Soils
• Well-designed systems
capture sediment near
the entrances
• Sediment loads vary
by facility
• Regular visual checks
are the key
City of Portland Environmental Services
Soils
City of Portland Environmental Services
Soils
• Visit the facility at least twice a winter after big
storms
• Check sediment accumulations as you’re doing
routine maintenance
• Monitor draw-down rates – how long does it take
for standing water to disappear after the end of a
storm ?
• Make notes for future reference
Plants and sediment can reduce depth
EMSWCD
When do You Need to Remove Sediment ?
• If 2-3 inches of
sediment
accumulates
• When drawdown rates
exceed about 36
hours
• Don’t let things
get out of
control (photo)
City of Portland Environmental Services
When do You Need to Remove Sediment ?
City of Portland Environmental Services
Soils: Removing Sediment
• Schedule all maintenance for dry weather unless
there’s an emergency
• Rakes and shovels (hand removal) are best to avoid
damaging the plants
• Be sure to loosen the underlying native soil
• If large equipment is needed avoid compacting the
soils
• If slow infiltration rates persist, remove the top
couple of inches of soil
When to Be Concerned….
Morguefile
• Petroleum sheen
• Foul smell
Nccwep.org
Soils: Sediment and Soil Disposal
• Check for evidence of contamination: color and smell
• In most cases stormwater sediment is not hazardous and
can be disposed of as solid waste.
• Places to be concerned: recycling facilities, fueling stations,
industrial storage areas, etc.
• If you have questions, contact DEQ at 503-229-5263.
• Or consult DEQ’s guidelines for hazardous waste at
http://www.deq.state.or.us/lq/hw/hwmanagement.htm
Mulch
• Suppresses weeds and
maintains soil moisture
• Is a surface for deposition
of sediment (for easy
sediment removal)
• Apply 2-3 inches after
planting, after removing
sediment, and any time
there are bare spots
• Common mulches:
medium hemlock,yarddebris compost. Gravel
“mulch” is sometimes used
at entrances
Green Girl Land Development Solutions
Mulch
• Mulch sometimes
floats in the first
storms just after
construction.
• Yard debris compost
is less prone to
floating, but it can
be a source of weeds
• Many LID systems
are densely planted
and need only spotmulching after the
first couple of years
Green Girl LDS
Do’s and Don’ts
Do
•
•
•
•
•
Visually monitor the facility on a regular basis
Remove sediment when it reaches 2-3 inches
Plan to take action if drawdown times exceed 36 hours
Mulch and plant bare spots for erosion control
Loosen the soil after removing sediment
Don’t
• Compact the soils by working in the facilities when the
soils are wet (wait until summer)
• Assume a facility is permanently clogged until steps have
been taken to remove sediment layers
• Handle soils that smell or look odd (contamination)
Structures
Prevent Erosion
• Rip rap vs. no erosion prevention
Green Girl LDS
Green Girl LDS
Structures
Remove Sediment & Debris
• Rip rap
Green Girl LDS
Structures
Remove Sediment & Debris
• Shallow forebay
Green Girl LDS
Structures
Remove Sediment & Debris
• Forebay with sump
Green Girl LDS
Structures
Remove Sediment & Debris
• Curb cuts
Green Girl LDS
Green Girl LDS
Structures
Remove Sediment & Debris
• Flat outlets vs. beehive outlets
Green Girl LDS
Green Girl LDS
Structures
Prevent Excessive Ponding
• Under drains
Green Girl LDS
Structures
Prevent Excessive Ponding & Flooding
• Overflows
Structures
Prevent Flooding
• Obstructions
Structures
Protect Structural Integrity
• Curb damage
Structures
Protect Structural Integrity
• Walls
Green Girl LDS
Structures
Protect Structural Integrity
Keystone Retaining Walls