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HomeMy WebLinkAboutFarmversion-Watermark-lowresolutionNOTE: Agencies or owners may have very specific requirements for any of the BMPs described in this guide. It is your responsibility to know those requirements and how they apply to your site. Last Updated: 2019 BMPPocketGuide EROSION&SEDIMENTCONTROL EROSION&SEDIMENTCONTROL ®CWTLLC 2 Erosion & sEdimEnt Control BMP Pocket GuideThis Best Management Practice (BMP) pocket guide will assist you in making informed decisions when selecting BMPs that provide the best erosion and sediment control (ESC) for your field. It will help you ask yourself and others the right questions that may impact overall BMP performance. Every operation has unique conditions that demand appropriate BMP selection. In addition, your informed discussions with suppliers and service vendors should ensure you get the appropriate BMP product or service for your site. This guide is from the construction industry for the agricultural community and is meant to supplement existing design manuals and is not a replacement for them. BMP considerations, technical drawings and installation options in this guide are a compilation of several state agency guidance manuals that have been reviewed to reflect the most current information. NOTE: Agencies or owners may have specific requirements for any of the BMPs described in this guide. It is the landowner’s responsibility to acquire any permits that may be necessary to install BMPs. This guide was developed and published byCWT, LLC (CleanWaterATS.com) in partnership withEnlighting Struck Design (EnlightingDesign.com).Image and information support was supplied byACF West (ACFWest.com),Clear Water Services (ClearWaterServices.com) andProfile Products (profileevs.com).Photos and illustrations were provided by the above companies and bySilver Sage Stock Photography (SilverSageStock.com). ®CWTLLC 3 HOW TO USE THIS GUIDE This guide includes practices used in the construction industry to control erosion and sediment loss off-site. A page address- ing cover crops/conservation cover has been added to provide another highly recommended option for erosion control. We hope this guide will provide new ideas and inspiration to install practices on your operation to keep YOUR soil on YOUR farm. THE GUIDE COLOR KEY IS AS FOLLOWS: PERIMETER CONTROLS COVERING, SLOPE PROTECTION & REVEGETATION CHANNELS, DITCHES & CONVEYANCE INLET & OUTLET PROTECTION 9 17 33 39 ®CWTLLC 4 CONSERVATION OBJECTIVES Oregon’s Soil and Water Conservation Districts provide technical assistance, educational outreach, and other conservation services to landowners, managers, and citizens. The Districts provide leadership in delivery of state water quality programs, watershed enhancement programs, and local conservation efforts that contribute to the Oregon Plan for Salmon and Watersheds. If you own or operate a farm, then you know that today’s farmers and ranchers are faced with a seemingly impossible task — to feed a rapidly growing global population with fewer farmable acres, less fresh water, and more pronounced climate change. More than ever before, sustaining the health and function of our natural resources is critical while we increase farm productivity and profitability. Reducing off-site impact of nutrients and fertilizers on water quality, preventing soil loss, dust suppression, reducing flooding by holding more water in the soil profile, and increasing wildlife and pollinator habitat are key objectives to improve the condition of our fields, forests and grazing lands. Erosion and sediment control is at the heart of reaching these objectives. ®CWTLLC 5 Project timing and phasing: Consider the duration of your crop and the local climatology when determining the practice installation schedule. How do you reduce your risk of exposed soils during high precipitation? Can you develop this project in phases where temporary practices provide additional erosion control during seasonal activites and already established vegetation provides stabilization or is available on the site for management of stormwater the rest of the year? What contingency plan(s) do you have in place for volume control and water quality protection, if you encounter high precipitation storms or seasons? Containment and waste management: What plan do you have for management of water that may come into contact with soil amendments or compost? Are your pesticides and fertilizers stored in a defined, covered, and secondarily contained area? Is your mixing and clean out area contained? Dewatering, containment, and waste management: Do you anticipate encountering groundwater (clean or contaminated) during excavation? What plan do you have for management of that water and excavated soil? The more contaminated the site and the more sensitive the receiving water, the more likely you are to need specialized treatment service support. Are all of your liquids (gas, oils, paint, etc.) and dry materials (fertilizer, etc.) stored in a defined, covered, and secondarily contained