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HomeMy WebLinkAbout1.00 General Application Materials_Part21EC-3 Soil Binders (SB) SB-4 Urban Drainage and Flood Control District November 2010 Urban Storm Drainage Criteria Manual Volume 3 o For sandy soil: 10 parts water to 1 part emulsion Application can be by water truck or hydraulic seeder with the emulsion and product mixture applied at the rate specified by the manufacturer. Polymeric Emulsion Blend Binders Acrylic Copolymers and Polymers: Polymeric soil stabilizers should consist of a liquid or solid polymer or copolymer with an acrylic base that contains a minimum of 55 percent solids. The polymeric compound should be handled and mixed in a manner that will not cause foaming or should contain an anti-foaming agent. The polymeric emulsion should not exceed its shelf life or expiration date; manufacturers should provide the expiration date. Polymeric soil stabilizer should be readily miscible in water, non-injurious to seed or animal life, non-flammable, should provide surface soil stabilization for various soil types without inhibiting water infiltration, and should not re-emulsify when cured. The applied compound should air cure within a maximum of 36 to 48 hours. Liquid copolymer should be diluted at a rate of 10 parts water to 1 part polymer and the mixture applied to soil at a rate of 1,175 gallons/acre. Liquid Polymers of Methacrylates and Acrylates: This material consists of a tackifier/sealer that is a liquid polymer of methacrylates and acrylates. It is an aqueous 100 percent acrylic emulsion blend of 40 percent solids by volume that is free from styrene, acetate, vinyl, ethoxylated surfactants or silicates. For soil stabilization applications, it is diluted with water in accordance with manufacturer's recommendations, and applied with a hydraulic seeder at the rate of 20 gallons/acre. Drying time is 12 to 18 hours after application. Copolymers of Sodium Acrylates and Acrylamides: These materials are non-toxic, dry powders that are copolymers of sodium acrylate and acrylamide. They are mixed with water and applied to the soil surface for erosion control at rates that are determined by slope gradient, as summarized in Table SB-3. Table SB-3. Application Rates for Copolymers of Sodium Acrylates and Acrylamides Slope (H:V) Flat to 5:1 5:1 to 3:1 2:2 to 1:1 Application Rate (lb/acre) 3.0-5.0 5.0-10.0 10.0-20.0 Polyacrylamide and Copolymer of Acrylamide: Linear copolymer polyacrylamide is packaged as a dry flowable solid. When used as a stand-alone stabilizer, it is diluted at a rate of 11 lb/1,000 gal. of water and applied at the rate of 5.0 lb/acre. Hydrocolloid Polymers: Hydrocolloid Polymers are various combinations of dry flowable polyacrylamides, copolymers, and hydrocolloid polymers that are mixed with water and applied to the soil surface at rates of 55 to 60 lb/acre. Drying times are 0 to 4 hours. Cementitious-Based Binders Gypsum: This formulated gypsum based product readily mixes with water and mulch to form a thin protective crust on the soil surface. It is composed of high purity gypsum that is ground, calcined and processed into calcium sulfate hemihydrate with a minimum purity of 86 percent. It is mixed in a hydraulic seeder and applied at rates 4,000 to 12,000 lb/acre. Drying time is 4 to 8 hours. Soil Binders (SB)EC-3 November 2010 Urban Drainage and Flood Control District SB-5 Urban Storm Drainage Criteria Manual Volume 3 Installation After selecting an appropriate soil binder, the untreated soil surface must be prepared before applying the soil binder. The untreated soil surface must contain sufficient moisture to assist the agent in achieving uniform distribution. In general, the following steps should be followed: Follow manufacturer's written recommendations for application rates, pre-wetting of application area, and cleaning of equipment after use. Prior to application, roughen embankment and fill areas. Consider the drying time for the selected soil binder and apply with sufficient time before anticipated rainfall. Soil binders should not be applied during or immediately before rainfall. Avoid over spray onto roads, sidewalks, drainage channels, sound walls, existing vegetation, etc. Soil binders should not be applied to frozen soil, areas with standing water, under freezing or rainy conditions, or when the temperature is below 40°F during the curing period. More than one treatment is often necessary, although the second treatment may be diluted or have a lower application rate. Generally, soil binders require a minimum curing time of 24 hours before they are fully effective. Refer to manufacturer's instructions for specific cure time. For liquid agents: o Crown or slope ground to avoid ponding. o Uniformly pre-wet ground at 0.03 to 0.3 gal/yd2 or according to manufacturer's recommendations. o Apply solution under pressure. Overlap solution 6 to 12 in. o Allow treated area to cure for the time recommended by the manufacturer, typically at least 24 hours. o Apply second treatment before first treatment becomes ineffective, using 50 percent application rate. o In low humidity, reactivate chemicals by re-wetting with water at 0.1 to 0.2 gal/yd2. Maintenance and Removal Soil binders tend to break down due to natural weathering. Weathering rates depend on a variety of site- specific and product characteristics. Consult the manufacturer for recommended reapplication rates and reapply the selected soil binder as needed to maintain effectiveness. Soil binders can fail after heavy rainfall events and may require reapplication. In particular, soil binders will generally experience spot failures during heavy rainfall events. If runoff penetrates the soil at the top of a slope treated with a soil binder, it is likely that the runoff will undercut the stabilized soil layer and discharge at a point further down slope. EC-3 Soil Binders (SB) SB-6 Urban Drainage and Flood Control District November 2010 Urban Storm Drainage Criteria Manual Volume 3 Areas where erosion is evident should be repaired and soil binder or other stabilization reapplied, as needed. Care should be exercised to minimize the damage to protected areas while making repairs. Most binders biodegrade after exposure to sun, oxidation, heat and biological organisms; therefore, removal of the soil binder is not typically required. Mulching (MU)EC-4 June 2012 Urban Drainage and Flood Control District MU-1 Urban Storm Drainage Criteria Manual Volume 3 Photograph MU-1. An area that was recently seeded, mulched, and crimped. Description Mulching consists of evenly applying straw, hay, shredded wood mulch, rock, bark or compost to disturbed soils and securing the mulch by crimping, tackifiers, netting or other measures. Mulching helps reduce erosion by protecting bare soil from rainfall impact, increasing infiltration, and reducing runoff. Although often applied in conjunction with temporary or permanent seeding, it can also be used for