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PRS Erosion Matrix Score Assessment Date Structure Mesa Top Bench Canyon Floor Channel Topography Explanation Ground Explanation Slope Explanation Runoff Evidence Channelized Channel Description Runoff Wetland Runoff Other Terminus Explanation Runoff Explanation Structure Run-On Structure Explanation NPDES Run-On NPDES Explanation Natural Run-On Natural Run-On Explanation ESH-18 Representative BMP Prescription BMP Description Not BMPs Sediment Comments 43-001(b1) 21.0 10/7/1997 43-24 YES NO NO NO Outfall behind TA-43-24 on the mesa top on the north side of Los Alamos Canyon. Outfall extends over the edge of the mesa top. NO NO NO NO YES Sheet flow from surrounding slope. T. Lemke NO Vegetation present on slope and no evidence of discharge from outfall. 43-001(b2) 26.7 10/7/1997 43-1 YES NO NO NO NPDES outfall discharging into watercourse west of TA-43-1. Vegetation in bottom of channel and some canopy cover. YES YES Natural channel west of TA-43-1 Discharge is in natural channel, no evidence of erosion from NPDES outfall. YES Run-off from TA-43-1. YES PRS is NPDES outfall EPA 03A040. YES Additional run-off in the channel. T. Lemke NO Vegetation and small natural check dam present at discharge point. No evidence of previous erosion. C-43-001 45.4 10/7/1997 43-1 YES NO NO NO Discharge point of former storm drain. Located on mesa top (north side of Los Alamos Canyon) south side of TA-43-1. Significant canopy cover. Heavy ground cover extending south from edge of asphalt for approximately 10 feet. <10% at edge mesa top. >30% over edge into the canyon. YES YES Natural channel extending down slope into Los Alamos Canyon. Rill erosion has formed a natural channel. YES Asphalt area on the south side of TA-43-1. NO YES Sheet flow from surrounding slope. T. Lemke NO Channel extending down the slope into the canyon has little ground cover vegetation.