area? ®CWTLLC 6 General BMP Selection Considerations All projects have a variety of conditions that need to be considered when selecting the appropriate BMP. These considerations include: · Soil type – The soil type you are working in greatly determines your ability to capture, collect, and filter the fine sediments when they are suspended by storm events. Soil chemistry also determines whether your seed is going to germinate and establish without amendment. · Water quality and wildlife considerations – Project’s proximity to sensitive receiving waters or the potential it has to endanger protected species can greatly impact your BMP selection. · Temporary or Engineered BMPs – There can be both temporary and post construction BMPs implemented on a site during active construction. Temporary BMPs are implemented during active construction. Engineer solutions, such as infiltration structures, used for temporary controls can be ®CWTLLC 7 rendered ineffective if impacted by highly turbid runoff during construction activity. It is important to know the difference and protect the post construction stormwater management infrastructure during construction activity. · Climate – The intensity, frequency and duration of precipitation in your area is a determining factor in how aggressively you implement BMP controls on a project. It also determines your stormwater volume control needs for the project as well as seed windows for germination. · Project size and Duration – The amount of exposed soil, the time of year, and the length of time that area is going to remain exposed must be considered when selecting appropriate BMPs for volume management and flow control. · Cost Benefit Analysis: Life-cycle BMP costs include purchase, installation, maintenance and removal/disposal. All costs must be factored into a decision. What may be inexpensive off-the-shelf, may cost significantly more in labor and replacement over the life of your project. Including these considerations in your production schedule is crucial in managing cost and demonstrating good performance. · Topography –The longer and steeper a slope is, the more velocity, and erosive force the runoff will have. The steepness and longevity of your slopes and the soil type in which you are working greatly influence your BMP selection. As you consider all these factors as well as the unique circumstances you may have at your site, you can use the following guide in selecting BMP products that will best assist you. Products mentioned in this guide may be able to fit into multiple categories depending on the application. ®CWTLLC 8 FOCUS POINTS • Take considerable effort in preventing soil from eroding and migrating by covering, stabilizing, and managing volume whenever and wherever you can.“Keep the dirt from moving in the first place!”• A raindrop that falls out of the air is “clean”. How do you keep that raindrop from getting dirty as it moves over your project? • There is a balance of footprint availability to volume control. The more exposed acreage, the more space you are going to need for stormwater volume and flow control management. • Are there design or phasing elements you can incorporate into your plan that aid in your success on the project? ®CWTLLC 9 PERIMETER CONTROLS Perimeter Controls are BMPs that prevent disturbed areas of your project from impacting off site areas. Sometimes these controls prevent water from running on a site as well. Often these controls also delineate project boundaries or areas of disturbance; however, perimeter controls may not be necessary around the entire project. These BMPs required on every project, are most visible to the public, and will at times require significant maintenance. FOCUS POINTS • This is one of the first areas of BMP focus for your project. Make sure the project or areas of disturbance are delineated accurately.• These BMPs are the last line of defense for your project. Once water passes these BMPs, the quality of the water should pose no risk or liability downstream. • These BMPs require diligent maintenance.• Public safety is also a consideration in your perimeter control BMP selection. PERIMETER CONTROLS ®CWTLLC 10 BMP: Sediment or Silt Fence Selection Considerations: • Do you need filtration capability? The geotextile material will determine if the fence will filter or retain. • How susceptible is your site to high wind and high flow velocity? This will determine the reinforcement strength the fence needs, as well as, your staking frequency. Many are ineffective in concentrated flows or high volumes. • Do you want or need high visibility fencing? Installation Considerations: • Fences need to be keyed in appropriately. Require depth configuration and backfill material can vary with local jurisdictions. Many sediment fences have a depth line on the geotextile fabric. You should be able to jerk up on the fence after installation and get very little movement. (image A.5.) • Staking is generally 6’ on center, but varies widely based on slope, soil type, flow, wind and sediment load. • Fences should be