7102 LOWER RIDGE RD 2018-07-25 - Laserfiche WebLink

Minimum Requirement #5 On-Site Stormwater Management As discussed above, stormwater will be managed through the use of On-Site Stormwater Management Requirements" using "Low Impact Development Performance Standards" specifically using List 2 of the DOE 2014 Stormwater Management Manual,Volume 1, Chapter 2,Table 2.5.1, and BMP T5.13 to address stormwater runoff. Under Minimum Requirement 5, the site requires the use of various on-site stormwater management BMPs provided they are not infeasible according to criteria set forth in this manual. Volume 1,Chapter 2 sets forth the selection process for these BMPs. Volume III, Chapter 3 contains specific information for the following on-site stormwater management BMPs and the following BMP's were reviewed and analyzed for use: TABLE 2.5.1 LIST#2 BMP FEASIBILITY Lawn and landscaped areas: 1. Post-Construction Soil Quality and Depth in accordance with BMP T5.13 in Volume V, Chapter 5 of this manual(Will be used) Roofs: 1. Full Dispersion in accordance with BMP T5.30 in Volume V,Chapter 5 of this manual, or,for single- family residential roofs and commercial roofs determined by Snohomish County to have similar runoff pollution characteristics to single-family residential roofs, Downspout Full Infiltration Systems in accordance with BMP T5.10A in Volume III, Chapter 3 of this manual (Not feasible due to site constraints and a review of the soils showed there was evidence of mottling at 18 inches,therefore the soils are not suitable for infiltration) 2. Bioretention in accordance with Volume V, Chapter 7 of this manual. (Not feasible due to required setbacks and grading for the site) 3. For single-family residential roofs and commercial roofs determined by Snohomish County to have similar runoff pollution characteristics to single-family residential roofs, Downspout Dispersion Systems in accordance with BMP T5.10B in Volume III,Chapter 3 of this manual.(Not feasible due to site constraints) 4. For single-family residential roofs and commercial roofs determined by Snohomish County to have similar runoff pollution characteristics to single-family residential roofs, perforated Stub-out Connections in accordance with BMP T5.10C in Volume III,Chapter 3 of this manual.(will be used) Other Hard Surfaces: 1. Full Dispersion in accordance with BMP T5.30 in Volume V,Chapter 5 of this manual.(not feasible due to site constraints). 2. Permeable pavement in accordance with BMP T5.15 in Volume V,Chapter 5 of this manual. NOTE: This is not a requirement to pave these surfaces.Where pavement is proposed,it must be permeable to the extent feasible unless full dispersion is employed. (A review of the soils showed there was evidence of mottling at 18-inches,therefore the soils are not suitable for infiltration. 3. Bioretention in accordance with Volume V, Chapter 7 of this manual. . (Not feasible due to required 7102 Lower Ridge RD Full Drainage Report Revised:November 3,2017 Page 10