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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 21-003 33.3 2/10/1998 21-61 YES YES NO NO Grassy and asphalt areas east of building 21-61, within fence and leading to edge of Los Alamos Canyon. May extend over canyon rim. Asphalt and grass ground cover. Gradual slope. At east end of site, a drainage swale has formed from asphalt pad area. YES NO Drainage swale east of asphalt pads. Runoff from swale passes under fence then south towards Los Alamos Canyon. None observed. YES Runoff from access road and asphalt pads. NO NO M. Alexander Re-install sandbags or other structure to divert storm water from site. Patch earthen berm which has been breached at eastern edge. Sandbags. BMPs installed 11/30/96 NO Need additional data for location and extent. 21-004(d) 10.6 9/23/1997 21-346 YES NO NO NO On mesa top on south side of DP Canyon. Ground cover consisting of grasses and pine needles with some additional canopy cover. NO NO NO NO YES Sheet flow from surrounding area. T. Lemke NO Heavy ground cover and very little slope. 21-005 17.5 7/20/1999 21-30 YES NO NO NO Sump removal area east of 21-30 in parking lot. Asphalt coverage on entire site, except near area of excavation. Flat area sloped towards the north. YES NO Runoff from site of excavation into bar ditch along access road on the northeast side of building. bar ditch Runoff appears to terminate along access road into the bar ditch on the northeast side of building 21-30. None observed, mostly asphalt cover. YES Area parking lot creates run-on to site. NO No operational impact. NO None in addtion to the parking area. Veenis, Steve NO Misc. plastic and debris from excavation. Will be removed prior to leaving site. 21-006(b) 30.5 9/23/1997 NO YES NO NO PRS is 2 inch cast iron outfall discharging on a bench just below the mesa top on the north side of Los Alamos Canyon. Rock and sparse ground cover. Outfall discharges just above bench. NO NO NO Vent line for a sump from a building that has been removed. NO YES Sheet flow from slope above discharge point. T. Lemke NO Primarily rock and vegetation on bench. Outfall no longer active. 21-011(c) 54.0 5/22/1997 21-257 YES NO YES NO Absorption beds within MDA-T. Site extends north of DP Road down slope towards DP Canyon. Clean fill cap, and grass/clover cover. No canopy cover. MDA-T is gently sloped to the north, but steepens on north side of DP Road. YES YES Two asphalt channels on east and west end of MDA-T divert flow. Natural channels have formed below DP road as a result of these channels and roadway runoff. Asphalt channels discharge under DP Road through culverts and onto the north facing slope of DP Canyon. Evidence of sediments being washed across DP Road. YES Two diversion ditches on the east and west end. NO NO M. Alexander Effort should be made to keep runoff from upper fenced portion of MDA-T from crossing DP Road. A bar ditch along the south side of road would divert into adjacent culverts. Flow dissipation in channels below site would help keep sediments out of watercourse. Asphalt diversion channels on east and west boundary of MDA-T fenced area. Straw bales places in drainages below DP Road. NO Need additional information on surface soil numbers and extent. Potential for SWPP Plan and monitoring.
Identical AP 4.5(b) for 21-011(c), 21-016(a), 21-016(b), and 21-016(c).21-011(k) 72.0 5/22/1997 NO YES YES NO Upper slope is where outfall is located. Discharges reach lower canyon floor. Grass, shrubs, rock outcrop, straw mulch. YES YES Channel on east boundary of site. West drainage was cut off. Rill erosion is visible at various locations. Large gully exists on east boundary. NO NO Former outfall inactive. NO S. Veenis Adequate BMPs are in place. Maintenance needs to be continued. Some sections of silt fence need to be reinstalled. Sand bags used on top for diversion of run-on. Silt fence