installed along contours of the slope. • When joining two ends of fence together make sure there is a significant overlap (shingled in the direction of flow) or wrapping the ends together (image A.4.). • Terminate all ends of fencing by wrapping the fence back into the project with an “L” or “J” hook. • Sewn-in pocket fence is the only sediment fence with the stakes installed on the uphill or inside of the project (image A.3.). • Tools – pick, shovel, trencher, t-post driver, wire cutters, knife Product Options: • Geotextile: Woven, filter fabric, high visibility, wire embedded, sewn in pocket, wire backed • Posts: 1x1 stapled stake, 2x2 stapled stake, metal t-posts PERIMETER CONTROLS ®CWTLLC 11PERIMETER CONTROLS A.4. Joining segments of fence by wrapping A.3. Sewn-in Pocket fence stake on the uphill side or inside the project is the correct installation MAXIMUM 6-8 FTBETWEEN POSTS c. FABRIC e. BA C K F I L L RUNOFF a. & b.d. STAKEA.5. a. Straight, “J” or “U” hook of fabric tail, b. Depth of backfill may vary c. Woven, filter, high visibility geotextile optionsd. Wood or t-post stakes, potentially with wirebacked supporte. Backfill material can be native fill, compost or pea gravel A.2. Fencing used to protect and delineate site features A.1. Orange colored, wire-backed fence®CWTLLC 12 BMP: Sediment Barriers Selection Considerations: • These types of perimeter controls are used on flat sites, smaller projects, and often in home building. They have a shorter profile then the sediment fence and therefore retain less water. What diameter will be the most effective? • As with sediment fence, these perimeter controls are most often runoff check devices and not used for filtration. • What flow velocity will contact this perimeter control? There should not be excessive volume against these BMPs. • One time use or reusable? Installation Considerations: • Cylindrical BMPs have very little surface area contacting the ground. Most need to be entrenched 2-4 inches (see B.1.) unless the material is heavy enough (ex. compost or rock socks) to make solid contact with the ground to not require trenching. • Backfill and compact the uphill or inside edge of the BMP to prevent runoff from migrating under the BMP. • Is there enough freeboard profile to contain the sediment loads expected based on slope, soil type, and rain events? • Connect segments together by overlapping. Butting segments end to end can leave a weakness in you perimeter controls for water to escape. Be mindful of direction of flow and shingle the overlap appropriately. • Staking options vary depending on slope, soil type and regulations. Sand bags are also used to hold the fiber rolls in place. Make sure to know your local requirements for allowable staking practices (wattles B.1.). • Tools – pick, shovel, stakes, pins, mallet or hammer. PERIMETER CONTROLS ®CWTLLC 13 BMP options: • Wattles – Straw, excelsior, brush barriers • Rock socks and berms • Fiber logs – coir, Terratube™ • Reusable synthetic wattle • Compost sock and berms PERIMETER CONTROLS VARIES DEPENDINGON SLOPE 2-4"DEPTH FLOWWATTLES - STAKING VARIES CRISS CROSSSTAKING 3/4 WATTLESTAKING CENTERSTAKING B.3. Overlapping wattlesB.2. Compost sock B.1. Wattle staking ®CWTLLC 14 B.7. Combination of perimeter controls PERIMETER CONTROLS B.5. Durable overlapB.4. Straw wattles used as perimeter control B.8. Wood fiber filtration wattleB.6. Reusable wattle ®CWTLLC 15 BMP: Entrances and Road Stabilization Entrances are the “welcome mat” to your project and demonstrate your level of ESC management. Dust suppression should be incorporated throughout the site. Selection Considerations: • How much traffic do you anticipate coming on and off your site? The more traffic, the more robust your entrance is going to need to be and the more maintenance you must factor in. • The entrance length should, at a minimum, be long enough for a turn and a half of the tires. • If you are considering a wheel wash, do you have access to clean water? What plan do you have in place for sludge and process water management to prevent commingling into stormwater runoff? PERIMETER CONTROLS B.10. Rock/Quarry spallB.9. Dust control B. 11. Construction entrance BMPs can be used individually or incombination to prevent trackout depending on traffic flow: a. Wheel Wash (may include subgrade installation of a sump)b. Rock/Quarry Spall with geogrid underlayment c. Rumble Strip ®CWTLLC 16 Installation Considerations: • Install geotextile fabric or geogrid down prior to installation of rock to create separation. In a wet or soft substrate the earth will consume the rock and the entrance or road base will no longer be effective. • Consider the gravel you are using as a base. Fines in the gravel (gravel ordered as “minus” for compaction purposes) can rinse through the rock and elevate NTUs (image B.14.). • Using crushed concrete can elevate pH in site discharge. • Polymers or tackifiers may be added to water trucks to prevent dust. • Tools: It generally takes heavy equipment (a skidsteer at minimum) to construct an entrance and a laydown area. BMP options: • Rock/Quarry spall • Rumble strip • FODS • Wheel wash • Mud mats PERIMETER CONTROLS B.13. Rumble stripB.12. Mud mat B.15. FODS unitB.14. Gravel with fines can elevate turbidity in discharge ®CWTLLC 17 COVERING AND REVEGETATION BMP These BMPs are used to prevent the impact of raindrops to the exposed surface, minimize transportation of sediment through sheet erosion, and encourage establishment of vegetation. These BMPs are often used in combination to achieve final stabilization of a site. FOCUS POINTS • BMPs protect against the impact forces of raindrops and minimize sheet erosion and concentrated flows.