Hazardous Waste Site Management Water Quality Issues (1988) / Chapter Skim
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4. THE CALIFORNIA SITE MITIGATION DECISION TREE PROCESS: SOLVING THE “HOW CLEAN SHOULD CLEAN BE?” DILEMMA
4. THE CALIFORNIA SITE MITIGATION DECISION TREE PROCESS: SOLVING THE “HOW CLEAN SHOULD CLEAN BE?” DILEMMA
Pages 67-97
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From page 67... ...
. This decision tree manual (also referred to as the decision tree process)
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From page 68... ...
They define exposure levels at which no observed adverse effect would be found. The decision tree process also allows one to set different cleanup levels for a particular site that reflect the different degrees of effectiveness of various remedial action combinations.
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From page 69... ...
Site Assessment After a site has been identified, a detailed quantitative assessment is then conducted by activating the site assessment component. The function of this component is threefold.
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From page 70... ...
The focus of site characterization and the development of environmental modules is ascertaining what the concentrations of toxic chemicals will be at the points of exposure to biologic receptors of concern. Risk Appraisal Risk appraisal, the next component, begins while the site assessment process is still going on.
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The project manager can quickly assess whether or not a biologic receptor is currently at risk through the use of three simple tests contained in the decision tree process. The three tests taken together make up the risk appraisal mechanism.
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The third test in the risk appraisal process determines whether a biologic receptor may receive excess exposure to an aggregate of substances that produces toxic manifestations. This test assumes additivity of such exposures across all media.
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The second case demonstrates how the decision tree process allows the project manager to evaluate the effectiveness of different remedial actions. It should be noted that the risk determination process used to establish the cleanup criteria is composed of the three simple tests that make up the risk appraisal mechanism.
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From page 74... ...
Development of a Mitigation Strategy and the Selection of Remedial Action If it is determined, either through the risk appraisal process or the risk determination process, that a biologic receptor of concern is or will be at risk, mitigation of that risk should be investigated. The development, evaluation, and selection of such remedial actions are presented as elements of the last component of the decision tree process.
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APPI~G To DECISION T=E PROCESS: TWO CASE STUDIES Two case studies are presented below. The first study illustrates how the decision tree process is used to set cleanup criteria quickly.
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From page 76... ...
Technical creeping of Specific Technolonles I~ Formulate Broad Alternative Remedial A~tl~nQ Environ rental, Pubilc Health, and Institutlonal Screening Cost Screening Identity Surviving Alternative Remedial Actions Phase 1: Phase 11: Project Scoping Identification of Specific Technologies Phase 111: Screening of Alternatives Technical Institutlonal Cost An:llVals Analysis Ana veils Statutory Environmental Impact Analysis Phase IV: Detailed Analyses of Surviving Alternatives Summ;rizatlon of Alternatives . Final Feasibillty Report I FIGURE 4-3 Feasibility study process.
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From page 77... ...
To set a health-based cleanup criterion for the site, the environmental fate and risk determination component was activated. To project what the future concentrations of arsenic compounds would be at the location of the biologic receptors, two conservative scenarios were created.
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The primary health concern for this second scenario was based on short-term acute exposure to arsenic compounds. It should be noted that the ground water pathway was excluded from the analyses of both scenarios.
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The threshold wind velocity (U~) is defined as the wind speed, as measured at a wind sensor station generally 7 meters above the ground, that is necessary to initiate soil erosion.
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, the annual average airborne arsenic concentration reaching the public at the site boundary would be 2 x 10-3 ,ug/m3. With this concentration value now in hand, a risk determination can be performed using the three simple tests previously discussed.
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Whereas a soil contaminant level of 2,000 ppm total arsenic may satisfy the conditions in the first scenario, the second scenario must be evaluated to assess the potential health impact to workers during intensive earth-moving activities. In order to compare the occupational exposure of the construction worker, the department reviewed several studies and surveyed various industrial hygienists within the department and Cal-OSHA (California Occupational Safety and Health Administration)
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From page 82... ...
Therefore, from the analysis of these two conservative scenarios a soil cleanup criterion of 400 ppm total arsenic or less would be required to protect both worker health and residential community health. Case Study 2: Site with Ground Water Contamination The following example emphasizes the approach of the decision tree process with respect to the ground water exposure pathway.
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From page 83... ...