temporary stabilization of areas that cannot be reseeded due to seasonal constraints. Mulch can be applied either using standard mechanical dry application methods or using hydromulching equipment that hydraulically applies a slurry of water, wood fiber mulch, and often a tackifier. Appropriate Uses Use mulch in conjunction with seeding to help protect the seedbed and stabilize the soil. Mulch can also be used as a temporary cover on low to mild slopes to help temporarily stabilize disturbed areas where growing season constraints prevent effective reseeding. Disturbed areas should be properly mulched and tacked, or seeded, mulched and tacked promptly after final grade is reached (typically within no longer than 14 days) on portions of the site not otherwise permanently stabilized. Standard dry mulching is encouraged in most jurisdictions; however, hydromulching may not be allowed in certain jurisdictions or may not be allowed near waterways. Do not apply mulch during windy conditions. Design and Installation Prior to mulching, surface-roughen areas by rolling with a crimping or punching type roller or by track walking. Track walking should only be used where other methods are impractical because track walking with heavy equipment typically compacts the soil. A variety of mulches can be used effectively at construction sites. Consider the following: Mulch Functions Erosion Control Yes Sediment Control Moderate Site/Material Management No EC-4 Mulching (MU) MU-2 Urban Drainage and Flood Control District June 2012 Urban Storm Drainage Criteria Manual Volume 3 Clean, weed-free and seed-free cereal grain straw should be applied evenly at a rate of 2 tons per acre and must be tacked or fastened by a method suitable for the condition of the site. Straw mulch must be anchored (and not merely placed) on the surface. This can be accomplished mechanically by crimping or with the aid of tackifiers or nets. Anchoring with a crimping implement is preferred, and is the recommended method for areas flatter than 3:1. Mechanical crimpers must be capable of tucking the long mulch fibers into the soil to a depth of 3 inches without cutting them. An agricultural disk, while not an ideal substitute, may work if the disk blades are dull or blunted and set vertically; however, the frame may have to be weighted to afford proper soil penetration. Grass hay may be used in place of straw; however, because hay is comprised of the entire plant including seed, mulching with hay may seed the site with non-native grass species which might in turn out-compete the native seed. Alternatively, native species of grass hay may be purchased, but can be difficult to find and are more expensive than straw. Purchasing and utilizing a certified weed-free straw is an easier and less costly mulching method. When using grass hay, follow the same guidelines as for straw (provided above). On small areas sheltered from the wind and heavy runoff, spraying a tackifier on the mulch is satisfactory for holding it in place. For steep slopes and special situations where greater control is needed, erosion control blankets anchored with stakes should be used instead of mulch. Hydraulic mulching consists of wood cellulose fibers mixed with water and a tackifying agent and should be applied at a rate of no less than 1,500 pounds per acre (1,425 lbs of fibers mixed with at least 75 lbs of tackifier) with a hydraulic mulcher. For steeper slopes, up to 2000 pounds per acre may be required for effective hydroseeding. Hydromulch typically requires up to 24 hours to dry; therefore, it should not be applied immediately prior to inclement weather. Application to roads, waterways and existing vegetation should be avoided. Erosion control mats, blankets, or nets are recommended to help stabilize steep slopes (generally 3:1 and steeper) and waterways. Depending on the product, these may be used alone or in conjunction with grass or straw mulch. Normally, use of these products will be restricted to relatively small areas. Biodegradable mats made of straw and jute, straw-coconut, coconut fiber, or excelsior can be used instead of mulch. (See the ECM/TRM Control Measure for more information.) Some tackifiers or binders may be used to anchor mulch. Check with the local jurisdiction for allowed tackifiers. Manufacturer's recommendations should be followed at all times. (See the Soil Binder Control Measure for more information on general types of tackifiers.) Rock can also be used as mulch. It provides protection of exposed soils to wind and water erosion and allows infiltration of precipitation. An aggregate base course can be spread on disturbed areas for temporary or permanent stabilization. The rock mulch layer should be thick enough to provide full coverage of exposed soil on the area it is applied.Maintenance and Removal After mulching, the bare ground surface should not be more than 10 percent exposed. Reapply mulch, as needed, to cover bare areas. Compost Blanket and Filter Berm (CB)EC-5 November 2010 Urban Drainage and Flood Control District CB-1 Urban Storm Drainage Criteria Manual Volume 3 Photograph CB-1. Application of a compost blanket to a disturbed area. Photo courtesy of Caltrans. Description A compost blanket is a layer of compost uniformly applied to the soil in disturbed areas to control erosion, facilitate revegetation, and retain sediment resulting from sheet-flow runoff. A compost filter berm is a dike of compost or a compost product that is placed perpendicular to runoff to control erosion in disturbed areas and retain sediment. Compost berms can be placed at regular intervals to help reduce the formation of rill and gully erosion when a compost blanket is stabilizing a slope. Appropriate Uses Compost blankets can be used as an alternative to erosion control blankets and mulching to help stabilize disturbed areas where sheet flow conditions are present. Compost blankets should not be used in areas of concentrated flows. Compost provides an excellent source of nutrients for plant growth, and should be considered for use in areas that will be permanently vegetated. Design and Installation See Detail CB-1 for design details and notes. Do not place compost in areas where it can easily be transported into drainage pathways or waterways. When using a compost blanket on a slope, berms should be installed periodically to reduce the potential for concentrated flow and rilling. Seeding should be completed before an area is composted or incorporated into the compost. Compost quality is an important consideration when selecting compost blankets or berms. Representative compost quality factors include pH, salinity, moisture content, organic matter content, stability (maturity), and physical contaminants. The compost should meet all local, state, and federal quality requirements. Biosolids compost must meet the Standards for Class A biosolids outlined in 40 CFR Part 503. The U.S. Composting Council (USCC) certifies compost products under