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 provide an initial basis to understanding the nature and extent of contamination which. in turn. aids in the design of appropriate corrective action programs for contaminated sites. Consequently, at any reasonable stage of a site investigation, all available site infor- tnation should be compiled and analyzed to develop a conceptual model for the site. This representation should incorporate contaminant sources and “sinks”. the nature and behavior of the site contaminants, migration pathways. the affected en vironmcnlal matrices, and potential receptors (Figure 2. I). In fact, the development of anadcquatc conceptual site model (CSM) is an impertant‘ aspect of the technical evaluation scheme necessary for the successful completion ofa site investigation. It integrates geologic and hydrologic inlormation, and provides a basis for human health and ecological risk assessments. The CSM is also relevant to the development and evaluation ofcorrective action programs for potentially contaminated sites. Several variables and parameters are important to the design of a realistic CSM that will meet the overall goals of the corrective action program anticipated for a potentially contaminated site (Box 2.2). In general. the CSM should be appropriately modified if the acquisition of additional data and new int-'m-tnation necessitates a redesign. Further discussions and illustrations of the framework for devetOping CSMs are given in Chapter 4. 2.2 A PHASED APPROACH TO THE lNVESTIGATIDN OF PDTENTIALLY CONTAMINATED SITE PROBLEMS Programs designed to investigate and remedy potentially contaminated site prob- lems typically consist of a number of phases. These phases reflect the "“ "ferent degrees of detail in the corrective action and/or risk management decision .........~Ithe site. 08/18 P. 805 893 7812 FAX N0. OCT-18-2UUU MON 03:01 PM BREN SCHOOL UCSB -. Hfl- mW.x.-W MANAGEMENT OF CONTAMINATED SITE PROBLEMS 26 umfiEEmnoo m 5.2... umfimvnmmm mntmcmum Eamon—Ha “Em .mmmfizpwadowfimg “BEER m5 E coaflcmmflue H uEflm m: 3 cawmgmcnu nmnnfiw 2:3an 1. \. =95 mangm s35 mfinam Bum}... All :ofiEmEogm €595 Enmuuxm cczfigdmfi €9.3flmafl £995.95 mum cefifiufim... . r .. ...... :ym.-..---..:-mEmhhmEE .Emfiofi mfi mammucou .1 _..N Emmi . . . I. fiafimm .25 comma? Erma. mcEumfl + £5. uEmEEmEoD Lmfiacmmm ,5 EMHEHEE EEEm 55 $ng OCT-lB-2UUU MON 03:01 PM BREN SCHOOL UCSB FAX N0. 805 893 7812 P. 09/18 27 BOX 2.2 Major Assessment Parameter Requirements for the Construction of a Detailed Conceptual Site Model (CSM) lluman. ecological. and welfare resources potentially at risk. - Routes of contaminant exposure to populations potentially at risk. I Spatial distribution of contaminants: v Atmospheric dispersion potential and proximity of target receptors. - Amount, concentration. hazardous nature. and environmental l'ate properties of the subatances present. - Site geology and hydrogeologicat factors. I Area climatic regime and hydrology. - Extent to which the sources can be adequately identified and characterized. - Likelihood of releases if the contaminants remain on‘site. - Extent to which natural and artificial barriers currently contain contaminants. and the adequacy of the harricrs. ‘ t Assessment of the potential migration pathways. - Extent to which site contaminants have migrated. or are expected to migrate From their sourcc(s). - Assessment ol’ the likelihood of contaminant migration posing a threat to public health. welfare, or the environment. - Extent to which contamination levels could exceed relevant regulatory stan- tlartls. in relation to public health or environmental standards and criteria. M Environmental site assessments conducted as part ol’a corrective action invcslih gallon for potentially contaminated sites may he classified into the following general phases: - “l-"l-lfitSE l" investigation. or Preliminary Site Assessment. consisting of a reconnaissance site appraisal and reporting. ' "Pl-lASE ll” investigation. or Comprehensive Site Assesment. comprising of a site investigation (that involves contamination and environmental damage as— sessment) and a preliminary feasibility study of corrective measures. I “PI-lASE Ill" investigation. or Remedial Measures Design and Implementa- tion. incorporating a l'ncuscd feasibility study and the detailed evaluation at sitc restoration measures. In general, the objective of the initial phase (which is comprised of basic back- ground information gathering) should he to determine the history of the site with respect to contamination sources and any relevant characteristics of the site that are readily obtainable from available records. reports. and interviews. The intermediate phase {involving a site characterization) has the primary objectives of defining the vertical and lateral extents of contamination. understanding how the contaminants are OCT-18-2UUU MON 03:02 PM BREN SCHOOL UCSB 28 MANAGEMENT OF CONTAMINATED SITE PROBLEMS TABLE 2.2 Summary Requirements oi the Site Assessment Process Level oi investigation . FfiAsa l: Preliminary site assessment PHASE llA: Initial site investigation PHASE Ill3: Eapandedsite investigation (or remedial investigation! ieasipiiity study) PHASE lll: Hemedial measuresr investigation