INSTRUCTORS
Curtis Hinman
Senior Scientist
Key project experience: Research
specialist in the performance and
design of LID applications.
CHRIS WEBB, PE
LEED FELLOW
Associate Engineer
Key project experience:
permeable pavement,
bioretention, rainwater
harvesting
introduction
water quality treatment
bioretention siting and design
construction, inspection & verification
AGENDA
wrap-up
LEARNING OBJECTIVES
1. Gain an intermediate level knowledge
necessary for proper entry level design
of bioretention systems.
2. Learn skills necessary for basic site
assessment and locating bioretention
areas in residential and commercial
settings.
3. Learn practical skills necessary for
construction of basic bioretention
systems.
LOGISTICS
SCHEDULE
8‐hour training
Lunch on your own
45 minute site visit
OTHER LOGISTICS
• Restrooms
• Food
• Turn off cell phones
• Sign in and sign out
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
• 49 trainings in western and
eastern WA in 2014‐2015.
• 42 trainings in western and
eastern WA in 2015‐2016.
• 39 trainings offered in
western and eastern WA in
2017.
• Three levels: Introductory,
Intermediate, and Advanced.
• Statewide LID Certificate now
available.
PROJECT LEAD
ADDITIONAL TRAINING SUPPORT
OVERVIEW OF PROGRAM
CORE TEAM
Introduction to LID
for Inspection &
Maintenance Staff
INTRODUCTORY
INTERMEDIATE
ADVANCED
Intermediate LID
Design: Rainwater
Collection Systems &
Vegetated Roofs
Intermediate LID
Topics: NPDES Phase
I & II Requirements
Intermediate
LID Design:
Permeable Pavement
Intermediate
LID Design:
Hydrologic Modeling
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
Advanced Topics in
LID Design: Rainwater
Collection Systems &
Vegetated Roofs
Advanced Topics in LID
Design: Bioretention
Media and Compost
Amended Soils
OVERVIEW OF PROGRAM
Advanced Topics for
Long‐term LID
Operations:
Bioretention
Intermediate
LID Design:
Bioretention
Advanced Topics for
Long‐term LID
Operations:
Permeable Pavement
Intermediate LID
Design: Site
Assessment, Planning
& Layout
Introduction to LID
for Inspection &
Maintenance Staff
INTRODUCTORY
INTERMEDIATE
ADVANCED
Intermediate LID
Design: Rainwater
Collection Systems &
Vegetated Roofs
Intermediate LID
Topics: NPDES Phase
I & II Requirements
Intermediate
LID Design:
Permeable Pavement
Intermediate
LID Design:
Hydrologic Modeling
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
Advanced Topics in
LID Design: Rainwater
Collection Systems &
Vegetated Roofs
Advanced Topics in LID
Design: Bioretention
Media and Compost
Amended Soils
OVERVIEW OF PROGRAM
Advanced Topics for
Long‐term LID
Operations:
Bioretention
Intermediate
LID Design:
Bioretention
Advanced Topics for
Long‐term LID
Operations:
Permeable Pavement
Intermediate LID
Design: Site
Assessment, Planning
& Layout
introduction
water quality treatment
bioretention siting and design
construction, inspection & verification
wrap-up
• 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
• 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: 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 < 2,000/7,000)
Min. Requirement #2 ‐Erosion control
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
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.
WHAT IS LOW IMPACT
DEVELOPMENT
Objectives
• Manage stormwater as close to its
origin as possible.
• Integrate stormwater controls into
the design—create a
multifunctional landscape.
2012 LID Technical Guidance Manual for Puget Sound
COMPONENTS
INTRODUCTION
• Flow Entrance
• Pre‐Settling
• Ponding Area
• Bioretention Soil
• Mulch/Compost
• Vegetation
• Filter Fabric (?)
• Liner (optional)
• Underdrain (optional)
• Overflow
• Bioretention will often include surface and
subsurface infrastructure
• Bioretention = designed soil mix
• Bioretention meets requirements for MR 6 and
7 and required for MR 5 if MR 1‐9 required
• Rain gardens will usually not include under‐
drains and may use less restrictive soil mix
guidelines (e.g. existing soil augmented with
compost and sand). Meets MR 5 requirements.
