{"id":126,"date":"2024-12-12T23:48:33","date_gmt":"2024-12-12T23:48:33","guid":{"rendered":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/chapter\/2-6-geotechnical-investigations-in-contaminated-sites\/"},"modified":"2026-03-16T13:55:09","modified_gmt":"2026-03-16T13:55:09","slug":"2-6-geotechnical-investigations-in-contaminated-sites","status":"publish","type":"chapter","link":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/chapter\/2-6-geotechnical-investigations-in-contaminated-sites\/","title":{"raw":"2.6 Geotechnical investigations in contaminated sites","rendered":"2.6 Geotechnical investigations in contaminated sites"},"content":{"raw":"Geotechnical investigations in potentially contaminated sites must follow certain procedures regarding personnel protection, avoiding contaminant migration through groundwater movement, and proper disposal of boring waste such as drilling water, soil samples etc. Some signs of possible contamination that should trigger further measures are (FHWA 2002):\n<ul>\n \t<li>Prior land use (e.g., old fill, landfills, gas stations).<\/li>\n \t<li>Stained soil or rock.<\/li>\n \t<li>Apparent lack of vegetation or presence of dead vegetation and trees.<\/li>\n \t<li>Odors. Note that highly organic soils will have a rotten egg odour, which should not be mistaken as evidence of contamination. However, this odour may be indicative of highly toxic hydrogen sulphide.<\/li>\n \t<li>Presence of liquids other than groundwater.<\/li>\n \t<li>Signs of previous ground fires at landfill sites. Established landfill will emit methane gas, which is explosive.<\/li>\n \t<li>Presence of visible elemental metals (mercury).<\/li>\n \t<li>Low (&lt;2.5) or High (&gt;12.5) pH.<\/li>\n<\/ul>\nEasy-to-use methods such as air quality monitoring devices, pH measurement kits or photoionisation detectors can be used to perform preliminary tests to identify the presence of some contaminants.\n\nConcentration of pollutants in soil and groundwater is determined via special chemical tests on soil and water samples, in the laboratory. These tests are often complemented with geophysical tests, such as electric resistivity tests or ground penetrating radar tests discussed in Part 1. The selection of the appropriate method depends on the type of pollutant.\n\nExcept of these common methods, a hydrogeological site investigation may be necessary, aiming to (CCME, 1994):\n<ul>\n \t<li>Determine the direction and rate of groundwater movement.<\/li>\n \t<li>Determine the principal pathways and factors controlling the migration of contaminants in the subsurface.<\/li>\n \t<li>Quantify the physical parameters controlling groundwater flow and contaminant transport in the subsurface.<\/li>\n<\/ul>\n<p style=\"text-align: center\">in other words, build the <em>hydrogeological model <\/em>of the site\u2026<\/p>\nDrilling monitoring wells (<a href=\"https:\/\/oercollective.caul.edu.au\/app\/uploads\/sites\/143\/2024\/12\/2.8-replace-e1747989441242.png\">Figure 2.8<\/a>) may be necessary for determining groundwater levels, and water quality via samples retrieved for laboratory tests. Measuring the hydraulic conductivity (permeability) of the subsurface formations with the constant or falling head test in the laboratory or <em>in situ<\/em> (<a href=\"https:\/\/oercollective.caul.edu.au\/app\/uploads\/sites\/143\/2024\/12\/2.9-replace-e1747989457298.png\">Figure 2.9<\/a>) will provide the necessary input for developing a groundwater flow and contaminant transport numerical model, that can predict contamination evolution over time as described in the following chapter, and lead to the evaluation of the effectiveness of different mitigation measures.\n\n[caption id=\"attachment_4048\" align=\"aligncenter\" width=\"400\"]<img class=\"wp-image-4048 size-full\" src=\"https:\/\/libraryresources.nse.org.ng\/wp-content\/uploads\/sites\/9\/2024\/12\/2.8-replace-e1747989441242.png\" alt=\"Diagram illustrating a well bored in coarse-grained soil with labeled components: casing, grout, disturbed material, screen interval.\" width=\"400\" height=\"267\"> Figure 2.8. Outline of a monitoring well in coarse-grained soil.[\/caption]\n\n[caption id=\"attachment_4050\" align=\"aligncenter\" width=\"400\"]<img class=\"wp-image-4050 size-full\" src=\"https:\/\/libraryresources.nse.org.ng\/wp-content\/uploads\/sites\/9\/2024\/12\/2.9-replace-e1747989457298.png\" alt=\"Diagram illustrating water flow in a well during a Maag test, showing initial and final water head levels as well as water flow from the well towards the soil.\" width=\"400\" height=\"245\"> Figure 2.9. In situ test (Maag) to measure soil permeability.[\/caption]","rendered":"<p>Geotechnical investigations in potentially contaminated sites must follow certain procedures regarding personnel protection, avoiding contaminant migration through groundwater movement, and proper disposal of boring waste such as drilling water, soil samples etc. Some signs of possible contamination that should trigger further measures are (FHWA 2002):<\/p>\n<ul>\n<li>Prior land use (e.g., old fill, landfills, gas stations).<\/li>\n<li>Stained soil or rock.<\/li>\n<li>Apparent lack of vegetation or presence of dead vegetation and trees.