The study is a follow-up on rubric-based assessment of level of attainment of Student Outcomes (SOs) in Environmental Engineering undergraduate education by the senior-year Graduation Design Project (GDP): the focal points are the process of and results from incorporation of additional assessment tools and implementation of "Performance Indicator (PI)-breakdown" to continue improving the SO Assessment and Evaluation (A&E) process. For several consecutive cycles, A&E to define attainment level of total of seven SOs by the GDP gave results below the set thresholds for some of them (SO1, 5, 8), which indicated a discrepancy and a need for improvement in the assessment tools and processes. Accordingly, two remedial actions were undertaken to meet those needs and the SOs were re-assessed. Results of the previous and improved SO A&E process revealed a clear progress in SO attainment addressed by the GDP, from 2014-15 to 2015-16, upon choice and addition of other tools. Yet, those still gave a general sense of deficiencies at SO-level. Therefore, some additional tools were added and the "PI-breakdown"-based approach was implemented. Those informative results are combined successfully with the formerly improved SO A&E process, facilitating attainment of more realistic results and further fine tuning of the SO A&E process.