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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 02-003(a) 57.6 8/6/1997 NO NO YES NO East of Bldg. 63 approx. 30-40 yards. Vegetation. Gentle slope to creek bank edge. YES YES Past erosion present, but vegetation has kept recent erosion in check. Drains to edge of LA creek. At edge of stream bank down to water. Rill is not within PRS but starts at edge. NO NO YES Storm Water run-on is minimal - potential exists due to above proximity to adjacent steep slope. R. Reynolds NO 02-003(b) 39.5 8/6/1997 NO NO YES NO <10% in canyon floor, <30% along side of canyon NO NO NO NO YES Sheet flow from surrounding terrain. T. Lemke NO 02-003(d) 27.8 8/6/1997 NO NO YES NO PRS is around large ponderosa pine approx. 200 feet north of watercourse. Canopy and ground cover. Ground slopes away from tree. NO NO NO NO YES Sheet flow from surrounding slope. T. Lemke NO 02-003(e) 40.5 8/6/1997 NO NO YES NO East of Bldg. 63 approx. 30-40 yards. Vegetation. Gentle slope to creek bank edge. YES YES Past erosion present, but vegetation has kept recent erosion in check. Drains to edge of LA creek. At edge of stream bank down to water. Rill is not within PRS but starts at edge. NO NO YES Storm Water run-on is minimal - potential exists due to above proximity to adjacent steep slope. R. Reynolds NO 02-005 19.6 8/6/1997 NO NO YES YES PRS described as cooling tower drift. Boundary encompasses entire TA. Further investigation needed for adequate evaluation. NO NO NO NO NO T. Lemke NO AIR POLLUTION SITE - INTERPRET WITH CAUTION. This is not a solid/liquid pollution site, for which the AP 4.5(b) erosion assessment was designed, but the region around a stack. Accordingly, it should be interpreted with care. Note added by D. Mays, per instruction from M. Alexander, 9/15/97. 02-006(a) 15.3 9/3/1997 YES NO NO NO Located on mesa top on south side of Los Alamos canyon. PRS is existing French drain and surrounding soil. NO NO PRS is a French drain located below the surrounding ground surface. NO NO NO T. Lemke NO 02-006(b) 51.8 10/1/2000 2-1 NO NO YES NO This PRS is an acid waste line that transported effluent from several labs in TA-2-1and discharged to the creek. The waste line was abandoned in place at least 35 years ago. It is unknown whether chemicals were released to the creek via this waste line. Outfall previously discharged directly into LA Canyon channel. Mostly rock and sediment. Area generally flat with the channel sloping towards the east. YES YES Outfall discharged to active canyon channel. Runoff terminates in LA Canyon channel. None observed. NO No structural impacts. NO Line abandoned in place, which hasn't been used for over 30 years. YES Upslope drainage from LA Canyon. Veenis, Steve Gabions line the channel in LA creek at TA-2. Run-on diversion walls and debris catchers were installed as a flood mitigation effort after the Cerro Grande Fire. NO Site reassessed to reflect outfall into LA Canyon. Orignal assessment completed on 8/6/97 with a score of 16. 02-006(c) 15.6 8/6/1997 NO NO YES NO South of TA-2-01 - from corner of building to creek edge, under paved parking lot. NO NO NO NO NO R. Reynolds NO 02-006(d) 15.6 8/6/1997 NO NO YES NO South of TA-2-01 - from corner of building to creek edge, under paved parking lot. NO NO NO NO NO R. Reynolds NO 02-006(e) 15.6 8/6/1997 NO NO YES NO South of TA-2-01 - from corner of building to creek edge, under paved parking lot. NO NO NO NO NO R. Reynolds NO 02-007 44.8 10/1/2000 2-1 NO NO YES NO Site of a decommissioned septic tank (TA-2-43) and drain line that received sanitary wastes from Building TA-2-1 until the 1950s. The septic tank was constructed of reinforced concrete and measured 13 ft x 8 ft x 6 ft deep; overflow from the tank was transported to a canyon outfall via the 6-in. clay drainline. Mostly open ground covered with pine needles, channel is sediment/rock covered. Gentle slope towards the east. YES NO Runoff evidence into adjacent channel. Runoff terminates directly into LA Canyon channel. None observed. NO No structural impacts. NO No operational impact. NO No upslope drainage impacts. Veenis, Steve Reseeding and straw mulch. NO Site re-evaluated to reflect updated information provided by ER Project (original assessment 8/6/97 with score of 27). Auger drilling and surface samples were collected and the site was disturbed. 02-008(a) 55.8 7/14/2000 2-49 NO NO NO YES Outfall from cooling tower. Discharged at edge of watercourse. Outfall has been removed. Mound of soil and broken asphalt where outfall was removed. Outfall has been removed. YES NO Outfall has been deleted, but runoff from surrounding areas impact site. The LA Canyon drainage channel is immediately adjacent to former outfall. Outfall discharged directly into LA Canyon channel. Non observed. YES Asphalt around cooling tower. NO Inactive NPDES outfall 03A020. YES High water flows in canyon can impact site. Veenis, Steve Gabions line the channel in LA creek at TA-2. Run-on diversion walls and debris catchers were installed as a flood mitigation effort after the Cerro Grande Fire. NO Original assessment completed on 8/6/97, site re-assessed to reflect current site conditions. 