Laserfiche WebLink
CITY OP EVERETT STORMWATER MANAGEMENT MANUAL <br /> 3.2.7 BMP C120: Temporary and Pertnanent Seeding ' <br /> Purpose <br /> Seeding is intended to reduce erosion by stabilizicg exposed soils. A well-cstablished vegetative co�er is <br /> one of the most effec4ve methods of reducing erosion. <br /> Conditions of Use # <br /> L Seeding may be used thrcughout the project on disturbed areas thzt have reached 6nal grade or <br /> that will remain unworked for more than 30 days. . <br /> 2. Channels that will be vegetated s6ould be instalied beCore major earthwork and hydrosceded with <br /> a Bonded Fiber Mahix. The vegetation should be well established(i.e.,75 percent cover)bcfore <br /> watet is allowed to flow in the ditch. With channels that will have high Flows,erosion convol <br /> blankets should be installed over the hydroseed. [f vegetation cannot be established from seed <br /> before water is allowed in thc ditch,sod should be iastalled in the botlom of t6e ditch ovcr <br /> hydromulch and blankets. <br /> 3. Retention/detention ponds should bc seeded as requ'vcd. <br /> 4. Mulch is requuad at all times because it protects seeds Gam heat,moishuc loss,and transport due <br /> to cunoff. <br /> S. All disturbed areas shall be reviewcd in lete August lo early September and all secding should be <br /> completed by the end of September. Othenvise,vegetation will not establish itsclf enough to <br /> provide more than average protection. <br /> 6. At final site stabilization,all disturbed amas not othewise vegetated or stabilized shall be secded <br /> and mulched. Final stabili�ation mcans the completion of all soil disturbing activities at the site <br /> and the rstablishment of a pem�anent vegetative covcr,or equivalent permaneut stabilization <br /> mcasures(such as pavement,riprap,gabions or,geotextiles)which will prevent erosion. <br /> Design and/nstallation Specifications <br /> I. Seeding s6ould be done during those seasons most conducive ro growth and will vary wit�the <br /> climate conditians of t6c regiun. Local experience should bc used to detemtinc the appropnate <br /> seeding periods. <br /> 2. T'he optimum sceding windows for westem Washington aze April I thmugh June 30 and <br /> September I through October 1. Seeding that occurs between July l and August 30 will require <br /> irtigation until 75 percent grass cover is established. Secding that occurs between October I and <br /> March 30 will require a mulch or plastic cover until 75 percent grass covcr is cstablished. <br /> 3. 'Co prevent seed from beiog washed away,confirtn lhat all required surfacc water wNrol <br /> measures have been installcd. <br /> 4. 'Chc scedbed should be finn and rough. All soil should bc roughened no roaner what the slopc. IF <br /> compaction is required for eogineering purposes,slopes must bc track walked before seeding. <br /> Back-blading or smoothing of slopes grcater than 4:1 is not allowed if thcy arc to bc seeded. <br /> 5. Ncw and moro effective restoratioo•based landscape practiccs rcty on deeper incotporation than <br /> that provided by a simQle single-pass rototilling treatmenL Wherever practical the subgrade � <br /> should be initially ripped to improve long-tertn permeability,infilRation,and water inflow <br /> qualities. At a minimum,pertnanent areas shall use soil amendments to achieve organic maner �I <br /> and pertneability perfortnancc defined in engineered soiVlandscape systems. For systems that are <br /> deeper than 8 inches ttie rototilling process should be done in multiple lifts,or the prepar^.d soil <br /> system shall be prepued properly and then placed to achieve the specificd depth. <br /> Volume ll—Construcfion Stwmwater Pollution Prevention <br /> 3-9 <br />