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Home My WebLink AboutR-394409I- W 5 W U Q J n W C0 Q J U) H a J a Z _O (D W Z O U (D Z_ V 6 J W I) J O Z O U Z O (n O LL1 E SE 1/4 ,SECTION 26, TOWNSHIP 23N, RANGE 4 E, W.M. EROSION CONTROL DETAILS -II D.2.1 ESC MEASURES D.2.1.2.6 TEMPORARY AND PERMANENT SEEDING Code: SE Symbol: � SE Purpose Seeding is intended to reduce erosion by stabilizing exposed soils. A well -established vegetative cover is one of the most effective methods of reducing erosion. Conditions of Use I . Seeding shall be used throughout the project on disturbed areas that have reached final grade or that will remain unworked for more than 30 days. 2. Vegetation -lined channels shall be seeded. Channels that will be vegetated should be installed before major earthwork and hydroseeded or covered with a Bonded Fiber Matrix (BFM). 3. Retention/detention ponds shall be seeded as required. 4. At the City's discretion, seeding without mulch during the dry season is allowed even though it will take more than seven days to develop an effective cover. Mulch is, however, recommended at all times because it protects seeds from heat, moisture loss, and transport due to runoff. 5. Prior to the beginning of the wet season, all disturbed areas shall be reviewed to identify which ones can be seeded in preparation for the winter rains (see Section D.2.4.2). Disturbed areas shall be seeded within one week of the beginning of the wet season. A sketch map of those areas to be seeded and those areas to remain uncovered shall be submitted to the CED inspector. The CED inspector may require seeding of additional areas in order to protect surface waters, adjacent properties, or drainage facilities. 6. At final site stabilization, all disturbed areas not otherwise vegetated or stabilized shall be seeded and mulched (see Section D.2.4.5). Design and Installation Specifications 1. The best time to seed is fall (late September to October) or in spring (mid -March to June). Irrigation is required during the first summer following installation if seeding occurs in spring or summer or during prolonged dry times of year. Areas may also be seeded during the winter months, but it may take additional spring seeding applications to develop a dense groundcover due to cold temperatures. The application and maintenance of mulch is critical for winter seeding. 2. To prevent seed from being washed away, confirm that all required surface water control measures have been installed. 3. The seedbed should not be compacted because soils that are well compacted will not vegetate as quickly or thoroughly. Slopes steeper than 3H:1 V shall be surface roughened. Roughening can be accomplished in a variety of ways, but the typical method is track walking, or driving a crawling tractor up and down the slope, leaving cleat imprints parallel to the slope contours. 4. In general, 10-20-20 N-P-K (nitrogen -phosphorus -potassium) fertilizer may be used at a rate of 90 pounds per acre. Slow -release fertilizers are preferred because they are more efficient and have fewer environmental impacts. It is recommended that areas being seeded for final landscaping conduct soil tests to determine the exact type and quantity of fertilizer needed. This will prevent the over - application of fertilizer. Disturbed areas within 200 feet of water bodies and wetlands must use slow - release low -phosphorus fertilizer (typical proportions 3-1-2 N-P-K). 5. The following requirements apply to mulching: a) Mulch is always required for seeding slopes greater than 3H:1 V (see Section D.2.1.2.2). b) If seeding during the wet season, mulch is required. c) The use of mulch may be required during the dry season at the City's discretion if grass growth is expected to be slow, the soils are highly erodible due to soil type or gradient, there is a water body close to the disturbed area, or significant precipitation (see Section D.2.4.2) is anticipated before the grass will provide effective cover. d) Mulch may be applied on top of the seed or simultaneously by hydroseeding. 6. Hydroseeding is allowed as long as tackifier is included. Hydroseeding with wood fiber mulch is adequate during the dry season. Application of hydroseeded wood fiber mulch should be appropriate for slope angle. Follow manufacturer specifications for application rates. 