Erosion, slope failure, or flooding
• Where adjacent impervious pavements compromised
• Threaten below grade basements
• Fill soils that can be unstable when saturated
• Excessively steep slopes meeting certain conditions
• Threaten pre‐existing underground utilities tanks, road sub‐grades
• Inadequate strength for heavy loads at industrial facilities
Requires site geotech evaluation & written recommendation
LID REGULATORY STATUS: Minimum Requirements
• Area designated as erosion or landslide hazard
• Within 50 feet from top of slopes greater than 20%
• Known soil or ground water contamination
• Fill soils that can be unstable when saturated
• At multi‐level parking garages and over culverts & bridges
• Where saturated conditions within 1 foot of bottom of base course
Criteria not requiring justification, but possibly professional services
LID REGULATORY STATUS: Minimum Requirements
Criteria not requiring justification, but possibly professional services
• On arterial or collector (see state RCW’s)
• Native soils don’t meet soil suitability criteria
• Infiltration less than 0.30 in/hr
• Soils unsuitable for loads when saturated
• Replacing impervious unless NON‐PGIS over soil > 4in/hr
• In high use sites
• Areas with “industrial activity”
• Where concentrated spill risk is higher
• Routine heavy sand applications in frequent snow zones
WHAT IS LOW IMPACT
DEVELOPMENT
• A land use development strategy that
emphasizes protection and use of on‐
site natural features to manage
stormwater.
• Careful assessment of site soils and
strategic site planning to best use those
soils for stormwater management
• Integrates engineered and non‐
engineered, small‐scale stormwater
controls into the site design to closely
mimic pre‐development hydrologic
processes.
WHAT IS LOW IMPACT
DEVELOPMENT
• Used at the parcel and subdivision
scale. Site scale necessary but not
sufficient. Regional land use planning
critical for effective stormwater
management.
• Primary goal: no measurable impacts
to receiving waters by maintaining or
approximating pre‐development
surface flow volumes and durations.
WHAT IS LOW IMPACT
DEVELOPMENT
Objectives
• Protect and restore native soils/vegetation.
• Reduce development envelope.
• Reduce impervious surfaces and eliminate
effective impervious area.
• Manage stormwater as close to its origin as
possible.
• Integrate stormwater controls into the
design—create a multifunctional landscape.
• Reduce concentrated surface flow, minimize
stormwater contact with impervious
surfaces, and increase stormwater contact
with soils and vegetation.
WHAT IS LOW IMPACT DEVELOPMENT
Rainwater collection
Low impact foundations
Vegetated roofs
Bioretention
Permeable pavement
INTERMEDIATE LID DESIGN:
PERMEABLE PAVEMENT
Statewide LID
3.3
Training Program
permeable pavement basics
AGENDA
• Wearing course
• Leveling/choker course
• Aggregate storage reservoir/base
• Geosynthetics
• Under‐ and elevated‐drains
• Native underlying soil
• Subsurface berms
PERMEABLE PAVEMENT COMPONENTS
PERMEABLE PAVEMENT BASICS
TYPES: Porous Asphalt
PERMEABLE PAVEMENT BASICS
• Flexible
• Similar to conventional asphalt, but fines < No. 30 sieve reduced
• Typically used for parking and light traffic loads; however, has been
used for medium and heavy applications
• ~16 % voids typical (2‐3 % for conventional)
• Industry engagement has been limited in this region, but increasing
porous asphalt wearing course
choker course (e.g. 1.5 in. to US sieve No. 8
crushed, washed stone)
coarse aggregate base (e.g. AASHTO No. 3)
subgrade (minimal compaction to retain
infiltration capability…consult geothech)
TYPES: Pervious Concrete
PERMEABLE PAVEMENT BASICS
• Rigid
• 1/4 to 5/8 round or crushed aggregate typical, Portland cement, and
admixtures (optional) to increase workability and strength
• 15 to 20 % voids typical
• Good experience and industry engagement in western WA.
TYPES: Permeable Pavers
PERMEABLE PAVEMENT BASICS
• Flexible
• Capable of high vehicle loads. Used for lower speeds
• High‐density concrete that interlock and transfer vertical loads to
surrounding pavers
• 12 % voids typical
• Good experience and industry engagement in western WA.
TYPES: Plastic Grids
PERMEABLE PAVEMENT BASICS
• Flexible
• Highest percent voids
• Plastic grid filled with gravel or soil and planted with grass
• Capable of high vehicle loads
• Used for lower speeds/infrequent use (grass)
• Consider Geogrid for additional strength
• Good experience and industry engagement in western WA
PERMEABLE PAVEMENT BASICS
HOW THE FACILITY WORKS
2012 LID Technical Guidance Manual for Puget Sound
• Storage
• Infiltration
PERMEABLE PAVEMENT BASICS
HOW THE FACILITY WORKS
• Inlets
• Outlets
• Slopes
APPLICATIONS
PERMEABLE PAVEMENT BASICS
• Low‐volume residential
streets
• Parking
• Public walkways
• Parks
• Plazas and patios
• Bike lanes
• Greenhouse floors
• Sports courts
• Noise barriers/walls
Photos: Kathy Gwilym, SVR
Private parking lot, Seattle
Bellingham bicycle lane
Seattle’s Ernst Park
Break
common siting, design and construction
2 design
SITING, DESIGN & CONSTRUCTION
1Siting
3 construction
OVERVIEW
SITING AND SELECTION OF MATERIALS
For a successful project, the team needs
to carefully assess site, select appropriate
materials and plan construction:
• Site selection
• Material specifications
• Design
• Planning & coordination
• Installation
• Construction
• Protection of work
• Operations/use as intended
• Maintenance (covered in Module 5.4)
Photo: Kathy Gwilym, SVR
USERS
SITING AND SELECTION OF MATERIALS
• Who will be the users of the
facility?
