AWWA MTC61100

The North Clackamas County Water Commission (NCCWC) owns and operates a 10 MGD slow sand filter plant, constructed in 1998, and services a rapidly growing community southeast of Portland, Oregon. The Oak Lodge Water District (OLWD) and the Sunrise Water Authority (SWA) are the direct customers/owners of the NCCWC. Raw water for the plant is drawn from the Clackamas River, a normally low-turbidity supply, subject to seasonal and periodic water quality challenges, including high turbidities, taste and odor (T&O), and algae. The Sunrise Water Authority (SWA) is expanding the existing plant to 25 mgd to meet increasing demands. The project was under a very tight schedule; the existing plant was at full capacity and additional water was needed as quickly as possible to meet demands. In addition, SWA was looking for a treatment technology capable of operating throughout the year without shutdowns due to raw water quality. Since the slow sand plant has been operational, periodic shutdowns have been required when the river's turbidity exceeds 10 NTU. Though schedule was a key driving force in the plant expansion, SWA regarded water quality as high, if not a higher priority than schedule. For this reason, membrane filtration was recommended for plant expansion. To address the potential raw water quality challenges, the membrane filtration plant was designed to allow for periodic addition of powdered activated carbon (PAC) and/or alum or ACH (aluminum chlorohydrate). The expanded facility will be a unique combination of new and old, combining the earliest filtration technology - slow sand filtration, with the latest water treatment technology - membrane filtration, operating in parallel. 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 break ground on construction in 10 months. A more traditional and conservative approach would likely have taken 18 months, or longer. This paper presents detailed descriptions of the following aspects of this project: to pilot or not to pilot lessons learned from the membrane procurement RFP process; pilot study results, and impacts on design; and, final design criteria and membrane building layout. Includes table, figures.