## 2 Background
### Life-Cycle Cost Analysis Framework  
The LCCA framework provides a structured approach to evaluate the long-term costs associated with trenchless renewal methods for sanitary sewers, encompassing three primary cost components: construction, environmental, and social costs. Construction costs focus on pipe dimensions, material type and thickness, and the rehabilitation design life [33; 34; 51; 52; 53; 54]. Environmental costs are influenced by material components, transportation logistics, project location, equipment use, and energy consumption [55; 56; 57; 58]. Social costs address impacts such as traffic disruption, noise, road restoration needs, and overall public inconvenience [26; 29; 59; 60; 61; 62].  
This framework integrates diverse parameters to calculate a comprehensive life-cycle cost. It accounts for quantifiable factors, including project specifics (e.g., length and diameter of the culvert, material properties), environmental considerations (e.g., emissions, energy use, and material sources), and socio-economic factors (e.g., traffic control, noise, and community impacts). Advanced computational tools like Minitab ([[https://www.minitab.com](https://www.minitab.com)]([https://www.minitab.com](https://www.minitab.com)) (accessed 25 December 2024)) and Microsoft Excel ([[https://www.microsoft.com/excel](https://www.microsoft.com/excel)]([https://www.microsoft.com/excel](https://www.microsoft.com/excel)) (accessed 25 December 2024)) software are employed for construction cost analysis. SimaPro ([[https://simapro.com/](https://simapro.com/)]([https://simapro.com/](https://simapro.com/)) (accessed 25 December 2024)) software is employed to quantify environmental impacts based on metrics such as global warming potential, smog generation, and resource depletion [18; 33]. LCCA can be used as an important and effective decision-making tool to determine the cost of rehabilitation alternatives based on each alternative's full life-cycle (service life). A survey of the largest municipalities in the U.S. indicated that 40% of municipalities use LCCA and that some have been using it for over 20 years [63]. The reasons why 60% of municipalities have not used LCC analysis include the lack of formal guidelines and the difficulty of estimating future expenses and income [64]. The life-cycle cost of the project, from its design to the decommissioning of the utility, includes the following categories [18; 20; 29; 65] (Figure 3):  
* Preconstruction cost: land acquisitions, design fees, planning, legal costs, etc.
* Construction cost: direct cost, indirect cost, social cost, etc.
* Post construction: cost operation and maintenance, etc.  
LCCA for trenchless rehabilitation projects is calculated by combining three key cost components, namely, construction cost (CC), environmental cost (EC), and social cost (SC), as expressed in Equation (1):  
\[\text{LCCA}=\text{CC}+\text{EC}+\text{SC} \tag{1}\]  
This method requires careful consideration of material service life, ensuring the costs of replacing limited-life materials are balanced with initial investments. To account for the monetary differences over time, Equation (2) provides a framework for evaluating the total effective costs of various trenchless rehabilitation methods [55]:  
\[EC(\text{LCCA})=\text{LCCA}*\left\{1+\frac{(1+\text{I})^{n}}{(1+\text{i})}\right\} \tag{2}\]  
where \(EC(\text{LCCA})\): Total effective cost; LCCA: Life-cycle cost analysis expressed in current dollars; I: Inflation rate throughout the project period; i: Interest rate applicable during the project period; \(n\): Number of years until disposal or the end of the design life.