and straw bale check dams and straw mulch are used extensively. BMPs installed 10/31/96 NO 21-013(b) 67.0 2/10/1998 21-14 YES YES NO NO PRS 21-013(b) and (g) are adjacent to each other, south of MDA-V, stretching from the MDA fence to the edge of the mesa. 21-013(b) is the western most PRS. Close to 75% cover, with a lot of exposed tuff and concrete chunks from D&D activity. Steep descent from mesa top southward to bench. YES YES Well defined channel exists at western boundary of PRS. The runoff into this channel flows into "BV Canyon", a bench/tributary of Los Alamos Canyon. BV Canyon Flows into BV Canyon, a tributary of Los Alamos Canyon. East part of site "capped" with asphalt. Western limit is a drainage channel which cuts to BV Canyon west of MDA-V. NO NO YES Sheet flow run-on from MDA V. D. Mays Run-on controls for MDA-V. Also, asphalt on site stabilizes slope. YES Runoff seems to be attenuating in bench of Los Alamos Canyon, "BV Canyon," so BMPs at base of hill would not make a significant improvement. 21-013(c) 15.7 6/25/1999 NO NO NO NO Surface disposal area east of MDA U. Mixed vegetation with some barren areas. Mostly flat, sloping towards access road. YES NO Evidence of sheetflow runoff. Sheetflow runoff occasional to access road to the north. None observed. NO None. NO None NO None Veenis, Steve NO 21-013(d) 24.9 6/25/1999 YES NO NO NO Surface disposal area across DP Road from MDA B and MDA V Mixed vegetation with some barren areas. Gravel, grasses and mixed pinon/juniper canopy Mostly flat, sloping towards DP Canyon. YES NO Evidence of sheetflow runoff throughout site.. Meadow Ruoff appears to infiltrate at site. Sheet flow erosion across site, minimal evidence of rills. NO None. NO None YES Minor upslope drainage. Veenis, Steve NO 21-013(e) 24.9 6/25/1999 YES NO NO NO Surface disposal area across DP Road from MDA B and MDA V Mixed vegetation with some barren areas. Gravel, grasses and mixed pinon/juniper canopy Mostly flat, sloping towards DP Canyon. YES NO Evidence of sheetflow runoff throughout site.. Meadow Ruoff appears to infiltrate at site. Sheet flow erosion across site, minimal evidence of rills. NO None. NO None YES Minor upslope drainage. Veenis, Steve NO 21-013(f) 15.8 2/10/1998 21-61 YES NO NO NO South of Building 21-61, stretching to the edge of the mesa, but not over the edge to Los Alamos Canyon. Site of soil piles 1949-50. Good grass cover. Gradual slope from Building 21-61 south toward canyon. NO NO YES Building 21-61 roof drains onto north side of PRS. NO NO D. Mays NO since PRS 21-013(f) is contained entirely within PRS 21-003, Gary McMath suggests an NFA for this PRS in favor of consideration under PRS 21-003. Good vegetative cover exists. 21-013(g) 67.0 2/10/1998 21-14 YES YES NO NO PRS 21-013(b) and (g) are adjacent to each other, south of MDA-V, stretching from the MDA fence to the edge of the mesa. 21-013(g) is the eastern most PRS. Close to 75% cover, with a lot of exposed tuff and concrete chunks from D&D activity. Steep descent from mesa top southward to bench. YES NO A small gully has formed from sheet runoff from MDA V which will flow into "BV Canyon", a bench/tributary of Los Alamos Canyon. BV Canyon Flows into BV Canyon, a tributary of Los Alamos Canyon. Small gully has formed from sheet flow runoff from MDA V. NO NO YES Sheet flow run-on from MDA V D. Mays YES Runoff seems to be attenuating in bench of Los Alamos Canyon, "BV Canyon," so BMPs at base of hill would not make a significant improvement. 