11517 AIRPORT RD 2025-07-24 - Laserfiche WebLink

• CITY OF EVERETT STORMWATER MANAGEMENT MANUAL Table 12.1 Estimating Soil Depth and Height Changes. Relative Elevation Procedure Calculation Inches Beginning Elevation 0 Rototill soil to a depth of 6 inches and Depth achieved by machinery x fluff +2.4 assuming 1.4-inch fluff factor factor of soil: (6 x 1.4) = 8.4 8.4—6 =2.4 Add compost, 2 units soil to 1 unit compost, Depth of soil+2: +4.2 by loose volume 8.4 +2 =4.2 Filling of pore spaces Depth of loose soil x percentage of -1.3 pore space filled by compost addition: 8.4 x (-.15) =-1.3 Rototill compost into soil and roll site to (Amended soil depth =compression -2.1 compact soil, assuming compression factor factor)—amended soil depth: of 1.2 Resulting Elevation Change Sum +3.2 Compost Quality • Compost shall be prepared by the controlled decomposition of organic materials. Acceptable feedstocks include,but are not limited to,yard debris,wood waste, land-clearing debris,brush, branches,manure,biosolids,food residuals,and forest byproducts. The product shall have a uniform,dark,soil-like appearance and an earthy loam-like odor. No ammonia or putrid smells shall be present. Minimum organic matter shall be 35 percent(dry-weight basis). Particles shall be 100 percent passing the 1-inch sieve. pH range shall be between 6.0 and 8.5 for wetlands and streamside locations,and 6.0 and 8.0 for other locations. Foreign material shall be no more than 2 percent on a dry-weight or volume basis,whichever provides the least foreign material. Material shall come from a source that is permitted by (or exempt from)Tacoma-Pierce County Health Department(TPCHD)rules. • Compost for the approved rates listed above must be Class A compost per Washington State Department of Ecology(Ecology)interim Compost Quality Guidelines("composted materials" defined in Washington Administrative Code(WAC)Chapter 173-350 Section 220)or topsoil manufactured from these composts plus sand or sandy soil. Products should be identified on the site development plans and recent product test sheets provided showing that they meet additional requirements for organic matter content and a carbon to nitrogen ratio below 25:1. The carbon to nitrogen ratio may be as high as 35:1 for plantings composed entirely of plants native to the Puget Sound Lowlands region. • Utilize alternatives to straw mulch,such as composted mulch or wood-based mulch,for construction erosion and sediment control. • Apply compost on slopes instead ofhydromulch. • Soils amendments should be installed postconstruction,prior to installation of landscaping and turf; unless used as a step in the lot preparation process involving minimal excavation foundation systems. Volume 11l—Flow Control and Treatment 12-6