• Covering BMPs work best on groomed surfaces. Slope preparation is important for good seed establishment and contact for blankets and mats.• If using cover BMPs such as straw or chipped grubbed material (i.e. “hog fuel”) it is important to consider the potential of undesired weeds. • The longer and steeper your slopes the more velocity and erosive energy the runoff will carry. Minimize slope length and steepness whenever possible. This can be accomplished through grading or slope checking controls. (see image C.11.) COVERING, SLOPE PROTECTION & REVEGETATION C.1. Wood chip mulch C.3. Plastics used for slope protection must be secured properly C.2. Straw mulch that is not applied thick enough ®CWTLLC 18 • For cut slopes, consider how you can vertically phase the project during excavation to permanently stabilize the slope while excavating the site. • Seed is an investment into the stabilization of your project and can be very expensive. Establishment and project termination is the goal. Make sure that the surface covering or mulch being applied will protect the investment, allow for oxygen to the seed, control moisture and temperature, and provide growth medium to allow for survival. • Not all “hydroseed” is equal! Understand what you are paying for. Look at the factors such as functional longevity, erosion protection effectiveness, mulch matrix, how long it will take the seed to germinate based on seed type, and the time of year of application before selecting. Site soil chemistry and slope steepness are also going to play a major factor in survivorship of your seed and effectiveness of your hydromulch. Know the time necessary for your mulch to “cure” before it rains. C.5. FLEX MSE livingretaining wallC.4. Horizontal and vertical phased stabilization C.6. Combination of jute mat and hydromulch COVERING, SLOPE PROTECTION & REVEGETATION ®CWTLLC 19 BMP: Stockpile Management and Surface Covering BMPs Covering BMPs prevent the precipitation from making a high energy impact to exposed soils. Selection Considerations: • How frequently do you need to access the stockpile(s)? • Are stockpiles composed of clean or contaminated soils? • Contaminated stockpiles should be contained with a berm or other appropriate method and removed as soon as possible for proper disposal. • Are the stockpile(s) necessary to keep on site or can they be a priority for removal from the project? • How are you going to prevent downstream issues when using plastic on a slope? • According to regulatory requirements, how soon does unworked earth need to be covered? • If soil is visible on the surface after applying the surface covering BMP, you need to install more. Installation Considerations: • Slope profile and contour, and wind direction will help determine the direction you shingle the overlapping edges. • You must be aggressive at anchoring so the wind does not blow your plastic or blankets out of place. • Increased runoff velocity must be reduced by energy dissipation BMPs at the toe of the slope to prevent downstream impacts. C.7. Slow the velocity of the runoff from stockpiles and slopes. Wattle is not secured in this image COVERING, SLOPE PROTECTION & REVEGETATION ®CWTLLC 20 • Straw should be incorporated into the soil surface through “crimping” with equipment, and/or a tackifier should be added to prevent drifting and displacement. • Tools – shovel, stakes, pins, mallet or hammer, knife. SAFETY NOTE: Wet plastic is slippery and should not be walked on or climbed! BMPs options: • Plastic – clear, black, reinforced with string • Mats and blankets - straw, excelsior, coconut, etc. • Spray applied – polyacrylamide tackifiers, hydraulically applied blankets (see Hydraulically Applied Products) • Covering BMPs – straw, brush chipping (“hog fuel”), compost C.8. Blanket and straw as covering BMPs C.10. Rolled blanket for restoration projectC.9. Compost mulch being blown on a slope COVERING, SLOPE PROTECTION & REVEGETATION ®CWTLLC 21 BMP: Slope Checks Slope checks are designed to minimize the length of the slopes. When used in combination with other covering BMPs, slope protection can very effective. Selection Considerations: • What installation frequency is necessary to reduce velocity and drop sediment out of suspension? • What length and diameter does the BMPs need to be? • How long does the product need to last? Are you doing a bioremediation or restoration project or are you managing sediment for a