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south-sou�hwest frc�m the south property line. The lowest point that collects <br />storm water is at the natural discharge point and because of the vines the <br />actuai swale iocation was not determinable. <br />item A- B is the reach found going through to the south end of the <br />blackberry vines at about 370' south of the sit�. At the downstream end it joins <br />a natural broad earth swale 1' deep x 80' wide with about 3" of slow running <br />water. <br />Item B- C is the short run of this stream going for 12'. A manmade <br />channel was cut 2' deep through a hill to vent the upper wetlands area to the <br />south for 193'. <br />Item C- D is the length of a manmade earth channel that goes south to <br />the somewhat dry wetlands area. The channel is about 3 to 4' wide and carries <br />some stagnant water with algae and green leafage on the water surface. The <br />channel ends at the upstream end of a natural channet that swales out to 25' <br />wide by 3' deep and generally goes south to 112th St Sw. The channel cut <br />must have been done 20 years ago or so, since some large trees have grown <br />near the channel. <br />Item D- E is the final natural earth channel going south-southwest to the <br />north road ditch on 112th St. At time of review it was carrying 3 to 8" of water <br />in a fairly steep profile at 2°r6 slope to 112th St. It goes parallel to the entrance <br />road to State Emissions Station on the north side of 112th St at 150' away. <br />Item E is the point where the above stream joins the north road ditch of <br />112th St SW. At this point the downstream 1/4 mile limit is reached. From <br />here in general the flow goes due west past an existing house at 1505 112th St <br />and under the driveway to the continuing storm drain, joins the storm drain <br />going west for 200' to the swamp creek swale and then southeasterly for 12 <br />miles to Lake Washington. <br />TASK 4. Describe Drainage System Problems: <br />In the reach of this analysis no apparent erosion or control problems <br />were noted in the field. There were no signs of siltation or erosion along the <br />stream going south-southwest to 112th St SW fromthe site. As a result no <br />additional construction is proposed at this time. <br />Task 5. Proposed Mitigation: <br />In summary no mitigation of controling drainage off site in the <br />downstream area is proposed. Onsite, the 2, 10 and 100 year storms will be <br />detained by the dry pond to the maximum 100 year-24 hr flow of 0_44 cfs. The <br />4 <br />