Recommendations for Site Investigations of Waste Disposal Sites and Contaminated Sites in Thailand

Transcription

1 Thai-German Research Project Geophysik GGD W A D I S BGD Recommendations for Site Investigations of Waste Disposal Sites and Contaminated Sites in Thailand Funded by the Ministry of Education and Research (BMBF) of the Federal Republic of Germany (FKZ ) The authors are responsible for the content of their contributions. Short Information about Why do we investigate waste disposal sites and sites suspected to be hazardous? Multi Barrier Concept as a high-level standard for the disposal of waste and the assessment of sites suspected to be hazardous Strategies for site investigations Searching for new waste disposal sites Check-up and assessment of operating landfills Investigation of sites suspected to be hazardous Common problems Objectives of site investigations and selection of suitable methods Examples of terms of reference Bangkok, Berlin, Hannover, Cottbus 2006

2 Why do we investigate waste disposal sites and sites suspected to be hazardous? Waste disposal sites are an absolutely necessary part of the infrastructure of an industrial society. Suitable new sites must be found and suitable methods must be available to show that such sites have layers in the subsurface that can function as a barrier to the entry of contaminants into the environment. Knowledge and experience with the disposal of waste and the operation of mines and industrial facilities in an ecologically nondetrimental way have been acquired only gradually during the past several decades. On the basis of this knowledge, numerous abandoned landfills, mining, and industrial sites must now be regarded as hazardous. Standards must be developed for site investigation, risk assessment, precautionary measures, remediation and monitoring. Environmental protection has a high priority on the national agenda. Site investigation is active environmental protection. Money for effective site investigations is well-invested. This is an investment in our future and that of our children. 2

3 Multi Barrier Concept as a high-level standard for the disposal of waste and the assessment of sites suspected to be hazardous High-level standards are necessary for the disposal of waste in order to avoid environmental damages. State of the art is the Multi Barrier Concept (MBC) for landfills which was introduced in Germany in 1993 under the regulation Technical Instructions on Wastes from Human Settlements (TASi). The MBC comprises the phases of planning, construction, operation and after-care of a waste site and is based on the combined effects of several, from each other largely independent barriers systems. Barriers are the landfill body, the landfill sealing and drainage system and the landfill site (geological barrier) as shown in the following Figure. Scheme of the Multi Barrier Concept A special position within the MBC takes the geological barrier. The geological barrier is the natural substratum beneath and surrounding a landfill which, on the basis of its properties and dimensions, extensively prevents the spread of pollution. The landfill formation level must be arranged in such a way that after the substratum has finished settling under the load of the landfill, it comes to rest above the highest expected groundwater surface. The criteria for an effective geological barrier for new landfill sites can also be applied in the assessment of operating landfills and abandoned sites suspected to be hazardous. In all cases a suitable characterization of the geological barrier requires a geoscientific investigation programme. The methods used must be tuned to the geological/hydrogeological conditions at the site. Monitoring during the operating time and after-care phase of a landfill is part of the Multi Barrier Concept. There are requirements on the waste to be deposited and the landfill body, the technical barriers and leachate and gas treatment. 3

4 Strategies for site investigations Public Participation It is important that all the steps of the site search process are open to the public. Transparency, mediation between disagreeing parties, and the right to participate as an equal partner in the discussion strengthen the site search process. Phases of Site Investigations A stepwise site investigation is usually carried out in at least two phases: (1) orientating investigation and (2) detailed investigation. In the orientating investigation, the following information is obtained from maps and other archived data sources: existence of excluding criteria as listed in the PCD guidelines as well as in the this book, topography, land use and vegetation, settlements, roads and railways, climate: precipitation, temperature, evapotranspiration, direction and intensity of wind, geology: soil, geological structures, stratigraphy, lithology, and barrier rocks, hydrological and hydrogeological conditions: streams, lakes and ponds, springs, wells, use and quality of surface and groundwater, runoff, water balance, aquifer/aquiclude properties and stratigraphy, groundwater table, groundwater recharge and discharge, ecological aspects: e.g. nature reserves, protected geotopes, water protection areas. This is accompanied by a reconnaissance survey in the field and by a historical review of former use of the site. The following aspects or parts of them must be taken into account for a detailed site investigation and assessment: geology: thickness and lateral extent of strata and geological units, lithology, homogeneity and heterogeneity, bedding conditions and tectonic structures, fractures, impact of weathering, groundwater: water table, water content, direction and rate of groundwater flow, permeability, value of aquifer. geochemical site characterization: chemical composition of soil, rocks and groundwater, estimation of contaminant retention. geotechnical stability: The geological barrier must be capable of adsorbing strain from the weight of a landfill, slag heap or industrial building. geogenic events: active tectonic faults, karst, earthquakes, subsidence, landslides. anthropogenic activities: mining damage, buildings, quarries, gravel pits, clay pits, etc. changes in soil and groundwater quality. Participants in site investigation LAR IR ARP client contractor local authority responsible, e.g. municipality institution responsible, in some cases more than one institution authority for regional planning local authority responsible (LAR) for commissioning site investigations responsible for handling site investigations commissioned by the client 4

