The cost of a rehabilitation pipe is associated with the pipe diameter and the rehabilitation action. Let c_k (e_k, d_k) be cost per unit length of a pipe for the k^th rehabilitation action e_k chosen from a set of possible action E⁰ of EC choices for the existing pipe of diameter d_k. The cost of rehabilitation pipes is formulated as:

For the pipes that are grouped into one design link, the same pipe size or rehabilitation action will be applied to the pipes.