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, The SCS map shows this area to be Alderwood Soils. The SCS soil map is <br /> aY.ached. <br /> Water sheet flows across the site with no noticeable flow channels to the north <br /> and east where it flows to Lexington and the neighbor to the east. <br /> 3. Developed Site Conditions <br /> The developed si!e will have a total of 5,622 s.f. of imperviaus. Being over 5,000 <br /> s.f. this requires detention. The driveway and tumaround is 2,763 s.f., which <br /> being less than 5,000 s.f. dces not require water treatment. The parking is under <br /> the units and the driveway comes out onto Lexington. The detention pipe was <br /> sized to meet the discharge requirements, then increased by 35% per the City <br /> Manual. The detention pipe is placed under the driveway. The pipe has been kept <br /> at a minimum aepth to keep the head on the orifice to a minimum. The results <br /> ftom the modeling are: <br /> Site Existing Developed Off-site flow' <br /> Area <br /> 2 yr. 0.02 cfs 0.06 cfs 0.01 cfs <br /> 10 r. 0.04 cfs 0.09 cfs 0.04 cfs <br /> 100 r. 0.09 cfs 0.14 cfs 0.09 cfs <br /> 'Theoretical flows before 35% pipe length and o�ifice increase <br /> 4. Erosion Sedimentation Control <br /> Erosion and sedimentation control will be accomplished by placing a Construction � <br /> Entrance before construction, and paving the driveway after construction. {�s <br /> addition, straw bales and silt fence will be installed at the project perimeter to <br />, prevent silt discharge offsite during construction and up to the time vegetation is � , <br /> re-established. ' i <br /> i <br /> , ,n <br /> 5. Downstream Analysis '� <br /> �I <br /> The current flow goes to Lexington either directly,,�aF through the neighboring lots, , ) <br /> flowing east down Lexington to the I-5 right-of-rvay. The overflow/release from the �,�-/ <br /> on-site detention system will go to Lexington via a.6.",PV�'ifn� running 145' east <br /> in the ROW. This line will daylight and discharge to an asphalt swale formed by <br /> tfie street paving and a driveway/parking area, <br /> The swale continues all the way to the end of Lexington. The flow is currently <br />�y spread out at the end of the street where it flows down the highway cut bank to <br /> the ditch flowing along I-5. Given the amount of storage being provided there will <br /> not be any noticeable increase in the flow to the downstream, and the easterly <br /> neighbor should not have water standing in the NW comer of their yard anymore. <br /> � <br />