5 Searching for new waste disposal sites There are regions for which at present no geological and hydrogeological data bases, no Potential Barrier Rock Maps (PBR maps) and/or Groundwater Vulnerability Map, and in some cases no geological map 1 : are available. In such cases a pragmatic approach in planning a new landfill can be used. Possible waste disposal sites are selected by political decision and/or applying non-geoscientific criteria (e.g. availability of public land, transport routes). In such cases the geoscientific site investigation and assessment must be carried out with thoroughness as in the systematic and semi-systematic approach with extensive geological and hydrogeological data. LAR: Definition of initial conditions kind of landfill (kind of waste), planning area (e.g. district), quantity of waste per day, now and expected in the next 25 years, size of landfill site in according to PCD guidelines. depending on utilization time LAR in cooperation with ARP: Selection of possible waste disposal sites for a suitability assessment. LAR and IR: First consultation with the IR advice on the basic principles of site searches, provision of available data for the proposed sites. LAR: Commissioning of the orientating site investigation and assessment (phase 1) Contractor: Conducts orientating site investigation and assessment (phase 1) specification of objectives for orientating site investigation and assessment, compilation of available data for the proposed sites, exclusion of unfavorable sites, implementation of orientating geoscientific investigations, comparative site assessment and recommendations for detailed follow-up investigations. LAR and IR: Second consultation with the IR (if needed) assessment of results of orientating site investigation If no selected site is suitable as a waste disposal site, LAR should select new sites with the support of IR LAR: Commissioning of the detailed site investigation and assessment (phase 2) Contractor: Conducts detailed site investigation and assessment (phase 2) IR: Assesses results of detailed site investigation and, if possible, gives approval of a landfill planning Specification of requirements for further investigations if necessary Flow chart for a search for a new waste disposal site (pragmatic approach) 5

6 Check-up and assessment of operating landfills Many operating landfills are not prepared according to the principles described in the PCDguidelines and in this book. Therefore a check-up and assessment of the landfills is necessary in order to protect the human health and environment. The strategies for site investigations are the same as in search for new waste disposal sites with additional investigation of the landfill body inclusive geotechnical stability of the waste body and the investigation of possible contaminant discharge. An evaluation of groundwater quality requires an accurate knowledge of the geology and hydrogeology of the site, suitable groundwater observation wells, and appropriately chosen monitoring methods and intervals that take the geology, hydrogeology, and the type of landfill into consideration. Gaps in the knowledge of the geology and hydrogeology of the landfill site and the surroundings must be closed. Targeted geoscientific investigations are necessary for the planning and approval of expansions of a landfill, for the closing of landfills as well as for clean-up and renaturation measures. LAR: Recognize the necessity to check-up an operating landfill and to assess its potential risk for human health and the environment LAR and IR: First consultation with the IR advice on the basic principles of site investigation, provision of available data for the site LAR: Commissioning of the orientating site investigation and assessment (phase 1) Contractor: Conducts orientating site investigation and assessment (phase 1) specification of objectives for orientating site investigation and assessment, compilation of available data for the sites, implementation of orientating geoscientific investigations, site assessment and recommendations for detailed follow-up investigations. LAR and IR: Second consultation with the IR (if needed) assessment of results of orientating site investigation LAR: Commissioning of the detailed site investigation and assessment (phase 2) Contractor: Conducts detailed site investigation and assessment (phase 2) IR: Assesses results of detailed site investigation and gives approval for action and further landfill planning Specification of requirements for further investigations if necessary Flow chart for a check-up and assessment of an operating landfill 6

