10521 19TH AVE SE 2022-05-23 - Laserfiche WebLink

Design Guidelines (see BMP T5.13) Soil retention. The duff layer and native topsoil should be retained in an undisturbed state to the maximum extent practicable. In any areas requiring grading remove and stockpile the duff layer and topsoil on site in a designated, controlled area, not adjacent to public resources and critical areas, to be reapplied to other por- tions of the site where feasible. Soil quality. All areas subject to clearing and grading that have not been covered by impervious surface, incorporated into a drainage facility or engineered as structural fill or slope shall, at project completion, demonstrate the following: 1. A topsoil layer with a minimum organic matter content of ten percent dry weight in planting beds, and 5% organic matter content (based on a loss on- ignition test) in turf areas, and a pH from 6.0 to 8.0 or matching the pH of the original undisturbed soil. The topsoil layer shall have a minimum depth of eight inches except where tree roots limit the depth of incorporation of amendments needed to meet the criteria. Subsoils below the topsoil layer should be scarified at least 4 inches with some incorporation of the upper material to avoid stratified layers, where feasible. 2. Planting beds must be mulched with 2 inches of organic material. 3. Quality of compost and other materials used to meet the organic content requirements: a. The organic content for "pre -approved" amendment rates can be met only using compost that meets the definition of "composted materials" in WAC 173-350-220. This code is available online at: hLtp://www.ecy.wa.fzoy/programs/swfa/facilities/350.htmi. Compost used in biore- tention areas should be stable, mature and derived from yard debris, wood waste, or other or- ganic materials that meet the intent of the organic soil amendment specification. Biosolids and manure composts can be higher in bio-available phosphorus than compost derived from yard or plant waste and therefore are not allowed in bioretention areas due to the possibility of export - Note: MR 5 is triggered on sites with more than 2, 000 sq. ft. of new, replaced, or new plus replaced impervious surface, or 7, 000 sq. ft. or greater of land disturbing activity.