its Seal of Testing Assurance (STA) Program. Compost producers whose products have been certified through the STA Program provide customers with a standard product label that allows comparison between compost products. Only STA certified, Class I compost should be used. Compost Blankets and Berms Functions Erosion Control Yes Sediment Control Moderate Site/Material Management No EC-5 Compost Blanket and Filter Berm (CB) CB-2 Urban Drainage and Flood Control District November 2010 Urban Storm Drainage Criteria Manual Volume 3 Maintenance and Removal When rills or gullies develop in an area that has been composted, fill and cover the area with additional compost and install berms as necessary to help reduce erosion. Weed control can be a maintenance challenge in areas using compost blankets. A weed control strategy may be necessary, including measures such as mechanical removal and spot application of targeted herbicides by licensed applicators. For compost berms, accumulated sediments should be removed from behind the berm when the sediments reach approximately one third the height of the berm. Areas that have been washed away should be replaced. If the berm has experienced significant or repeated washouts, a compost berm may not be the appropriate control measure for this area. Compost blankets and berms biodegrade and do not typically require removal following site stabilization. Compost Blanket and Filter Berm (CB)EC-5 November 2010 Urban Drainage and Flood Control District CB-3 Urban Storm Drainage Criteria Manual Volume 3 EC-5 Compost Blanket and Filter Berm (CB) CB-4 Urban Drainage and Flood Control District November 2010 Urban Storm Drainage Criteria Manual Volume 3 Rolled Erosion Control Products (RECP)EC-6 November 2010 Urban Drainage and Flood Control District RECP-1 Urban Storm Drainage Criteria Manual Volume 3 Photograph RECP-1. Erosion control blanket protecting the slope from erosion and providing favorable conditions for revegetation. Description Rolled Erosion Control Products (RECPs) include a variety of temporary or permanently installed manufactured products designed to control erosion and enhance vegetation establishment and survivability, particularly on slopes and in channels. For applications where natural vegetation alone will provide sufficient permanent erosion protection, temporary products such as netting, open weave textiles and a variety of erosion control blankets (ECBs) made of biodegradable natural materials (e.g., straw, coconut fiber) can be used. For applications where natural vegetation alone will not be sustainable under expected flow conditions, permanent rolled erosion control products such as turf reinforcement mats (TRMs) can be used. In particular, turf reinforcement mats are designed for discharges that exert velocities and sheer stresses that exceed the typical limits of mature natural vegetation. Appropriate Uses RECPs can be used to control erosion in conjunction with revegetation efforts, providing seedbed protection from wind and water erosion. These products are often used on disturbed areas on steep slopes, in areas with highly erosive soils, or as part of drainageway stabilization. In order to select the appropriate RECP for site conditions, it is important to have a general understanding of the general types of these products, their expected longevity, and general characteristics. The Erosion Control Technology Council (ECTC 2005) characterizes rolled erosion control products according to these categories: Mulch control netting: A planar woven natural fiber or extruded geosynthetic mesh used as a temporary degradable rolled erosion control product to anchor loose fiber mulches. Open weave textile: A temporary degradable rolled erosion control product composed of processed natural or polymer yarns woven into a matrix, used to provide erosion control and facilitate vegetation establishment. Erosion control blanket (ECB): A temporary degradable rolled erosion control product composed of processed natural or polymer fibers which are mechanically, structurally or chemically bound together to form a continuous matrix to provide erosion control and facilitate vegetation establishment. ECBs can be further differentiated into rapidly degrading single-net and double-net types or slowly degrading types. Rolled Erosion Control Products Functions Erosion Control Yes Sediment Control No Site/Material Management No EC-6 Rolled Erosion Control Products (RECP) RECP-2 Urban Drainage and Flood Control District November 2010 Urban Storm Drainage Criteria Manual Volume 3 Turf Reinforcement Mat (TRM): A rolled erosion control product composed of non-degradable synthetic fibers, filaments, nets, wire mesh, and/or other elements, processed into a permanent, three- dimensional matrix of sufficient thickness. TRMs, which may be supplemented with degradable components, are designed to impart immediate erosion protection, enhance vegetation establishment and provide long-term functionality by permanently reinforcing vegetation during and after maturation. Note: TRMs are typically used in hydraulic applications, such as high flow ditches and channels, steep slopes, stream banks, and shorelines, where erosive forces may exceed the limits of natural, unreinforced vegetation or in areas where limited vegetation establishment is anticipated. Tables RECP-1 and RECP-2 provide guidelines for selecting rolled erosion control products appropriate to site conditions and desired longevity. Table RECP-1 is for conditions where natural vegetation alone will provide permanent erosion control, whereas Table RECP-2 is for conditions where vegetation alone will not be adequately stable to provide long-term erosion protection due to flow or other conditions. Rolled Erosion Control Products (RECP)EC-6 November 2010 Urban Drainage and Flood Control District RECP-3 Urban Storm Drainage Criteria Manual Volume 3 Table RECP-1. ECTC Standard Specification for Temporary Rolled Erosion Control Products (Adapted from Erosion Control Technology Council 2005) Product Description Slope Applications* Channel Applications* Minimum Tensile Strength1 Expected Longevity Maximum Gradient C Factor2,5 Max. Shear Stress3,4,6 Mulch Control Nets 5:1 (H:V) ≤0.10 @ 5:1 0.25 lbs/ft2 (12 Pa) 5 lbs/ft (0.073 kN/m) Up to 12 months Netless Rolled Erosion Control Blankets 4:1 (H:V) ≤0.10 @ 4:1 0.5 lbs/ft2 (24 Pa) 5 lbs/ft (0.073 kN/m) Single-net Erosion Control Blankets & Open Weave Textiles 3:1 (H:V) ≤0.15 @ 3:1 1.5 lbs/ft2 (72 Pa) 50 lbs/ft (0.73 kN/m) Double-net Erosion Control Blankets 2:1 (H:V) ≤0.20 @ 2:1 1.75 lbs/ft2 (84 Pa) 75 lbs/ft (1.09 kN/m) Mulch Control Nets 5:1 (H:V) ≤0.10 @ 5:1 0.25 lbs/ft2 (12 Pa) 25 lbs/ft (0.36 kN/m) 24 months Erosion Control Blankets & Open Weave Textiles (slowly degrading) 1.5:1 (H:V) ≤0.25 @ 1.5:1 2.00 lbs/ft2 (96 Pa) 100 lbs/ft (1.45 kN/m) 24 months Erosion Control Blankets & Open Weave Textiles 1:1 (H:V) ≤0.25 @ 1:1 2.25 lbs/ft2 (108 Pa) 125 lbs/ft (1.82 kN/m) 36 months * C Factor and shear stress for mulch control nettings must be obtained with netting used in conjunction with pre-applied mulch material. (See Section 5.3 of Chapter 7 Construction BMPs for more information on the C Factor.) 