and corrective action implementation Purpose of investigation To provide a qualitative indication of potential contamination at a site To identity the known or suspected sourcels) oi contamination To dellne the nature and extent oi the contamination To deline the hydrogeoiogy oi the region and direction of contaminant plume migration To determine and evaluate these remedial options potentially applicable to the site restoration To recommend the site restoration method which is most feasible in terms or technical performance and cost-eilectiveness Typical "see-on" tasks pertcrmed Records search. including geologic and hydrogeoiogic literature search. aerial photo reviews. review at archival and regulatory agency . records {to deiine the historical uses at site}. and anecdotal reports (on site history and practices as made available by former employees, local residents. and local historians) Site inspectionfreconnaissance survey (to deline present conditions at the site) Personal interviews (to sopptement historical use data) Written report of findings (to document results and recommendations) Sampling oi potentially impacted media at the surface Subsurlaca borings. well installations. and groundwater sample collection Sample analysis to identity and quantity contaminants Evaluation of sampling results and detailed report of findings. with conclusions Development at rernediation goals and cleanup criteria identification-oi alternative methods} technologies for site remediation Screening of alternatives in order to select those that are most leasioie option Evaluation oi alternatives in terms cost, probable eliectiveness. etc. Ranking oi feasible alternatives and recommendation of the overall best method/technology lot implementation Design and implementation of remedial options and monitoring programs initiated by liytlrogenloglc conditions, and providing the data necessary to design appropriate and appli ~ahle remedial measures. The final phase (that may include a risk evaluation of remedial alternatives as part ot’the focused l‘easibilty study) targets the development. selection, and implementation of appropriate corrective action plans for lhc site Tahle 2‘2 summarizes the requirements of the different levels of effort associated with the site assessment process. 2.2.1 PHASE l investigations A preliminary assessment (PA) is usually conducted to determine il‘ a site is poietltiii‘ inlaruiualcd as a result ol‘ past or current site activities. either due to FAX N0. 805 893 7812 10/18 OCT-18-2UUU MON 03:02 P11 BREN SCHOOL UCSB FHX N0. 805 893 7812 P. 11/18 "-4- H‘n-iI-WW-fl DIAGNOSTIC ASEESSMENT OF CONTAMINATED SlTE PROBLEMS 29 unauthorized dumping or disposal. or from the migration ol‘ contaminants t‘rom adjacent or nearby properties. The objective of tire l-‘A is to qualitatively determine possible significant rinks aesociated with the ease-site. The PA wit-l. at a minimum. involve record scarcitng and a superficial physicai survey that includes carrying out 'the following activities: I l. A review of historical records (such as site history. past operation aml disposal practices. etc.). 2. A review of readily available files and databases maintained by regulatory agettcies (to obtain information on site hydrogcnlogy. characteristics at adja- cent properties. known environmental problems in the area. etc). 3. A licid t‘eCtmnaissance ol' the subject site anti adjacent properties (to ascertain local soil and groundwater conditions. the proximity ot‘ the site to drinking water supplies and surface water discharges. existence of obvious contaminant sources or areas. etc.). The PA is typically designed to document known or potential. areas ol‘ concern doc to the presence of contaminants. to establish tlte characteristics of the containi- nants, to identify potential migration pathways. mid to determitte the potential for migration of the contaminant constituents. Data collection for the PA is accomplished by sequentially perforating a records search/review. a site reconnaissance, and where practicable and/or appropriate. a soil vapor contaminant assessntent. A Phase 1 inves- tigation will generain conclude that either: I. No current or historic evidence of contamination considered likely to have affected the site was found. attd no further investigation is reconnnended; or 2. Sources ol‘ contaminatimt that may have al'l‘ectcd the site have been identified. and a Phase 11 investigation is recommended. Thus. depending on the results of the PA. a “l'urthcr~response~action“ or a “no- l'ttrther—response-action” may be recommended for the potentially contaminated site. Where warranted. the next level of detail in the site assessment is carried out to ascertain this initial indication of possible contamination. Whereas the PA provides some important site information. a more detailed characterization Hi the extent of soil and groundwater contrtntimttion may he necessary to properly assess iOllngCl'l'll risks posed by a contantinated site. 2.2.2 PHASE il investigations The comprehensive site assessment typically comprises a site investigation (5]) andlor a remedial investigation/feasibility study (RI/PS). In general. comprehensive site assessments usuaiiy will involve sampling and testing