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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
11-001(a) 3.6 3/18/1998 11-2 YES NO NO NO  Inactive HE firing pit located near Drop Tower at TA-11.  Now covered with a concrete apron. 100% covered by asphalt and concrete for sump and catch basin. Less than 10% at the asphalt & concrete. NO NO Site is subsurface below existing drop pad area.         NO No, site is subsurface NO   NO Drainage from hillside into channel. C. McLean   Asphalt covered with 12" concrete curb around drop pad. NO Site re-evaluated after the 3/12/98 SWAT meeting.  Since the site is subsurface, the score was modified to reflect the actual site condition.
11-001(b) 22.7 12/1/1998 11-24 YES NO NO NO Firing pit between 11-2 and 11-3 located within the asphalt covered pad which is totally contained within the concrete curbed area. Covered with asphalt. Drop tower pad is generally flat YES NO Runoff from pad area collects in sumps which are NPDES permitted.   collection sump Runoff terminates into a collection sump None YES  Asphalt covered area creates local run-on. NO   NO Natural storm water flow down slopes. Steve Veenis     NO Site score was recalculated based on recommendations from the Surface Water Assessment Team.  The original assessment performed on 8/15/97 more accurately described PRSs 11-004(a-f).
11-001(c) 56.2 10/10/1997 16-370 YES YES NO NO On north rim of Water Canyon.  Extends approximately 40 feet back from rim and approximately 40 feet into canyon. Some vegetation (scrub bushes) but mostly bare soil and rocks, especially on portion of PRS over canyon rim. Flat on mesa top; steep descent into Water Canyon. YES NO Sheet flow into Water Canyon.     Due to proximity to canyon edge. No clear cut channels. NO   NO   NO   D. Mays   Rock check dam - looks okay on rim.  Silt fence - needs maintenance. BMPs installed 9/30/96 NO  
11-002 15.3 8/15/1997   YES NO NO NO   Small shrubs for ground cover.   NO NO           NO   NO   NO   R. Reynolds     NO  
11-003(a) 81.0 10/10/1997   NO YES YES NO North slope down from TA-11 drop tower.  (Not really bench of canyon floor). Generally good grassy cover, except for "fire road" which cuts straight through PRS. Steep area, formerly had bad gully erosion on fire road. YES YES Channel potential along fire road, but not currently too bad.  Also, several drainage features within the PRS boundary were observed.     Terminates in tributary of Water Canyon of which an established wetland occurs. Rills on fire road and drainage channels around sloped area. NO   NO   YES Fire road is lower than surrounding area so it traps run-on. D. Mays OPTION 1:  Realign road to avoid straight descent into canyon then revegetate old roadway.

Option 2:  Install 4-6 water bars to direct runoff into ditch at east side of fire road then build rock check dams, sediment pond or other sediment control at base of hill.		 Firebreak access road regraded to create ditch, more level driving area.  Naturally occurring wetland below site within canyon channel. NO  
11-003(b) 55.5 8/15/1997 11-24 YES NO NO NO Main activity on top, flat area.  Mortar impact area. Sparse vegetation around the area Upper level, where runoff from site occurs, is less than 10%.  Steeper slope has more vegetation, what holds back runoff. YES YES Small rill through middle of PRS.      Tributary of Water Canyon   NO   NO   NO   C. McLean Remove trash/debris.   NO Soil is eroding through rill in middle of site.
11-004(a) 56.0 8/15/1997   YES NO NO NO Area outside curbed area surrounding drop pad.  Debris area extends completely around pad. Mostly established vegetative cover of grass & pine. Slopes and hillsides surrounding drop pad. YES YES Mostly sheet & rills leading from site.     Tributary of Water Canyon Area surrounding pad presents varying erosion features. NO   NO   YES Natural storm water flow down slopes. R. Reynolds Remove trash/debris.  Erosion features at outfall on south end needs water/energy dissipaters at periodic intervals.   NO Trash: Mostly debris from drop experiments such as wire and cord debris.
11-004(b) 56.0 8/15/1997   YES NO NO NO Area outside curbed area surrounding drop pad.  Debris area extends completely around pad. Mostly established vegetative cover of grass & pine. Slopes and hillsides surrounding drop pad. YES YES Mostly sheet & rills leading from site.       Area surrounding pad presents varying erosion features. NO   NO   YES Natural storm water flow down slopes. R. Reynolds Remove trash/debris.  Erosion features at outfall on south end needs water/energy dissipaters at periodic intervals.   NO Trash: Mostly debris from drop experiments such as wire and cord debris.
