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CN 301- GEOENVIRONMENTALENGINEERING

PREPARED BY :

HAZWANI AYUNI BT MOHD HANAFIRUZAINI BT MAT NAWINURUL AJLAA BT ABDUL MALIK

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Defined as investigation on the physical characteristics of the site and includes documentary studies, site surveys and ground investigation.

4.0 Site investigation

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Site investigation and analysis of soils provides gidance on how to gather information and collect soils samples to provide data that allows an assessment of land where hazardous substances are present or suspected.

4.1 Principle site investigation

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Set investigation objectives

Review existing data- preminary site study and

inspection

Establish conceptual model and data quality

objectives

Analyse soil samples

Collect soil sample

Determine detailed site investigation

sampling design and strategy

Interpret data Revise conceptual model Report data

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Data quality objective (DQOs) are qualitative and quantitative statement that specify the quality of the data required. The most common purposes are to :

4.1.1 The data quality objective process

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Establish the condition of a site before sale, purchase or redevelopment and determine environmental liabilities

Determine the environmental or health risks posed by contaminants in the soil

Determine if hazardous substances in the soil pose a hazard to an ecosystem

Assess the applicability of a particular remediation option

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Is asystem diagram identifying contaminant sources, routes of exposure (pathways), and what receptors are effected by contaminat s moving along those pathways.

4.1.2 Conceptual site model

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Main investigation phases

USEPA and ministry of Zealand Enironment guidelines

Common alternative descriptor

Preliminary site investigation(study)

Preliminary site study, stage 1: phase 1 desk top study; phase 1 background information study’ phase 1 contaminated site audit; phase 1 environmental site assessment(ESA)

Preliminary site inspection Site walkover survey;phase 1 site inspection

Detailed site investigation Stage 2; phase 2 field investigation; phase 2 ESA; environmental benchmarking

Supplementary site investigation

Additional phase 2 ESA; phase 3 ESA

Site validation investigation Remediation validation investigation; soil benchmarking

4.2 Investigation Phases

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Is to establish clear sampling objectives. These must define why and how samples are being collected, and lead to the formulation of the sampling strategy(e.g where to collect the samples). The sampling objectives will be site specific and depend on the purpose of the investigation

4.3.1 intrusive ground investigation 4.3.2 sampling ground and groundwater

4.3 preparing for fieldwork and soil sampling for site investigation

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a) Density of the groundi. auger boringsii. Drive boringsiii. The standard penetration test (SPT)iv. Cone penetration boringsv. field vanes shear testsvi. Rock core boring

4.3.3 in-situ test in trial pits and boreholes

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Figure 4.3: (a) wash boring (b) field vane tests (c) CPT

Figure 4.4: Spill barrel for standard penetration test (SPT)

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Figure 4.4; diagram representing boring record, penetration record and result of soil test samples from drills holes trough compsite shore deposits.

Figure 4.5; sampling tool for exploratory borings. (a) earth auger (b) bailer (c) chopping bits (d) spring core catchers (e) split spoon samplers (f) scraper buckets

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b) Permeability of the groundi. tests in piezometers or wellsii. Pumping tests.iii. Permeability of rock

Figure 4.6: tests in piezometers

Figure 4.7: tests in piezometers and pumping well

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Geophysical exploration consists of making indirect measurements from the earth’s surface or in boreholes to obtain subsurface information. Geologic information is obtained through analysis or interpretation of these measurements.

4.3.4 Geophysical methods

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Surface geophysical

survey method

Applications Advantages

Limitations

Seismic Refraction and Reflection - Travel time of compressional waves through subsurface layers - Determines lithological changes in subsurface

Groundwater resource evaluations Geotechnical profiling Subsurface stratigraphy including top of bedrock

Relatively easy accessibility High depth of penetration dependent on source of vibration Rapid areal coverage

Resolution can be obscured in layered Susceptibility to noise from urban development Difficult penetration in cold weather (depending on instrumentation) Operation restricted during wet weather

Electrical resistivity - Electrical resistance of a volume of material between probes - Delineates subsurface resistivity contrasts due to lithology, groundwater, and changes in ground-water quality

Depth to water table estimates Subsurface stratigraphic profiling Groundwater resource evaluations High ionic strength contaminated groundwater studies

Rapid areal coverage High depth of penetration possible (400–800 ft) High mobility Results can be approximated in the field

Susceptibility to natural and artificial electrical interference Limited use in wet weather Limited utility in urban areas Interpretation that assumes a layered subsurface Lateral heterogeneity not easily accounted for

Ground-penetrating radar - Travel time and amplitude of a reflect signal microwave - Provides continuous visual profile of shallow subsurface objects, structure, and lithology

Locating buried objects Delineation of bedrock subsurface and structure Delineation of karst features Delineation of physical integrity of man-made earthen structures

Great areal coverage High vertical resolution in suitable terrain Visual picture of data

Limited depth of penetration (a meter or less in wet, clayey soils; up to 25 m in dry, sandy soils) Accessibility limited due to bulkiness of equipment and nature of survey Interpretation of data qualitative Limited use in wet weather

Magnetics - Variations of earth‘s magnetic Field - Detects presence of buried metallic objects

Location of buried ferrous objects Detection of boundaries of landfills containing ferrous objects Location of iron-bearing rock

High mobility Data resolution possible in field Rapid areal coverage

Detection dependent on size and ferrous content of buried object Difficult data resolution in urban areas Limited use in wet weather Data interpretation complicated in areas of natural magnetic drift.

