## 1 Introduction
### Problem Statement and Research Scope  
The literature review identifies that inefficient utility management from design to operation phase put earthwork operations at a high risk. The current utility management system uses 2D CAD drawings during the design and construction stages, which contains very limited information. Furthermore, the information significant for the operation and maintenance stages is gathered and managed in multiple formats such as excel spreadsheet, PDFs and Word documents, and images and photographs, which makes the workflow inefficient because it is very difficult to retrieve or update information from such a system. The use of such a poor utility management system may lead to property damage, injuries, fatalities, disruption to urban services such as water supply in case of water pipelines, wastewater distribution networks in case of sewage, telecommunication in case of telephone lines, and energy in electric cables, etc. Moreover, it can create significant social and economic impacts as well as causing delays in the construction activities. Storing and managing the geographic location, size, materials, and other properties of the underground utility infrastructure in an integrated system can play a significant role in facilitating the visualization, digitization, and management of the utility infrastructure. However, it is very difficult in case of underground utilities because of their long geographic distribution, lack of standards, and the lack of information technology systems. Geographic information system (GIS) contains information about the geographic location and spatial coordinates, while building information modeling (BIM) contains information about the geometry and semantics in every detail. BIM integration with the GIS technology has been used in the AEC industry for many purposes such as supply chain management [15], geotechnicalproperty modeling [29], cost estimation of roads [30], tunnel facility management [31], heritage facility management [13], site layout and construction safety planning [32], and space planning. However, the use of such an integrated system is rarely explored for the underground utility infrastructure. This paper presents a novel integrated BIM-GIS framework for the management of underground utility infrastructure on the basis of modern construction engineering and information technology tools. BIM uses the IFC schema, while GIS is based on the CityGML schema. IFC contains information about the asset geometry and semantic in detail, while CityGML contains assets geographic information, location, geometry, and other spatial information in less detail. In the proposed study, the integration was achieved using open standard data model, IFC, and CityGML mapping. The use of open standard data model has the advantage of providing a collaborative environment and allows the stakeholders to manage, analyze, and exchange the utility infrastructure information at different stages. The integrated BIM-GIS model can be used for different project stages such as preliminary design, construction, and operation and maintenance stage, which has novelty because the application of the previous studies has mainly been focused on a single project stage. This framework provides a ready-to-use integrated BIM-GIS 3D utility infrastructure model with all the semantic information that can be used in the preliminary design stages to know about the geographic location, size, type, depth, and material of each pipe. The application of the integrated BIM-GIS model in the construction stage is to provide visual assistance in real-time design and underground utilities to the excavator operator with the machine guidance systems. Moreover, the integrated BIM-GIS utility infrastructure model contains all the significant information in a database that can be used by stakeholders in the operation and maintenance stage for making decisions. Finally, we implemented our novel integrated BIM-GIS framework on a real case study.