temporary construction project? • Do you want filtration or retention? • Retaining water on the slope adds weight. The soil type you are working in will determine both the frequency and the length of the stakes needed to keep the check BMP anchored to the slope and frequency of slope. WATER WILLFIND LOW POINT& BREAKTHROUGH ONLY USINGPARITIAL LENGTH,OVER WEIGHTING SLOPE CHECKS GOODOVERLAP FOLLOW ALONGCONTOUR LINES CONTOUR LINE C.11. Slope checks should be inserted along the contour lines of the slope, unless otherwise designed, to maximize the full length of the BMP and prevent breakthrough and failure due to concentrated weight. COVERING, SLOPE PROTECTION & REVEGETATION ®CWTLLC 22 Installation Considerations: • Products must be keyed in and backfilled on the uphill side to retain runoff. • Many of these products are labor intensive and tiring for installers to pack up and down the slope; additionally, increased foot traffic weakens the integrity of the slope. • Overlap ends of BMPs to create a continuous contour which prevents gap breakthrough at butted ends • Unless an alternative configuration is designed, the BMP should be installed straight along contour lines to prevent sagging. Water will concentrate in low point or sagged points and overtop, and you will not receive the benefit of the entire length of the BMP. (image C.11.) • Some jurisdictions have restrictions on usage of flocculants that may be incorporated in some of these BMPs. • Refer to image B.1. for staking considerations. • Tools – pick, shovel, stakes, pins, mallet or hammer C.12. Slope checks and covering BMPs used in combination are effective for erosion prevention and seed establishment COVERING, SLOPE PROTECTION & REVEGETATION ®CWTLLC 23 BMPs options: • Constructed slope checks: water bars, gradient terracing, brush barriers, gravel berms • Wattle type BMPs: straw wattles, coir logs, compost socks, excelsior wattles, wood fiber (ex. Terratubes™), gravel/rock tubes or berms • Flocculants can be an aid in sediment removal. Refer to you local and state agency guidance on use. C.13. Breaking up slope length to slow velocity andsupport the weight of growable substrate C.14. Wattles retaining soil on slope to allow for revegetation COVERING, SLOPE PROTECTION & REVEGETATION ®CWTLLC 24 BMP: Blankets and Mats Blankets and mats are chosen based on steepness of slope, sheer velocity strength, wildlife escapability, and functional longevity for seed germination or slope retention. Selection Considerations: • How long coverage is needed is the major determining factor in selecting mats or blankets. • What sheer velocities from runoff are expected over the blanket? • Do you need permanent netting for additional strength on an engineered slope or is it a temporary covering? • Are you working in an area with sensitive wildlife that could get entangled in the netting? Installation Considerations: • Have your slopes been “groomed” or prepped by “track walking” up and down the slope? Graded slope preparation is necessary to provide a good contact surface for the blankets. C.15. 1. Rolled out and making firm contact with the groomed slope 2. Keyed in at the top of the slope 3. Staple size and frequency based on slope and soil type 4. Overlapping adjoining blankets 5. Shingle down the slope COVERING, SLOPE PROTECTION & REVEGETATION ®CWTLLC 25 • Rolled products need to be keyed in at the top of the slope. (image C.14.) The upslope blanket should be shingled and covering the top of the downslope blanket. • Must stay in firm contact with the slope. • Gaps between the blanket and the slope may cause rilling under the BMP. • Determine stapling size and frequency based on steepness of slope, surface velocities, wind and soil type. • Spray or spread seed first before blanket or mat installation. Compost and jute are the only BMPs where seed can establish after being applied on top. • Tools – pick, shovel, pins, mallet or hammer Product options: • Permanent or temporary • Netting surrounding blanket media: permanent, biodegradable, photodegradable • Media: jute, straw, straw/coconut, coconut, excelsior, compost, synthetic fibers, polypropylene, plastic C.17. Track walked slopeC.16. Jute mat installation COVERING, SLOPE PROTECTION & REVEGETATION ®CWTLLC 26 BMP: Hydraulically Applied Products The BMPs are sprayed on with water for erosion control and revegetation purposes. Selection Considerations: • Are you spray applying a blanket for erosion protection without including seed, or are you trying to get vegetation to establish? Both? • How long do you need it to last and what type of protection performance do you need from it? How long does it take for the seed to germinate and establish? Choose a mulch that can create a growing environment and prevents the seed from washing away based on that timeline. • Slope angle and soil type determine what type of spray mulch will be effective. Do you need mechanical or chemical bonding agents in the mulch to adhere to the slope? Is your slope steep enough that it may require a turf reinforcement mat to anchor mulch