Transcript Module 5: Bioretention Design Specs Details

Module 5: Bioretention Design Specs/Details
Melanie Mills, MLA
Central Coast LIDI
Specifications & Standard Details
100
Standard Details
BIORETENTION DESIGN NOTES
CONSTRUCTION NOTES
1. Overflow structure required for in-line systems without overflow bypass, Detail
140.
1. Scarify subgrade before installing bioretention
area aggregate and BSM.
2. Provide spot elevations on civil plans (TBSM, OE, GIE, IE). See Detail 120.
2. Compact each 6" lift of BSM with landscape
roller or by lightly wetting. If wetting, allow to
dry overnight before planting.
3. Edge condition will vary for new and retrofit projects. Curb details may be
modified for project by civil and geotechnical engineers.
4. If check dams are needed, see Concrete Check Dam Detail 131.
3. Never work within bioretention area limits
during rain or under wet conditions.
5. If Caltrans Class 2 Permeable is not available, substitute Class 3 Permeable with
an overlying 3" deep layer of 3/4" (No. 4) open-graded aggregate.
4. Keep all heavy machinery outside bioretention
area limits.
6. Bioretention Soil Media (BSM) specification per BASMAA Soils for Biotreatment
or Bioretention Facilities.
7. Plant Selection per LIDI Plant Guidance for Bioretention Areas Technical
Assistance Memo (TAM).
8. Mulch (optional) per LIDI Plant Guidance for Bioretention Areas TAM. Grading to
allow for specified soil and mulch depths while achieving finished elevations per
civil plans.
9. Locate energy dissipation cobble only as specified in inlet details - avoid
decorative use.
LOW IMPACT DEVELOPMENT STORMWATER MANAGEMENT STANDARD DETAILS
Bioretention Area
Planter
Municipality
Department Name
detail number
100
Design Specifications
Design Guidance Review
Expert Panel Review
DRAFT
Low Impact Development Initiative (LIDI)
Bioretention Area Design Specifications (without underdrain)
Text in blue represents changes based on group comments.
Highlighted text indicates items related to discussion topics.
Facility Design/Dimensions
Develop narrative for each section?
Bottom width – provide 2’ wide minimum flat bottom for facilities with side slopes
and longitudinal slope
Drawdown time – 72 hours.
–
Drawdown time is typically associated with mosquito vector control, and
varies by location. Confirm with local vector control agency to confirm
appropriate drawdown time for facility.
Energy dissipation – provide an aggregate or concrete splash pad at inlet per
LIDI details.
–
For aggregate: 6” depth, 3" – 6" rounded, washed cobble (CalTrans Class 2 or
3 Permeable)
–
For sloped sided facilities, extend a cobble flow path from pad 1’ into
bioretention area bottom.
Planter minimum widths are typically associated with their application.
Considerations influencing minimum widths include:
–
3’ minimum for planters in ROW with trees
–
2’ minimum for planters without trees
Planter depth – (from pedestrian surface to top of facility planting surface) is
related to planter width. Planters can be deeper as they get wider, and need to
be shallower as they narrow. This is a perception and safety issue.
Recommended ratios are:
–
Need further input. Will provide a table with width/depth or bulleted
guidelines.
Ponding depth - Min. 6", max. 12"
Design Specifications
• Facility Design and Dimensions
– width, depth, slope, ponding
• Hard Infrastructure
– inlets, check dams, overflow structures
• Facility Media
– soil, aggregate base, mulch
• Landscape
– plant selection, irrigation
Standard Details
• Facility Type
– planter
– sloped sided
• Elements related to facility
–
–
–
–
walls
curb inlets
overflows
check dams
Standard
Details
BIORETENTION DESIGN NOTES
CONSTRUCTION NOTES
1. Overflow structure required for in-line systems without overflow bypass, Detail
140.
1. Scarify subgrade before installing bioretention
area aggregate and BSM.