1 Minimum Average Roll Values, Machine direction using ECTC Mod. ASTM D 5035. 2 C Factor calculated as ratio of soil loss from RECP protected slope (tested at specified or greater gradient, H:V) to ratio of soil loss from unprotected (control) plot in large-scale testing. 3 Required minimum shear stress RECP (unvegetated) can sustain without physical damage or excess erosion (> 12.7 mm (0.5 in) soil loss) during a 30-minute flow event in large-scale testing. 4 The permissible shear stress levels established for each performance category are based on historical experience with products characterized by Manning's roughness coefficients in the range of 0.01 - 0.05. 5 Acceptable large-scale test methods may include ASTM D 6459, or other independent testing deemed acceptable by the engineer. 6 Per the engineer’s discretion. Recommended acceptable large-scale testing protocol may include ASTM D 6460, or other independent testing deemed acceptable by the engineer. EC-6 Rolled Erosion Control Products (RECP) RECP-4 Urban Drainage and Flood Control District November 2010 Urban Storm Drainage Criteria Manual Volume 3 Table RECP-2. ECTC Standard Specification for Permanent1 Rolled Erosion Control Products (Adapted from: Erosion Control Technology Council 2005) Product Type Slope Applications Channel Applications TRMs with a minimum thickness of 0.25 inches (6.35 mm) per ASTM D 6525 and UV stability of 80% per ASTM D 4355 (500 hours exposure). Maximum Gradient Maximum Shear Stress4,5 Minimum Tensile Strength2,3 0.5:1 (H:V) 6.0 lbs/ft2 (288 Pa) 125 lbs/ft (1.82 kN/m) 0.5:1 (H:V) 8.0 lbs/ft2 (384 Pa) 150 lbs/ft (2.19 kN/m) 0.5:1 (H:V) 10.0 lbs/ft2 (480 Pa) 175 lbs/ft (2.55 kN/m) 1 For TRMs containing degradable components, all property values must be obtained on the non- degradable portion of the matting alone. 2 Minimum Average Roll Values, machine direction only for tensile strength determination using ASTM D 6818 (Supersedes Mod. ASTM D 5035 for RECPs) 3 Field conditions with high loading and/or high survivability requirements may warrant the use of a TRM with a tensile strength of 44 kN/m (3,000 lb/ft) or greater. 4 Required minimum shear stress TRM (fully vegetated) can sustain without physical damage or excess erosion (> 12.7 mm (0.5 in.) soil loss) during a 30-minute flow event in large scale testing. 5 Acceptable large-scale testing protocols may include ASTM D 6460, or other independent testing deemed acceptable by the engineer. Design and Installation RECPs should be installed according to manufacturer’s specifications and guidelines. Regardless of the type of product used, it is important to ensure no gaps or voids exist under the material and that all corners of the material are secured using stakes and trenching. Continuous contact between the product and the soil is necessary to avoid failure. Never use metal stakes to secure temporary erosion control products. Often wooden stakes are used to anchor RECPs; however, wood stakes may present installation and maintenance challenges and generally take a long time to biodegrade. Some local jurisdictions have had favorable experiences using biodegradable stakes. Rolled Erosion Control Products (RECP)EC-6 November 2010 Urban Drainage and Flood Control District RECP-5 Urban Storm Drainage Criteria Manual Volume 3 Staking patterns are also provided in the design details according to these factors: ECB type Slope or channel type For other types of RECPs including TRMs, these design details are intended to serve as general guidelines for design and installation; however, engineers should adhere to manufacturer’s installation recommendations. Maintenance and Removal Inspection of erosion control blankets and other RECPs includes: Check for general signs of erosion, including voids beneath the mat. If voids are apparent, fill the void with suitable soil and replace the erosion control blanket, following the appropriate staking pattern. Check for damaged or loose stakes and secure loose portions of the blanket. Erosion control blankets and other RECPs that are biodegradable typically do not need to be removed after construction. If they must be removed, then an alternate soil stabilization method should be installed promptly following removal. Turf reinforcement mats, although generally resistant to biodegradation, are typically left in place as a dense vegetated cover grows in through the mat matrix. The turf reinforcement mat provides long-term stability and helps the established vegetation resist erosive forces. EC-6 Rolled Erosion Control Products (RECP) RECP-6 Urban Drainage and Flood Control District November 2010 Urban Storm Drainage Criteria Manual Volume 3 Rolled Erosion Control Products (RECP)EC-6 November 2010 Urban Drainage and Flood Control District RECP-7 Urban Storm Drainage Criteria Manual Volume 3 EC-6 Rolled Erosion Control Products (RECP) RECP-8 Urban Drainage and Flood Control District November 2010 Urban Storm Drainage Criteria Manual Volume 3 Rolled Erosion Control Products (RECP)EC-6 November 2010 Urban Drainage and Flood Control District RECP-9 Urban Storm Drainage Criteria Manual Volume 3 Temporary Slope Drains (TSD)EC-7 November 2010 Urban Drainage and Flood Control District SD-1 Urban Storm Drainage Criteria Manual Volume 3 Photograph TSD-1. A temporary slope drain installed to convey runoff down a slope during construction. Photo courtesy of the City of Aurora. Description A temporary slope drain is a pipe or culvert used to convey water down a slope where there is a high potential for erosion. A drainage channel or swale at the top of the slope typically directs upgradient runoff to the pipe entrance for conveyance down the slope. The pipe outlet must be equipped with outlet protection. Appropriate Uses Use on long, steep slopes when there is a high potential of flow concentration or rill development. Design and Installation Effective use of temporary slope drains involves design of an effective collection system to direct flows to the pipe, proper sizing and anchoring of the pipe, and outlet protection. Upgradient of the temporary slope drain, a temporary drainage ditch or swale should be constructed to collect surface runoff from the drainage area and convey it to the drain entrance. The temporary slope drain must be sized to safely convey the desired flow volume. At a minimum, it should be sized to convey the 2-year, 24-hour storm. Temporary slope drains may be constructed of flexible or rigid pipe, riprap, or heavy (30 mil) plastic lining. When piping is used, it must be properly anchored by burying it with adequate cover or by using an anchor system to secure it to the ground. The discharge from the slope drain must be directed to a stabilized outlet, temporary