esm223_05_Other_Reading_Diagnostic_Assessment_summary

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Unformatted text preview: OCT-18-2UUU MON 02:58 PM BREN SCHOOL UCSB FAX N0. 805 893 7812 P. 01/18 i --' DIAGNOSTIC ASSESSMENT 2 OF CONTAMINATED SITE PROBLEMS W The existence of contaminated sites may result in the teleaso of chetni 'al con- tatninants into various environmental compartments. Any contaminant released itttn ' the environment. will be controlled by a complex Set of processes (such as interntedia transfers. degradation. and biological uptake). in fact. many chemical contaminants are persistent in the environment and undergo complex interactions in more than one environmental medium. Ctmtaminated sites should therefore he caret'nlly amt than onghly investigated so that risks to potentially exposed populations can be determined with a reasonably high degree of accuracy. Typically, different levels of effort in the investigation will generally be required for different contaminated site problems. Ultimately, the apptication of a well-designed diagnostic assessment plan to a com laminated site problem will ensure that appropriate and cost-effective corrective measures are identified and implemented for the site. 2.1 lNVESTIGATiON 0F PDTENTIALLY CONTAMINATED SITES Site investigations consist of the planned and managed sequence ot' activities carried out to determine the nature and distribution of contaminants at potentially contatninated sites. The activities involved usually are compriSed of the identification of the principle hazards. the design ol' sampling and analysis programs. the collection and analysis of environmental samples. and the reporting of laboratory results for further evaluation 0351, 1938). The most important primary sources of contaminant releasc to the various envi- romnental media are usually associated with constituents in soils at contaminated sites. The contaminated soils can subsequently impact other environmental matrices. The impacted media. having once served as “sinks”. may eyentuaity become secondary sources of contaminant releases into other environmental compartments. “faith: 2.] summarizes the important sources and "sinks" or receiving media associated with typical contaminated site probtetns. In general, all relevant sottt'ces and intpactetl media should be thoroughly evaluated as part of the site investigation efforts. in order to get the most out ol' :1 site investigation, it must be conducted in a systematic manner. Systematic methods help focus the purpose. the required mm of detail. and the several topics of interest— such as physical site conditions, likely 19 OCT-18-2UUU MON 02:69 PM BREN SCHOOL UCSB FAX N0. 805 893 7812 P. 02/18 20 Table 2.1 Target Media Primary contaminant source Surlace Impoundmente (e.g.. lagoons. ponds. pits) Waste management units (e.g.. Iandlill. land treatment unit. and waste pile) Waste management zones (e.g.. container storage area and storage tanks) Waste treatment plantsllaclilties Incinerators injection wells W aims: Asante-Duah. 1993, MANAGEMENT DF CONTAMINATED SITE PROBLEMS Typical release causes and mechanisms Loadingtunloading activities ' Ovenopplng dikes and surlace runoll Seepage and Infiltration/percolation Fugitive dust generation Volatillzalion Migration of releases outside unit's runoll collection and containment system Migration ol releases outside the containment area lrom loading and unloading operations Seepage and inliltration Leachale migration Fugitive dust generation Volatiiization ‘ Migration of runoit outside containment area Loading/unloading area spills Leaking drums. leaks through tank shells; and leakage from cracked or corroded tanks Fleleases lrom overllows Leakage lrorn coupling! uncoupling operations Eliluenl discharge to surlace water and groundwater resources Fiouline releases lrom waste handlingipreparation activities Leakage due to mechanical lallure Stack emissions Leakage trom waste handling operations at the wall head Potential Release Mechanisms tron-i Various Contaminant Sources and Primary receiving or impacted media Air - ' Soils and sediments ' ' Surlaee water Groundwater Air Soils and sediments Surtace water - Groundwater Subsuriace gas (in soil pores. vents. and cracks migrating through soil) Air Soils and sediments Surlace water Groundwater Subsurface gas (in soil pores. vents. and cracks migrating through cell) Surlac water (by dissolution, dispersion, transport. etc.) Sediments (lrom adsorbed chemicals) Groundwater Air Foliage (lrom particulate deposition and atmospheric fallout) Soils (lrorn particulate deposition and atmospheric washout) Sunace water (from particulate deposition and atmospheric washout) Groundwater (by dissolution. dilluslon. dispersion. etc.) Surlaca water (from groundwater recharge) OCT-18-2UUU MON 02:59 PM BREN SCHOOL UCSB FAX N0. 805 893 7812 DIAGNOSTIC ASSESSMENT OF CONTAMINATED SITE PROBLEMS 21 contaminants. extent and severity of contamination. effects on populations potentially at risk. potential for environmental harm. and hazards during construction activities (Cairney. 