to identity the types of Contaminants. analyzing preselected or priority pollutants. attd determining the Itori- roots! and vertical extents of the contamination. This typically includes subsurface investigations. soil and water sampling. laboratory analyses. tank testing. attd other relevant engineering investigations to quantify potential risks previoust identified in the PA. The St is designed to verify findings front tire PA. to determine the presence or absence and the extent ol‘contamination at the site. and to identify prt 't'ctnt-diai OCT-lB-2UUU MON 03:02 PM BREN SCHOOL UCSB 3c) MANAGEMENT OF CONTAMINATED SITE PROBLEMS measures. Typically. the investigation identifies specific contaminants, their concen— trations, the area] extent of contamination, the fate and transport properties of the contaminants. anti the potential migration pathways of concern. In an expanded 51. the RI strives to improve the initial site characterization. The PS investigates the most cost-effective methods of remediation that will protect public health. the environment. and public and private property under applicable and appro- priate standards or regulations. At a minimum. a comprehensive site assessment wrll include the collection and analysis of as many soil samples as necessary to determine the full extent of the cuntamimttion. If etmtamination is found to be confined to the unsaturated (vadose) zone. then no groundwater investigation tnay be required; otherwise, groundwater investigation is initiated. The level ol‘ detail for the data collection activities will he site-specific. and is dependent on the degree of soil and groundwater contamination found at the site. 2.2.2.1 PHASE "A Investigations An initial Phase II assessment will normally be usod to confirm whether or not a release has occurred. This is accomplished by implementing a limited program to collect and analyze appropriate site samples. To complete this process, a sampling plan must first be developed. Subsequently, site visits are conducted during which sampling activities will be carried out. The results of this initial comprehensive site assessment will determine the need for a "l’urther-response-action” or a "rto~t’ur‘tlter'— rcsponse-acuon“. A Phase IIA investigation will generally conclude that either: 1. No evidence of contamination was discovered. and no further investigation is recommended; or 2. Contamination that may require remediation has been found, and a Phase ltB investigation is recommended. In fact, if the site is determined to pose significant public health or environmental risks. extensive studies will typically be required to quantify the magnitude of con. taminants present. delineate the limits of contamination. ciiaractdrize in detail the specific chemical constituents present at the site, and assess the fate and transport properties of the specific substances at the site. 2.2.2.2 PHASE NB investigations Where necessary. an expanded Phase II assessment is conducted with the main ohjectivc to characterize the contamination confirmed from the initial Phase I]. inves- tigations. The characterization process involves specifying the type of contamination present. assessing the threcadiniensional occurrence of the contamination. eVaiuating the contaminant fate and transport, determining possible human and ecological recep- tors potentially at rislt, estimating the risks posed to the populations at risk, establishw ing a database to facilitate doeumentation of changes in the occurrences of the contamination. and conducting a preliminary screening of corrective measures. A Phase Illi investigation will generally conclude that either: FAX N0. 805 893 7812 R 12/18 OCT-18-2UUU lION 03:03 PM BREN SCHOOL UCSB FHX N0. 805 893 7812 P. i3/18 DIAGNOSTIC ASSESSMENT OF CONTAMINATED SITE PROBLEMS 31 I. No evidence of extensive contamination was discovered that requires remediation. and no further investigation is recommended; or 2. Contamination that may require remediation has been found, and a Phase III investigation is recommended. Typically,‘ttte Phase IIB assessment will generate a report made up of a site characterization, a risk assessntent. and an evaluation of mitigation and remediation options with an indication oi" the preferred corrective action plan. 2.2.3 PHASE ttt Investigations The remedial measures study involves an evaluation of corrective action pro- grams previously identified during the expanded comprehensive site assessment. an engineering design rat the selected remedial plan, and the implementation of the cleanup or mitigation measures necessary to abate public health and environmental concerns. This also includes a review ot‘" the environmental and public health risks and costs associated with a variety ol“ proposed remedial alternatives. The documentatit‘nt ot'l'cred will Facilitate the development of amiropriate corrective action programs consistent with appropriate regulatory guidelines. The selected remedy will fulfill the jurisdietional requirements for cnviromnental conditions at the site. and should present tninimal risk to the environment and/or to public health. The Phase III assesstncnt will typically report on the preferred corrective action plan, incorporating the design and implementation