21-015 17.9 9/23/1997 YES NO NO NO MDA-B on north side of Los Alamos Canyon. Ground cover only in unpaved areas (25-75%); remainder of area covered with asphalt (100%). YES NO Evidence of sheet flow along south fence line in a few places. Contained within site. Mesa top on south side of site. In a few localized places evidence of minor erosion from sheet flow. Contained within the site. NO NO NO T. Lemke NO Potential exists for erosion within the site. Vegetation is present along the fence line. Significant erosion will have to occur before sediment is transported off site. 21-016(a) 54.0 5/22/1997 21-257 YES NO YES NO Absorption beds within MDA-T. Site extends north of DP Road down slope towards DP Canyon. Clean fill cap, and grass/clover cover. No canopy cover. MDA-T is gently sloped to the north, but steepens on north side of DP Road. YES YES Two asphalt channels on east and west end of MDA-T divert flow. Natural channels have formed below DP road as a result of these channels and roadway runoff. Asphalt channels discharge under DP Road through culverts and onto the north facing slope of DP Canyon. Evidence of sediments being washed across DP Road. YES Two diversion ditches on the east and west end. NO NO M. Alexander Effort should be made to keep runoff from upper fenced portion of MDA-T from crossing DP Road. A bar ditch along the south side of road would divert into adjacent culverts. Flow dissipation in channels below site would help keep sediments out of watercourse. Asphalt diversion channels on east and west boundary of MDA-T fenced area. Straw bales places in drainages below DP Road. NO Need additional information on surface soil numbers and extent. Potential for SWPP Plan and monitoring.
Identical AP 4.5(b) for 21-011(c), 21-016(a), 21-016(b), and 21-016(c).21-016(b) 54.0 5/22/1997 21-257 YES NO YES NO Absorption beds within MDA-T. Site extends north of DP Road down slope towards DP Canyon. Clean fill cap, and grass/clover cover. No canopy cover. MDA-T is gently sloped to the north, but steepens on north side of DP Road. YES YES Two asphalt channels on east and west end of MDA-T divert flow. Natural channels have formed below DP road as a result of these channels and roadway runoff. Asphalt channels discharge under DP Road through culverts and onto the north facing slope of DP Canyon. Evidence of sediments being washed across DP Road. YES Two diversion ditches on the east and west end. NO NO M. Alexander Effort should be made to keep runoff from upper fenced portion of MDA-T from crossing DP Road. A bar ditch along the south side of road would divert into adjacent culverts. Flow dissipation in channels below site would help keep sediments out of watercourse. Asphalt diversion channels on east and west boundary of MDA-T fenced area. Straw bales places in drainages below DP Road. NO Need additional information on surface soil numbers and extent. Potential for SWPP Plan and monitoring.
Identical AP 4.5(b) for 21-011(c), 21-016(a), 21-016(b), and 21-016(c).21-016(c) 54.0 5/22/1997 21-257 YES NO YES NO Absorption beds within MDA-T. Site extends north of DP Road down slope towards DP Canyon. Clean fill cap, and grass/clover cover. No canopy cover. MDA-T is gently sloped to the north, but steepens on north side of DP Road. YES YES Two asphalt channels on east and west end of MDA-T divert flow. Natural channels have formed below DP road as a result of these channels and roadway runoff. Asphalt channels discharge under DP Road through culverts and onto the north facing slope of DP Canyon. Evidence of sediments being washed across DP Road. YES Two diversion ditches on the east and west end. NO NO M. Alexander Effort should be made to keep runoff from upper fenced portion of MDA-T from crossing DP Road. A bar ditch along the south side of road would divert into adjacent culverts. Flow dissipation in channels below site would help keep sediments out of watercourse. Asphalt diversion channels on east and west boundary of MDA-T fenced area. Straw bales places in drainages below DP Road. NO Need additional information on surface soil numbers and extent. Potential for SWPP Plan and monitoring.
