Melanie Mills, MLA
Central Coast LIDI

100
Standard Details Design Specifications
BIORETENTION DESIGN NOTES
1. Overflow structure required for in-line systems without overflow bypass, Detail
140.
2. Provide spot elevations on civil plans (TBSM, OE, GIE, IE). See Detail 120.
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.
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.
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.
CONSTRUCTION NOTES
1. Scarify subgrade before installing bioretention area aggregate and BSM.
2. Compact each 6" lift of BSM with landscape roller or by lightly wetting. If wetting, allow to dry overnight before planting.
3. Never work within bioretention area limits during rain or under wet conditions.
4. Keep all heavy machinery outside bioretention area limits.
LOW IMPACT DEVELOPMENT STORMWATER MANAGEMENT STANDARD DETAILS detail number
Municipality
Department Name
Bioretention Area
Planter
100

DRAFT
Low Impa ct Development Initia tive (LIDI)
Bioretention Area Design Specifica tions (without underdra in)
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"
Slope/grades
– Side slope - 4:1 preferred
· Max. 3:1 allowed with 12" shoulder (2% slope) adjacent to pedestrian use or curb
– Longitudinal slope – Max. 6% longitudinal slope of bottom.
9/16/12 page 1/3

– width, depth, slope, ponding
– inlets, check dams, overflow structures
– soil, aggregate base, mulch
– plant selection, irrigation

– planter
– sloped sided
– walls
– curb inlets
– overflows
– check dams

100
BIORETENTION DESIGN NOTES
1. Overflow structure required for in-line systems without overflow bypass, Detail
140.
2. Provide spot elevations on civil plans (TBSM, OE, GIE, IE). See Detail 120.
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.
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.
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.
CONSTRUCTION NOTES
1. Scarify subgrade before installing bioretention area aggregate and BSM.
2. Compact each 6" lift of BSM with landscape roller or by lightly wetting. If wetting, allow to dry overnight before planting.
3. Never work within bioretention area limits during rain or under wet conditions.
4. Keep all heavy machinery outside bioretention area limits.
LOW IMPACT DEVELOPMENT STORMWATER MANAGEMENT STANDARD DETAILS detail number
Municipality
Department Name
Bioretention Area
Planter
100

• 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 DESIGN NOTES
1. Overflow structure required for in-line systems without overflow bypass, Detail
140.
2. Provide spot elevations on civil plans (TBSM, OE, GIE, IE). See Detail 120.
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.
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.
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.
CONSTRUCTION NOTES
1. Scarify subgrade before installing bioretention area aggregate and BSM.
2. Compact each 6" lift of BSM with landscape roller or by lightly wetting. If wetting, allow to dry overnight before planting.
3. Never work within bioretention area limits during rain or under wet conditions.
4. Keep all heavy machinery outside bioretention area limits.
LOW IMPACT DEVELOPMENT STORMWATER MANAGEMENT STANDARD DETAILS detail number
Municipality
Department Name

BIORETENTION DESIGN NOTES
1. Overflow structure required for in-line systems without overflow bypass, Detail 140.
2. Provide spot elevations on civil plans (TBSM, OE, GIE, SIE). See Details 121, 122.
3. Max. longitudinal slope 6% with check dams. See details 130, 131.
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.
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.
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.
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
CONSTRUCTION NOTES
1. Scarify subgrade before installing bioretention area aggregate and BSM.
2. Compact each 6" lift of BSM with landscape roller or by lightly wetting. If wetting, allow to dry overnight before planting.
3. Never work within bioretention area limits during rain or under wet conditions.
4. Keep all heavy machinery outside bioretention area limits.
detail number
Municipality
Department Name

– needs shoulder

BIORETENTION DESIGN NOTES
1. Overflow structure required for in-line systems without overflow bypass, Detail 140.
2. Provide spot elevations on civil plans (TBSM, OE, GIE, SIE). See Details 121, 122.
3. Max. longitudinal slope 6% with check dams. See details 130, 131.
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.
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.
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.
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
CONSTRUCTION NOTES
1. Scarify subgrade before installing bioretention area aggregate and BSM.
2. Compact each 6" lift of BSM with landscape roller or by lightly wetting. If wetting, allow to dry overnight before planting.
3. Never work within bioretention area limits during rain or under wet conditions.
4. Keep all heavy machinery outside bioretention area limits.
detail number
Municipality
Department Name

– PVC SDR 35
– holes downward
– cleanout
BIORETENTION DESIGN NOTES
1. Overflow structure required for in-line systems without overflow bypass, Detail 140.
2. Provide spot elevations on civil plans (TBSM, OE, GIE, IE). See Detail 120.
3. Edge condition will vary for new and retrofit projects. Curb details may be modified for project by civil and geotechnical engineers.
4. Provide capped, threaded PVC cleanout for underdrain, 4" min. dia. with sweep bend.
5. If check dams are needed, see Concrete Check Dam Detail 131.
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.
7. Bioretention Soil Media (BSM) specification per BASMAA Soils for Biotreatment or
Bioretention Facilities.
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
CONSTRUCTION NOTES
1. Scarify subgrade before installing bioretention area aggregate and BSM.
2. Install underdrain with holes facing down.
Underdrain discharge elevation shall be near top of aggregate layer. Underdrain slope may be flat.
3. Compact each 6" lift of BSM with landscape roller or by lightly wetting. If wetting, let dry overnight before planting.
4. Never work within bioretention area limits during rain or under wet conditions.
5. Keep all heavy machinery outside bioretention area limits.
detail number
Bioretention Area
Municipality
Department Name
Planter w/ Underdrain
102

