{"id":921444,"date":"2026-09-24T10:00:00","date_gmt":"2026-09-24T08:00:00","guid":{"rendered":"https:\/\/djya2ldob4.wpdns.site\/?page_id=921444"},"modified":"2026-10-27T09:16:03","modified_gmt":"2026-10-27T08:16:03","slug":"og4","status":"publish","type":"page","link":"https:\/\/www.cqop.com\/en\/list-of-soa-categories\/general-works\/og4\/","title":{"rendered":"SOA Category OG4"},"content":{"rendered":"\n\n<div class=\"cqop-v6 cqop-v6-soa-categoria-og4\" data-v6-page=\"Categoria-OG1\">\n\n<div id=\"contenuto\" class=\"cqop-v6-pannello-829311a\">\n    \n\n<div aria-hidden=\"true\" class=\"cqop-v6-pannello-fd08351 gb-text\"><\/div>\n\n\n\n    \n\n<div aria-hidden=\"true\" class=\"cqop-v6-pannello-d3705ba gb-text\"><\/div>\n\n\n\n    \n\n<div class=\"cqop-v6-contenuto-06a0e85\">\n      <nav style=\"--separator: &quot;\/&quot;\" class=\"cqop-breadcrumbs wp-block-breadcrumbs\" aria-label=\"Breadcrumbs\"><ol><li><a href=\"https:\/\/www.cqop.com\/en\/\">Home<\/a><\/li><li><a href=\"https:\/\/www.cqop.com\/en\/list-of-soa-categories\/\">List of SOA categories<\/a><\/li><li><a href=\"https:\/\/www.cqop.com\/en\/list-of-soa-categories\/general-works\/\">SOA general works categories<\/a><\/li><li><span aria-current=\"page\">SOA Category OG4<\/span><\/li><\/ol><\/nav>\n\n      \n\n<div class=\"cqop-v6-pannello-f3875ab\">\n        \n\n<span class=\"cqop-v6-pannello-4855609 gb-text\">OG4<\/span>\n\n\n\n        \n\n<span class=\"cqop-v6-pannello-ea96d22 gb-text\">General works categories<\/span>\n\n\n\n      <\/div>\n\n\n\n      \n\n<h1 class=\"cqop-v6-titolo-b35a3b5 gb-text\">SOA Category <span class=\"cqop-v6-pannello-8a3115e\">OG4<span aria-hidden=\"true\" class=\"cqop-v6-pannello-f4fc0bb\"><\/span><\/span><\/h1>\n\n\n\n      \n\n<p class=\"cqop-v6-testo-7496375 gb-text\">Everything required for underground civil engineering works<\/p>\n\n\n\n\n\n    <\/div>\n\n\n\n  <\/div>\n\n\n\n\n  \n\n<div class=\"cqop-v6-pannello-13e79de\">\n    \n\n<div class=\"cqop-v6-griglia-642d0e4\">\n      \n\n<div>\n        \n        \n\n<p class=\"cqop-v6-testo-f811e2c gb-text\">The OG4 category within the SOA qualification system covers underground civil works \u2013 specifically the construction, maintenance, and renovation of road and railway tunnels. As one of the 13 general categories, OG4 plays a strategic role in the transport\u2011infrastructure sector. OG4 certification attests to a company\u2019s technical and financial capability to build highly complex underground structures, often carried out in challenging geological or environmental conditions. The category includes natural tunnels, cross\u2011mountain passages, underground corridors, and excavated transit structures in soil or rock, designed for vehicle or rail traffic.