7 Investigation of sites suspected to be hazardous Inventory and Initial Assessment (Phase I) The institution responsible (IR) must be authorized by law or by political decision to prepare an inventory of sites suspected to be hazardous and a National Priorities List (NPL). The IR defines basic principles for the nationwide inventory and initial assessment of suspected hazardous sites and the NPL. The objective of this phase is the collection, survey and evaluation of all available documents, data and information on sites suspected to be hazardous. The desk study is followed by a site inspection. Field or laboratory investigations are generally not required in this phase. The initial assessment is usually systematized (checklist, assessment forms, computer programs). The need for further investigation is determined. The inventory and initial assessment work is carried out in two steps: Step 1: Registration of sites suspected to be hazardous The registration of sites suspected to be hazardous is carried out nationwide or for regions (e.g. districts, provinces) following the basic principles defined by the IR. Clues, that a site might be hazardous, are present, when over a longer period of time at the site dangerous materials are kept, used, and/or deposited. Sites suspected to be hazardous are classified as follows: industrial site (e. g. galvanizing plant, metallurgical workshop, mechanical engineering, motor vehicle garage, gas/petrol station, tannery, workshop in which wood is impregnated or is worked), waste deposit (landfill, sewage sludge deposition, small site with buried and/or heaped waste and litter), and mining site (e.g. spoil/slag heap, smelter). The work starts with the registration of master data as locally used site name, owner/user of the site, geographical coordinates (e.g. determined by GPS), etc. Step 2: Limited-scope investigation and initial assessment The master data registered in Step 1 are completed by analysis of archived documents, multitemporal analysis of satellite images and aerial photographs and maps in order to evaluate the chronological development of waste disposal, industrial or mining sites, analysis of historical land use, interviews with persons who live/lived or work/worked in the area, geological, hydrogeological and hydrological conditions, and site inspection. With these limited-scope investigations particularly the following information should be gathered as indications for flooding, emission (escaping gas, smell, dust, seepage), conspicuous changes (e.g. change in color of soil, disturbance of growth of plants, vegetation damages), affected pathways (groundwater, surface water, soil, air), and health effects observed or reported. For both steps commissioning of the investigations by IR or LAR to contractor(s) is possible. In any case the IR must assess the results, handle the NPL (if existing), and gives approval for further activities. 7

8 Investigation of Sites Suspected to be Hazardous and Hazard Assessment (Phase II) If need for further investigation is determined, an orientating site investigation with hazard assessment is carried out. Subsequently detailed site investigations with concluding hazard assessment and decision as to need for action is carried out. The criteria for the site assessment are given in the Multi Barrier Concept (MBC). The stepwise procedure for site investigation is described above. The assessment of the hazard depends mainly on the toxicity of the material at the site, source strength, groundwater recharge and seepage, contaminant spreading, geological and hydrogeological conditions as well as on land use. IR/LAR: Information from Phase I: It is necessary to investigate a site suspected to be hazardous and to assess its hazard to human health and the environment provision of available data for the site from Phase I, specification of objectives for orientating site investigation and hazard assessment. IR/LAR: Commissioning of the orientating site investigation and hazard assessment Contractor: Conducts orientating site investigation and hazard assessment compilation of available data for the sites, implementation of orientating geoscientific investigations, hazard assessment and recommendations for detailed follow-up investigations. LAR/IR: First result assessment assessment of results of orientating site investigation, specification of requirements for detailed follow-up investigations. IR/LAR: Commissioning of the detailed site investigation with concluding hazard assessment Contractor: Conducts detailed site investigation with concluding hazard assessment IR: Assesses results of detailed site investigation and gives approval for action if necessary Specification of requirements for further investigations if necessary Flow chart for an investigation and assessment of a site suspected to be hazardous Precautionary Measures, Remediation and Monitoring (Phase III) If precautionary measures or remediation on a contaminated site are necessary, additional remedial investigations may be necessary in order to specify and/or test the precautionary measures/remediation concept. An evaluation of groundwater quality requires an accurate knowledge of the geology and hydrogeology of the site, suitable groundwater observation wells, and appropriately chosen monitoring methods and intervals. All work to be done can be commissioned to contractors. 8