or permanent channel, and/or sedimentation basin. See Detail TSD-1 for additional sizing and design information. Temporary Slope Drains Functions Erosion Control Yes Sediment Control No Site/Material Management No EC-7 Temporary Slope Drains (TSD) SD-2 Urban Drainage and Flood Control District November 2010 Urban Storm Drainage Criteria Manual Volume 3 Maintenance and Removal Inspect the entrance for sediment accumulation and remove, as needed. Clogging as a result of sediment deposition at the entrance can lead to ponding upstream causing flooding or overtopping of the slope drain. Inspect the downstream outlet for signs of erosion and stabilize, as needed. It may also be necessary to remove accumulated sediment at the outfall. Inspect pipe anchors to ensure that they are secure. If the pipe is secured by ground cover, ensure erosion has not compromised the depth of cover. Slope drains should be removed when no longer needed or just prior to installation of permanent slope stabilization measures that cannot be installed with the slope drain in place. When slope drains are removed, the disturbed areas should be covered with topsoil, seeded, mulched or otherwise stabilized as required by the local jurisdiction. Temporary Slope Drains (TSD)EC-7 November 2010 Urban Drainage and Flood Control District SD-3 Urban Storm Drainage Criteria Manual Volume 3 EC-7 Temporary Slope Drains (TSD) SD-4 Urban Drainage and Flood Control District November 2010 Urban Storm Drainage Criteria Manual Volume 3 RLC-1 A channel that is shaped or graded and protected with an erosion resistant rock riprap underlain with filter or bedding material used to convey stormwater runoff without allow- ing channel erosion. Rock channel protection provides for the safe conveyance of runoff from areas of concentrated flow without damage from erosion or flooding, where vegetated waterway / conveyance channel / swales would be inadequate. Rock lined channel may also be necessary to control seepage, piping, and sloughing or slides. The riprap section extends up the side slopes to designed depth. The earth above the rock should be vegetated or otherwise protected. This practice applies where the following conditions exist: • Concentrated runoff will cause erosion unless a liner is provided • Steep grades, wetness, seepage, prolonged base flow, or piping would cause erosion • Damage by vehicles or animals will make the establishment or maintenance of vegetation difficult • Soils are highly erosive or other soil or climatic conditions preclude the use of vegetation • Velocities are expected that will erode the channel or outlet without protection Caution should be used when design flow greater than 100 cubic feet per second (cfs) from a 10-yr.-frequency storm is expected. Chapter __ - Stream Channel Restoration, should be referenced for planning and design of larger channels. 4.3 Rock Lined Channel Description Conditions Where Practice Applies RLC-2 Planning Considerations Permits A construction permit may be required by the local government. Additionally, the U.S. Army Corps of Engineers and the Ohio Environmental Protection Agency, through Sections 404 and 401, respectively, of the Clean Water Act, may require a permit for rock lined channel / outlet that are located adjacent to a stream. It is best to contact your local Soil and Water Conservation District (SWCD) office to determine what both agencies’ permit requirements are for your project. Water Quality Rock lined channels and outlet protection provide water quality benefits by providing chan- nel stability, prevention of excessive erosion, and limiting subsequent downstream sedi- mentation. Runoff Runoff computation will be based upon the most severe soil and cover conditions that will exist in the area draining into the channel during the planned life of the structure. Use the NRCS Technical Release 55 (TR 55) or other suitable method shall be used to determine peak rate of runoff. Capacity The design capacity of the rock lined channel shall be adequate to carry the peak rate of runoff from a 10-yr. frequency storm. Where high-hazard conditions exist, higher fre- quency storms should be chosen to provide protection compatible with conditions. The rock-lined channel must have design capacity as required if it to be used as an outlet for a grassed waterway, diversion, terrace, or other measure. Capacity shall be computed using Manning’s Equation with a coefficient of roughness “n” listed in the “rock size” table below. Rock-lined channels / outlets shall be designed by accepted engineering methods such as the Federal Highway Administration Circular No. 15 or Figure 2-1 (Maximum depth of Flow for Riprap Lined Channels) that can be used to determine rock size using flow depth and velocity obtained from Manning’s equation. Procedures are also available in the NRCS Engineering Field Handbook. Velocity Design Flow Depth Maximum Velocity 0 - 0.5 ft 25 fps 0.5 – 1.0 ft 15 fps > 1.0 ft 10 fps Design Criteria Table 4.3.1 Maximum Design Velocity RLC-3 Cross Section Shape The cross sectional shape of rock lined waterway / outlets shall be parabolic, trapezoidal, or triangular. •Parabolic channels most closely approximate natural flow characteristics at low as well as high flows. Although generally preferred for esthetic reasons, design and construction procedures are more complex. •Trapezoidal channels often are used where the quantity of water to be carried is large and velocities high. The steepest permissible side slopes, horizontal to vertical, shall be 2 to 1. •Triangular shaped channels generally is used where the quantity of water to be handled is relatively small, such as roadside ditches. The steepest permissible side slopes, hori- zontal to vertical, shall be 2 to 1. Rock Lining The rock-lined channel shall consist of the rock riprap layer and an underlying filter or bed- ding. Minimum thickness of the rock riprap layer shall be the maximum stone size. Stone used for riprap shall be dense and hard enough to withstand exposure to air, water, freezing and thawing. Figure 4.3.2 gives the maximum depth of flow for riprap lined channels. Rock riprap must have a well-graded distribution and be placed in a to obtain a solid, compact layer of riprap. This may require some hand placing and tamping with construction equip- ment. Spreading gravel or soil over top of the placed riprap surface will fill the voids by interlocking the riprap together. Filter or Granular Bedding Filter or granular bedding must be placed beneath all riprap to prevent the underlying soil from eroding and undermining the riprap, and to collect seepage and base flow. Minimum bedding thickness shall be 4 inches. Use of large size riprap may necessitate the use of a thicker bedding layer or 2 differently sized bedding layers. Care should be taken to select a granular bedding that that is suitable with the subgrade material. Type of Rock or Riprap (ODOT)“n” value Size of Rock 50% by weight 85% by