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 draw-down 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….

Nccwep.org

• Petroleum sheen• Foul smell

Morguefile

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,yard-debris 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 spot-mulching 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)

StructuresPrevent Erosion

• Rip rap vs. no erosion prevention

Green Girl LDSGreen 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 LDSGreen Girl LDS

Structures Remove Sediment & Debris

• Flat outlets vs. beehive outlets

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StructuresPrevent Excessive Ponding

• Under drains

Green Girl LDS

StructuresPrevent Excessive Ponding & Flooding

• Overflows

StructuresPrevent Flooding

• Obstructions

StructuresProtect Structural Integrity

• Curb damage

StructuresProtect Structural Integrity

• Walls

Green Girl LDS

StructuresProtect Structural Integrity

Keystone Retaining Walls