Identical AP 4.5(b) for 21-011(c), 21-016(a), 21-016(b), and 21-016(c).21-017(a) 8.8 6/18/1998 21-152 YES NO NO NO MDA-U is located on the north side of DP Mesa and covers an area of approximately .2 acres. It contains two absorption beds (21-017(a&b)) and a sump 21-017(c). MDA-U is covered with 90% thick grasses and sage. MDA-U generally slopes to the north. The NE and NW corners steepen to 15-20% to the north towards DP Canyon. The middle of the site is <10% slope to the north. NO NO NO A run-on channel has been cut above the site, and directs run-on to the NE around the MDA towards DP Canyon. NO Fire hydrant +/- 100' south of MDA-U. A swale/depression, and run-on channel divert run-on away from site. NO Run-on is diverted around and away from MDA-U J. Waltersheid Run-on diversion swale/depression are in place and effective. NO 21-017(b) 8.8 6/18/1998 21-152 YES NO NO NO MDA-U is located on the north side of DP Mesa and covers an area of approximately .2 acres. It contains two absorption beds (21-017(a&b)) and a sump 21-017(c). MDA-U is covered with 90% thick grasses and sage. MDA-U generally slopes to the north. The NE and NW corners steepen to 15-20% to the north towards DP Canyon. The middle of the site is <10% slope to the north. NO NO NO A run-on channel has been cut above the site, and directs run-on to the NE around the MDA towards DP Canyon. NO Fire hydrant +/- 100' south of MDA-U. A swale/depression, and run-on channel divert run-on away from site. NO Run-on is diverted around and away from MDA-U J. Waltersheid Run-on diversion swale/depression are in place and effective. NO 21-017(c) 8.8 6/18/1998 21-152 YES NO NO NO MDA-U is located on the north side of DP Mesa and covers an area of approximately .2 acres. It contains two absorption beds (21-017(a&b)) and a sump 21-017(c). MDA-U is covered with 90% thick grasses and sage. MDA-U generally slopes to the north. The NE and NW corners steepen to 15-20% to the north towards DP Canyon. The middle of the site is <10% slope to the north. NO NO NO A run-on channel has been cut above the site, and directs run-on to the NE around the MDA towards DP Canyon. NO Fire hydrant +/- 100' south of MDA-U. A swale/depression, and run-on channel divert run-on away from site. NO Run-on is diverted around and away from MDA-U J. Waltersheid Run-on diversion swale/depression are in place and effective. NO 21-018(a) 18.1 5/18/1999 YES NO NO NO According to the approved TA-21 RFI work plan, 21-018(a) is material disposal area V (MDA V) which contained three absorption beds. The absorption beds were used for liquid waste disposal from a laundry operation at Building TA-21-20 (PRS 21-018(b)) and were in used from October 1945 to 1961. Site fenced off with heavy vegetation throughout. Fenced area is generally flat and back from the mesa +/- 50 feet. YES NO Sheet flow runoff, doesn't appear to reach canyon rim very often. Bench Periodic discharges over edge of mesa, but at relatively low volumes. None observed. See 21-013(b&g) for downslope PRS assessments. NO None NO None NO None Veenis, Steve ISV Project ongoing on the northside of the MDA. If future ISV project includes the MDA, then the need for BMPs should be re-assessed. Asphalt run-on diversion channel on northside of site. NO 21-018(b) 15.8 9/30/1997 YES NO NO NO MDA-V on south side of DP Mesa just west of the entrance to TA-21. Ground cover. Vegetation along the majority of the perimeter fence. Slopes gradually to the south. NO NO NO NO YES Sheet flow across site. T. Lemke Asphalt channel diverts southwest run-on around site. NO 21-022(h) 27.5 9/23/1997 YES YES NO NO NPDES outfall located at edge of mesa top on north side of Los Alamos Canyon. Discharges to a bench within the canyon. Heavy vegetation at outfall. Sparse vegetation along bench. NO NO NO YES NPDES outfall EPA03A032 NO T. Lemke NO Bench within canyon consists of either rock or vegetated areas. 