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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 39-001(a) 20.8 8/4/1997 NO NO YES NO Inactive landfill. Sand, asphalt, grasses. Generally. NO NO Adjacent to established watercourse, approximately 50 feet east. NO NO NO S. Veenis YES 39-001(b) 15.6 8/4/1997 NO NO YES NO Landfill, inactive. Heavy grasses. NO NO Adjacent to established channel, 150-200 yards, original channel diverted away from landfill. NO NO NO S. Veenis YES 39-002(a) 20.8 12/9/1997 39-2 NO NO YES NO Material storage area located between buildings 39-62 and 39-2. Site located in the bottom on Ancho Canyon. No canopy cover. Ground covered with weeds and grasses. NO NO NO NO NO T. Lemke NO No source of run-on and established vegetation on site. 39-002(b) 15.6 8/4/1997 39-6 NO NO YES NO Storage area near firing pad 39-004(c). NO NO NO NO NO S. Veenis NO 39-002(c) 29.5 8/4/1997 NO NO YES NO 2-300 yards from main channel. Heavy vegetation around buildings. Relatively flat. YES YES Minimal swale on north side, no evidence of recent run-off from past rain events. vegetated swale NO NO YES From cliffs above. S. Veenis NO 39-002(d) 15.6 8/4/1997 NO NO YES NO Storage area near firing pad 39-004(d). NO NO NO NO NO S. Veenis NO 39-002(f) 15.6 8/4/1997 NO NO YES NO Storage area near firing pad 39-004(e). NO NO NO NO NO S. Veenis NO 39-004(a) 74.0 12/16/1997 NO NO YES NO Channel bermed to prevent run-on to site. 39-004(a) machine site to the north. Pad is bare, surrounding area rocky with minimal asphalt coverage to south. Flat pad area. Steep cliffs surrounding site. YES YES Bermed channel on east side. Active area contributing potential pollutants. NO YES Active firing site. YES Cliffs and slopes have run-on. S. Veenis Down slope remedy within canyon, i.e., sediment traps. NO Assessment data from field visit 8/4/97. 39-004(b) 74.5 8/4/1997 39-8 NO NO YES NO Firing Site (inactive). Firing site bare of any vegetation - 0-25 drainage - moderate vegetation in and around. Pad level <10% slopes surrounding building at 10-30% YES YES Down slopes. Pad scrapings are pushed off from pad to west side where run-off flows down and through. Small pebble bare course applied as pad eroded, erosion on steep slope to north. YES Pad site and building drainage, parking lot. NO YES From above and from sides (drainage off of steep slope). R. Reynolds Protect pad scrapings from Storm Water run-off and run-on, with intermittent or other stabilizing methods. NO See attached sketch. 39-004(c) 85.0 8/4/1997 NO NO NO YES Firing pad 39-6. Pad clear. Surrounding area has dense vegetation. Pad flat, slopes steeply into drainage. YES YES Culverts. Drainage adjacent to pad. Off pad into drainage. NO NO YES From cliffs and terrain. S. Veenis Debris on firing pad (remove), some visible in drainage stabilize north edge firing pad. Potential silt fence along south side of drainage. NO See attached sketch. 39-004(d) 74.0 8/4/1997 NO NO YES NO Channel bermed to prevent run-on to site. 39-004(a) machine site to the north. Pad is bare, surrounding area rocky with minimal asphalt coverage to south. Flat pad area. Steep cliffs surrounding site. YES YES Bermed channel on east side. Active area contributing potential pollutants. NO YES Active firing site. YES Cliffs and slopes have run-on. S. Veenis Down slope remedy within canyon, i.e., sediment traps. NO 39-004(e) 78.5 8/4/1997 NO NO YES NO Active site. Pad bare, surrounding area vegetated and/or asphalt. Flat pad, sloped down into drainage. YES YES Upstream channel north of site. Visible of access ramp to firing pad. NO YES Active firing site. YES Steep cliffs run-on, ditch attempts to divert. S. Veenis Run-on diversion improved, gravel access road, silt fence on down slope of access road. NO 39-005 15.8 5/24/1999 39-4 YES NO NO NO HE seepage pit located north of 39-4. Moderate vegetation with sage and grasses. Flat area. NO NO None observed. None observed. NO No impact. NO No operational impact. YES Run-on from cliffs behind the site. Veenis, Steve NO 39-006(a) 15.6 8/4/1997 NO NO YES NO Inactive septic/leach field. Dense vegetation. NO NO Watercourse adjacent to site, approximately 50 feet west. NO NO NO S. Veenis YES 39-006(b) 15.6 8/4/1997 NO NO YES NO Active septic from 39-111. NO NO Natural swale impedes any run-off into adjacent watercourse, approximately 50 feet east. NO NO NO S. Veenis YES 39-007(d) 10.6 5/24/1999 39-142 YES NO NO NO Storage area covered with roof, curbed containment with lockout/tagout valve. Total asphalt covered. Flat area. NO NO Contained within curbing. None YES Roof drains into containment area. NO No operational impact. NO None Veenis, Steve Curbed containment and propanel cover. NO Misc debris throughout site. 39-008 29.5 8/4/1997 NO NO YES NO 2-300 yards from main channel. Heavy vegetation around buildings. Relatively flat. YES YES Minimal swale on north side, no evidence of recent run-off from past rain events. _______ vegetated swale NO NO YES From cliffs above. S. Veenis NO 39-009 22.6 12/9/1997 39-69 NO NO YES NO Outfall located on north side of building at cooling tower. Mostly asphalt. Level asphalt pad. NO NO No apparent conveyance - sheet flow. YES Building roof run-off. NO NO R. Reynolds NO