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Table 11-3.6: Mulch Standards and Guidelines <br />Mulch Mater- <br />Guideline <br />Description <br />ial <br />Quality <br />Air-dried; free from undesirable seed and coarse matedai. <br />Standards <br />Application <br />2"-3" thick; 5 bales per 1,000 sf or 2-3 tons per acre <br />Rates <br />Cost-effective protection when applied with adequate thickness. Hand - <br />application generally requires greater thickness than blown straw. The <br />thickness of straw may be reduced by half when used in conjunction with <br />Straw <br />seeding. In windy areas straw must be held in place by crimping, using a <br />tackifier, or covering with netting. Blown straw always has to be held in <br />Remarks <br />place with a tackifier as even light winds will blow it away. Straw, however, <br />has several deficiencies that should be considered when selecting mulch <br />materials. It often introduces and/or encourages the propagation of weed <br />species and it has no significant long-term benefits It should also not be <br />used within the ordinary high-water elevation of surface waters (due to flot- <br />ation). <br />Quality <br />No growth inhibiting factors. <br />Standards <br />Application <br />Approx. 35-45 Ibs per 1,000 sf or 1,500 - 2,000 Ibs per acre <br />Hydromulch <br />Rates <br />Shall be applied with hydromulcher. Shall not be used without seed and <br />Remarks <br />tackifier unless the application rate is at least doubled. Fibers longer than <br />about 3/4 - 1 inch clog hydromulch equipment. Fibers should be kept to less <br />than 3/4 inch. <br />Quality <br />No visible water or dust during handling. Must be produced per WAC 173- <br />Standards <br />350, Solid Waste Handling Standards, but may have up to 35% biosolids. <br />Application <br />2" thick min.; approx. 100 tons per acre (approx. 750 Ibs per cubic yard) <br />Rates <br />More effective control can be obtained by increasing thickness to 3". Excel - <br />Compost <br />lent mulch for protecting final grades until landscaping because it can be dir- <br />ectly seeded or tilled into soil as an amendment. Compost used for mulch <br />Remarks <br />has a coarser size gradation than compost used for BMP C 125- Topsoiling <br />/ Composting or BMP T5.13: Post -Construction Soil Quality and Depth. It <br />is more stable and practical to use in wet areas and during rainy weather <br />conditions. Do not use near wetlands or near phosphorous impaired water <br />bodies. <br />Quality <br />Gradations from fines to 6 inches in length for texture, variation, and inter - <br />Chipped <br />Standards <br />locking properties. Include a mix of various sizes so that the average size <br />Site Veget- <br />is between 2- and 4- inches. <br />ation <br />Application <br />Rates; <br />2" thick min. <br />2019 Stormwater Management Manual for Western Washington <br />Volume 11 - Chapter 3 - Page 291 <br />