BIORETENTION AND RAIN GARDENS
INTRODUCTION
• Primary functions
• Hydrologic benefits
• Water quality treatment
• Aesthetic amenity
BIORETENTION AND RAIN GARDENS
INTRODUCTION
• Bioretention is a “bio‐infiltration” BMP
• Ponding system
• Treatment via vertical flow through treatment soils while being
infiltrated
• Treatment goal = % volume infiltrated
• Bioretention is NOT a “bio‐filtration” BMP
• Flow‐through system (ex. biofiltration swale)
• Treatment via lateral flow through vegetation while being
conveyed
• Treatment goal = hydraulic residence time
BIORETENTION: Treatment Category
INTRODUCTION
• Shallow landscaped depressions
that are engineered (bioretention)
or non‐engineered (rain gardens) to
receive stormwater from small
contributing areas
• Small scale, dispersed facilities
• Types:
• Bioretention cells
• Bioretention swales
• Bioretention planters
• Bioretention planter boxes
• Online and offline
BIORETENTION: Definition and Types
INTRODUCTION
Cells
Shallow vegetated depressions
Gentle side slopes typical
Not designed as conveyance
system
Optional underdrains/control
structures
BIORETENTION: Types
INTRODUCTION
Bioretention swales
Same design features as cells
Interconnected series of cells
Provide conveyance (overflow
directed to downstream cell)
BIORETENTION: Types
INTRODUCTION
Bioretention planters
Vertical walled reservoir (typically
concrete)
Often used in ultra‐urban settings
Open bottom to allow infiltration to
native soil
Optional underdrains/control
structures
BIORETENTION: Types
INTRODUCTION
Bioretention planter boxes
Same design features as planters
Closed, impermeable bottom
Must include underdrain
Optional control structure
BIORETENTION: Types
INTRODUCTION
introduction to course and bioretention
water quality treatment
bioretention siting and design
construction, inspection & verification
wrap-up
All primary pathways for removing
pollutants from storm flows active
in bioretention
• Stormwater volume reduction
• Sedimentation
• Filtration
• Phytoremediation
• Thermal attenuation
• Adsorption
• Volatilization
Note that rain gardens can provide these
pollutant capture pathways, but not approved
for WQ treatment (MR6) in SWMMWW.
PRIMARY PATHWAYS
WATER QUALITY TREATMENT
VOLUME REDUCTION
Project
Completed
Infiltration
Sizing
Volume Reduction (%)
Siskiyou Green Street
Oct 2003
1.5 ‐2.0 in/hr
*(1/04 – 12/05) 83%
Glencoe Rain Garden
Oct 2003
1.8 ‐ 3.0 in/hr
(1/04 – 12/05) 94%
Greensboro NC
2001
0.2 – 0.6 in/hr
(2002) 78%
Sea Street
2001
variable
~2%
(2001 – present) 98%
110th Cascade
2003
(10/04 – 06) 74%
Meadow on the Hylebos
2006
0.0 – 0.8 in/hr
15%
(10/07 – 5/08) 99.99%
WATER QUALITY TREATMENT
MTCA
Pb: 250 mg/kg
Hg: 2 mg/kg
SOIL CONTAMINANT LEVELS
Project
e. Coli
(mpn/g)
(mg/kg)
Siskiyou Green Street
0‐6”
280
34.4
56.8
0.103
170
6‐12”
17.0
12.2
0.032
100
12‐18”
17.6
10.9
0.054
SW 12th & Montgomery
0‐6”
30.1
29.9
0.043
120
12‐18”
22.2
18.9
0.082
WATER QUALITY TREATMENT
* Percent reduction at 18 cm (upper) and 61 cm (lower) depths (lab) **Herrera from Barrett
Event mean concentrations
TKN (mg/L)
NO3 (mg/L)
TP (mg/L)
Hydrocarbons
(µg/L)
Davis et al 2006*
38% (u) 68% (l) ‐96% (u) 24% (l)
1% (u) 81% (l)
Greenbelt
57%
16%
65%
Largo
67%
15%
87%
Mass removal
97%
99%
Hunt etal 2006
Greensboro
‐4.9%
75%
‐240%
Chapel Hill
45%
13%
65%
Hsieh 2005
>97%
PNW Bioswales
(Herrera 2006)
18%
‐10%
Nat’l Bioswales**
‐88%
PERCENT REMOVAL OF NUTRIENTS
WATER QUALITY TREATMENT
* Percent reduction at 18 cm (upper) and 61 cm (lower) depths (lab)
** Percent mass removal (lab)
Event mean concentrations
TSS (mg/L)
Cu (µg/L)
Pb (µg/L)
Zn (µg/L)
Davis et al 2001*
89% (u) 92%
(l)
>98% (u) >98
(l)
>98% (u) >98
(l)
Davis et al 2003**
>99%
Greenbelt
97%
>95%
Largo
43%
70%
64%
Hunt etal 2006
Greensboro
‐180%
99%
81%
98%
Chapel Hill
Hsieh, Davis 2005
91%
PNW Bioswales (Herrera 2006)
64%
47%
National Bioswales (Herrera
from Barrett)
43%
53%
PERCENT REMOVAL OF TSS & METALS
WATER QUALITY TREATMENT
BIORETENTION FLUSHING
WATER QUALITY TREATMENT
City of Redmond study: Herrera
BIORETENTION FLUSHING
WATER QUALITY TREATMENT
City of Redmond study: Herrera
Analyte
Units
Median
Influent
Min
Median
Effluent
Max
Sand
Result
TSS
mg/L
4.9
5.3
22.5
Diss Zn
µg/L
20.0
Diss Cu
µg/L
1.7
8.6
15.9
14.0
PO4
mg/L
0.016
0.086
0.236
0.461
0.15
NO3‐NO2
mg/L
0.361
0.05
0.145
1.03
0.36
Fecal coliform CFU/100mL
229
22.5
BIORETENTION FLUSHING EXPERIMENTS
WATER QUALITY TREATMENT
WSU large‐scale lysimeter study (unpublished)
DISSOLVED COPPER CAPTURE
WATER QUALITY TREATMENT
WSU large‐scale
lysimeter study
(unpublished)
Filtration: bioretention provides excellent sediment filtration…
Does not appear to be concentration dependent.
