Program Management Presentations

Post-Fire Environmental Sampling Data

Post-Fire Accelerated Actions

Maps

Fire Information

ER Project Post-Cerro Grande Fire Environmental Sampling Data

• Purpose
• Data Analysis
• Conceptual Exposure Model
• Matrix of Baseline Characterization Activities
  (matrix contains links to sampling data

Purpose

The Cerro Grande fire impacted a large area in the eastern Jemez Mountains, the Los Alamos townsite, and on Los Alamos National Laboratory (the Laboratory) land. Therefore, the Laboratory and other agencies (e.g., the New Mexico Environment Department, San Ildefonso Pueblo, the US Army Corps of Engineers, and the US Environmental Protection Agency [EPA]) are conducting extensive sampling, analysis, and monitoring activities to address contaminant movement issues that are associated with increased fire-related flood potential. A Laboratory sampling and analysis plan that decribes the many Laboratory sampling and monitoring activities currently under way is available on the Emergency Rehabilitation Team home page. Continued sampling and analysis activities are necessary, because although the Laboratory has implemented numerous engineering efforts to minimize the effects of potential floods, some contaminant movement still could occur.

Within this institutional framework, the Laboratory's Environmental Restoration (ER) Project is sampling sediments, surface water, and alluvial groundwater to obtain the data needed to evaluate the impacts of floods on these potential transport media. Data obtained from these sampling activities also will support the Project's assessment of risk to human health and the ecology, for areas that would be affected by floods.

Sampling in the watersheds affected by the fire was prioritized, based on known or suspected contaminant concentrations and the prefire inventory of contaminants. Three watersheds warranted highest priority: Pueblo Canyon, Los Alamos Canyon, and Pajarito Canyon. Other fire-affected watersheds that are being sampled are Cañada del Buey, Guaje Canyon, Mortandad Canyon, Rendija Canyon, Sandia Canyon, and Water Canyon.

The ER Project's characterization activities also address fire-related changes in the spatial distribution of contaminant inventory and concentrations within the affected watersheds. Some areas and media within canyons on and off Laboratory lands were not well characterized before the fire. Therefore, additional baseline (preflood) characterization was expedited in order to understand and document potential changes that could be associated with flooding.

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Data Analysis

The ER Project has analyzed environmental samples from fire- and flood-affected media for a range of metals, radionuclides, and organic chemicals. Data summary tables will be prepared that compare these analytical results with available Laboratory-specific background values and risk screening levels appropriate to each medium. For example, water-sample screening levels are regulatory standards. For soil and sediment samples analyzed for the presence of inorganic and organic chemicals, project screening levels are risk-based values published by EPA Region 6; these screening levels are derived using the most current toxicity information, default toxicity parameters, and equations. For soil and sediment samples analyzed for the presence of radionuclides, screening levels are derived using the US Department of Energy's residual radioactive material code (RESRAD); these screening levels are based on a dose limit of 10 millirems per year (mrem/yr).

Screening levels are intended to provide an initial generic assessment of potential risk under conservative exposure conditions; if a contaminant exceeds its screening level, immediate action (e.g., remediation) may not be necessary but the sampled area should be evaluated further. This evaluation may include additional sample collection, which could lead to a baseline risk assessment. If enough potential-exposure-pathway data are available, evaluating the potential risk under a more realistic scenario (e.g., more representative exposure conditions) may be required.

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Conceptual Exposure Model

The purpose of a conceptual exposure model is to describe the contaminated media, exposure points, and exposure pathways related to potential flood events. The Cerro Grande fire modified the potential for extreme runoff and erosion events in several watersheds that encompass Laboratory lands. The primary watersheds with significant potential fire impact in their headwaters areas are Pueblo Canyon, Los Alamos Canyon, Mortandad Canyon, Pajarito Canyon, and Cañon de Valle/Water Canyon. The severity of the fire in each watershed and the engineering measures put in place to mitigate or manage flood magnitude determines the likelihood that flooding may occur.

Postfire flooding may affect contaminated media in several ways.

· Flooding could result in bank erosion and/or vertical incision, which could mobilize canyon-floor sediment. Sediment deposits that contain elevated radionuclides, metals, and organic compounds may be mobilized.

· Increased surface-water runoff within the canyons could affect alluvial groundwater and base flow surface water chemistry.

· The ash in surface-water runoff could produce alkaline pH conditions. These pH conditions may influence the distribution and mobility of contaminants, including strontium-90, uranium, plutonium, and americium.

Floods originating in the burned upper portions of watersheds not affected by Laboratory activities also may contain elevated metal and radionuclide levels from ashes of plant material and organic compounds (partially burned trees, other plants, and litter). Fire retardant chemicals are also present in the burned watersheds in varying concentrations and spatial distributions. The concentrations of these constituents in floodwaters or sediments currently are not known. However, while large floods probably would dilute concentrations of dissolved constituents, they also could carry more sediment downstream to the Rio Grande.

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Matrix of Baseline Characterization Activities

Matrix Key

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