21-022(j) 3.6 6/25/1999 21-3 YES NO NO NO Sump pump in south end of building 21-3. No drain lines for the sump have been identified. Enclosed within building and concrete. Flat area within building. NO NO None observed. None observed. NO None NO None NO None Veenis, Steve NO No exposure, located indoors/subsurface. 21-023(c) 35.5 4/12/1999 YES NO NO NO On north side of Los Alamos Canyon between MDA-B and MDA-V. Former septic system. Sparse ground cover where tank was originally located. Pine needles and trees cover location of former outfall. Flat near former tank location, gradually steepens toward canyon. YES NO Outfall located on slope where some minimal evidence of runoff occurs. BV Canyon Runoff sheet flows over slope and infiltrates into local sediments NO NO YES Sheet flow from surrounding area. T. Lemke NO Asphalt storm water conveyance north of site directs runoff away from site. Site re-evaluated as part of field assessment for 21-027(d). Original assessment performed on 9/23/97. 21-024(a) 3.6 9/20/1997 21-009 YES NO NO NO Abandoned septic tank on south side of TA-21. SE of TA-21-009 no surface expression of drain line from tank. Heavy ground cover. NO NO NO NO NO T. Lemke NO 21-024(b) 15.8 11/25/1997 YES NO NO NO Outfall from a septic tank that served TA-21-17, which was removed in 1969. Outfall is not active. Located on the north side of Los Alamos Canyon. Area around old septic tank and outfall is heavily vegetated with ground cover. PRS is located on the slope adjacent to the roadway. NO NO NO NO YES Sheet flow down adjacent slope. T. Lemke Straw bale check dam installed down-slop of excavation. Plastic sheeting used to cover project upon completion. Reseeding and jute mat used for final stabilization. BMPs installed 7/31/95 (V. Hesch, 4/98). BMPs inspected: 7/31/95 (V. Hesch, 4/98) NO Outfall is not active and the area is well vegetated. 21-024(c) 14.0 9/30/1997 YES NO NO NO Located at edge of canyon - south side of mesa. Large boulders. Very steep. NO NO NO NO NO R. Reynolds NO 21-024(d) 24.0 5/22/1997 YES YES NO NO Within the rim and the first slope of the canyon. Grass, weeds ground cover. Minimal canopy cover, scrub oak. NO NO YES Hay bales up top. NO NO M. Alexander Straw bale check dam installed down-slop of excavation. Plastic sheeting used to cover project upon completion. Reseeding and jute mat used for final stabilization. BMPs installed 7/31/95 (V. Hesch, 4/98). NO BMPs currently in place, on mesa top. 4 straw bales. No additional BMPs recommended for mesa top. Unknown for first bench. 21-024(e) 56.0 2/10/1998 21-14 YES YES NO NO Filled-in septic tan AND outfall Southeast of MDA-V. On edge of mesa, above "BV Canyon," a bench/tributary of Los Alamos Canyon. About 30 ft from edge. Close to 25%. Some vegetation, some exposed tuff. Septic tank and outfall are on flat mesa top. Runoff channel below outfall is steep descent to BV Canyon. YES YES Apparent historical flows from septic tank outfall, which have been concentrated more recently by MDA-V run-on diversion flows. Los Alamos Canyon Steep descent below outfall leads to BV Canyon, or bench/tributary of Los Alamos Canyon. It's an apparent channel but you could cross it with a Bronco. YES Run-on controls for MDA-V have the effect of increasing flows here. NO YES Natural sheet flow collects near outfall. D. Mays Direct run-on from MDA-V to avoid this PRS. Then use berms or vegetation to stabilize the area around the 21-024(e) outfall. Straw bale check dam installed down-slope of excavation. Reseeding and jute mat used for final stabilization installed 8/31/95 effectively stabilized site. NO "Plumbers were real good at finding the natural drainage points" Gary McMath 2/10/98. 