1993). In addition to establishing the concentration ol'contaminants at a case site. the site investigation should he designed to provide an indication of the general background or "reference" level of the target contaminants in the local environment. The systematic process required For the site investigation essential ly involves the early design ol‘ a representative conceptual model of the site. This model is used to assess the physical conditions at the site as well as to identity the mechanisms and processes that could produce significant risks at the site. When good quality assurance/quality control (QAIQC) procedures have been used in the overall process. the information derived from the investigation of a potentially contaminated site will be both reliable and ol‘ known quality. 0n the other hand. failure to follow good QAIQC procedures may seriously jeopardise the integrity of the data needed to make critical site restoration decisions. which could adversely impact costs of possible remediation requirements for the contaminated site. 2.1.1 A Site Investigation Strategy Ot‘tentimes. site investigation activities are designed and implemented in accor- dance with several regulatory and legal requirements oi‘ the region or area in which the potentially contaminated site or property is located. In a typical investigation. the influence of the responsible regulatory agencies may al't‘cct several operational ele- ments. including site control measures. health and safety platts. soil borings and excavations. monitoring well permitting and specifications. excavated utaterials con- trol/disposal and the management of investigation-derived wastes in general. sample collection and analytical procedures. decontamination proactlures. and tral'tic disrup- lion/control. Irrespective ot’ whichever regulatory authority is involved. the basic site investigationstrategy generally adopted for contaminated site problems typically will comprise of the elements summarized in Box 2.1 (Cairney. 1993). As an important starting point in the site investigation process. the quality of data acquired from the study should he clearly delincd. Once the level of confidence required for site data is established. strategies for sampling and analysis can he developed (USEI’A. tilt-lit). The identification (it"sampling rcquircmcuts involves specifying the sampling design. the sampling method. sampling numbers. types. and locations. and the level of sampling quality control. in tact. sampling program designs must seriously consider the quality of data needed. It’ the samples are not collected. preserved. and stored correctly helorc they are analyzed. the analytical data may he compromised. Also. it' sut'l'icient sample amounts are not collected. the method sen- sitivity requirements may not he achieved. I Et'l'ective analytical protocols in the sampling and laboratory procedures are required to help minimize uncertainties in the site investigation process. In a another of situations. the lahoratory designated to perform the sample analyses provides sample hottlcs. preservation materials. and explicit sample collection instructions hccause ol" the complexity of gathering many different samples from various matrices that may have to he analyzed using a wide range of analytical protocols. The deter- mination of analytical requirements involves specifying the most cost-effective anad lytical tncthod that. together with the sampling methods. will tnect the overall data quantity and quality objectives for the site investigation. p 51-1 P. 03/18 OCT-lB-2UUU MON 02:59 PM BREN SCHOOL UCSB FAX N0. 805 893 7812 MANAGEMENT OF CONTAMlNATED SITE PHOBLEMS BOX 2.1 Tasks and Elements of a Site Investigation Program Problem Definition and Preparatory Evaluation: * Define objectives (including the level of detail and topics of interest) - Collect and analyze existing information (i.e., review available background information. previous report's. etc.) - Conduct visual inspection (i.c.. field reconnaissance surveys) ' Construct preliminary conceptual model of site Sampling Design: i identify information required to refine conceptual model of the site - identify constraints and limitations (e.g., access, presence of services, financial limitations) 0 Define sampling and interpretation strategy - Determine exploratory techniques and testing program haplemenmrirm ofSnmpling and Analysis Plans: Ctmduct exploratory work on site (e.g., exploratory borings, test pits, geophysi- cal surveys, etc.) Perform in aim testing Carry out sampling activities Coinpite record of investigation logs, photographs. and sample details Perform laboratory analyses Dam Evaluation and Results Interpretation: - Compile and preSent relevant data - Carry out logical analysis of data - Refine conceptual model for site - Enumeratc implications of results I Report on findings 2.1.2 Selecting Target Contaminants During Site Investigations Because of the inherent variability in the materials and the diversity of processes used in industrial activities, it is not unexpected to find a wide variety ol’contaminants at a contaminated site. As a consequence. there is a corresponding variability in the range and type of hazards and risks that may be anticipated from different contami— nated site problems. In general, detailed background information on the Critical contaminants of potential concern should be compiled as part‘ot" the site investigation pl'ngt'tttlt. P. 04/18 OCT-18-2000 l’lON 03:00 PM BREN SCHOOL UCSB FHX N0. 