<\/p>\n\n\n\n\n<img class=\"gb-media-cqogillusog41 cqop-v6-pannello-e34122a cqop-og-illustration\" src=\"https:\/\/www.cqop.com\/wp-content\/uploads\/2026\/10\/og4-illustrazione-1-hero-blu-bordeaux.webp\" alt=\"Underground civil engineering works \u2014 OG4 illustration\" width=\"840\" height=\"360\" loading=\"lazy\" decoding=\"async\" style=\"display:block;width:100%;max-width:700px;height:auto;margin:28px auto;object-fit:contain;\"\/>\n\n\n\n\n<\/div>\n\n\n\n      \n\n<div class=\"cqop-v6-pannello-136555f\">\n        \n<img role=\"presentation\" loading=\"lazy\" decoding=\"async\" src=\"https:\/\/www.cqop.com\/wp-content\/uploads\/2026\/10\/OG4-bianco-bordeaux-chiaro.webp\" alt=\"\" aria-hidden=\"true\" width=\"201\" height=\"201\" class=\"cqop-og-original-icon\" style=\"display:block;width:120px;height:120px;max-width:100%;object-fit:contain;margin:0 0 28px;\" \/>\n\n        \n\n<div class=\"cqop-v6-pannello-96ce454 gb-text\">Simulate the cost of SOA certification<\/div>\n\n\n\n        \n\n<a href=\"https:\/\/www.cqop.com\/en\/online-services\/fee-and-requirements-calculation\/\" class=\"cqop-v6-pulsante-5eba899 cqop-v6-state-6d47db8 gb-text\">Calculate fees and requirements<\/a>\n\n\n\n      <\/div>\n\n\n\n    <\/div>\n\n\n\n  <\/div>\n\n\n\n\n  \n\n<div class=\"cqop-v6-pannello-1d12dfc\">\n    \n\n<div class=\"cqop-v6-griglia-74a4c6d\">\n      \n\n<div class=\"cqop-v6-titolo-sticky-1c8b9f9\">\n        \n        \n\n<h2 class=\"cqop-v6-titolo-ecc189a gb-text\">Types of underground works covered by OG4<\/h2>\n\n\n\n      <\/div>\n\n\n\n      \n\n<div>\n\n\n<img class=\"gb-media-cqogillusog42 cqop-v6-pannello-e34122a cqop-og-illustration\" src=\"https:\/\/www.cqop.com\/wp-content\/uploads\/2026\/10\/og4-illustrazione-2-fronte-blu-bordeaux.webp\" alt=\"Underground civil engineering works \u2014 OG4 illustration\" width=\"840\" height=\"448\" loading=\"lazy\" decoding=\"async\" style=\"display:block;width:100%;max-width:700px;height:auto;margin:28px auto;object-fit:contain;\"\/>\n\n\n\n\n<p class=\"cqop-v6-testo-7febc91 gb-text\">OG4 is a highly specialized category, required in numerous major infrastructure tenders and reserved for companies with strong technical expertise, dedicated equipment, and integrated competencies. OG4 activities include:<\/p>\n\n\n\n\n\n<ul class=\"cqop-v6-pannello-f72340a\">\n\n<li class=\"cqop-v6-griglia-eaa3518 gb-text\">\n              <span aria-hidden=\"true\" class=\"cqop-v6-pannello-17317d0\">01<\/span>\n              Road and highway tunnels: Alpine tunnels and major road galleries, including excavation, lining, ventilation, and safety systems.<\/li>\n\n\n\n            \n\n<li class=\"cqop-v6-griglia-eaa3518 gb-text\">\n              <span aria-hidden=\"true\" class=\"cqop-v6-pannello-17317d0\">02<\/span>\n              Railway tunnels: from high\u2011speed lines to cross\u2011border megaprojects, built with strict technical standards and dedicated systems.<\/li>\n\n\n\n            \n\n<li class=\"cqop-v6-griglia-eaa3518 gb-text\">\n              <span aria-hidden=\"true\" class=\"cqop-v6-pannello-17317d0\">03<\/span>\n              Metro and underground tram systems: excavated beneath densely populated urban areas, with constraints related to groundwater, existing buildings, and traffic.<\/li>\n\n\n\n            \n\n<li class=\"cqop-v6-griglia-eaa3518 gb-text\">\n              <span aria-hidden=\"true\" class=\"cqop-v6-pannello-17317d0\">04<\/span>\n              Underpasses and minor underground passages: natural\u2011tunnel works or microtunnelling in confined environments.