of the remedial action plans and postrcmediatien monitoring. This level ot‘ the site assessment will also generally include remediation cost estimates as part of the detailed evaluation process For the alternative remedial options identified for the site. This aspect of the assessment will involve evaluating the feasibility of various corrective action strategies applicable to the site scenario, and also evaluating the impact el'the mitigated site on the current and future land uses at and near the site. 2.3 THE SITE ASSESSMENT DECISION PROCESS Prior to the deveIOpment of a corrective action plan for a contaminated site problem, a site assessment must be conducted to determine the true extent ol’ contami- nation at the site, The use of a systematic approach will result in an optimal data gathering and evaluation process that meets uncompromising data quantity and quality objectives (Figure 22). Such a strategy will indeed help address potentially contami- nated site problems in a cost-effective manner. In general, once a diagnostic assessment ol’possihle environmental contamination problems is completed for a potentially contaminated site, plans can be made towards the implementation of effectual corrective actionsl where warranted. The underlying goal in conducting site assessments is to determine an appropriate level ot’el’l'ort in the corrective action required For a site at which contamination is suspected, or knovvn to have occurred. The type of” corrective action selected for the contaminated site proh- Icm will depend on the nature of contamination, tltc amount of contamination that could safely remain at the site following site restoration. and several other site-specific I'acltirs. OCT-18-2UUU MON 03:03 PM BREN SCHOOL UCSB FHX N0. 805 893 7812 P. 14/18 Prelin'iinany identification oi potentially eoniemlnented site Construct rellmlnary conceptu model of site Conduct a preliminary site assessment (Phase 1 Design at implement limited monitoring ngl’fin‘l Potential risks apparent? Yea Porlorm an Initial site investigation {Phase IIAi Significant risks ' apparent? Yes Develop Institutional control tit corrective action ITJBElfilJI'BS Remediation required? Yes Carry out an a: ended site investigation {PR nee us) Conduct a remedial! meesureslcorrective action investigation (Phase III) Design at Implement monitoring Implement site closure pro ram for performance (Le.I no-lunher-response eve uation -ectlonl plane Figure 2.2 Overview of the decision process required tor the systematic assessment of contaminated site problems. A project manager needs to be cautious in accepting the results of any site investigation activity as being an absolute indicator oi“ the true situation at a suspect site In practice, rather than simply wall: away from a site purported to be “clean”, it often is a good idea to implement some form of monitoring program for the candidate site even when no evidence of contamination has been found during the site assess- ment. This is important if for no other reason than to account for uncertainty, because even a carefully executed site investigation program may still miss some isolated pockets of contaminants that may become longderm release sources and therefore a ptitonlial liahility issue. OCT-iB-2UUU MON 03:03 PM BREN SCHOOL UCSB FHX N0. 805 893 7812 _. cc...” “mum tau curt: rnueILttvna 33 2.4 AN ILLusrnartve EXAMPLE on A CORRECTIVE ACTION INVESTIGATION This section illustrates the nature of decision elements typically employed in the investigation ofpotentiall y contaminated sites. The example discusses a poten- tial contamination problem at a small shopping center located in a rttral township that depends almost exclusively on groundwater from a contiguous aquifer for its water supplies. The trigger for this investigation is the diacovery that dry-cleaning solvents have spilled on concrete floor slabs at a dry-cleaning facility within this I‘nini—rnall. . Hackgrountl — A preliminary environmental site assessment carried out for the Village Shopping Center (VSC) indicated the potential for soil and groundwater Contamination at this facility as a result of releases from dry—cleaning and laundry activities at one section of the tnall. A't‘ollow-up phase il-type assessment conducted for the site confirmed the presence of elevated levels of perchloroethylene (PETE) in the sampled soils. The soils beneath the facility location consist predominantly ot‘ fine sands, or fine sand with occasional gravels. Some plastic liner materials (lilter to have been used as a plastic moisture barrier beneath the concrete floor slabs) were found in some ol'the exploratory borings at the site. it is believed that the plastic liner materials found beneath the concrete floor may have prevented extensive contamination of the subsurface environmental compartments. I Recommendations for the corrective action investigation 1—. Since PCE spills would have occurred on the concrete floors at the VSC facility, and because the plastic liner material may have been serving as a “barrier” against further contaminant migration, it is very possible that any PCE encountered in the exploratory soil borings could have been introduced into the soil after the barrier was broken during the soil sample