131 LA UR 03 5862 - National Nuclear Security Administration ...

Table 2.17.3-1. Evaluated and Stabilized PRSs following the Cerro Grande Fire• Conduct baseline sampling to characterize post-fire, pre-flood conditions (i.e., beforemonsoon season rains) in fire-impacted watersheds. The Contaminant Transport Teamcompleted a Baseline Characterization Sampling Plan on June 24, 2000. Pre-flood fieldwork,including collection of sediment, surface water, and alluvial groundwater samples, was completedon July 14, 2000. Post-flood fieldwork was carried out in August and September of 2000, asnecessary.• Evaluate, stabilize, or remove sites subject to flooding. The Accelerated Actions Team identified77 PRSs in fire-impacted canyons that were potentially vulnerable to post-fire flooding. Themajority of these sites were in Los Alamos Canyon (TA-2 and TA-41) and Pajarito Canyon (TA-18 and TA-27) and included outfalls, storm drains, septic systems, and other structures (includingthose associated with the Omega West Reactor at TA-2). Few of the sites assessed actually requiredcorrective actions except for several in TA-2 where excavation, soil removal, and site restorationactivities were completed during July and August 2000.In addition, one flood-impacted sediment deposition area and five fire-impacted sites were identifiedthat required corrective actions to remove debris or contaminated soils. ER Project personnel completedaccelerated actions at the following sites:MDA-RNO. OF PRSs PRS LOCATIONS START DATE COMPLETION DATE10 TA-11 5/21/00 5/24/0029 TA-06, 09, 14, 15, 22, 36, 40, 49 6/14/00 7/15/0034 TA-16, 46, 15, (R-44) 5/29/00 7/15/0018 TA-04, 05, 42, 48 6/27/00 7/15/00• Los Alamos Canyon, “Garden Plot”: excavation of 765 cubic meters of low-level radioactivelycontaminated soil, waste removal, and site restoration,• TA-16, MDA-R: excavation and waste removal,• TA-15, R-44 firing site surface disposal area: debris removal,• TA-36 surface disposal area: debris removal,• TA-40 surface disposal area: debris removal, and• TA-16 “silver” outfall: removal of contaminated soil and stabilization of drainage channel.MDA-R (a 2.25-acre site) is located in TA-16, north of TA-16-260 (high explosives machining building)and south of Cañon de Valle. It lies on level terrain with a moderate-to-steep slope to the north, dropping off80 feet into the canyon. MDA-R ignited during the Cerro Grande Fire and continued to burn for over twoweeks.Historically, MDA-R was a burn ground and waste disposal site for S-Site’s weapons experiments fromthe mid-1940s until the early 1950s, probably 1951. Initially, waste materials were burned in an open field atMDA-R; later, three U-shaped bermed pits (75 feet by 75 feet) were constructed for burning. High explosivesscrap was collected, broken up, and burned in these pits. When the 260 Line was constructed, the bermsand the surface soil at MDA-R were graded northward into Cañon de Valle. A 1992 inspection of MDA-Rrevealed the presence of oil cans, glass vials, metal structures, and coaxial cables below MDA-R on the southside of the canyon.During the week of May 15, 2000, LANL personnel observed that MDA-R was smoldering, noting thattree roots, tree trunks, railroad ties, and cabling were burning. Over the next two weeks, emergency personnel2-184SWEIS Yearbook—2002