21-024(f) 30.9 5/18/1999 YES YES NO NO Outfall pipe terminates at edge of bench into seepage pit on south side of DP Canyon, northwest of blue water storage tank - 150 yards. Moderate cover of pine needles and rocks; no grass; some pine trees surrounding the area. Gradual slope to canyon edge or rim. YES NO Mostly sheetflow with a drainage swale in the vicinity. mesa top and seepage pit at end of pipe Sheet flow from area appears to rarely reach the mesa edge if ever. None observed. NO None NO None YES Minimal upslope sheetflow. Veenis, Steve None at this time. NO Site was re-evaluated to reflect the outfall, septic and drainline. The original assessment was completed on 09/30/1997 and had an erosion matrix score of (17.0). 21-024(g) 17.0 9/30/1997 21-31 NO YES NO NO Just off old road/pipeline for TA-50 - TA-21 RLWL, on north side. Abandoned site - 30 years ago. Site north of 21-31 at edge of rim. Mostly grass and weed cover with intermittent Pipe terminates on slop facing north. NO NO NO NO NO R. Reynolds NO 21-024(h) 54.0 5/22/1997 21-155 YES YES NO YES Within the rim and first slope of DP Canyon. Also, within a tributary of a watercourse. Pine needles, shrubs and grass ground cover. Ponderosa pine canopy cover. Flat area drops into tributary of DP Canyon. YES YES Natural outfall to drainage. Tributary of DP Canyon below 21-155, north of DP Road. NO NO NO M. Alexander The channel needs to be looked at for sediment controls. Need to look at sample data and locations. Install flow dissipation in channel until final determination. Straw bale check dam installed down-slop of excavation. Plastic sheeting used to cover project upon completion. Reseeding and jute mat used for final stabilization. BMPs inspected: 7/31/95. NO 21-024(i) 53.7 5/22/1997 21-209 YES YES NO NO Within the rim, first slope, and first bench of Los Alamos canyon. No ground cover. Scrub oak canopy cover. 75-100% cover refers to tank. Steep slope below tank, shallow slope at tank. YES YES Natural drainage from outfall. Runoff from site terminates on bench setting below site, above LA Canyon Minimal evidence of sediment transport at mesa top location. NO NO YES Upper slope of PRS discharges below to bench setting. M. Alexander Provide better runoff control at site on mesa top. BMPs may be necessary on bench below site if access allows. Straw mulch, sandbags and straw bales are being maintained on-site. BMPs installed 11/30/96. Additional BMPs were installed 11/98 after Interim Action. NO Site is under Phase II investigation and VCA report being developed. Provide runoff controls. Need surface water data! 21-024(j) 3.6 9/30/1997 21-155 YES NO NO NO Abandoned in 1966. Unknown if outfall existed, site located inside fence - south of TA-21-155. Mostly grass and weeds, sparse oak shrubs. NO NO NO NO NO R. Reynolds NO 21-024(k) 3.6 9/30/1997 21-155 YES NO NO NO Septic tank, abandoned in place, leach field cannot be located. Directly south of TA-21-155 by 100 yards, outside of fence. Weeds and grassy cover. Gently slopes to canyon. NO NO NO NO NO R. Reynolds NO 21-024(l) 8.8 9/30/1997 21-21 YES NO NO NO North of TA-21-21 in grassy opening. Thick grass, heavy vegetative cover (weeds). NO NO NO NO NO R. Reynolds NO 21-024(m) 20.5 9/30/1997 21-209 YES NO NO NO Original outfall location for septic system cannot be located. Approximate location described in RFI photographed south of TA-21-209. 30% steep slope. NO NO NO NO NO R. Reynolds NO 21-024(n) 8.8 9/30/1997 21-213 YES NO NO NO East of 21-213 approximately 100 feet - at east end of TA-21. Area a floor drain from 21-152 - some evidence of discharge from end of pipe. Grass and weeds. Fairly flat. NO NO NO NO NO R. Reynolds NO 21-024(o) 10.6 11/25/1997 21-46 YES NO NO NO Area evaluated is probable outfall location for 4 inch VCP from TA-21-46. Outfall has never been located. Location is on the north side of Los Alamos Canyon. Heavy ground cover consisting of various types of grasses, canopy cover long canyon edge. NO NO NO NO YES Sheet flow from adjacent slope to the north. T. Lemke NO 21-026(d) 39.5 9/23/1997 21-227 YES NO YES NO Inactive WWTP near 21-227 on eastern portion of TA-21. Canopy and some ground cover along side of canyon. PRS boundary extends from edge of mesa top on south side of DP Canyon to bottom of DP Canyon. NO NO NO Outfall from treatment facility that is no longer active. NO Outfall is an NPDES outfall EPASSS05S that is inactive. YES Sheet flow from surrounding slope. T. Lemke NO Outfall not active and natural BMPs in place on side of canyon. 