2. Provide spot elevations on civil plans (TBSM, OE, GIE, IE). See Detail 120.
2. Compact each 6" lift of BSM with landscape
roller or by lightly wetting. If wetting, allow to
dry overnight before planting.
3. Edge condition will vary for new and retrofit projects. Curb details may be
modified for project by civil and geotechnical engineers.
4. If check dams are needed, see Concrete Check Dam Detail 131.
3. Never work within bioretention area limits
during rain or under wet conditions.
5. If Caltrans Class 2 Permeable is not available, substitute Class 3 Permeable with
an overlying 3" deep layer of 3/4" (No. 4) open-graded aggregate.
4. Keep all heavy machinery outside bioretention
area limits.
6. Bioretention Soil Media (BSM) specification per BASMAA Soils for Biotreatment
or Bioretention Facilities.
7. Plant Selection per LIDI Plant Guidance for Bioretention Areas Technical
Assistance Memo (TAM).
8. Mulch (optional) per LIDI Plant Guidance for Bioretention Areas TAM. Grading to
allow for specified soil and mulch depths while achieving finished elevations per
civil plans.
9. Locate energy dissipation cobble only as specified in inlet details - avoid
decorative use.
LOW IMPACT DEVELOPMENT STORMWATER MANAGEMENT STANDARD DETAILS
Bioretention Area
Planter
Municipality
Department Name
detail number
100
Facility Design & Dimensions
• Bottom width – provide 2’ wide minimum flat bottom
for facilities with side slopes and longitudinal slope
• Allowable standing water – 72 hours.
– Allowable ponding time is typically associated with
mosquito vector control, and varies by location. Confirm
with local vector control agency to confirm appropriate
drawdown time for facility.
• Energy dissipation – provide an aggregate or
concrete splash pad at inlet per LIDI details.
– For aggregate: 6” depth, 3" – 6" rounded, washed cobble
– For sloped sided facilities, extend a cobble flow path from
pad 1’ into bioretention area bottom.
100
Bioretention w/ Flat Bottom (Planter)
BIORETENTION DESIGN NOTES
CONSTRUCTION NOTES
1. Overflow structure required for in-line systems without overflow bypass, Detail
140.
1. Scarify subgrade before installing bioretention
area aggregate and BSM.
2. Provide spot elevations on civil plans (TBSM, OE, GIE, IE). See Detail 120.
2. Compact each 6" lift of BSM with landscape
roller or by lightly wetting. If wetting, allow to
Bioretention w/ Sloped Sides
(rain garden, linear swale)
BIORETENTION DESIGN NOTES
1. Overflow structure required for in-line systems without overflow bypass, Detail 140.
CONSTRUCTION NOTES
Side Slope Grades
• 3:1 max
– needs shoulder
• 4:1 recommended
Bioretention w/ Sloped Sides
BIORETENTION DESIGN NOTES
1. Overflow structure required for in-line systems without overflow bypass, Detail 140.
CONSTRUCTION NOTES
Facility Elevations
• Overflow elevation
• Curb gutter inlet
elevation
• Top of curb
• Adjacent surface
photo: bluegreenbldg.org
• Finished grade in
facility
Bioretention w/
Underdrain
Planter
• Class 2
permeable
BIORETENTION DESIGN NOTES
CONSTRUCTION NOTES
1. Overflow structure required for in-line systems without overflow bypass, Detail 140.
1. Scarify subgrade before installing bioretention
area aggregate and BSM.
2. Provide spot elevations on civil plans (TBSM, OE, GIE, IE). See Detail 120.
2. Install underdrain with holes facing down.
Underdrain discharge elevation shall be near
top of aggregate layer. Underdrain slope may
be flat.
• No filter fabric
3. Edge condition will vary for new and retrofit projects. Curb details may be modified
for project by civil and geotechnical engineers.
