819 N BROADWAY WASHINGTON STATE UNIVERSITY 2018-05-11

Table 4.7 Mulch Standards and Guidelines Mulch Application Material Quality Standards Rates Remarks Straw Air-dried;free from 2"-3"thick;5 Cost-effective protection when applied with adequate undesirable seed and bales per 1000 sf thickness. Hand-application generally requires greater coarse material. or 2-3 tons per thickness than blown straw.The thickness of straw may be acre reduced by half when used in conjunction with seeding. In windy areas straw must be held in place by crimping,using a tackifier,or covering with netting. Blown straw always has to be held in place with a tackifier as even light winds will blow it away.Straw,however,has several deficiencies that should be considered when selecting mulch materials.It often introduces and/or encourages the propagation of weed species and it has no significant long-term benefits. Straw should be used only if mulches with long-term benefits are unavailable locally. It should also not be used within the ordinary high-water elevation of surface waters(due to flotation). Hydromulch No growth Approx.25-30 Shall be applied with hydromulcher. Shall not be used inhibiting factors. lbs per 1000 sf without seed and tackifier unless the application rate is at or 1500 -2000 least doubled. Fibers longer than about 3/a-1 inch clog lbs per acre hydromulch equipment. Fibers should be kept to less than% inch. Composted No visible water or 2"thick min.; More effective control can be obtained by increasing Mulch and dust during approx. 100 tons thickness to 3". Excellent mulch for protecting final grades Compost handling. Must be per acre(approx. until landscaping because it can be directly seeded or tilled purchased from 800 lbs per yard) into soil as an amendment. Composted mulch has a coarser supplier with Solid size gradation than compost.It is more stable and practical Waste Handling to use in wet areas and during rainy weather conditions. Permit(unless exempt). Chipped Site Average size shall 2"minimum This is a cost-effective way to dispose of debris from Vegetation be several inches. thickness clearing and grubbing,and it eliminates the problems Gradations from associated with burning. Generally,it should not be used on fines to 6 inches in slopes above approx. 10%because of its tendency to be length for texture, transported by runoff. It is not recommended within 200 variation,and feet of surface waters. If seeding is expected shortly after interlocking mulch,the decomposition of the chipped vegetation may tie properties. up nutrients important to grass establishment. Wood-based No visible water or 2"thick;approx. This material is often called"hog or hogged fuel." It is Mulch dust during 100 tons per acre usable as a material for Stabilized Construction Entrances handling. Must be (approx.800 lbs. (BMP C105)and as a mulch. The use of mulch ultimately purchased from a per cubic yard) improves the organic matter in the soil. Special caution is supplier with a Solid advised regarding the source and composition of wood- Waste Handling based mulches. Its preparation typically does not provide Permit or one any weed seed control,so evidence of residual vegetation in exempt from solid its composition or known inclusion of weed plants or seeds waste regulations. should be monitored and prevented(or minimized). I February 2005 Volume II— Construction Stormwater Pollution Prevention 4-21