weight Type D .036 > 6 in.3 - 12 in. Type C .04 > 12 in.6 - 18 in. Type B .043 > 18 in.12 - 24 in. Type A .045 > 24 in.18 - 30 in. Figure 4.3.1 Table 4.3.2 Rock Riprap Size RLC-4 Adjustments to Naturalize Rock Lining In order to more closely reflect the nature of the bed of a natural channel, smaller size graded stone may be used to fill the voids left in typical riprap applications. Besides channel shape and pattern, typical rock lined channels depart from the flow behav- ior of natural channels by having to much pore space in the rock. Therefore regular flow is often entirely below the surface. This will be improved by extending the gradation of stone down to the gravel-sized material. This addition will increase velocity and reduce capacity slightly; therefore corresponding adjustments should be made. Geotextile Geotextile may be used as a filter to be placed beneath the riprap to prevent piping of the soil where wetness, seepage, or prolonged base flow is the reason for lining the channel with riprap. If design of the rock lined channel results in high velocities and steep grades, granular bedding should be used instead of geotextile. Care should be taken to prop- erly anchor the geotextile to prevent unraveling under flowing water. Geotextile shall be woven or nonwoven monofilament yarn and shall meet Class I criteria in the attached table “Requirements for Geotextile”. A maintenance program shall be established to maintain capacity, vegetative cover above the riprap, and associated structural components such as inlets, outlets, and tile lines. Items to consider in the maintenance program include: • Determine responsible party to inspect and maintain the channel after construction • Protect the channel from damage by equipment, traffic, or livestock • Fertilize the vegetated area annually to and maintain a vigorous stand of grass • Mow the vegetated area to maintain a healthy and vigorous stand of grass. • Repair damage to channels immediately. Missing riprap should be replaced as soon as possible. All broken subsurface drains should be repaired. Seed and mulch any bare areas that develop. • Remove sediment and debris that have accumulated. • Easements, or other means, should be obtained to ensure the channel is maintained as constructed Additional guidance for evaluation, planning, and design of rock lined channels is given in: • National Cooperative Highway Research Program Report 108 – Tentative Design Procedure for Riprap – Lined Channels • NRCS Ohio Practice Standard 468, Lined Waterway Or Outlet • NRCS Engineering Field Handbook, Chapter 6 - Structures • NRCS Design Note 24, Guide for Use of Geotextiles Maintenance References RLC-5 Property Test method Woven - Class I Nonwoven - Class I Tensile strength (pounds) 1/ASTM D 4632 grab test 200 minimum in any principal direction 180 minimum Elongation at failure (percent) 1/ASTM D 4632 grab test <50 ≥ 50 Puncture (pounds) 1/ASTM D 4833 90 minimum 80 minimum Ultraviolet light (% residual tensile strength) ASTM D 4355 150-hr exposure 70 minimum 70 minimum Apparent opening size (AOS)ASTM D 4751 As specified, but no smaller than 0.212 mm (#70) 2/ As specified max. #40 2/ Percent open area (percent)CWO-02215-86 4.0 minimum --------------- Permitivity sec-1 ASTM D 4491 0.10 minimum 0.70 minimum 1/ Minimum average roll value (weakest principal direction). 2/ U.S. standard sieve size. Note: CWO is a USACE reference. Table 4.3.3 Requirements for Geotextiles Figure 4.3.2 Maximum Depth of Flow for Riprap Lined Channels This chart is valid only if condition 1) and 2) are satisfied: 1) Side slopes 3:1 or flat or Side slopes 2;1 or flatter and a bottom width to depth ratio (BW/d) greater than 3. 2) Straight channel or Curved channel, where curve radius divided by bottom width (Rc/BW) is greater than 9. Equation: d(50) = (62.4lb/cu.ft.)*d*S/4 Where: d = max. depth of flow, ft S = channel slope, ft/ft Adapted from Highway Research Board Report 108 RLC-6 1. Subgrade for the filter and riprap shall be prepared to the required lines and grades as shown on the plan. The subgrade shall be cleared of all trees, stumps, roots, sod, loose rock, or other material. 2. Riprap shall conform to the grading limits as shown on the plan. 3. No abrupt deviations from the design grade or horizontal alignment shall be permitted. 4. Geotextile shall be securely anchored according to manufacturers recommendations. 5. Geotextile shall be laid with the long dimension parallel to the direction of flow and shall be laid loosely but without wrinkles and creases. Where joints are necessary, strips shall be placed to provide a 12-in. minimum overlap, with the upstream strip overlapping the downstream strip. 6. Gravel bedding shall be ODOT No. 67’s or 57’s unless shown differently on the drawings. 7. Riprap may be placed by equipment but shall be placed in a manner to prevent slippage or damage to the geotextile. 8. Riprap shall be placed by a method that does not cause segregation of sizes. Extensive pushing with a dozer causes segregation and shall be avoided by delivering riprap near its final location within the channel. 9. Construction shall be sequenced so that riprap channel protection is placed and functional without delays when the channel becomes operational. 10.All disturbed areas will be vegetated as soon as practical. Specifications for Rock Lined Channel Rough Cut Street Control (RCS)EC-9 November 2010 Urban Drainage and Flood Control District RCS-1 Urban Storm Drainage Criteria Manual Volume 3 Photograph RCS-1. Rough cut street controls. Description Rough cut street controls are rock or earthen berms placed along dirt roadways that are under construction or used for construction access. These temporary berms intercept sheet flow and divert runoff from the roadway, and control erosion by minimizing concentration of flow and reducing runoff velocity. Appropriate Uses Appropriate uses include: Temporary dirt construction roadways that have not received roadbase. Roadways under construction that will not be paved within 14 days of final grading, and that have not yet received roadbase. Design and Installation Rough cut street controls are designed to redirect sheet flow off the dirt roadway to prevent water from concentrating and eroding the soil. These controls consist of runoff barriers that are constructed at intervals along the road. These barriers are installed perpendicular to the longitudinal slope from the outer edge of the roadside swale to the crown of the road. The barriers are positioned alternately from the right and left side of the road to allow construction traffic to pass in the lane not barred. If construction traffic is expected to be congested and a vehicle tracking control has been constructed, rough-cut street controls may be omitted for 400 feet from the entrance. Runoff from the controls should be directed to another stormwater control measure such as a roadside swale with check dams once removed from the roadway. See Detail