9 Common problems Getting Started A catalogue of questions is given to draw attention to conditions and problems which can influence the planning of the site investigation and the selection of suitable investigation methods. These questions should be answered before planning the site investigation in order to optimize the investigation program and to save many. Commissioning of Site Investigations The "rules" for commissioning site investigations differ from country to country, very often depending on national or international regulations (e.g. for World Bank or EU projects). The "rules" must be well formulated and known and accepted by both client and the contractor. Invitations to tender must contain a specification of the investigation aims and detailed terms of references for the commissioned work. The bidding contractor has to prove that he is able to carry out the requested work. Before a bid is submitted the site should be inspected by all prospective contractors. It has to be kept in mind, that the lowest bid is not always the best one! The contract awarded to the best bidder should include a listing of the rights and duties of both client and contractor, a description of the work to be carried out, quality assurance measures, time schedule for the work, including the delivery of the reports and data, as well as the terms of payment. The quality of the work should be checked by the client. If the client is not able to do so, the geological survey and/or the environmental protection authorities will provide advice and can help with the quality assurance of such work. Collection and Use of Existing Data An important preparatory step for a geoscientific site investigation and data interpretation is the collection of already existing information. Information Campaign and Permit Application Investigation of a operating, abandoned and planned landfill, mining or industrial site requires the approval of the relevant authorities at the state, district and/or local levels and of the affected private property owners. The objectives of the investigations, the estimated duration, and the scope of the work, as well as the methods and their likely impacts, should be explained in detail to those affected before approval for the operations is requested. Recommendations and information from public and private sources should be integrated into the working concept. A check list for the preparation of site investigations is given. Land Surveying Geotechnical measures, for example, drilling and cone penetration tests, or geophysical investigations are often carried within the scope of site investigations. The exact determination of measuring points and profiles is very important in order to document consistently all investigations in a site map of an appropriate scale. It is often necessary to relate the surveyed profiles and measured points to the country's national topographic grid. A map of the site and surroundings at a scale appropriate for the aims of the survey should be made available by the client. This will make it possible to compare the results of several contractors working in the same project area and to plan follow-up work. Quality Assurance and Reporting Quality assurance is an important part of the field work, the data processing, the interpretation, and the reporting. It must be documented in field protocols as well as summarized in the reports. The reports must contain all information needed to understand the report. 9

10 Objectives of site investigations and selection of suitable methods Objectives of site investigations are listed above on the page Strategies for site investigations. Methods to achieve the objectives are available. Selection tables help to find the suitable methods. Remote-sensing methods Remote-sensing methods can provide geoscientific data for large areas in a relatively very short time. They are not limited by extremes in terrain or hazardous conditions that may be encountered during an on-site appraisal. In many cases aerial photographs and satellite images must be used to prepare a base map of the investigation area. Remote sensing methods can enable a preliminary assessment and site characterization of an area prior to the use of more costly and time-consuming methods, such as field mapping, geophysical surveys and drilling. The data obtained from satellite-based remote-sensing systems is best suited for regional studies as well as for detecting and monitoring large-scale environmental problems. Mapping scales of 1 : or larger are required for a detailed geoenvironmental assessment of landfills, mining sites or industrial sites. High-resolution aerial photographs, airborne scanners, and some satellite-based remote-sensing systems provide data at the required spatial resolution (e.g. 70 cm and better). Aerial photographs made at different times can reveal the changes at sites suspected to be hazardous. Photographic images can be evaluated not only with respect to size, shape, and position of objects, but also to color, hue, texture, and patterns of distribution of these aspects with regard to their geoscientific information. Photogrammetry is a method to obtain reliable measurements from photographic images. The main tasks of photogrammetry are to prepare maps and digital elevation models (DEM), orthophotos, photomosaics, terrain cross sections, and obtain vector data (e.g. height of a terrain slope, length of a creek, volume of a landfill) from remote-sensing data. Nonphotographic imaging systems detect the incoming electromagnetic (EM) radiation with semiconductor detectors or special antennas instead of using light-sensitive film. While photography is limited to the spectral range 0.3 to 0.9 µm the range of sensing for a multispectral scanner (MSS) covers wavelengths from 0.3 to approximately 14 µm. MSS can operate within very narrow spectral bands. Both passive and active methods are used for nonphotographic imaging. Passive methods sense the natural electromagnetic radiation reflected, scattered, and transmitted at the Earth s surface. In active methods, EM radiation (e.g. laser beam or radar wave) is transmitted and the response of the ground is detected. Geological and hydrogeological methods Methods to be used to investigate lithological structures, to determine the homogeneity of the rock, to locate fractures, to determine the permeability of the rock with respect to water, gases and various contaminants, to assess the mechanical stability of the ground, and to obtain data on the groundwater system. Flow and transport models must be developed to estimate groundwater recharge and the potential for groundwater contamination. The main tasks of geological and hydrogeological surveys are to gain information directly by examining outcrops, digging trenches and drilling boreholes, conducting hydraulic tests (e.g. pumping tests and tracer tests) in wells to determine hydraulic properties in situ. This work is augmented by geological mapping, examination of drill cores, construction and expansion of a network of groundwater observation wells. Rock, soil and groundwater samples are taken to determine physical, chemical, petrographic and mineralogical parameters. Special laboratory experiments can be carried out to estimate migration parameters and the texture of rock and soil samples. Data from cone penetration tests and other field and laboratory methods are used to assess the stability of the ground. 10