• No filter layer
5. If check dams are needed, see Concrete Check Dam Detail 131.
3. Compact each 6" lift of BSM with landscape
roller or by lightly wetting. If wetting, let dry
overnight before planting.
6. If Caltrans Class 2 Permeable is not available, substitute Class 3 Permeable with
an overlying 3" deep layer of 3/4" (No. 4) open-graded aggregate.
4. Never work within bioretention area limits
during rain or under wet conditions.
7. Bioretention Soil Media (BSM) specification per BASMAA Soils for Biotreatment or
Bioretention Facilities.
5. Keep all heavy machinery outside bioretention
area limits.
• Underdrain
– PVC SDR 35
– holes downward
– cleanout
4. Provide capped, threaded PVC cleanout for underdrain, 4" min. dia. with sweep
bend.
8. Plant Selection per LIDI Plant Guidance for Bioretention Areas Technical
Assistance Memo (TAM).
9. Mulch (optional) per LIDI Plant Guidance for Bioretention Areas TAM. When used,
excavate to allow for specified soil and mulch depths and achieve finished
elevations as shown on plans.
10. Locate energy dissipation cobble only as specified in inlet details - avoid
decorative use.
LOW IMPACT DEVELOPMENT STORMWATER MANAGEMENT STANDARD DETAILS
Bioretention Area
Planter w/ Underdrain
Municipality
Department Name
DRAFT
detail number
102
Bioretention w/
Underdrain
Side Slope
• Underdrain design
considerations
BIORETENTION DESIGN NOTES
CONSTRUCTION NOTES
1. Overflow structure required for in-line systems without an overflow bypass, Detail 140.
1. Scarify subgrade before installing bioretention
area aggregate and BSM.
2. Provide spot elevations on civil plans (TBSM, OE, GIE, SIE). See inlet details 121, 122.
3. Max. longitudinal slope 6% with check dams. See details 130, 131.
– design w/ future
modification
– adjustable orifice
– open/close drain
4. Edge condition will vary for new and retrofit projects. Curb, wall, and sidewalk details may
be modified for project by civil and geotechnical engineers.
2. Install underdrain with holes facing down.
Underdrain discharge elevation shall be near
top of aggregate layer. Underdrain slope may
be flat.
5. If Caltrans Class 2 Permeable is not available, substitute Class 3 Permeable with an
overlying 3" deep layer of 3/4" (No. 4) open-graded aggregate.
3. Compact each 6" lift of BSM with landscape
roller or by lightly wetting. If wetting, let dry
overnight before planting.
6. Bioretention Soil Media (BSM) specification per BASMAA Soils for Biotreatment or
Bioretention Facilities.
4. Never work within bioretention area limits
during rain or under wet conditions.
7. Plant Selection per LIDI Plant Guidance for Bioretention Areas Technical Assistance
Memo.
5. Keep all heavy machinery outside bioretention
area limits.
8. Mulch (optional) type/depth per LIDI Plant Guidance for Bioretention Areas TAM. Grades
to allow for specified soil and mulch depths while achieving finished elevations per civil
plans.
9. Locate energy dissipation cobble only as specified in inlet details - avoid decorative use.
LOW IMPACT DEVELOPMENT STORMWATER MANAGEMENT STANDARD DETAILS
Bioretention w/ Side Slope and
Underdrain
Municipality
Department Name
DRAFT
detail number
103
Design Specifications
• Hard Infrastructure
Edge
Infrastructure
BIORETENTION DESIGN NOTES
CONSTRUCTION NOTES
1. Special design consideration or structural review may be required
for longer swale edge spans. Steel reinforcement or additional
concrete check dams may be needed for stability.
1. Finish all exposed concrete surfaces.
2. When sidewalk drains to planter, provide 6" wide notch openings
spaced to convey flows.
3. Concrete and expansion joints shall meet the requirements of the
municipality.
