This paper reviews the process used to design the construction dewatering system at the Influent Pumping Station at Annacis Island Wastewater Treatment Plant. The design process followed the "observational method," as applied to soil mechanics by K. Terzaghi and set out by R.B. Peck in the Ninth Rankine Lecture. The design was based on a working hypothesis of behaviour anticipated under the most probable conditions identified in the data gathering and assessment program. The sensitivity of the design was evaluated by considering potentially unfavourable conditions evident in the available data. The design development included a review of monitoring feedback obtained during the pumping-well installation, a pumping test, and the dewatering system start-up. The monitoring program and review process are presented.Key words: dewatering, observational method, case study, pumping test.