02-008(b) 15.6 9/25/1997 2-4 NO NO YES NO Former outfall from Building 2-4. Could not locate exact outfall location. Thick vegetation above retaining wall on south bank of Los Alamos creek. Area of suspected outfall flat, approximately 30 feet from 8-foot drop off to creek. NO NO NO NO Building 2-4 inactive since early 1980s. NO D. Mays NO 02-008(c) 20.8 8/6/1997 NO NO YES NO At north edge of stream banks leading into stream. NO NO NO NO NO R. Reynolds NO 02-009(a) 57.0 10/24/2000 NO NO YES NO This PRS consists of an area radioactive soil contamination located above a boulder, south of the fence corner behind TA-2-50. It was identified during the decommissioning of several buildings at TA-2 in 1986, when a survey uphill of the boulder was conducted and contamination was detected. Mixed grasses with bare soil and rocks. Site generally flat with gentle slope toward the north into LA Creek. YES NO Sheet flow runoff evidence was observed. Gentle slope towards LA Canyon drainage +/- 50 yds. None observed. NO No structural impacts. NO No operational impacts. YES Upslope drainage from hillside. Veenis, Steve Jute matting, reseeding and straw wattles below site. NO Site was originally assessed on 8/6/97, was reevaluated to reflect current site conditions. Site was remediated 9/2000, BMPs were installed to stabliize. 02-009(b) 44.8 2-1 NO NO YES NO Subsurface soil contamination located north of TA-2-19 and the bridge at TA-2. It was identified during the decommissioning of several buildings at TA-2 in 1986. The bridge at TA-2 was being used as a temporary truck staging area when detectable activity was found in the area. Low vegetation - grass, clover, a few small oak trees. Site generally flat with gentle slope towards LA Canyon channel to the south. YES NO Evidence of sheetflow runoff observed. Runoff terminates into LA Canyon. None observed. NO No structural impacts. NO No operational impact. NO No upslope drainage impacts. Veenis, Steve NO Site re-assessed to reflect updated information from ER Project (original assessment 8/6/97 with score of 21). 02-009(c) 51.3 10/1/2000 2-47 NO NO YES NO Two areas of radioactive soil contamination south of former structure TA-2-48 identified during decommissioning activities in 1986. One area may be associated with a condensating trap from the gaseous effluent stack line for the Water Boiler Reactor and the other may be associated with a leach field that was part of PRS 2-007 septic tank. Bare ground, sparse vegetation with some pine needle coverage. Gentle slope on both sides of channel towards the center of the drainage. YES NO Sheet flow runoff evidence in and around the drainage channel. Runoff terminates directly into LA Canyon drainage. None observed. NO No structural impacts. NO No operational impacts. NO No upslope drainage impacting the site. Veenis, Steve The contaminated areas were removed during the summer of 2000 as an accelerated cleanup due to the Cerro Grande Fire. The sites were reseeded and covered with straw mulch and geotextiles. NO Site re-assessed to reflect updated information from ER Project (original assessment 8/6/97 with score of 27). 02-009(d) 20.8 8/6/1997 NO NO YES NO East of 63 approx. 100 yards, upon toe of south facing slope - approx. 60 yards from creek bottom. Low vegetation - grass, clover, a few small oak trees. NO NO NO NO NO R. Reynolds NO 02-010 15.6 9/3/1997 NO NO YES NO PRS located under current building TA-2-63. Area currently covered by building. Building surrounded by soil and asphalt. Flat surface. NO NO Site is under a building. NO Site is under a building. NO NO T. Lemke NO 02-011(a) 57.0 9/3/1997 NO NO YES NO Series of drains on west side of TA-2-1, on hillside behind TA-2-1, and in front of TA-2-1. Asphalt around building and vegetation on hillside. Less than 10% on asphalt, 10-30% on hillside. YES YES Storm water run-off collected and channelized in concrete conveyances, drop inlets and culverts. Discharges into creek. YES PRS is storm drain and collects water from asphalt around TA-2-1. NO YES Sheet flow from hillside behind TA-2-1. T. Lemke NO Storm water conveyed into man-made channels. 02-011(b) 22.6 9/3/1997 NO NO YES NO PRS in vegetated area adjacent to creek. Site of former buildings TA-2-19 and TA-2-35. Heavy vegetation - no canopy cover. NO NO NO NO YES Sheet flow from adjacent hillside. T. Lemke NO 02-011(c) 20.8 9/3/1997 NO NO YES NO Site of old drain line and outfall on west side of TA-2-49, adjacent to creek. Natural vegetation. NO NO Drain line now discharges into 3 underground tanks. Outfall discharging to creek removed in 1963. NO NO NO T. Lemke NO 02-011(d) 20.8 9/3/1997 NO NO YES NO Site of old drain line and outfall on west side of TA-2-49, adjacent to creek. Natural vegetation. NO NO Drain line now discharges into 3 underground tanks. Outfall discharging to creek removed in 1963. NO NO NO T. Lemke NO 02-011(e) 31.8 8/6/1997 NO NO NO YES Outfall from cooling tower. Discharged at edge of watercourse. Outfall has been removed. Mound of soil and broken asphalt where outfall was removed. Outfall has been removed. NO NO YES Asphalt around cooling tower. NO YES High water flows in canyon can impact site. T. Lemke NO