LOW IMPACT DEVELOPMENT STORMWATER MANAGEMENT STANDARD DETAILS
Deep Curb
Municipality
Department Name
detail number
111
Edge
Infrastructure
for Sloped
Sides
BIORETENTION DESIGN NOTES
CONSTRUCTION NOTES
1. Special design consideration or structural review may be required
for longer swale edge spans. Steel reinforcement or additional
concrete check dams may be needed for stability.
1. Finish all exposed concrete surfaces.
2. Concrete and expansion joints shall meet the requirements of the
municipality.
LOW IMPACT DEVELOPMENT STORMWATER MANAGEMENT STANDARD DETAILS
Thickened Edge Sidewalk
Municipality
Department Name
detail number
112
Curb Cut Inlets
for Planters
A
A
PERSPECTIVE VIEW
• Inlet design has
evolved
PLAN VIEW
BIORETENTION DESIGN NOTES
1. For use with stormwater facilities with flat
bottoms.
2. Provide spot elevations on plans (TBSM, OE,
GIE, IE). See Detail 100.
3. Refer to municipal standard drawings and
match gutter pan of adjacent curb and gutter.
CONSTRUCTION NOTES
SECTION A-A
1. After construction place sand bags at gutter
openings to keep storm flows from entering
facility until vegetation is established.
LOW IMPACT DEVELOPMENT STORMWATER MANAGEMENT STANDARD DETAILS
Curb Cut Inlet
for Planters
Municipality
Department Name
detail number
120
Concrete Splash Pad
Curb Cut Inlets
for Sloped
Sides
A
A
PERSPECTIVE VIEW
PLAN VIEW
BIORETENTION DESIGN NOTES
1. For use with stormwater facilities with side
slopes.
2. Provide spot elevations on plans (TBSM,
OE, GIE, IE). See Detail 100.
3. Refer to municipal standard drawings and
match gutter pan of adjacent curb and
gutter.
City of Portland, Environmental Services
CONSTRUCTION NOTES
SECTION A-A
1. After construction place sand bags at gutter
openings to keep storm flows from entering
facility until vegetation is established.
LOW IMPACT DEVELOPMENT STORMWATER MANAGEMENT STANDARD DETAILS
Municipality
Department Name
Curb Cut Inlet
for Side Slopes
(rain garden or swale)
detail number
121
Curb Cut Inlets
w/ Gravel
A
A
SECTION A-A
PLAN VIEW
BIORETENTION DESIGN NOTES
CONSTRUCTION NOTES
1. For use with stormwater facilities with
sloped sides or flat bottoms.
1. After construction place sand bags at gutter
openings to keep storm flows from entering
facility until vegetation is established.
2. Provide spot elevations on plans (TBSM,
OE, GIE, IE). See Details 100, 101.
3. Drop from inlet to aggregate pad will be
greater for planters.
4. Refer to municipal standard drawings and
match gutter pan of adjacent curb and
gutter.
LOW IMPACT DEVELOPMENT STORMWATER MANAGEMENT STANDARD DETAILS
Curb Cut Inlet
with Gravel Energy Dissipation
Municipality
Department Name
detail number
122
Energy Dissipation Cobble
• Use it for energy
dissipation
– at inlets
– sloped sides/extend
down to facility bottom
• Avoid decorative use
– difficult to maintain
– weeds can establish
in sediment/cobble
B
A
SW 12th Ave., Portland, Kevin Perry
Inlet w/ Grate
A
GRATE AND FRAME
B
PLAN VIEW
SECTION B-B
SECTION A-A
BIORETENTION DESIGN NOTES
1. For use with stormwater facilities with sloped sides or flat bottoms.
CONSTRUCTION NOTES
2. Provide spot elevations on plans (TBSM, OE, GIE, IPE). See Details 100, 101.
1. After construction place sand bags at gutter
openings to keep storm flows from entering
facility until vegetation is established.
