The North Clackamas County Water Commission (NCCWC) WTP is located along the Clackamas River, and is co-owned by the Sunrise Water Authority (SWA), Oak Lodge Water District and City of Gladstone. The plant serves over 40,000 customers in the southeast suburbs of Portland, Oregon. The existing 10 mgd Slow Sand Filter Plant was constructed in 1997 and was expanded to 25 mgd using low pressure, submerged membrane technology. US Filter's CMF submerged microfiltration system was selected for the expansion. The expanded facility is a unique combination of new and old, combining the earliest filtration technology ¿¿¿¿¿¿¿¿ slow sand filtration ¿¿¿¿¿¿¿¿ with the latest in technology ¿¿¿¿¿¿¿¿ submerged membranes ¿¿¿¿¿¿¿¿ operating in parallel. The project was under a tight schedule. The existing plant was at capacity, and additional water was needed as quickly as possible to meet summer peak demands. Through a fast-tracked and innovative process focused on partnership and cooperation, the project team was able to select the membrane supplier, complete the design, select the general contractor and substantially complete construction in 17 months. Following membrane vendor selection, validation pilot testing was performed concurrent with design. This pilot testing confirmed that the vendor proposed conservatively appropriate design criteria, and the plant design could proceed unchanged. Interestingly, this was a qualifications-based selection process for the membrane manufacturer, which promoted more reasonable design criteria than a traditional low-bid approach. Following validation testing, NCCWC elected to participate in an AWWARF Study entitled "Optimization of Membrane Treatment for Direct and Clarified Water Filtration" (AWWA, 2005). This study provided the unique opportunity to compare and contrast results from bench- and pilot-scale analysis. This presentation summarizes the findings from each of the two types of data collection efforts, clearly demonstrating the benefits of each in developing full-scale design criteria and predicting the performance of the full-scale plant. This predicted performance is also compared to full-scale data collected during the first 10-months of plant operation. Finally, this study presents a summary of recommendations to design professionals on the benefits and appropriate use of bench and pilot scale data to efficiently and cost-effectively develop full-scale membrane treatment plant designs. This information will assist those in the water industry as full-scale implementation of membrane technology continues to grow. Includes table.