TSS CAPTURE
WATER QUALITY TREATMENT
WSU large‐scale lysimeter study (unpublished)
SUMMARY
• Initial flushing of nitrogen, phosphorus and low
levels of copper at low influent concentrations.
• Excellent zinc at installation and very good copper
capture at typical influent concentrations after
initial flushing.
• Reasonable TN capture at typical influent
concentrations.
• Very good TSS capture
• TP and PO4 remain challenges
• Overall, very good performance in relation to
other treatment technologies
WATER QUALITY TREATMENT
Q&A
Break
introduction
water quality treatment
bioretention siting and design
construction, inspection & verification
wrap-up
BIORETENTION SITING, DESIGN & CONSTRUCTION
2 design
BIORETENTION SITING, DESIGN & CONSTRUCTION
3 construction
BIORETENTION SITING, DESIGN & CONSTRUCTION
INFILTRATIING SITING CONSIDERATIONS
Bioretention with Underdrain
Planter with Underdrain
All bioretention facilities infiltrate water through bioretention
soil for treatment
BIORETENTION SITING, DESIGN & CONSTRUCTION
INFILTRATIING SITING CONSIDERATIONS
Infiltration siting considerations apply to facilities that ALSO:
infiltrate water into underlying native soils
• Insufficient vertical separation from
bottom of facility to hydraulic
restriction layer (water table,
bedrock, compacted soil layer)
• 1 foot clearance if the contributing area is
less than:
• 5,000 square feet of pollution‐generating
impervious surface
• 10,000 square feet of impervious area
• ¾ acres of lawn and landscaped area
• 3 foot clearance for larger contributing
areas
Restrictions (sources: SWMMWW Volume III,
Section 3.4)
BIORETENTION SITING, DESIGN & CONSTRUCTION
INFEASIBILITY CRITERIA: Infiltration
Restrictions
Associated Earth Sciences
Infiltration not required in:
• Areas that geotechnical evaluation deems imprudent
• Erosion, slope failure, flooding
• Erosion/landslide hazard areas
• Groundwater protection area
Restrictions (sources: SWMMWW
Infeasibility Criteria)
BIORETENTION SITING, DESIGN & CONSTRUCTION
INFEASIBILITY CRITERIA: Infiltration
Restrictions
Bigstory.ap.org
Feature
Setback
Drinking water well
100 feet
Spring used for drinking water
100 feet
Known deep soil contamination
100 feet
Closed or active landfill
100 feet
Small on‐site septic drainfield
10 feet
INFEASIBILITY CRITERIA: Infiltration Setbacks
Setbacks (source: SWMMWW Infeasibility Criteria)
BIORETENTION SITING, DESIGN & CONSTRUCTION
INFEASIBILITY CRITERIA: Infiltration Setbacks
Feature
Setback
Native Growth Protection
Easement
≥ 20 feet
Top of slopes >20% and over 10
feet of relief
≥ 50 feet
Underground storage tanks
10‐100 feet
Wellheads, basements,
foundations, utilities, slopes,
contaminated areas, and property
lines
Consult local
jurisdiction
guidelines
Setbacks (source: SWMMWW Infeasibility Criteria)
BIORETENTION SITING, DESIGN & CONSTRUCTION
• Understand fate of infiltrated water
• Intent is to infiltrate to native underlying soil
• Arterial ROW with dense underground infrastructure
(preferenƟal pathway → uƟlity trenches)
• Potential for excessive shallow interflow emerging at
slopes, development cuts, or in basements
• Use engineering controls
• Ex. trench water stops to prevent re‐infiltration to pipes
• Ex. liners to protect adjacent infrastructure
BIORETENTION SITING, DESIGN & CONSTRUCTION
SITING CONSIDERATIONS
• Native soil and vegetation
preservation
• Site Slopes
• Cross & Longitudinal Slopes
• Positive Drainage from drainage
area to BR to overflow
• Setbacks (e.g., utilities &…