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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