805 803 7812 P. 05/18 DIAGNOSTIC ASSESSMENT or: CONTAMINATED srrE PHDSLEMS . 23 The investigation of a potentially contamimucd site muSt provide'i'nlormation on all contaminants known, suspected, or believer] to be present at the site. Thus. the investigation should cover all compounds for which the history of site activities, current visible contamination, or public concerns suggest the possibility of contami- nation by sttcb compounds. Ultimately, several chemical-Specific factors (such as toxicitylpotency, concentration, mobility, persistence, bioaccumulative/bioconcentration potential, synergistic/antagonistic effects, potentiation/neutralizing effects, frequency ofdetectioa, and naturally occurring background thresholds) are used to further screen and select the specific target contaminants that will beeotne the focus of the detailed site evaluation process. 2.1.3 Contaminant Fate and Transport Considerations Environmental contamination can be transported far away front its primary sourcc(s) of origination via natural erosional processes, resulting in the possible birth of new contaminated site problems. On the other hand, some natural processes Work to lessen or attenuate Contaminant concentrations in the environment through mecha- nisms of natural attenuation such as dispersionldilution, ion exchange, precipitation. adsorption and absorption, filtration, gaseous exchange, photodegradation, and bio- degradation. Typically, environmental fate analysis is used to assess the movement of chemicals between environmental compartments. Simple mathematical models can be used to guide the decisions involved in estimating the potential Spread of contaminant plumes. Where applicable, wells or monitoring equipment can then be located in areas expected to have elevated contaminant concentrations and/or in areas considered upgradient and downgradient of a plume. in general, as pollutants are released into various environmental media, several factors contribute to their migration and transport. A number of important physical and chemical properties affecting the environmental fate and transport of chemical con- taminants are annotated in Appendix C. A more detailed discussion of the pertinent factors affecting the environmental fate and/or intermedia transfers for chemical constituents at contaminated sites canbe found elsewhere in the literature (e.g., Swami and Eschenroeder, [983; Lyman et at, 1990). The affinity that contaminants have for soils can particularly affect their mobility by retarding transport, For instance, hydrophobic or cationic contaminants that are migrating in solution are subject to retardation effects. In fact, the hydrophobicity of a contaminant can greatly affect its fate, which explains some of the different rates of contaminant migration occurring in the subsurface environment. Also, the phenom- enon of adsorption is a major reason why the sediment zones of surface water systems may become highly contaminated with specific organic and inorganic chemicals. to the groundwater system, the solutes in the porous media will "ineve with the mean velocity of the solvent by an advective mechanism. in addition, other mecht- nisms governing the spread of contaminants include hydraulic dispersion and molccts lar diffusion (which is named by the random Brownian motion of molecules in solution that occurs whether the Solution in the porous media is stationary or has an average motion). Furthermore, the transport and concentration of the solute-(s) are affected by reversible ion exchange with soil grains, chemical degeneration with other constituents, fluid compression and expansion. and, in the case of radioactive mate- rials, by radioactive decay. OCT-10-2000 llON 03:00 PM BREN SCHOOL UCSB FHX N0. 