<\/li>\n<li>Odors. Note that highly organic soils will have a rotten egg odour, which should not be mistaken as evidence of contamination. However, this odour may be indicative of highly toxic hydrogen sulphide.<\/li>\n<li>Presence of liquids other than groundwater.<\/li>\n<li>Signs of previous ground fires at landfill sites. Established landfill will emit methane gas, which is explosive.<\/li>\n<li>Presence of visible elemental metals (mercury).<\/li>\n<li>Low (&lt;2.5) or High (&gt;12.5) pH.<\/li>\n<\/ul>\n<p>Easy-to-use methods such as air quality monitoring devices, pH measurement kits or photoionisation detectors can be used to perform preliminary tests to identify the presence of some contaminants.<\/p>\n<p>Concentration of pollutants in soil and groundwater is determined via special chemical tests on soil and water samples, in the laboratory. These tests are often complemented with geophysical tests, such as electric resistivity tests or ground penetrating radar tests discussed in Part 1. The selection of the appropriate method depends on the type of pollutant.<\/p>\n<p>Except of these common methods, a hydrogeological site investigation may be necessary, aiming to (CCME, 1994):<\/p>\n<ul>\n<li>Determine the direction and rate of groundwater movement.<\/li>\n<li>Determine the principal pathways and factors controlling the migration of contaminants in the subsurface.<\/li>\n<li>Quantify the physical parameters controlling groundwater flow and contaminant transport in the subsurface.<\/li>\n<\/ul>\n<p style=\"text-align: center\">in other words, build the <em>hydrogeological model <\/em>of the site\u2026<\/p>\n<p>Drilling monitoring wells (<a href=\"https:\/\/oercollective.caul.edu.au\/app\/uploads\/sites\/143\/2024\/12\/2.8-replace-e1747989441242.png\">Figure 2.8<\/a>) may be necessary for determining groundwater levels, and water quality via samples retrieved for laboratory tests. Measuring the hydraulic conductivity (permeability) of the subsurface formations with the constant or falling head test in the laboratory or <em>in situ<\/em> (<a href=\"https:\/\/oercollective.caul.edu.au\/app\/uploads\/sites\/143\/2024\/12\/2.9-replace-e1747989457298.png\">Figure 2.9<\/a>) will provide the necessary input for developing a groundwater flow and contaminant transport numerical model, that can predict contamination evolution over time as described in the following chapter, and lead to the evaluation of the effectiveness of different mitigation measures.<\/p>\n<figure id=\"attachment_4048\" aria-describedby=\"caption-attachment-4048\" style=\"width: 400px\" class=\"wp-caption aligncenter\"><img decoding=\"async\" class=\"wp-image-4048 size-full\" src=\"https:\/\/libraryresources.nse.org.ng\/wp-content\/uploads\/sites\/9\/2024\/12\/2.8-replace-e1747989441242.png\" alt=\"Diagram illustrating a well bored in coarse-grained soil with labeled components: casing, grout, disturbed material, screen interval.\" width=\"400\" height=\"267\" \/><figcaption id=\"caption-attachment-4048\" class=\"wp-caption-text\">Figure 2.8. Outline of a monitoring well in coarse-grained soil.<\/figcaption><\/figure>\n<figure id=\"attachment_4050\" aria-describedby=\"caption-attachment-4050\" style=\"width: 400px\" class=\"wp-caption aligncenter\"><img decoding=\"async\" class=\"wp-image-4050 size-full\" src=\"https:\/\/libraryresources.nse.org.ng\/wp-content\/uploads\/sites\/9\/2024\/12\/2.9-replace-e1747989457298.png\" alt=\"Diagram illustrating water flow in a well during a Maag test, showing initial and final water head levels as well as water flow from the well towards the soil.\" width=\"400\" height=\"245\" \/><figcaption id=\"caption-attachment-4050\" class=\"wp-caption-text\">Figure 2.9. In situ test (Maag) to measure soil permeability.<\/figcaption><\/figure>\n","protected":false},"author":1,"menu_order":6,"template":"","meta":{"pb_show_title":"","pb_short_title":"2.6 Geotechnical investigations in contaminated sites","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-126","chapter","type-chapter","status-publish","hentry"],"part":106,"_links":{"self":[{"href":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-json\/pressbooks\/v2\/chapters\/126","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-json\/wp\/v2\/users\/1"}],"version-history":[{"count":1,"href":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-json\/pressbooks\/v2\/chapters\/126\/revisions"}],"predecessor-version":[{"id":127,"href":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-json\/pressbooks\/v2\/chapters\/126\/revisions\/127"}],"part":[{"href":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-json\/pressbooks\/v2\/parts\/106"}],"metadata":[{"href":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-json\/pressbooks\/v2\/chapters\/126\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-json\/wp\/v2\/media?parent=126"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-json\/pressbooks\/v2\/chapter-type?post=126"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-json\/wp\/v2\/contributor?post=126"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-json\/wp\/v2\/license?post=126"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}