<\/li>\n\n\n\n            \n\n<li class=\"cqop-v6-griglia-eaa3518 gb-text\">\n              <span aria-hidden=\"true\" class=\"cqop-v6-pannello-17317d0\">05<\/span>\n              Tunnel auxiliary works: access ramps, retaining structures, technological systems, and railway track installations linked to the main gallery.<\/li>\n\n\n\n            <\/ul>\n\n\n\n\n\n<img class=\"gb-media-cqogillusog43 cqop-v6-pannello-e34122a cqop-og-illustration\" src=\"https:\/\/www.cqop.com\/wp-content\/uploads\/2026\/10\/og4-illustrazione-3-sezione-blu-bordeaux.webp\" alt=\"Underground civil engineering works \u2014 OG4 illustration\" width=\"840\" height=\"448\" loading=\"lazy\" decoding=\"async\" style=\"display:block;width:100%;max-width:700px;height:auto;margin:28px auto;object-fit:contain;\"\/>\n\n\n<\/div>\n\n\n\n    <\/div>\n\n\n\n  <\/div>\n\n\n\n\n  \n\n<div class=\"cqop-v6-pannello-13e79de\">\n    \n\n<div class=\"cqop-v6-contenuto-c7714c8\">\n      \n      \n\n<h2 class=\"cqop-v6-titolo-e915111 gb-text\">Categories that integrate with OG4<\/h2>\n\n\n\n      \n\n<p class=\"cqop-v6-testo-1e0df31 gb-text\">Underground works are rarely isolated; major infrastructure projects require the integration of multiple SOA categories:<\/p>\n\n\n\n\n\n<div class=\"cqop-v6-griglia-9e34a50\">\n\n<div class=\"cqop-v6-pannello-12843ab\">\n            \n\n<div class=\"cqop-v6-pannello-947e167 gb-text\">OG3<\/div>\n\n\n\n            \n\n<p class=\"cqop-v6-testo-8d82677 gb-text\">Roads and railways: OG3 and OG4 are complementary. OG3 covers open\u2011air sections, viaducts, and embankments; OG4 covers natural tunnels. New highways or railways usually require both.<\/p>\n\n\n\n          <\/div>\n\n\n\n          \n\n<div class=\"cqop-v6-pannello-12843ab\">\n            \n\n<div class=\"cqop-v6-pannello-947e167 gb-text\">OS21<\/div>\n\n\n\n            \n\n<p class=\"cqop-v6-testo-8d82677 gb-text\">Special structural works: consolidation of tunnel faces, soil injections, diaphragm walls, and deep foundations. In unstable ground, OG4 and OS21 are almost always paired.<\/p>\n\n\n\n          <\/div>\n\n\n\n          \n\n<div class=\"cqop-v6-pannello-12843ab\">\n            \n\n<div class=\"cqop-v6-pannello-947e167 gb-text\">OS28<\/div>\n\n\n\n            \n\n<p class=\"cqop-v6-testo-8d82677 gb-text\">\/ OS30 \u2013 Technological systems: ventilation, fire\u2011safety systems, lighting, electrical supply, and communication systems. In complex tenders, these may be replaced by OG11, which covers all integrated tunnel systems.<\/p>\n\n\n\n          <\/div>\n\n\n\n          \n\n<div class=\"cqop-v6-pannello-12843ab\">\n            \n\n<div class=\"cqop-v6-pannello-947e167 gb-text\">OG5<\/div>\n\n\n\n            \n\n<p class=\"cqop-v6-testo-8d82677 gb-text\">Dams and hydraulic tunnels: sometimes overlaps with OG4 for diversion or relief tunnels; however, OG5 remains the leading category for hydraulic works.<\/p>\n\n\n\n          <\/div>\n\n\n\n          \n\n<div class=\"cqop-v6-pannello-12843ab\">\n            \n\n            \n\n<p class=\"cqop-v6-testo-8d82677 gb-text\">Support categories: OS8 (waterproofing), OS10 (signage), OS11 (structural equipment), OS12\u2011B (safety barriers), OS19 (telecommunications).