to the slope? (image C.19.) C.18. Spray mulch infilled into Turf Reinforcement Mat (TRM) COVERING, SLOPE PROTECTION & REVEGETATION ®CWTLLC 27 • Soil chemistry is extremely important when reestablishing vegetation. Consider taking a soil test prior to applying seed to determine the soil pH and nutrient characteristics. • In general, when evaluating a site greater than a half acre, you will want to consider the cost comparison of hydraulic applied blankets to rolled blankets and mats. • Can I apply this in the rain? Installation Considerations: • Availability of onsite water for the application. • Acreage to cover as well as access to the project. • Spray applications should not be placed in concentrated flow areas without reinforcement and seed protection.THE STEEPER THE SLOPE THEHIGHER THE SHEAR STRESSVELOCITY AND THE MORE DIFFICULTY INHOLDING WEIGHT OF GROWTH MEDIUMTRM, SHOTCRETE ORHARD ARMORMENT≤1:1 TYPES OF EROSION CONTROLBLANKETS & REINFORCEDMULCHES ≤1.5:1FGM - Flex Growth MediumFRM - Fiber Reinforced MatrixBFM - Bonded Fiber MatrixMBFM - Mechanical Bonded Fiber Matrix MULCHES WITH TACKIFIERS≤4:1 WOOD/STRAW/PAPER MULCHES≤5:1 HYDRAULIC PERFORMANCE PROFILE C.19. This illustration is a simple guide for when reviewing specifications and when in communication with vendors to determine which hydraulically applied product is best for your project depending on the slope, seed, and soil type. COVERING, SLOPE PROTECTION & REVEGETATION ®CWTLLC 28 BMP options:• Hydroseed – mulch, green dye, wood/paper/straw mulch • Hydromulch - Mulches built with cross linked tackifiers or fiber reinforcement FGM – Flex Growth Media FRM – Fiber Reinforce Matrix BFM – Bonded Fiber Matrix MBFM – Mechanical Bonded Fiber Matrix • Biotic soil amendments - Could include mycorrhiza, biochar, and other growth media • Additives: fertilizer, polymers, nutrients, etc. C.20. Hydraulic Mulch Matrix Elements C.21. Mulch bonding capability COVERING, SLOPE PROTECTION & REVEGETATION ®CWTLLC 29 APPROXIMATE INSTALLATION COSTS Category Dry AppliedStraw Pelletized Base HydraulicMulch BFM FGM ExtendedFGM Appl. Rate(lbs/Acre) 2,000- 3,000 1,500- 2,500 1,500- 2,500 3,000- 4,000 3,000- 4,000 3,000- 4,000 InstallationCost ($sq.ft.) $.02 - .04 $.03 - .05 $.03 -.06 $.09 -.11 $.11 - .16 $.15 - $.20 FunctionalLongevity 3 - 6 months(if in place) 3 - 6 months < 3 months 6 - 12 months 12 - 18 months 18 - 24 months %Effectiveness 15 - 40% 40 - 50% 50 - 65% 90 - 95% 99.9% 99.99% C.22. Hydraulically Applied Blanket Application Chart (seed costs not included) C.24. Spray applied erosion blanket after 9 months C.23. Spray applied soil amendments for revegetation C.26. Mulch application with truck canonC.25. Soil amendmentcomposition COVERING, SLOPE PROTECTION & REVEGETATION ®CWTLLC 30 C.27. Fish habitatimprovementC.26. Landslide stabilization BMP: Revegetation Whether planting starts or spraying seed, soil chemistry is very important to understand. Soil test should be taken prior to seed application or plantings. A soil test should analyze nutrient levels, moisture retention capability, pH, organic material and salt content. Seed can be hundreds of dollars a pound and each type germinates and establishes at different rates. Seed is an investment to site restoration, and protecting it should be the first priority. Whether your project involves a restoration/reclamation or temporary stabilization, vegetation provides the best erosion control. Installation Considerations: • Has the soil been tested? • Will the site need irrigation in the dry times? Freeze protection for cold weather? • How long do I need to protect the seed or plant before it roots and establishes? • Will my covering BMPs allow for oxygen exchange, moisture control, light penetration, and temperature control while protecting the seed? • Know your climate. Dry climates take longer to establish. • Soil amendments increase likelihood of establishment success. COVERING, SLOPE PROTECTION & REVEGETATION ®CWTLLC 31 BMP: Cover Crops and Conservation Cover Vegetation helps to hold soil in place. Also, minimizing tillage on highly erodible soils or slopes greater than 5-10 percent will reduce erosion risk. BMP Options: • Mid-slope buffer strips • Between row vegetation • Field borders • Cover crops (annual) • Conservation cover (perennial) • Vegetated treatment areas (i.e. swales, outlets) • Critical area seeding (steep or sensitive) COVERING, SLOPE PROTECTION & REVEGETATION ®CWTLLC 32COVERING, SLOPE PROTECTION & REVEGETATION Installation considerations: • Use a seed mixture that combines tall plants with shorter growing plants in both between row and field border situations. This two-story approach provides better protection from raindrops that detach soil particles. • Seeding rates will depend on the species you choose for your seed mixture. Your seed dealer can provide assistance for both questions. Maintenance consideration: • Avoid using field borders as access roads • Control invasive weeds • Remove soil deposited at a field border when it reaches six inches • Repair gullies and rills created