Sewerages are critical infrastructure assets for wastewater carriage in urban lifelines, but their function can be seriously affected by blockages or deterioration. Existing sewer pipeline inspection methods, such as closed-circuit television and sonar detection, have been blamed for low efficiency and considerable noise in the collected data. Therefore, this paper attempts to enhance the blockage and deterioration assessment inside the sewer pipeline by proposing a whale optimization algorithm-based point cloud data (WOAPCD) processing method. The method consists of an improved WOA for data clustering and fitting and a reverse slicing method for modeling the as-is conditions. The applicability of this proposed approach is validated in an actual sewerage system, and the results show that the WOAPCD can accurately and effectively reconstruct the 3D model of the sewer, providing valuable information for quantifying siltation conditions. The proposed method has better performance than PSO and GA in terms of the fitting error and modeling speed.