600 RIVERSIDE RD 2022-01-25 - Laserfiche WebLink

Figure 1-1: 2. Minimum Requirements MINIMUM REQUIREMENT NO. 1: PREPARATION OF STORMWATER SITE PLANS This Stormwater Site Plan has been prepared according to Volume I, Chapter 3 of the 2012 Washington State Department of Ecology Stormwater Management Manual for Western Washington (SWMMWW), as amended in December 2014. MINIMUM REQUIREMENT NO. 2: CONSTRUCTION STORMWATER POLLUTION PREVENTION (SWPP) The project disturbs over 1 acre; therefore, a SWPP Plan is required. See Section 6 for additional details. MINIMUM REQUIREMENT NO. 3: SOURCE CONTROL OF POLLUTION Source controls will be installed to prevent sediment from entering waterways. See Section 6 for additional details. MINIMUM REQUIREMENT NO. 4: PRESERVATION OF NATURAL DRAINAGE SYSTEMS AND OUTFALLS The site currently drains toward the Snohomish River though a series of low points along the shoreline. This project maintains those low points and mimics the natural discharge locations. MINIMUM REQUIREMENT NO. 5: ON -SITE STORMWATER MANAGEMENT This project only triggers Minimum Requirements 1-5; therefore, a feasibility study for the items in List No. 1 was performed. Feasibility for Roof area mitigation was not considered as there are no structures proposed with this project. The results of this study are outlined below. Lawn and Landscaped Areas Post -Construction Soil Quality and Depth in accordance with Best Management Practice (BMP) T5.13 in Chapter 5 of Volume V. • Feasible —All disturbed areas will be amended in accordance with BMP T5.13 in Chapter 5 of Volume V. Existing surfaces to receive plantings will either be tested and shown to support healthy plant growth or be amended per BMP T5.13. Other Hard Surfaces I Full Dispersion in accordance with BMP T5.30 in Chapter 5 of Volume V. • Infeasible — The required 15 percent slope and 100-foot length downstream of the proposed hard surfaces cannot be achieved within the site boundary. KPFF Consulting Engineers 2