• Pedestrian
• Bicycle
• Parking Lot
• Low‐volume residential
streets
• Aesthetics
• One size does not fit all. Use
appropriately.
Photos: Kathy Gwilym, SVR
PUBLIC VS PRIVATE FACILITIES
SITING AND SELECTION OF MATERIALS
• Design life
• Maintenance effort
• Material selection
Photos: Kathy Gwilym,
SVR
N. Gay Ave, Portland. Porous Asphalt Concrete
(2005 ‐ 8” porous
AC over 6” sub‐
base)
Grand Central Parking Lot, Vancouver, WA
32nd Ave. SW, Seattle. Pervious Concrete
(2005 – 8” PPCC
over 18” sub‐base)
INFILTRATION ASSESSMENTS
SITING AND SELECTION OF MATERIALS
Site characterization criteria
(Volume 3, Section 3.3.5)
Geology/soil characteristics
Groundwater conditions
Infiltration potential
Mounding analysis
INFILTRATION TESTS
SITING AND SELECTION OF MATERIALS
Exploration
• Continuous sampling
• At least 10 ft below base
of facility
• Grain size analyses
Exploration Approaches
• Exploration pits
• Deep exploration
borings/wells
• Vactor explorations (cost
effective in developed
areas)
INFILTRATION ASSESSMENT
SITING AND SELECTION OF MATERIALS
Readily available resources
USGS and DNR Geologic Maps
Publicly available logs at DNR
Washington State Geologic
Information Portal
Well logs at Ecology
Streams, lakes, and wetlands
generally indicate groundwater
elevations
INFILTRATION ASSESSMENT
SITING AND SELECTION OF MATERIALS
Groundwater Separation
At least one foot between base of permeable pavement
section and seasonal high groundwater table
If site assessment shows at least 5 feet of separation,
groundwater monitoring not required
Separation from both groundwater and hydraulic restriction
(perching) layer
Ideally, groundwater monitoring occurs between Dec. 21 ‐
Mar 21 during a winter of normal to high precipitation
Professional judgment may be sufficient
INFILTRATION TESTS
SITING AND SELECTION OF MATERIALS
Design infiltration rate (3.3.3)
Special Case Only
Grain Size Distribution
Outdated
Small‐scale falling head test (EPA)
Double Ring Infiltrometer
Preferred
Large‐diameter single ring
Pilot‐scale PIT (large‐ and small‐scale)
US STANDARD SIEVE NOS.
100
0.01
0.1
100
Grain Size, mm
Percent Finer
#200 sieve
silt/clay
INFILTRATION TESTS
SITING AND SELECTION OF MATERIALS
Ecology 2012, Sieve Analysis (USDA/ASTM)
• Recessional Outwash or Holocene only
• Need to assess if deeper layers will limit infiltration (equation 2
in 3.3.6 not recommended)
INFILTRATION TESTS
SITING AND SELECTION OF MATERIALS
Old school infiltration testing (not
recommended)
Falling head test (EPA)
Scale too small for many
applications
Double Ring Infiltrometer
Scale too small for many
applications, time consuming
and expensive for scale
INFILTRATION TESTS
SITING AND SELECTION OF MATERIALS
Small‐scale Pilot Infiltration Test (PIT)
Difference from Large‐Scale: Pit bottom area 12‐32 sf
INFILTRATION TESTS
SITING AND SELECTION OF MATERIALS
Large‐scale Pilot Infiltration Test (PIT)
INFILTRATION TESTS
SITING AND SELECTION OF MATERIALS
Modified Pilot Infiltration Test (PIT)
INFILTRATION TESTS
SITING AND SELECTION OF MATERIALS
Modified Pilot Infiltration Test (PIT) for finished sub‐grade
INFILTRATION ASSESSMENT
SITING AND SELECTION OF MATERIALS
Correction factor for permeable pavement design infiltration rates
Site variability and # test locations
• CFv=0.33‐1.0
Quality of pavement base material
• CFm=0.9‐1.0
Kdesign = Kmeasured * CFv*CFm
• Total correction ranges from 0.3 to 1.0
• Personal recommendation: use correction factor of 0.5
INFILTRATION ASSESSMENT
SITING AND SELECTION OF MATERIALS
Soil suitability criteria for treatment of runoff from pollution‐
generating hard surfaces (SSC 6)
Cation exchange capacity > 5 meq/100 grams dry soil
Organic content > 1%
Measured K < 12…