11 Geophysical methods Geophysical methods are used to develop a geological model of subsurface of a site, to locate fracture zones, to investigate the groundwater system, to detect and delineate abandoned landfills and contamination plumes, as well as to obtain information on the lithology and physical parameters of the ground. A broad spectrum of geophysical methods is available for the investigation of the subsurface: Magnetics, gravity methods, dc resistivity, electromagnetics, ground penetrating radar, refraction seismics, reflection seismics, surface nuclear magnetic resonance (SNMR), geophysical borehole logging, and geophysical monitoring methods. A necessary condition for a meaningful use of geophysical methods is the existence of differences in the physical parameter values (magnetization, susceptibility, density, electrical resistivity, seismic velocities, etc.) of different geological structures. The parameter values to be expected at a site must be considered before a geophysical survey is conducted. Geophysical methods supplement each other because they detect different physical properties. Seismic methods are used to investigate structures and lithology. Electrical and electromagnetic methods are very sensitive to changes in electrolyte concentrations in pore water. Ground penetrating radar can be used in areas with dry, low-conductivity rocks. Both magnetic and electromagnetic mapping have proved useful for locating and determining the edges of concealed landfills. Both methods are fast and easy to conduct, enabling large areas to be investigated in a short time. Seismic, dc resistivity, electromagnetic and gravity methods are used to investigate groundwater systems on a regional scale. Geophysical surveys help to find suitable locations for drilling groundwater observation wells and provide information between boreholes and for areas where it is impossible to drill. Borehole logging is absolutely necessary. Logging data are not only necessary for processing and interpretation of surface geophysical data but also as a bridge between geophysical surveys and hydrogeological modeling. Geochemistry Geochemistry studies the properties, distribution, circulation, and interactions among the chemical elements and compounds found in the minerals, ores, rocks, soils, water and atmosphere of the Earth. The geochemical site investigation is primarily focused on characterizing the complex chemical inventory of soil, rock, stream and lacustrine sediments, groundwater, surface water, and soil gas. It includes the differentiated determination of geogenic background values and anthropogenic input. This differentiation is only possible if the size of the area and the number of sampling points is adequate for a statistical evaluation. The geochemical investigations usually take place following the geological and hydrogeological survey, on the basis of which a focused and representative sampling strategy can be drafted. 11

12 Examples of terms of reference (TOR) are given for: General contractor for planning of new landfills, General contractor for investigation of a site suspected to be hazardous, Remote sensing, Geophysics, Drilling, well logging, and construction of groundwater observation wells, Pumping tests, and Geochemistry. aquifer filling material filter gravel counter filter L F seal screen d BH casing water level Schematic sketch of monitoring well filter section Authors: Dr. Klaus Knoedel Contact Address: Dr. Christoph Grissemann, Federal Institute for Geosciences and Natural Resources, Hannover, Germany, Christoph.Grissemann@bgr.de 12