coring activities. If this hypothesis is true. then the extent ofsoil contamination may be even less than suspected; in addition. the possibility of any extensive ground- water contamination can also be ruled out. Under such circumstances. a more detailed assessment may indicate that no extensive and expensive remediation or cleanup program is necessary for the VSC facility. in fact, this reasoning will also support the the importance of studying complete building plans/layouts before any drilling activi- ties that could actually facilitate the spreading of contaminants that would otherwise be Sitting as a more easily removable free product. To complete the requisite investigations for the VSC facility that will allow for appropriate corrective action decisions, at number of issues must be fully explored and evaluated, including the following; I. Groundwater beneath the site should be investigated in order to complete the site assessment. This is because soils beneath the site have already been impacted, and PCE is reasonably mobile in the type of soil formations at this site. That is. considering the mobility of PCB and the sandy nature of soils found at the VSC facility. the possibility ofa contaminated aquifer beneath the facility cannot be ignored. in particular, if it cartnot be established that the liner materials may have prevented the PCE from migrating further into the subsur- t‘aCe environment. then the groundwater system beneath the site should be fully investigated. On the other hand. if it can be positively established that the plastic liner material did serve to prevent or minimize PCE migration into the subsurface environments, then a different set of exposure scenarios may he developed for the corrective action investigation at this facility. R 15/18 OCT-18-2UUU MON 03:04 PM BREN SCHOOL UCSB FAX N0. 805 893 7812 P. 18/18 -d4 lVlHNHUEWil—T-Wi Ul‘ LIUN l HIVIINH l EU all C F HUDLEIVIQ 2. Site conditions should be adequately characterized. in order to fully define the lateral and vertical extents ofthe PCE contamination. In this regard. it is noted that PCE has rather low adsorptivity to soil; consequently, if released to sells, it will generally be subject to an accelerated migration into the groundwater. in particular. PCE can move rapidly through sandy soils and may therefore reach groundwater more easily in the type of geological formations found at the VSC facility. 3. Risk assessment procedures are typically used to establish cleanup objectives for contaminated environmental media requiring corrective actions and/or for the implementation of risk management programs for contaminated sites. Such an assessment should he used to help focus corrective action assessments and risk management plans for the VSC facility. The site-specific risk assessment may also include the development of appropriate site restoration goals with reference to site conditions. land uses. and exposure scenarios pertaining spe— cil‘icaliy to this shopping center and its vicinity. it is believed that the develop- ment of site-specific cleanup levels can result in significant cost savings in this type of investigation. A complete characterization of the "contaminated none" at the site should facili- tate the screening and selection of the best available technology for a remedial action plan that is developed for the VSC facility. Prior to implementing any remediation plan for this site, appropriate risk-based cleanup criteria should he developed anti compared with the current levels of contamination present at the site (i.e.. under the ntisel'me conditions). Based on such a criteria. it niay become apparent under the appropriate types of exposure scenarios that no cleanup is warranted. In fact. even if it is determined that some degree ofcleanup is required. the cleanup criteria developed will aid in optirrtiairtg the efforts involved. so as to arrive at more cost-effective solutions than could otherwise have been achieved. REFERENCES Asnnl‘c—Dttttlt. UK. 1993. Hazardous Waste Risk Assessment. CRC Press/Lewis Publish- ers. Boca Raton. FL. _ l-ftSl (British Standards institution). 1988. Draft for Development. DDlTS: 1988 Code of Practice for the identification of Potentially Contatninutetl Land and its investigation. list, London, U.l{. Ct'tit'l'toy. T. (Edd. l993. Contaminated [and (Problems and Solutions). Lewis Publishers. Boca Raton. FL. Lyman. W..l.. W.F. Reehl and DH. Rosenblatt.-liltltl..Hrmc/book of Chernicni Property Estimation Methods: Hitt'ir'rmrrterurrf Behavior of Organic Compounds. American Chemical Society. Washington. D.C. Swann. R.L.. and A. Eschenrocder (Eds). l983. Fate of Chemicals in the Enchantment. AC3 Sytnp. Set. 225. American Chemical Society. Washington. DC. US EPA. 1988. Guidance for Conducting Remedial investigations and Feasibility Studies Under CERCLA. EPA/54WG‘89/Dtl4. OSWER Directive 9355.3-0l. Office of Emergency and Romedial Response. LLS. Environmental Protection Agency. Washington; DC. USEPA. I989. Risk Assessment Guidance for Superfund. Vol. I. Human Health Evaluation Manual (Part A). EPA/540/h89/002. Office of Emergency and Ren‘tediai Response. US. Environmental Protection Agency. Washington. DC. ...
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