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The description of soils in geotechnical and geoenvironmental investigations is carried out according to BS 5930:1999 and forms an important part of ground investigation, the results of which may be required long after the disposal of the samples. A standard description contains the following:

i. mass characteristics comprising state and structure: • density/compactness/field strength; • discontinuities; • bedding;

ii. material characteristics comprising nature and state • colour; • composite soil types: particle grading and composition; shape and size; • principle soil type (name in capitals), based on grading and plasticity

shape;

iii. stratum name: geological formation, age and type of deposit; classification (optional)

4.4 Soil-sampling techniques

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There are a number of different soil-sampling techniques available, and the actual method used will depend on a variety of factors, including the objectives of the investigation, cost, access, degree of disturbance, and reinstatement. The following techniques can be considered when undertaking soil sampling: • surface and shallow subsurface grab sampling • hand auger sampling • test pit sampling • borehole sampling.

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Technique Advantages Disadvantages Grab sampling (trowel, push tubes, shovel or scoop – plastic or stainless steel)

Low cost Quick No access restrictions Minimal soil disturbance

Depth limit: surface – 0.5 m Impractical in difficult soil conditions Care is required to ensure the quality of sample recovered Contaminant brought to surface Lost of volatile organic compound (VOC)

Hand auger, split-barrel devices

Low cost Quick No access restrictions Minimal soil disturbance

Depth limit: 2–3 m (with ease) Impractical in difficult soil conditions Care is required to ensure the quality of sample recovered Limited ability to observe the nature of the material Labour intensive

Test pits (machine dug) Lower cost than boreholes Relatively quick Ability to make detailed observations of the strata Ability to recover samples

Extent of soil disturbance, occupational exposure, compaction Depth limit is 3–5 m depending on excavator Impractical in unstable soil conditions and hard rock Not suitable for installing monitoring bores due to disturbance

Boreholes (drilling rigs – hollow-stem auger, air rotary drilling, shell and auger)

Minor disturbance of soils Limited occupational exposure Accurate recovery of samples Ability to sample at depth Suitable for most ground conditions Can be used for installing groundwater and gas monitoring wells

More expensive than other techniques Limited ability to observe materials Air rotary rigs not suitable for volatiles Can cause preferential pathways for contaminant migration, if not appropriately constructed

Table 4.4: Soil-sampling techniques

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Judgmental :Samples are based on prior knowledge of the site

Systematic; Samples are located at regular intervals

Stratified: The study area is divided into non-overlapping sub-areas and samples are obtained from each sub-area sampling

Table 4.5: Soil-sampling pattern

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Soil Samples - these can be obtained as disturbed or as undisturbed samples.

i. Disturbed Soil Samples - these are soil samples obtained from boreholes and trial pits. The method of extraction disturbs the natural structure of the subsoil but such samples are suitable for visual grading, establishing the moisture content and some laboratory tests. Disturbed soil samples should be stored in labelled air tight jars.

ii. Undisturbed Soil Samples - these are soil samples obtained using coring tools which preserve the natural structure and properties of the subsoil. The extracted undisturbed soil samples are labelled and laid in wooden boxes for dispatch to a laboratory for testing. This method of obtaining soil samples is suitable for rock and clay subsoils but difficulties can be experienced in trying to obtain undisturbed soil samples in other types of subsoil.

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Composite sampling consists of collecting

individual samples from different locations and bulking and mixing an equal mass of the samples (called sub-samples) together to form one composite sample. Compositing can be used to characterize a stockpile of material; for example, to determine an acceptable disposal location, or for characterizing sites with similar contaminant levels (such as horticultural sites).

Background samples Background samples are

collected in the area near the site that is not affected by the contaminant sources on the site. Background samples are used as a reference point to represent undisturbed natural soil at or near the surface. Suitable locations for background samples should be chosen based on the:

site geology (background concentrations of metals are related to the parent rock types)

site history (should indicate no disturbance at the location)

topography (sample collection should not be from any low-lying areas, such as ditches, but from areas of raised ground).

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It is important that the chemical analysis techniques are fully defined in specifications prior to the investigation fieldwork. There are direct links between the analysis methods (including sample preparation and extraction) and the results obtained. The test method must be fully compatible with the method to be used for assessing the results

4.4.2 laboratory testing

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