805 803 7812 24 MANAGEMENT OF CONTAMINATED SITE PROBLEMS The degree of chemical migration from a contaminated site depends on both the physical and chemical characteristics of the individual constituents at the site, and also on the physical, chemical, and biological characteristics of the site. Physical charac- teristics of the contaminants, such as solubility and volatility, influence the rate at which chemicals leach into groundwater or escape into the atmoSphere. The charac. teristics of the site environment (such as the geologic or hydrogeologic features) also affect the rate of contaminant migration. In addition, under various environmental conditions some chemicals will readily degrade to Substances of relatively low toxic— ity, while other chemicals may undergo complex reactions to become more toxic than the parent chemical constituent. All other factors being equal, the extent and rate of contaminant movmnent are a function of the physical containment of the chemical constituents or the contaminated zone. A classical illustration pertains to the fact that a low permeability cap over a contaminated site will minimize water percolation from the surface and therefore minimize leaching of chemicals into an underlying aquifer. invariably, the fate of chemical compounds released into the environment forms an important basis for evaluating the exposure of biological and ecological receptors to l'taitardous chemicals. 2.1.4 Design of Data Collection and Evaluation Programs The general types of site data and information required in the investigation of potentially contaminated sites relate to contaminant identities, contaminant cote centrations in the key sources and media of interest, characteristics of sources and contaminant release potential, and characteristics of the physical and environmen- tal setting that can affect the fate, transport, and persistence of the contaminants (USEPA. 1989). The'dcsign and implementation of a substantive data collection and evaluation program is vital to the effective management of contaminated site problems. ' Data are generally collected at several stages of the site investigation, with initial data collection efforts usually limited to developing a general understanding of the site. Typically, a preliminary gas survey using subsurface probes and portable equip- ment will give an early indication of likely problem areas. Soil gas surveys are generally carried out as a precursor to exploratory excavations, in order to identify areas that warrant closer scrutiny. They cart also be used to assist in the delineation of previously identified plumes of contamination. This is an important step to complete prior to the start of a full~scale site investigation. Gases produced at contaminated sites will tend to migrate through the paths of least resistance, The presence of volatile contaminants or gas-producing materials can be determined by satnpling the soil atmosphere within the ground. installation of a gas-monitoring well network, in conjunction with sampling in buildings in the area, can be used to determine the need for corrective measures. This information can be used to determine the possibility for human exposures and to determine appropriate locations for monitoring Wells and gas collection systems. On-site vapor screening of soil samples during drilling can provide indicators nl‘nrganie contamimttion. For example, organic vapor analyzer/gas cltrontatograph (OVA/(3C) or gas chromatographlphotoionication detector (QC/F113) screening pro- vides a relative measure of contamitmtion by volatile organic chemicals. Also, predictive models can he used to estimate tltc extent of gas migration from a suspected sun', "ace source. Tltis information can subsequently be ttscd to identify apparent “ho. , abs" and to select and samples for detailed chemical analyses. The P. 00/18 OCT-IB-EUUU lION 03:01 PM BREN SCHOOL UCSB FHX N0. 805 893 7812 P. 07/18 DIAGNOSTIC ASSESSMENT OF CONTAMINATED SITE PROBLEMS 25 vapor analyses on-site can also be helpful in selecting screened intervals for moni- toring wells. In areas where the contamination source is known, the sampling program should be targeted around that source. Normally sampling points should be located at regular distances along lines radiating from the contaminant sottrce. Provisions should also he made in the investigation to collect additional samples of small, isolated pockets of material which are visually suspect. In general, a phased sampling approach encourages the identification of key data needs as early in the site investigation process as possible. This ensures that the data collection effort is always directed toward providing adequate information that meets the data quantity and quality requirements of the study. As a basic understanding of the site characteristics is achieved, subsequent data collection efforts focus on iden- tifyng and filling in data gaps. Any additionally acquired data should be such as to further improve the understanding of site characteristics and also consolidate informa- tion necessary to effectively manage the contaminated site problem. ltt this way. the overall site investigation effort can he continually t'escoped to minimize the collection of unnecessary data and to maximize the quality of data acquired. Overall, the data gathering process should provide a logical, objective. and quantitative balance be- tween the time and resources available for collecting the data and the quality of data. based on the intended use of such data. 2.1.5 Analyzing Site Information The analysis of previously acquired and newly generated data serves to provi...
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