RCS-1 for additional information. Maintenance and Removal Inspect street controls for erosion and stability. If rills are forming in the roadway or cutting through the control berms, place the street controls at shorter intervals. If earthen berms are used, periodic recompaction may be necessary. When rock berms are used, t Rough Cut Street Control repair and/or replace as necessary when damaged. Stree controls may be removed 14 days prior to road surfacing and paving. Functions Erosion Control Yes Sediment Control Moderate Site/Material Management No EC-9 Rough Cut Street Control (RCS) RCS-2 Urban Drainage and Flood Control District November 2010 Urban Storm Drainage Criteria Manual Volume 3 Rough Cut Street Control (RCS)EC-9 November 2010 Urban Drainage and Flood Control District RCS-3 Urban Storm Drainage Criteria Manual Volume 3 Earth Dikes and Drainage Swales (ED/DS) EC-10 November 2010 Urban Drainage and Flood Control District ED/DS-1 Urban Storm Drainage Criteria Manual Volume 3 Photograph ED/DS-1. Example of an earth dike used to divert flows at a construction site. Photo courtesy of CDOT. Description Earth dikes and drainage swales are temporary storm conveyance channels constructed either to divert runoff around slopes or to convey runoff to additional sediment control measures prior to discharge of runoff from a site. Drainage swales may be lined or unlined, but if an unlined swale is used, it must be well compacted and capable of resisting erosive velocities. Appropriate Uses Earth dikes and drainage swales are typically used to control the flow path of runoff at a construction site by diverting runoff around areas prone to erosion, such as steep slopes. Earth dikes and drainage swales may also be constructed as temporary conveyance features. This will direct runoff to additional sediment control treatment control measures, such as sediment traps or basins. Design and Installation When earth dikes are used to divert water for slope protection, the earth dike typically consists of a horizontal ridge of soil placed perpendicular to the slope and angled slightly to provide drainage along the contour. The dike is used in conjunction with a swale or a small channel upslope of the berm to convey the diverted water. Temporary diversion dikes can be constructed by excavation of a V-shaped trench or ditch and placement of the fill on the downslope side of the cut. There are two types of placement for temporary slope diversion dikes: A dike located at the top of a slope to divert upland runoff away from the disturbed area and convey it in a temporary or permanent channel. A diversion dike located at the base or mid-slope of a disturbed area to intercept runoff and reduce the effective slope length. Depending on the project, either an earth dike or drainage swale may be more appropriate. If there is a need for cut on the project, then an excavated drainage swale may be better suited. When the project is primarily fill, then a conveyance constructed using a berm may be the better option. All dikes or swales receiving runoff from a disturbed area should direct stormwater to a sediment control measure such as a sediment trap or basin. Earth Dikes and Drainage Swales Functions Erosion Control Yes Sediment Control Moderate Site/Material Management No EC-10 Earth Dikes and Drainage Swales (ED/DS) ED/DS-2 Urban Drainage and Flood Control District November 2010 Urban Storm Drainage Criteria Manual Volume 3 Unlined dikes or swales should only be used for intercepting sheet flow runoff and are not intended for diversion of concentrated flows. Details with notes are provided for several design variations, including: ED-1. Unlined Earth Dike formed by Berm DS-1. Unlined Excavated Swale DS-2. Unlined Swale Formed by Cut and Fill DS-3. ECB-lined Swale DS-4. Synthetic-lined Swale DS-5. Riprap-lined Swale The details also include guidance on permissible velocities for cohesive channels if unlined approaches will be used. Maintenance and Removal Inspect earth dikes for stability, compaction, and signs of erosion and repair. Inspect side slopes for erosion and damage to erosion control fabric. Stabilize slopes and repair fabric as necessary. If there is reoccurring extensive damage, consider installing rock check dams or lining the channel with riprap. If drainage swales are not permanent, remove dikes and fill channels when the upstream area is stabilized. Stabilize the fill or disturbed area immediately following removal by revegetation or other permanent stabilization method approved by the local jurisdiction. Earth Dikes and Drainage Swales (ED/DS) EC-10 November 2010 Urban Drainage and Flood Control District ED/DS-3 Urban Storm Drainage Criteria Manual Volume 3 EC-10 Earth Dikes and Drainage Swales (ED/DS) ED/DS-4 Urban Drainage and Flood Control District November 2010 Urban Storm Drainage Criteria Manual Volume 3 Earth Dikes and Drainage Swales (ED/DS) EC-10 November 2010 Urban Drainage and Flood Control District ED/DS-5 Urban Storm Drainage Criteria Manual Volume 3 Terracing (TER)EC-11 November 2010 Urban Drainage and Flood Control District TER-1 Urban Storm Drainage Criteria Manual Volume 3 Photograph TER-1. Use of a terrace to reduce erosion by controlling slope length on a long, steep slope. Photo courtesy of Douglas County. Description Terracing involves grading steep slopes into a series of relatively flat sections, or terraces, separated at intervals by steep slope segments. Terraces shorten the uninterrupted flow lengths on steep slopes, helping to reduce the development of rills and gullies. Retaining walls, gabions, cribbing, deadman anchors, rock-filled slope mattresses, and other types of soil retention systems can be used in terracing. Appropriate Uses Terracing techniques are most typically used to control erosion on slopes that are steeper than 4:1. Design and Installation Design details with notes are provided in Detail TER-1. The type, number, and spacing of terraces will depend on the slope, slope length, and other factors. The Revised Universal Soil Loss Equation (RUSLE) may be helpful in determining spacing of terraces on slopes. Terracing should be used in combination with other stabilization measures that provide cover for exposed soils such as mulching, seeding, surface roughening, or other measures. Maintenance and Removal Repair rill erosion on slopes and remove accumulated sediment, as needed. Terracing may be temporary or permanent. If terracing is temporary, the slope should be topsoiled, seeded, and mulched when the slope is graded to its final configuration and terraces are removed. Due to the steepness of the slope, once terraces are graded, erosion control blankets or other stabilization measures are typically required. If terraces are permanent, vegetation should be established on slopes and terraces as soon as practical. Terracing Functions Erosion Control Yes Sediment Control Moderate Site/Material Management No EC-11 Terracing (TER) TER-2 