11-004(c) 56.0 8/15/1997   YES NO NO NO Area outside curbed area surrounding drop pad.  Debris area extends completely around pad. Mostly established vegetative cover of grass & pine. Slopes and hillsides surrounding drop pad. YES YES Mostly sheet & rills leading from site.       Area surrounding pad presents varying erosion features. NO   NO   YES Natural storm water flow down slopes. R. Reynolds Remove trash/debris.  Erosion features at outfall on south end needs water/energy dissipaters at periodic intervals.   NO Trash: Mostly debris from drop experiments such as wire and cord debris.
11-004(d) 56.0 8/15/1997   YES NO NO NO Area outside curbed area surrounding drop pad.  Debris area extends completely around pad. Mostly established vegetative cover of grass & pine. Slopes and hillsides surrounding drop pad. YES YES Mostly sheet & rills leading from site.       Area surrounding pad presents varying erosion features. NO   NO   YES Natural storm water flow down slopes. R. Reynolds Remove trash/debris.  Erosion features at outfall on south end needs water/energy dissipaters at periodic intervals.   NO Trash: Mostly debris from drop experiments such as wire and cord debris.
11-004(e) 56.0 8/15/1997   YES NO NO NO Area outside curbed area surrounding drop pad.  Debris area extends completely around pad. Mostly established vegetative cover of grass & pine. Slopes and hillsides surrounding drop pad. YES YES Mostly sheet & rills leading from site.       Area surrounding pad presents varying erosion features. NO   NO   YES Natural storm water flow down slopes. R. Reynolds Remove trash/debris.  Erosion features at outfall on south end needs water/energy dissipaters at periodic intervals.   NO Trash: Mostly debris from drop experiments such as wire and cord debris.
11-004(f) 56.0 8/15/1997   YES NO NO NO Area outside curbed area surrounding drop pad.  Debris area extends completely around pad. Mostly established vegetative cover of grass & pine. Slopes and hillsides surrounding drop pad. YES YES Mostly sheet & rills leading from site.       Area surrounding pad presents varying erosion features. NO   NO   YES Natural storm water flow down slopes. R. Reynolds Remove trash/debris.  Erosion features at outfall on south end needs water/energy dissipaters at periodic intervals.   NO Trash: Mostly debris from drop experiments such as wire and cord debris.
11-005(b) 8.8 8/15/1997   YES NO NO NO South side of roadway south and west about 50 yards from TA-11 Building 24. Grassy cover.   NO NO           NO   NO   NO   R. Reynolds     NO  
11-006(a) 10.6 3/18/1998 11-2 YES NO NO NO Active HE sump located near Drop Tower at TA-11.  Discharges are re-routed to NPDES permitted outfall. 100% covered by asphalt and concrete for sump and catch basins. Flat area surrounding drop tower area. NO NO The sump currently discharges through NPDES outfall 05A097 which is covered under PRS 11-006(d).      Surface water discharges from the pad area collect in basins prior to discharging into canyon.   YES Runoff from drop tower pad enters into the sump. NO  NPDES outfall 05A097 sump discharges from the pad but is scored as erosion potential at the discharge point (11-006(b,c,d)). NO   C. McLean   Curbed containment around drop tower pad. NO Site re-evaluated after the 3/12/98 SWAT meeting.  Original score was 61.8.  Since the site is a sump, the score was modified to reflect the actual site condition.  The discharges from the sump are addressed by PRSs 11-006(b,c,d).
11-006(b) 52.0 3/18/1998 11-50 YES YES NO NO Catch basin and discharge channel  located on TA-11 Drop Tower pad.  Discharges are re-routed to NPDES permitted outfall and are no longer discharged at this location. Discharge channel fully covered with asphalt.  Below channel, the drainage is exposed tuff and alluvium. Channel has about 20% slope. YES YES  Former discharges were into asphalt lined channel from former NPDES permitted outfall.       Channel formerly discharged into tributary of Water Canyon.  Exposed volcanic tuff, no erosion observed. YES   Run-on from Drop Tower pad. YES  Formerly EPA 05A069 outfall. Re-routed to 05A097 outfall. NO   C. McLean   Asphalt lined discharge channel below catch basin.  12" concrete curb around drop tower. NO  
11-006(c) 68.8 3/18/1998 11-2 YES YES NO NO  Catch basin and discharge channel located near Drop Tower at TA-11.  Discharges have been re-routed to the remaining NPDES permitted outfall. Discharge channel fully covered with asphalt.  Below channel, the drainage is exposed tuff and alluvium. Less than 10% at the asphalt & concrete.  The drainage is close to 30%. YES YES Large cement channel. At  end of channel, cement ends and makes natural channel.      Surface water discharges from the pad area collect in catch basin and are re-routed to 05A097  prior to discharging into canyon. Former high velocity runoff from cement channel caused erosion at discharge point. YES Run-on from drop tower pad. YES Former NPDES outfall 05A096 has been re-routed to 05A097. NO   C. McLean Remove trash/debris.  Flow dissipation device downstream from sump/NPDES discharges may be needed. Asphalt lined discharge channel.  12" concrete curb around drop tower pad. NO Visible un-detonated HE chunks are visible throughout the site.
