A Design-Driven Full-Process Cost-Control Framework for EPC Projects Under Preliminary-Design Bill-of-Quantities Bidding

With the increasing adoption of the Engineering, Procurement, and Construction (EPC) contracts in government-funded and large-scale infrastructure projects, bill-of-quantities bidding based on preliminary design has emerged as a new procurement approach. Although this approach improves early-stage investment control, it also imposes higher requirements on contractors’ cost-management capabilities. Based on whole-process cost-control theory, this study develops a design-driven full-process cost-control framework for EPC projects using a reclaimed water plant project in northwest China as a case study. The model comprises three layers: a design-driven decision-making layer, a whole-process cost-control layer, and a collaborative management support layer. It covers the key stages of bidding, design, procurement, construction, and final settlement, and integrates design, cost, and procurement management with Building Information Modeling (BIM) and dynamic monitoring based on Earned Value Management (EVM). The case results show that the model can effectively identify and control cost risks, promote the integration of design optimization and cost control, and improve cost management performance. The final settlement price was 0.93% below the contractual settlement ceiling and about 6.6% below the initial investment estimate. This study provides both theoretical support and practical guidance for enhancing full-process cost control in EPC projects under preliminary-design bill-of-quantities bidding.