This information was immediately used, through the risk appraisal process, to determine whether any biologic receptors of concern were currently at risk. The level of chloroform detected in the sample from the agricultural well exceeded the applied action level (AAL)
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From page 84... ...
Through the decision tree process, all other contaminants detected in samples of the ground water from the agricultural well would also be evaluated through test 1 of the risk appraisal mechanism. For toxic chemicals with similar adverse toxicologic manifestations, potential cumulative effects of multichemical and multimedia/multichemical exposures would be evaluated through
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From page 85... ...
In practice, there are ranges of values of hydraulic properties as well as intrinsic uncertainties associated with geologic interpretations. Environmental Fate and; Risk Determination Based on site assessment data, a two-dimensional representation of the ground water exposure pathway for the site was constructed (Figure 4-6~.
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From page 86... ...
Monitor Wells ' | Source I Area ll ~1 it ~^ ~ l Ground Water Flop ~ ; ~Rive I` FIGURE 4-6 Site assessment: ground water exposure pathway. Capture Radlus ~ ~ _ _ ~ Source , Area L -- l DL ~ Detection Limit l ~ 1 ~¢, l l ~ +< +~4 "L ~ !
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From page 87... ...
The continuing operation of the agricultural and municipal wells to harvest contaminated ground water and thereby work to protect the private well cannot be assumed without formal commitments from the farmer and water purveyor. Therefore, the level of chIoroform at the private well would be expected to exceed the AAL in the future; test 1 of the risk appraisal mechanism fails; and a risk management process should be considered to protect those biologic receptors demonstrated to be at risk in the future.
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From page 88... ...
Specifically, the potential risks of future adverse impacts on biologic receptors of concern have been evaluated and defined through the risk appraisal mechanism. Those risks deterrn~ned to be significant have been identified as media specific, receptor specific, chemical specific, and site specific.
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From page 89... ...
The no-action remedial alternative would not alleviate or reduce the risk posed to downgradient water users, nor would it protect future human biologic receptors wishing to use the ground water resource as a drinking water supply. Although humans would be at risk here, the nonhuman biologic receptors of concern, the fish in the nearby river, are not considered to be at significant risk.
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HAZARDOUS WASTE SITE MANAGEMENT ~ Hi_ ~ 9 : . ~ ~3 ~ ', River River l
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Controlling the pumping of the municipal well would protect downgradient ground water users. This alternative also protects those biologic receptors identified as being at risk and, like other remedial alternatives, has associated costs and problems in implementation.
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From page 92... ...
The availability of financial resources to remediate all sites to the standard implied in Alternative 2 is a serious consideration for project managers. Alternatives 3 and 4 rely on administrative and resource management practices rather than the traditional soil removal/ground water treatment program; yet, if rigorously enacted, they would also meet the criterion of protecting the biologic receptors of concern.
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From page 93... ...
DECISION TREE PROCESS TABLE 4-1 Remedial Alternative Analysis 93 Remedial Public Alternative Cost Technical Health Aquatic Species Concerns Public Input No action None Unacceptable Unacceptable Aquifer restoration with source control t500X Acceptable Acceptable Alternate $50X Acceptable Acceptable Acceptable water supply Plume $20X Acceptable Acceptable Acceptable monitoring maintenance Acceptable Unacceptable Acceptable Acceptable Water agency reluctant Water agency reluctant of * meteorology Hydrology COMA Inflltratlon .
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From page 94... ...
The role of the decision tree process is to provide that decisionmaker with the strongest possible technical basis for making such a decision, in part with the goal of making the decision defensible in the event of a challenge in a public or legal forum. CONCLUSION The California Site Mitigation Decision Tree Manual has been created as a technical guidance document to assist project managers in making decisions that have a strong analytical basis and technical merit.
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Prepared for Hazard Waste Engineering Research Laboratory, Cincinnati, Ohio, and Office of Emergency and Remedial Response and Office of Waste Programs Enforcement, Washington, D.C. PROVOCATEUR'S COMMENTS Joan Berkowitz The California decision tree process, which is outlined in the report that David was kind enough to send to me, is really a "howto" manual for conducting a remedial investigation/feasibility study (RI/FS)
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From page 96... ...
. These action levels are set at the point at which contaminants in air, surface water, ground water, and soils impinge on target organisms.
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From page 97... ...
1984. Ground Water Contamination from Hazardous Waste.
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