Quantitative Approach in Evaluating Water and Waste Water Projects and Operations

Every water utility undergoes tariff reviews (done by governing regulatory body) by validating the expenses incurred by the utility company on project improvements and operations.

Are there any best practices or references that improve projects evaluated quantitatively (using sort of a score card) and if the projects do not meet the criteria, such projects are not be recovered in the tariff, hence, the tariff will not increase. 

Your thoughts please? Thank you.