– design w/ future modification
– adjustable orifice
– open/close drain
BIORETENTION DESIGN NOTES
1. Overflow structure required for in-line systems without an overflow bypass, Detail 140.
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.
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.
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.
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.
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
CONSTRUCTION NOTES
1. Scarify subgrade before installing bioretention area aggregate and BSM.
2. Install underdrain with holes facing down.
Underdrain discharge elevation shall be near top of aggregate layer. Underdrain slope may be flat.
3. Compact each 6" lift of BSM with landscape roller or by lightly wetting. If wetting, let dry overnight before planting.
4. Never work within bioretention area limits during rain or under wet conditions.
5. Keep all heavy machinery outside bioretention area limits.
detail number
Bioretention w/ Side Slope and
Municipality
Department Name
Underdrain
103

BIORETENTION DESIGN 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.
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.
CONSTRUCTION NOTES
1. Finish all exposed concrete surfaces.
LOW IMPACT DEVELOPMENT STORMWATER MANAGEMENT STANDARD DETAILS
Deep Curb
Municipality
Department Name detail number
111

BIORETENTION DESIGN 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.
2. Concrete and expansion joints shall meet the requirements of the municipality.
CONSTRUCTION NOTES
1. Finish all exposed concrete surfaces.
LOW IMPACT DEVELOPMENT STORMWATER MANAGEMENT STANDARD DETAILS
Thickened Edge Sidewalk
Municipality
Department Name detail number
112

A
PLAN VIEW
A
PERSPECTIVE VIEW
SECTION A-A
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
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

A A
PERSPECTIVE VIEW
PLAN VIEW
SECTION A-A
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.
CONSTRUCTION NOTES
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 Side Slopes
(rain garden or swale)
Municipality
Department Name detail number
121

122
A A
SECTION A-A
PLAN VIEW
BIORETENTION DESIGN NOTES
1. For use with stormwater facilities with sloped sides or flat bottoms.
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.
CONSTRUCTION NOTES
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 with Gravel Energy Dissipation
Municipality
Department Name detail number
122

– at inlets
– sloped sides/extend down to facility bottom
– difficult to maintain
– weeds can establish in sediment/cobble

A
B
B
PLAN VIEW
A
GRATE AND FRAME
SECTION B-B
BIORETENTION DESIGN NOTES
1. For use with stormwater facilities with sloped sides or flat bottoms.
2. Provide spot elevations on plans (TBSM, OE, GIE, IPE). See Details 100, 101.
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
SECTION A-A
CONSTRUCTION NOTES
1. After construction place sand bags at gutter openings to keep storm flows from entering facility until vegetation is established.
detail number
Inlet with Grate
123
Municipality
Department Name

• Mild longitudinal slope
A
A
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.
4. Space check dams per detail 132.
5. Ensure that check dam elevations do not cause stormwater to overflow to sidewalk.
CONSTRUCTION NOTES
1. Do not work during rain or under wet conditions.
2. Keep all heavy machinery outside bioretention area limits.
detail number LOW IMPACT DEVELOPMENT STORMWATER MANAGEMENT STANDARD DETAILS
Gravel Check Dam
Municipality
Department Name
130

BIORETENTION DESIGN NOTES
1. For use with bioretention planters or sloped sided swales/rain gardens.
2. For check dams longer than 12' specify rebar overlap length.
3. Space check dams per detail 132.
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.
CONSTRUCTION NOTES
1. Embed #3 rebar 3" into curb and planter wall.
2. Do not work during rain or under wet conditions.
3. Keep all heavy machinery outside bioretention area limits.
LOW IMPACT DEVELOPMENT STORMWATER MANAGEMENT STANDARD DETAILS detail number
Concrete Check Dam
131
Municipality
Department Name

• Work w/ steep longitudinal slope
• Series of bathtubs

– steel
– clear plexiglass
– concrete w/ wood

140
• 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.
2. To incorporate flexibility into design overflow elevation or correct elevation of an existing structure, install overflow collar, per detail 141.
CONSTRUCTION NOTES
1.
LOW IMPACT DEVELOPMENT STORMWATER MANAGEMENT STANDARD DETAILS
Overflow Structure w/ Beehive Grate
Municipality
Department Name detail number
140

BIORETENTION DESIGN NOTES
1. Provide collar overflow elevation (COE) on plans.
CONSTRUCTION NOTES
1. Center collar on overflow grate.
LOW IMPACT DEVELOPMENT STORMWATER MANAGEMENT STANDARD DETAILS
Overflow Structure
Collar
Municipality
Department Name detail number
141

TOP
10

– potential for clogging
– inhibits infiltration
– provide 3” depth filter layer for Class 3

– street edge with parking
– curb extensions
– bioretention with pedestrian crossing
– parking lot layouts