7. Areas to be permanently landscaped shall use soil amendments. Good quality topsoil shall be tilled into the top six inches to reduce the need for fertilizer and improve the overall soil quality. Most native soils will require the addition of four inches of well -rotted compost to be tilled into the soil to provide a good quality topsoil. Compost used should meet specifications provided in Reference Section 11-C of the SWDM. 8. The seed mixes listed below include recommended mixes for both temporary and permanent seeding. These mixes, with the exception of the wetland mix, shall be applied at a rate of 80 to 100 seeds per square foot. Wet sites should apply 120 to 150 seeds per square foot. Local suppliers should be consulted for information on current Pure Live Seed (PLS) rates and species specific seeds per pound in order to determine seed mix PLS pounds of seed per acre. The appropriate mix depends on a variety of factors, including exposure, soil type, slope, and expected foot traffic. Alternative seed mixes approved by the City may be used. Table D.2.1.2.13 presents the standard mix for those areas where t a temporary or permanent vegetative cover is required. The following mix assumes a desired 150 seeds per square foot and should be applied at approximately 37 pounds of pure live seed per acre. TABLE. D.2.1.2.11 EROSION CONTROL. SEED MIX Common Name/Latin Name % Species Composition Desired Seeds per Square Foot PLS Pounds/Acre Spike bentgrass/Agrostis exarata 6 9 0.1 California brome/Bromus carinatus 15 23 9.8 Tufted hairgrass/Deschampsia cespitosa 15 23 0.4 Blue wildrye/E/ymus glaucus 18 27 10.7 California oatgrass/Danthonia californica 18 27 5.6 Native red fescue/Festuca rubra var. rubra 18 27 2.4 Meadow barley/Hordeum brachyantherum 1 10 15 7.7 Table D.2.1.2.0 provides just one recommended possibility for landscaping seed. It assumes a desired 100 seeds per square foot and should be applied at 12 pounds of pure live seed per acre. F_ TABLE D.2.1.2.0 LANDSCAPING SEED MIX Common Name/Latin Name % Species Composition Desired Seeds per Square Foot PLS Pounds/Acre Sideoats grama/Bouteloua curtipendula 20 30 6.8 California oatgrass/Danthonia californica 20 30 6.2 Native red fescue/Festuca rubra var, rubra 30 45 3.9 Prairie junegrass/Koe/eria macrantha 30 45 0.8 The meadow seed mix in Table D.2.1.2.G is recommended for areas that will be maintained infrequently or not at all and where colonization by native plants is desirable. Likely applications include rural road and utility right-of-way. Seeding should take place in September or very early October in order to obtain adequate establishment prior to the winter months. This seed mix assumes a target goal of 120 seeds per square foot and an application rate of 23 pounds of pure live seed per acre. TABLE D.2.1.2.G MEADOVI' SEED MIX Common Name/Latin Name % Species Composition Desired Seeds per Square Foot PLS Pounds/Acre Common yarrow/Achillea millefolium 4 5 0.1 Pearly eve rlastin /Ana halis mar artacae 1 1 0.0 California bromelBromus carinatus 15 18 7.8 California oat rass/Danthonia californica 15 18 3.7 Blue wildrye/Elymus glaucus 16 19 7.6 Festuca idahoensis 15 18 1.7 Native red fescue/Festuca rubra var. rubra 18 22 1.9 Sickle keeled lu inelLu inus albicaulis 1 1 2.2 Fowl blue rass/Poa palustris 15 1 18 1 0.4 Maintenance Standards for Temporary and Permanent Seeding 1. Any seeded areas that fail to establish at least 80 percent cover within one month shall be reseeded. If reseeding is ineffective, an alternate method, such as sodding or nets/blankets, shall be used. If winter weather prevents adequate seed establishment and growth, this time limit may be relaxed at the discretion of the City when critical areas would otherwise be protected. 2. After adequate cover is achieved, any areas that experience erosion shall be re -seeded and protected by mulch. If the erosion problem is drainage related, the problem shall be fixed and the eroded area re- seeded and protected by mulch. 3. Seeded areas shall be supplied with adequate moisture, but not watered to the extent that it causes runoff. KT`�TEIVIPORARY AND PERMANENT SEEDING C5i APPENDIX D, D.2.1.2.6 OF 2017 CITY OF RENTON SURFACE WATER DESIGN MANUAL SURVEYED: SCALE: AALA HORIZONTAL: NAD 19 3/1991 DESIGNED: AS NOTED GXLE DRAWN: SGR ONE INCH DATUM CHECKED: AGC AT FULL SCALE IF NOT ONE INCH NO. REVISION BY DATE AP P R APPROVED:AGC SCALE ACCORDINGLY CITY OF P"RI RENTON Planning/Building/Public Works Dept ff A O CV CV CV 0 A CALL BEFORE YOU DIG Call: TOLL FREE -800-424-5555 IN COMPLIANCE WITH CITY OF RENTON STANDARDS SURFACE WATER UTILITY U rstraka 11 /29/2018 111411130 WICDAVID EVANS ANDASSOCIATES INC. 14432 SE Eastgate Way, Suite 400 Bellevue Washington 98007 DEVELOPMENT ENGINEERING a rnair 11 /30/2018 %J KING COUNTY REGIONAL DATE. 1/3/2018 AFIS LAB REPLACEMENT FIELDBOOK: PAGE: EROSION CONTROL C5.3 DETAILS -II SHEET:10 OF:135 R-399409 co CD CD CD 06 U N co CD CD CD T Q J 00 CD CD CD I ti T ri1 I- Z W 5 W U Q J a_ Q J _W H a J Z O LL1 0 (D Z Y