<\/p>\n\n\n\n          <\/div>\n\n\n\n          <\/div>\n\n\n\n\n<div class=\"cqop-v6-griglia-ac0de1b\">\n        \n\n        \n\n      <\/div>\n\n\n\n    <\/div>\n\n\n\n  <\/div>\n\n\n\n\n  \n\n\n\n<div id=\"faq\" class=\"cqop-v6-pannello-481eee7\">\n    \n\n<div class=\"cqop-v6-griglia-28a732f\">\n      \n\n<div>\n        \n\n<h2 class=\"cqop-v6-titolo-2c72ce6 gb-text\">FAQ SOA Category OG4<\/h2>\n\n\n\n\n\n<div class=\"cqop-category-download cqop-category-download-minimal cqop-category-download-faq\">\n\n\n<a class=\"gb-text cqop-category-download-button\" href=\"https:\/\/www.cqop.com\/wp-content\/uploads\/2026\/10\/Modulistica-UK.pdf\" target=\"_blank\" rel=\"noopener noreferrer\" aria-label=\"Download PDF technical data sheets \u2014 opens in a new tab\">\n<svg role=\"presentation\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"22\" height=\"22\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"1.7\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\" focusable=\"false\"><path d=\"M12 3v12m-5-5 5 5 5-5M4 16v5h16v-5\"\/><\/svg>\n\n\n<span class=\"gb-text\">Download PDF technical data sheets<\/span>\n<\/a>\n\n<\/div>\n\n\n\n      <\/div>\n\n\n\n      \n\n<div>\n        \n<div class=\"wp-block-essential-blocks-accordion cqop-faq-accordion root-cqop-faq-94002-0\"><div class=\"eb-parent-wrapper eb-parent-cqop-faq-94002-0 \"><div class=\"eb-accordion-container cqop-faq-94002-0\" data-accordion-type=\"accordion\" data-tab-icon=\"\" data-expanded-icon=\"\" data-transition-duration=\"500\"><div class=\"eb-accordion-inner\">\n<div class=\"wp-block-essential-blocks-accordion-item cqop-faq-94002-0-1 eb-accordion-wrapper\" data-clickable=\"false\"><div class=\"eb-accordion-title-wrapper eb-accordion-title-wrapper-cqop-faq-94002-0\" tabindex=\"0\"><div class=\"eb-accordion-title-content-wrap title-content-cqop-faq-94002-0\"><h2 class=\"eb-accordion-title\">What is the official \u201cdeclaratory\u201d of OG4?<\/h2><\/div><\/div><div class=\"eb-accordion-content-wrapper eb-accordion-content-wrapper-cqop-faq-94002-0\"><div class=\"eb-accordion-content\">\n<div class=\"gb-text cqop-faq-answer\"><p>The OG4 category covers underground works excavated in natural terrain (soil or rock) intended for road or railway use, built using specialized technical equipment such as TBMs (Tunnel Boring Machines), traditional excavation, or controlled blasting. It includes complementary and accessory works such as access ramps, lining systems, consolidation, ventilation, lighting, and safety systems.<\/p>\n<p><strong>Official Declaratory:<\/strong> OG4 concerns the construction, maintenance, or renovation\u2014using specialized technical equipment\u2014of underground works required for road and rail mobility, regardless of scale. These works include all connected, complementary, or accessory structures, whether network\u2011based or site\u2011specific, such as access roads of any type, at\u2011grade or elevated interchanges, surface car parks, slope\u2011support structures, and all electromechanical, electrical, telephone, electronic, and railway\u2011track installations necessary to provide safe, reliable, and user\u2011friendly service. It includes natural tunnels, cross\u2011mountain passages, underground corridors, and excavated tunnels.