21-027(a) 52.0 5/22/1997 21-3 YES YES NO NO Outfall from former cooling tower (21-143) south of 21-3. Minimal canopy cover, scrub oak. Within the first slope, first bench, and second slope of Los Alamos canyon. YES YES Yes, the outfall is connected to the storm water drain collection system. Outfall pipe hangs over mesa's edge. YES 24" CMP, to canyon rim. Parking lot at inlet. YES 03A-031, believed inactive. NO M. Alexander Divert storm water into culvert or move culvert. NO 21-027(b) 46.8 9/23/1997 21-209 YES YES NO NO Active NPDES outfall on mesa top approximately 30-40 feet from edge of Los Alamos Canyon (north side). Wetlands area has developed at base of the outfall. Discharge over mesa edge onto bench. YES NO Active outfall discharges into wetland and overflows into LA Canyon. Wetland area below outfall discharges periodically over mesa edge. NO YES PRS is active NPDES outfall EPA 03A034. YES Sheet flow from surrounding area. T. Lemke NO Wetlands at base of outfall stabilizes the soil and contains the majority of the discharge. 21-027(c) 8.8 11/25/1997 YES NO NO NO Area evaluated is probable outfall location for a 4 inch VCP that was associated with TA-21-6. The building was removed in 1966 and it is presumed that the outfall was abandoned. PRS is on the north side of Los Alamos Canyon. Ground cover only in the PRS boundary. NO NO NO NO NO T. Lemke NO Outfall no longer present. Significant vegetation in the area. 21-027(d) 45.0 4/12/1999 YES YES NO NO On north side of Los Alamos Canyon between MDA-B and MDA-V. Former drain line from secondary containment around AOC-21-028, AST for diesel. The drainline discharged over mesa's edge onto bench below. Sparse ground cover where AST was originally located. Pine needles and trees cover location of former outfall. Flat near former tank location, gradually steepens toward canyon. The outfall discharged over the edge of mesa onto steep cliffs below. YES NO Outfall located on slope where some minimal evidence of runoff occurs. BV Canyon Runoff sheet flows over slope and infiltrates into local sediments on bench below. None observed NO NO YES Sheet flow from surrounding area. Veenis, Steve NO Site re-evaluated as part of field assessment for AOC-21-028. Original assessment performed on 9/23/97. 21-029 67.0 9/23/1997 YES NO NO NO Mesa top on south side of DP Canyon. Both ground and canopy cover present. YES NO Rills and gullies present along north fence line primarily in the eastern portion of the site. YES Run-off from the edge of DP road appears to be flowing under the east gate and down the old roadway through the site. NO YES Sheet flow from slope within the PRS and drainage along what used to be the main roadway through the site. T. Lemke Repair gullies and place straw bales at these points of discharge. Jute matting, straw bales. BMPs installed 4/30/96. NO Evidence of erosions and run-off along the north fence line. C-21-015 22.7 5/18/1999 YES NO NO NO Generally north trending towards DP Canyon. Former sump location. Mixed vegetation with some local bare spots. Mostly flat near sump location. YES NO Minimal evidence of sheetflow run off from site. Mesa top Infiltration mostly to mesa top. None observed NO NO YES Natural upslope sheetflow run-on. Veenis, Steve NO C-21-028 15.3 4/12/1999 YES NO NO NO On north side of LA Canyon between MDA-B and MDA-V. Former catch basin around diesel AST. Sparse vegetation where AST was originally located. Flat area between MDAs NO NO None observed None observed NO NO NO Veenis, Steve NO Site currently within boundary of ISV project ongoing for MDA-V. Project has no impact on the PRS.