during storm events. • Fertilize and mow borders to maintain plant vigor. • Maintain vegetation to provide 80% groundcover throughout the year. ®CWTLLC 33CHANNELS, DITCHES & CONVEYANCE CONVEYANCE BMP These BMPs allow you to convey water through, around or under your site without causing further downstream erosion; however, as water is conveyed in concentrated flow, velocity and energy can build. Your conveyance plan must incorporate means of reducing if not eliminating the velocity of the water moving over your site. FOCUS POINTS• A raindrop that falls is “clean”. How do you keep that raindrop from getting dirty as it moves over your project? • There is a balance of footprint to volume control. The more exposed the area, the more volume you are going to need to manage. Are your conveyance BMPs large enough to handle the flow? Are you incorporating additional storage as you expose more of the site? • Concentrating flow in pipes, channels and ditches can add velocity to the water. What is your plan to reduce the velocity to prevent scouring and downstream detrimental impacts?• Are your channels, ditches, traps and ponds stable before you add the water? If not, are you lining them? ®CWTLLC 34 BMP: Channels and Ditches Selection Considerations: • How long does it need to last? Is the lining temporary or a permanent feature of the channel or ditch? • What are the volumes and velocities of water being conveyed in the channel? • How much water can your channels and ditches detain in a runoff event? • What energy reduction BMPs are you implementing throughout and at the terminal end of the channel or ditch to prevent scouring and reduce velocity? • Are plantings being incorporated in banks or shoulders? How long will it take for the plants to establish flow resistant root base? That will impact the cover material you select. Installation Considerations: • If the channel is going to be vegetated, spray the seed first and then roll the blanket over the top for protection of the seed during flow events. • Allow time for stabilization before submerging and adding sheer velocities to the channel or ditch to ensure seed survivorship. • Do your channels and ditches need to be straight or can they be constructed in the shape of an “S” or “U”? • If using sod, make sure it is aggressively pinned in place. CHANNELS, DITCHES & CONVEYANCE D.2. Concrete cloth lined channelD.1. Channel outlet stabilization ®CWTLLC 35 BMP options: • Constructed or Prefabricated • Linings – mats or blankets, plastic, halved corrugated ADS pipe, vegetation, geotextiles, TRMs, SmartDitch™, Concrete Cloth™ D.3. Blanket covered ditch with check dams D.4. 1. Grade and groom the slope 2. Key in the top of the blanket at the head of the channel 3. Shingle in direction of flow 4. Anchor overlapping edges 5. Key in edges of the blanket on the top of the channel shoulder6. Overlap side slope blankets over base channel material 7. Double staple seems 8. Key in the tail of the blanket CHANNELS, DITCHES & CONVEYANCE ®CWTLLC 36 BMP: Check Dams Selection Considerations: • How much volume and velocity reduction you need will determine the size and frequency of the check dam(s). • Do you want filtration or retention capabilities? If you desire filtration, do you want or are you allowed to use the aid of a flocculant for pretreatment? • If used for diverting run-on, make sure that the BMP does not create a runoff backup and subsequent safety or property damage issue upstream of your disturbed area. Consider incorporating pipe slope drains to convey water over the face of the slope and through your disturbed area. Installation Considerations: • For wattle installation, see B.1. • If using rock, make sure it is washed and absent of fine sediment which will elevate turbidity in runoff. • Make sure staking and anchoring is adequate to the expected flow velocities and volume control. D.7. Spring Berm check dam BMP CHANNELS, DITCHES & CONVEYANCE ®CWTLLC 37 • Does the low spot of the check dam need to be centered all the way down the channel or can the low spot be alternated side to side to make the water flow in more of a serpentine path down the channel? • Make sure that backed up water on the lead edge will not migrate up the channel slope and bypass the check dam around the outside. • For any check dam that creates a “waterfall” type scenario, you must have a splash apron to reduce the energy and prevent scouring on the back side of the check dam. BMP options: • Triangular silt dike • Quarry spall • Georidge™ • Wattles • Sand bags • Brush Barriers • Bio bags • Compost socks • Spring Berm D.8. Triangular Silt Dike CHANNELS, DITCHES & CONVEYANCE ®CWTLLC 38 D.9. Conveyance channel and check dams D.10. Filter log check dams CHANNELS, DITCHES & CONVEYANCE ®CWTLLC 39 INLET AND OUTLET PROTECTION These BMPs reduce velocity and are able to filter or deposit sediment. These are high maintenance BMPs and should be monitored closely on a project. FOCUS POINTS • Filters must be maintained to remain effective. Each site may have a different maintenance and/or replacement frequency.