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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 48-001 34.0 9/24/1997 48-1 YES NO NO NO a) Areas of side of road - sparse vegetative cover.
c) Roadway and asphalt covered areas along side of Building 48-1.
c) off to north and east of building 48-1 along side of canyon.
NO NO Air stack emissions from area stacks run-off not completely determinable throughout entire site survey. YES NO YES Contoured slopes and drainage pathways heading away from site. R. Reynolds NO 48-002(a) 15.3 7/30/1997 48-1 YES NO NO NO NO NO NO NO NO C. McLean Areas covered with tarp during excavation, clean backfill provided and revegetation measures applied. BMPs installed 8/31/95 (V. Hesch, 4/98). BMPs inspected: 8/31/95 (V. Hesch, 4/98) NO 48-002(b) 15.3 7/30/1997 48-1 YES NO NO NO NO NO NO NO NO C. McLean Areas covered with tarp during excavation, clean backfill provided and revegetation measures applied. BMPs installed 8/31/95 (V. Hesch, 4/98). BMPs inspected: 8/31/95 (V. Hesch, 4/98) NO 48-002(e) 22.3 7/30/1997 YES NO NO NO Inside fence at TA-48. NO NO YES From slanted roof of building. NO NO C. McLean NO 48-003 40.7 9/2/1999 YES YES NO NO PRS extends from site of old septic tank E of TA-48 to bench within Mortandad Canyon. Vegetation is mixed grasses with exposed volcanic tuff. Dense canopy cover below mesa's edge. Flat on mesa top, greater over canyon edge. YES NO Runoff is mostly sheet flow from area where septic was located to the mesa edge. Bench Sheet flow runoff terminates within bench setting below site. Sheetflow run-off below site of old septic tank. NO None observed. NO None. YES Sheet flow from surrounding terrain. Veenis, Steve Visible debris, mostly windblown trash. NO Site was re-evaluated base on a recommendation from the SWAT. (Originally assessed on 07/30/1997, score 60.5). NMED was originally copied 8/20/97. 48-007(a) 55.8 7/30/1997 YES NO YES NO NPDES outfalls to existing wetland. 10 - 30% on mesa top. YES YES Culvert from outfalls. YES Run-off from parking lots. YES NPDES outfall. NO T. Lemke NO Combined with PRS 48-010 at SWAT meeting 12/9/97. 48-007(b) 49.3 7/30/1997 YES YES NO NO PRS extends from NPDES outfall to bench within Mortandad Canyon. Active outfall, heavy vegetation. YES YES YES NPDES outfall. NO YES Sheet flow down slope from surrounding area. T. Lemke NO Heavy vegetation acts as natural BMP. 48-007(c) 69.5 7/30/1997 48-1 YES YES NO NO PRS extends from NPDES outfall on mesa top to bench within Mortandad Canyon. Outfall at edge of canyon. YES YES NPDES outfall. Evidence of erosion just below outfall. No visible evidence beyond canyon edge. NO YES PRS is NPDES outfall. YES Sheet flow down slope around PRS T. Lemke NO Vegetation, logs and rocks just below outfall act as natural BMP. Erosion possible down steep slope beyond canyon edge. 48-007(d) 55.8 7/30/1997 YES NO YES NO NPDES outfalls to existing wetland. 10 - 30% on mesa top. YES YES Culvert from outfalls. Wetland east of TA-48. YES Runoff from parking lots. YES NPDES outfall. NO T. Lemke NO Combined with PRS 48-010 at SWAT meeting 12/9/97. 48-007(e) 3.6 9/24/1997 48-8 YES NO NO NO Grassy, meadow-like area between building and Mortandad Canyon Thick grasses, down natural wood, weeds. Gentle slope NO NO NO NO Former NPDES outfall EPA 04A126 no longer outfalls to environment - redirected to internal process. NO D. Mays NO Trash: A few aluminum cans, pieces of cardboard, etc. (no big problem). 48-007(f) 76.5 7/30/1997 48-1 YES YES NO NO PRS boundary extends from outfall on mesa top to bench within Mortandad Canyon. YES YES Gully formed from run-off. Evidence of sediment transport within gully, and along channel banks. YES Outfall is from run-off, from asphalt surrounding TA-48-46. NO YES Sheet flow from surrounding terrain. T. Lemke NO Energy dissipaters within gully below outfall. 48-009 22.3 9/24/1997 YES NO NO NO Asphalt covered road. Loading dock spill from compressors located under overhead cover, asphalt covered road. Level roadway. NO NO YES NO NO R. Reynolds NO 48-010 80.3 7/30/1997 YES NO YES NO PRS extends from wetlands on mesa top to bottom of Mortandad Canyon. 10 -0 30% on mesa top, >30% over canyon edge. YES YES Leaving wetlands area. Gully formed at edge of canyon. NO Cooling water from NPDES outfalls contribute to run-on. NO YES Drainage from wetland area. T. Lemke Straw bales or other energy dissipater at canyon edge. NO Evidence of erosion and run-off discharge at canyon edge. This PRS was considered along with its contributing PRSs, 48-007(a) and 48-007(d) at the SWAT meeting of 12/9/97.