3. Refer to municipal standard drawings and match gutter pan of adjacent curb and gutter.
4. If sloped sides, extend cobble from splash pad 1' into bottom of facility.
5. Base material for curb, gutter, and sidewalk per municipal standards.
LOW IMPACT DEVELOPMENT STORMWATER MANAGEMENT STANDARD DETAILS
Inlet with Grate
Municipality
Department Name
detail number
123
Gravel Check
Dam
A
A
• Mild longitudinal
slope
City of Portland, Environmental Services
SECTION A-A
BIORETENTION DESIGN NOTES
1. For use with stormwater facilities with sloped sides.
2. Best suited for facilities with > 2% longitudinal slope.
3. Provide elevations and stationing and/or
dimensioning for check dams.
CONSTRUCTION NOTES
1. Do not work during rain or under wet
conditions.
2. Keep all heavy machinery outside
bioretention area limits.
4. Space check dams per detail 132.
5. Ensure that check dam elevations do not cause
stormwater to overflow to sidewalk.
LOW IMPACT DEVELOPMENT STORMWATER MANAGEMENT STANDARD DETAILS
Gravel Check Dam
Municipality
Department Name
detail number
130
Pittsburgh Courthouse, photo: bluegreenbldg.org
Concrete
Check Dam
BIORETENTION DESIGN NOTES
CONSTRUCTION NOTES
1. For use with bioretention planters or sloped sided
swales/rain gardens.
1. Embed #3 rebar 3" into curb and planter
wall.
2. For check dams longer than 12' specify rebar overlap
length.
2. Do not work during rain or under wet
conditions.
3. Space check dams per detail 132.
3. Keep all heavy machinery outside
bioretention area limits.
4. Provide elevations and stationing and/or dimensioning
for check dams.
5. Ensure that check dam elevations do not cause
stormwater to overflow to sidewalk.
6. Show planter wall embedded in existing subgrade or
drainrock.
LOW IMPACT DEVELOPMENT STORMWATER MANAGEMENT STANDARD DETAILS
Concrete Check Dam
Municipality
Department Name
detail number
131
Concrete Check Dams
• Work w/ steep
longitudinal slope
photo: Tracy Tackett, SPU
• Series of bathtubs
Check Dams
• Other rigid materials
– steel
– clear plexiglass
– concrete w/ wood
Overflow
Structure w/
Beehive Grate
• Required for systems
without overflow bypass
• Overflow raised to allow
ponding
• Connects to
downstream structure or
stormdrain
BIORETENTION DESIGN NOTES
1. Provide grate overflow elevation on plans.
CONSTRUCTION NOTES
1.
2. To incorporate flexibility into design
overflow elevation or correct elevation of an
existing structure, install overflow collar, per
detail 141.
photo: SvR Design
LOW IMPACT DEVELOPMENT STORMWATER MANAGEMENT STANDARD DETAILS
Overflow Structure
w/ Beehive Grate
Municipality
Department Name
detail number
140
Overflow
Structure w/
Collar
BIORETENTION DESIGN NOTES
1. Provide collar overflow elevation (COE) on
plans.
CONSTRUCTION NOTES
1. Center collar on overflow grate.
photo: Kevin Perry
LOW IMPACT DEVELOPMENT STORMWATER MANAGEMENT STANDARD DETAILS
Overflow Structure
Collar
Municipality
Department Name
detail number
141
Location of Overflow
• Not adjacent to inlet
• Raised to allow for
design ponding
TOP
10
Design
Specifications
• Facility Media
• Landscape
Aggregate
• Optional use – per project requirements
• Cal Trans Class 2 Permeable
• No filter fabric
– potential for clogging
– inhibits infiltration
• Aggregate filter layer not needed for Class 2
• If Class 2 not available, substitute Class 3
– provide 3” depth filter layer for Class 3
Future Standard Details
• Layout details for bioretention
– street edge with parking
– curb extensions
– bioretention with pedestrian
crossing
– parking lot layouts
www.centralcoastlidi.org