<\/p>\n<\/div>\n<\/div><\/div><\/div>\n\n\n<div class=\"wp-block-essential-blocks-accordion-item cqop-faq-94002-0-2 eb-accordion-wrapper\" data-clickable=\"false\"><div class=\"eb-accordion-title-wrapper eb-accordion-title-wrapper-cqop-faq-94002-0\" tabindex=\"0\"><div class=\"eb-accordion-title-content-wrap title-content-cqop-faq-94002-0\"><h2 class=\"eb-accordion-title\">What is the difference between OG3 and OG4?<\/h2><\/div><\/div><div class=\"eb-accordion-content-wrapper eb-accordion-content-wrapper-cqop-faq-94002-0\"><div class=\"eb-accordion-content\">\n<div class=\"gb-text cqop-faq-answer\"><p>OG3 covers surface infrastructure (roads, viaducts, railways, artificial tunnels), whereas OG4 covers true underground works \u2013 natural tunnels excavated in soil or rock.<\/p>\n<\/div>\n<\/div><\/div><\/div>\n\n\n<div class=\"wp-block-essential-blocks-accordion-item cqop-faq-94002-0-3 eb-accordion-wrapper\" data-clickable=\"false\"><div class=\"eb-accordion-title-wrapper eb-accordion-title-wrapper-cqop-faq-94002-0\" tabindex=\"0\"><div class=\"eb-accordion-title-content-wrap title-content-cqop-faq-94002-0\"><h2 class=\"eb-accordion-title\">Which SOA categories are commonly required alongside OG4?<\/h2><\/div><\/div><div class=\"eb-accordion-content-wrapper eb-accordion-content-wrapper-cqop-faq-94002-0\"><div class=\"eb-accordion-content\">\n<div class=\"gb-text cqop-faq-answer\"><p>Most commonly OG3, OS21 (consolidation and ground engineering), OS28\/OS30 (technological systems), or OG11 for integrated systems.<\/p>\n<\/div>\n<\/div><\/div><\/div>\n\n\n<div class=\"wp-block-essential-blocks-accordion-item cqop-faq-94002-0-4 eb-accordion-wrapper\" data-clickable=\"false\"><div class=\"eb-accordion-title-wrapper eb-accordion-title-wrapper-cqop-faq-94002-0\" tabindex=\"0\"><div class=\"eb-accordion-title-content-wrap title-content-cqop-faq-94002-0\"><h2 class=\"eb-accordion-title\">What are notable examples of OG4 works in Italy?<\/h2><\/div><\/div><div class=\"eb-accordion-content-wrapper eb-accordion-content-wrapper-cqop-faq-94002-0\"><div class=\"eb-accordion-content\">\n<div class=\"gb-text cqop-faq-answer\"><p>Major OG4 projects include the Brenner Base Tunnel, the Turin\u2013Lyon line, Rome Metro Line C, and the Variante di Valico on the A1 highway.<\/p>\n<\/div>\n<\/div><\/div><\/div>\n<\/div><\/div><\/div><\/div>\n\n<\/div>\n\n\n\n    <\/div>\n\n\n\n  <\/div>\n\n\n\n\n  \n\n\n  \n\n<div class=\"cqop-v6-pannello-5e842af\">\n    \n<svg focusable=\"false\" role=\"presentation\" aria-hidden=\"true\" class=\"cqop-v6-icona-71ff866\">\n      <defs>\n        <pattern id=\"mattoniOG1\" width=\"72\" height=\"36\" patternUnits=\"userSpaceOnUse\">\n          <rect x=\"0\" y=\"2\" width=\"32\" height=\"14\" fill=\"rgba(255,255,255,0.022)\"><\/rect>\n          <rect x=\"36\" y=\"2\" width=\"32\" height=\"14\" fill=\"rgba(255,255,255,0.022)\"><\/rect>\n          <rect x=\"18\" y=\"20\" width=\"32\" height=\"14\" fill=\"rgba(255,255,255,0.022)\"><\/rect>\n          <rect x=\"-18\" y=\"20\" width=\"32\" height=\"14\" fill=\"rgba(255,255,255,0.022)\"><\/rect>\n          <rect x=\"54\" y=\"20\" width=\"32\" height=\"14\" fill=\"rgba(255,255,255,0.022)\"><\/rect>\n        <\/pattern>\n      <\/defs>\n      <rect