Urban Drainage and Flood Control District November 2010 Urban Storm Drainage Criteria Manual Volume 3 3 (3/2012) Check dams should be installed closely enough to one another to sufficiently slow the flow of water to prevent both damage to the dams and passage of the water under or around them. The steeper the slope, the more closely the dams will need to be spaced. If the dams are proving insufficient for the flow, more of them may need to be installed. Ideally, the top of one dam would be level with the toe of the next upstream dam. 3 (3/2012) 3 (3/2012) 3 (3/2012) 4" to 7" weir depth (approximately) Derived from: *This design may be scaled up for a bigger ditch or swale. Derived from: Virginia Soil and Water Conservation Commission, 1989 ROCK CHECK DAM 2:1 or flatterFlow 1' (approx.), or height of ditch 3 (3/2012) Streambank Stabilization (SS)EC-13 November 2010 Urban Drainage and Flood Control District SS-1 Urban Storm Drainage Criteria Manual Volume 3 Photograph SS-1. Streambank stabilization using geotextiles following installation of a permanent in-stream grade control structure. Description Streambank stabilization involves a combination of erosion and sediment control practices to protect streams, banks, and in-stream habitat from accelerated erosion. Control measures associated with streambank stabilization may include protection of existing vegetation, check dams/grade control, temporary and permanent seeding, outlet protection, rolled erosion control products, temporary diversions, dewatering operations and bioengineering practices such as brush layering, live staking and fascines. Appropriate Uses Streambank stabilization may be a construction activity in and of itself, or it may be in conjunction with a broader construction project that discharges to a waterway that is susceptible to accelerated erosion due to increases in the rate and volume of stormwater runoff. Depending on the health of the stream, water quality sampling and testing may be advisable prior to and/or during construction to evaluate health and stability of the stream and potential effects from adjacent construction activities. Design and Installation Streambank stabilization consists of protecting the stream in a variety of ways to minimize negative effects to the stream environment. The following lists the minimum requirements necessary for construction streambank stabilization: Protect existing vegetation along the stream bank in accordance with the Vegetated Buffers and Protection of Existing Vegetation Fact Sheets. Preserving a riparian buffer along the streambank will help to remove sediment and decrease runoff rates from the disturbed area. Outside the riparian buffer, provide sediment control in the form of a silt fence or equivalent sediment control practice along the entire length of the stream that will receive runoff from the area of disturbance. In some cases, a double-layered perimeter control may be justified adjacent to sensitive receiving waters and wetlands to provide additional protection. Stabilize all areas that will be draining to the stream. Use rolled erosion control products, temporary or permanent seeding, or other appropriate measures. Ensure all point discharges entering the stream are adequately armored with a velocity dissipation device and appropriate outlet protection. See individual design details and notes for the various control measures referenced in this practice. Additional information on bioengineering techniques for stream stabilization can be Streambank Stabilization Functions Erosion Control Yes Sediment Control No Site/Material Management No EC-13 Streambank Stabilization (SS) SS-2 Urban Drainage and Flood Control District November 2010 Urban Storm Drainage Criteria Manual Volume 3 found in the Major Drainage chapter of Volume 1 and additional guidance on control measures for working in waterways can be found in UDFCD’s Best Management Practices for Construction in Waterways Training Manual. Maintenance and Removal Inspect control measures protecting the stream for damage on a daily basis. Maintain, repair, or replace damaged control measures following the guidance provided in individual Control Measure Fact Sheets for practices that are implemented. Some stream bank stabilization control measures are intended to remain in place as vegetation matures (e.g. erosion control blankets protecting seeded stream banks and turf reinforcement mats). For control measures that are not to remain in place as a part of final stabilization such as silt fence and other temporary measures, control measures should be removed when all land disturbing activities have ceased and areas have been permanently stabilized. Wind Erosion/Dust Control (DC) EC-14 November 2010 Urban Drainage and Flood Control District DC-1 Urban Storm Drainage Criteria Manual Volume 3 Photograph DC-1. Water truck used for dust suppression. Photo courtesy of Douglas County. Description Wind erosion and dust control control measures help to keep soil particles from entering the air as a result of land disturbing construction activities. These control measures include a variety of practices generally focused on either graded disturbed areas or construction roadways. For graded areas, practices such as seeding and mulching, use of soil binders, site watering, or other practices that provide prompt surface cover should be used. For construction roadways, road watering and stabilized surfaces should be considered. Appropriate Uses Dust control measures should be used on any site where dust poses a problem to air quality. Dust control is important to control for the health of construction workers and surrounding waterbodies. Design and Installation The following construction control measures can be used for dust control: An irrigation/sprinkler system can be used to wet the top layer of disturbed soil to help keep dry soil particles from becoming airborne. Seeding and mulching can be used to stabilize disturbed surfaces and reduce dust emissions. Protecting existing vegetation can help to slow wind velocities across the ground surface, thereby limiting the likelihood of soil particles to become airborne. Spray-on soil binders form a bond between soil particles keeping them grounded. Chemical treatments may require additional permitting requirements. Potential impacts to surrounding waterways and habitat must be considered prior to use. Placing rock on construction roadways and entrances will help keep dust to a minimum across the construction site. Wind fences can be installed on site to reduce wind speeds. Install fences perpendicular to the prevailing wind direction for maximum effectiveness. Maintenance and Removal When using an irrigation/sprinkler control system to aid in dust control, be careful not to overwater. Overwatering will cause construction vehicles to track mud off-site. Wind Erosion Control/ Dust Control Functions Erosion Control Yes Sediment Control No Site/Material Management Moderate