11-006(d) 74.0 3/18/1998 11-50 YES YES NO NO Catch basin and discharge channel  located on TA-11 Drop Tower pad.  Active NPDES permit 05A097 discharges here. Discharge channel fully covered with asphalt.  Below channel, the drainage is exposed tuff and alluvium. Channel has about 20% slope. YES YES  Discharges into asphalt lined channel from active NPDES permitted outfall.       Channel discharges into tributary of Water Canyon. Erosion has occurred within channel where discharges have and are currently ongoing. YES   Run-on from Drop Tower pad. YES  EPA  outfall  05A097 NO   C. McLean remove visible undetonated HE from area.  Install straw bale check dams down stream of outfall within drainage channel. Asphalt lined discharge channel below catch basin, 12" concrete curbing around drop pad, gabions below outfall have been installed as flow dissipation controls. NO  
11-010(b) 10.6 10/10/1997 11-1 YES NO NO NO West of berm, TA-11-1, which is west of TA-11 drop tower. Asphalt, grass, several small trees. Flat area surrounds PRS. NO NO           YES Run-on from upslope pavement depositing gravel at end of bunker driveway. NO   NO   D. Mays     NO  
11-011(a) 19.3 8/15/1997   YES NO NO NO Building and outfall (EPA 03A130) TA-11-30.  Steep, grassy bank. Steep bank covered with thick grass.   NO NO           NO   YES EPA 03A130 NO   R. Reynolds     NO  
11-011(b) 19.3 8/15/1997   YES NO NO NO Building and outfall (EPA 03A130) TA-11-30.  Steep, grassy bank. Steep bank covered with thick grass.   NO NO           NO   YES EPA 03A130 NO   R. Reynolds     NO  
11-011(c) 10.6 10/10/1997 11-1 YES NO NO NO West of berm, TA-11-1, which is west of TA-11 drop tower. Asphalt, grass, several small trees. Flat area surrounds PRS. NO NO           YES Run-on from upslope pavement depositing gravel at end of bunker driveway. NO   NO   D. Mays     NO  
11-011(d) 8.8 8/15/1997   YES NO NO NO South side of roadway south and west about 50 yards from TA-11 Building 24. Grassy cover.   NO NO           NO   NO   NO   R. Reynolds     NO  
11-012(a) 8.8 7/25/1997   YES NO NO NO   Pea gravel left over from 1944-45 access road.  Thick grasses and canopy cover. Flat lying meadow area. NO NO None observed.         NO   NO   NO   D. Mays     NO  
11-012(b) 15.3 7/25/1997   YES NO NO NO   Pea gravel left over from 1944-45 access road.   NO NO           NO   NO   NO   D. Mays     NO  
11-012(c) 8.8 10/10/1997   YES NO NO NO Along ridge west of TA-11 drop tower, on fire road, just outside of TA-11 hazard radius.  Former building, probably a magazine. Base course, grass.   NO NO           NO   NO   NO On ridge; no run-on. D. Mays     NO  
11-012(d) 8.8 8/15/1997   YES NO NO NO South side of roadway south and west about 50 yards from TA-11 Building 24. Grassy cover.   NO NO           NO   NO   NO   R. Reynolds     NO  
C-11-001 3.6 3/18/1998 11-2 YES NO NO NO  Inactive AOC associated with photofission experiments located near Drop Tower at TA-11.  Now covered with a concrete apron. 100% covered by asphalt and concrete for sump and catch basin. Less than 10% at the asphalt & concrete. NO NO Site is subsurface below existing drop pad area.         NO No, site is subsurface NO   NO Drainage from hillside into channel. C. McLean   Asphalt covered with 12" concrete curb around drop pad. NO Site re-evaluated after the 3/12/98 SWAT meeting.  Since the site is subsurface, the score was modified to reflect the actual site condition.
C-11-002 35.0 11/9/1998 11-24 YES NO NO NO Main activity on top, flat area. Former  7 x 9 ft wood from buidling 11-12.  Building removed and monitored for contamination. Mix of vegetation including trees and native shrubs Upper level, where runoff from site occurs, is less than 10%.  Steeper slope has more vegetation, what holds back runoff. YES NO No channelization was observed at the site. sheet flow near tributary    Tributary of Water Canyon  None observed NO   NO   NO   C. McLean     NO Assessment data provided by information gathered from a field visit to the area on 8/15/97.  Site re-calced when the location was positively identified and was not part of original assessment.