width=\"100%\" height=\"100%\" fill=\"url(#mattoniOG1)\"><\/rect>\n    <\/svg>\n\n    \n\n<div class=\"cqop-v6-griglia-7a21026\">\n      \n\n<div class=\"cqop-original-cta-copy\">\n\n<p class=\"cqop-v6-testo-3c2b5d5 gb-text\">OG4 is the category that certifies the ability to build safe, sustainable, and long\u2011lasting underground infrastructure that connects territories and communities. Obtaining OG4 SOA certification means investing in innovation, technology, and the future of mobility.<\/p>\n\n\n\n\n\n<p class=\"cqop-v6-testo-3c2b5d5 gb-text\">To excel in OG4, companies must combine experience, advanced training, and cutting\u2011edge technology. Qualified enterprises must ensure safety, quality, and strict compliance with timelines \u2013 critical elements for competing in public\u2011works tenders.<\/p>\n\n\n\n\n\n<p class=\"cqop-category-conclusion-accent cqop-v6-testo-23dd753 gb-text\">Interested in expanding into underground engineering? Make sure you have the appropriate OG4 qualification and continue investing in people, skills, and innovation.<\/p>\n\n\n\n<\/div>\n\n\n\n      \n\n<div class=\"cqop-v6-pannello-4cdb9ad\">\n        \n\n<a href=\"https:\/\/www.cqop.com\/en\/contacts\/\" class=\"cqop-v6-pulsante-5eba899 cqop-v6-state-f859560 gb-text\">Contact us<\/a>\n\n\n\n        \n\n      <\/div>\n\n\n\n    <\/div>\n\n\n\n  <\/div>\n\n\n\n\n  <\/div>\n\n\n\n\n","protected":false},"excerpt":{"rendered":"<p>OG4 General works categories SOA Category OG4 Everything required for underground civil engineering works The OG4 category within the SOA qualification system covers underground civil works \u2013 specifically the construction, maintenance, and renovation of road and railway tunnels. As one of the 13 general categories, OG4 plays a strategic role in the transport\u2011infrastructure sector. OG4 &#8230; <a title=\"SOA Category OG4\" class=\"read-more\" href=\"https:\/\/www.cqop.com\/en\/list-of-soa-categories\/general-works\/og4\/\" aria-label=\"Read more about SOA Category OG4\">Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"parent":921039,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"_eb_attr":"","_eb_data_table":"","footnotes":""},"class_list":["post-921444","page","type-page","status-publish"],"acf":{"h1_seo":""},"publishpress_future_workflow_manual_trigger":{"enabledWorkflows":[]},"_links":{"self":[{"href":"https:\/\/www.cqop.com\/en\/wp-json\/wp\/v2\/pages\/921444","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.cqop.com\/en\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.cqop.com\/en\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.cqop.com\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.cqop.com\/en\/wp-json\/wp\/v2\/comments?post=921444"}],"version-history":[{"count":7,"href":"https:\/\/www.cqop.com\/en\/wp-json\/wp\/v2\/pages\/921444\/revisions"}],"predecessor-version":[{"id":922184,"href":"https:\/\/www.cqop.com\/en\/wp-json\/wp\/v2\/pages\/921444\/revisions\/922184"}],"up":[{"embeddable":true,"href":"https:\/\/www.cqop.com\/en\/wp-json\/wp\/v2\/pages\/921039"}],"wp:attachment":[{"href":"https:\/\/www.cqop.com\/en\/wp-json\/wp\/v2\/media?parent=921444"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}