• As with sediment fence, filters are one of the first things installed on projects, but should not be considered the only line of defense. They are generally the last line of defense to water quality compliance to the project and effort should be focused at preventing erosion and sediment transport well upstream of these BMPs.• Armoring and dispersal of concentrated flow at your outlets and outfalls is essential to consider. • If discharging to a drywell or underground injection control (UIC) monitoring and pollutant removal may be required prior to introduction. INLET & OUTLET PROTECTION ®CWTLLC 40 BMP: Inlet Protection SAFETY NOTE: Do not stick your head down into a catchbasin to reach something that has fallen into a sump. Selection Considerations: • Are you polishing the water to reduce NTUs or trying to capture bulk materials? • Is there an overflow or bypass for high flow events to prevent ponding on the surface? • Is the insert self-supporting in the structure or is it held in place by the grate? • Are you implementing surface separation BMPs to remove the bulk load prior to impacting the insert? • Are there other pollutants of concern on the site besides turbidity? You may need additional media to remove other pollutants. • Is the entire insert replaced or media within the insert? • Where can the insert be disposed? • Is the sump of the structure deep enough to allow the water to filter through the bottom of the insert and prevent obstruction to the sump inlet and outlet? • What is the configuration of the catchbasin structure? Drop in? Curb cut? Shape? • High traffic activity over catchbasins can damage integrity of the filter installed. INLET & OUTLET PROTECTION F.2. Gravel sock inlet protectionF.1. Insert in catchbasin ®CWTLLC 41 Installation Considerations: • When lifting the grate to install or maintain, filters make sure that the grate is pulled away from the opening to prevent the grate from falling into the sump. Perform the maintenance event as quickly as possible to prevent the open structure from creating a fall hazard. • When removing an old filter, make sure you have a hold of the filter when you remove the grate so as not to lose the filter down the sump. Some filters may be full and weigh more than 50 pounds and therefore replacement often becomes a two person job. • Consider surface inlet protection to accumulate the bulk load of the material on the surface where it can be maintained and allow the insert to polish and lower turbidity through filtration. • All filters require change out. Each project will have a different change-out frequency based on applied erosion prevention BMPs and soil type. Product options: • Inserts /”Silt Sacks” • Inlet guards • Bio bags • Above ground coir pads • Sand bags F.4. Recessed inlet protectionF.3. Wood chip bag on surface to prevent filter loading INLET & OUTLET PROTECTION ®CWTLLC 42 BMP Type: Outlet Protection Selection Considerations: • Is it a temporary outlet or permanent? • Is there an established vegetative area usable for dispersal? Installation Considerations: • When using spall or other rock armament, it is a good idea to install a geotextile underneath to prevent under-scouring of the rock material. Size rock according to expected velocity. BMP options: • Rip rap • Dispersal systems • Concrete splash apron • Wattles and socks • Sediment fence • Sand Bags F.7. Flow dissapator F.6. Outlet ProtectionF.5. Wattle and fabric protection INLET & OUTLET PROTECTION ®CWTLLC ®CWTLLC 43 FINAL THOUGHTS Farming and erosion control go hand in hand. The more connected the field conditions are to the practice selected, generally, the better performance and control of the project. No two projects are exactly the same and each site will require problem solving and proactive adaptive management to keep the site in compliance and on budget. Here are some final thoughts to consider: • BMPs and maintenance frequencies may change over the life of the project due to changes in crops, unexpected storms, changing phases of crop development, and monitored effectiveness of existing selected BMPs. Budgets need to have some flexibility to implement what is necessary to meet performance goals of the site. • Design specifications for BMP installation and maintenance may be different. However the principles of performance are generally the same. Managing a project’s budget and schedule, while constantly adapting to environmental conditions and keeping in compliance with regulatory requirements is a significant challenge. It takes a tremendous amount of communication and coordination with all parties on a project to understand the importance of erosion and sediment control management and engagement from all parties to make the project successful. ®CWTLLC ®CWTLLC 503-210-6000 WMSWCD.ORG www.polkswcd.com 503-623-9680 email info@tualatinswcd.org visit tualatinswcd.org East Multnomah Soil and Water Conservation District (503) 222-7645 | info@emswcd.org | emswcd.org 456 SW Monroe Ave, Suite 110, Corvallis, OR 97333 www.bentonswcd.org · 541-753-7208®CWTLLC