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4. NARRATIVE OF DEVELOPED SITE CHARACTERISTICS <br /> This development proposes to create 3 new lots. It was calculated that approximately <br /> 22% of the site would be converted to impervious surfaces at this time. The future building <br /> permits will address the individual lot impervious area at a later date, however, the site has <br /> been analyzed based on the desired future building footprints along with future walks, <br /> patios and driveway areas. <br /> Site Areas <br /> Total Area Disturbed Area Impervious Pervious <br /> (ac) (ac) (ac) (ac) <br /> Basin A 0.12 0.12 0.12 0.00 <br /> Basin B 0.10 0.10 0.10 0.00 <br /> Basin C 0.51 0.51 0.10 0.41 <br /> This is shown in the stormwater calculations in Appendix A. <br /> All new PGIS in Basin A will be infiltrated and treated using pervious pavement and the <br /> existing soils found on-site. The Geotech report details the site soils analysis and the <br /> capacity of the soils to treat the runoff as it is infiltrated. The runoff from both roof areas <br /> on lots 1 and 2 will be conveyed to a common infiltration trench located on the common <br /> property line between both lots. The runoff from Basin C will be allowed to sheet flow <br /> naturally over the on-site pervious surfaces and if concentrated the flows will be conveyed <br /> to a level spreader located west of the future SFR on lot 3. <br /> This report along with the engineering plans submitted to the City combine to satisfy <br /> Minimum Requirement#1: Stormwater Site Plan. <br /> Minimum Requirement#3: Source Control of Pollution <br /> This project is a proposed residential sub-division and as a result does not fall <br /> under any of the reasonable/required source control BMPs provided in Volume IV <br /> of the 2010DM. <br /> Minimum Requirement#4: Preservation of Natural Drainage Systems and Outfalls <br /> The drainage design for this project will use a combination of infiltration and sheet <br /> flow dispersion to handle the site runoff. All runoff from this site will be directed in <br /> the existing downstream direction/flow path which will mimic the existing <br /> conditions. The preliminary drainage design disperses a peak 100-year flow rate <br /> of 0.10 cfs and will be dispersed using level spreaders or from the existing <br /> landscaping. The flow path length on-site prior to any of the dispersed runoff <br /> leaving the site is a minimum of 140-feet. In addition the flow path will be covered <br /> with native/existing vegetation and the project Geotech has reviewed the slopes <br /> below the level spreader and found them to be stable if the existing vegetation is <br /> retained. Therefore, this project meets the supplemental information section <br /> provided in Volume I, Section 2.2.4. <br /> Thompson Short Plat 11-012 <br /> May 2011 Page 7 <br />