AWWA INF55787

As the system operated by the Orange Water and Sewer Authority (OWASA), North Carolina, continually expands to accommodate increasing water demand, the agency is also working to replace aging infrastructure. This paper describes how OWASA and design consultant McKim & Creed collaborated on a project that involved the replacement of existing raw water lines, including an asbestos-cement raw water transmission main installed in 1942 and a cast iron main installed in 1932. OWASA's intent was to replace the two 12-inch raw water mains with a new larger diameter main. Concurrent with the design stage of this project, OWASA was also developing a Comprehensive Water and Sewer Master Plan. As part of the Master Plan, it was decided to size the new Raw Water Transmission Main to provide the 36 MGD conveyance capacity projected for the year 2050, and have additional capacity to pump raw water from University Lake Reservoir via the water treatment plant's proposed future pump station to the Stone Quarry Reservoir. This increases the overall raw water system redundancy and reliability. In the event that OWASA experiences problems with raw water conveyance from its Cane Creek Reservoir, the new University Lake Raw Water Main will have sufficient conveyance capacity to serve the OWASA community. To determine the size of the new main required for the projected 36 MGD conveyance capacity, an evaluation of the University Lake Raw Water Pumping Station was initiated by OWASA. A thorough hydraulic analysis of various pipe diameters and materials was performed, whereby it was determined that a 42-inch diameter ductile iron pipe was the most cost effective choice to meet OWASA's needs. Prior to the design stage, OWASA realized the sensitivity of the neighborhoods that would be impacted by this project and understood that routing of the pipeline would be critical. The preliminary design stage focused on the evaluation of several alternative routes for the new raw water main, with particular emphasis on impacts to the neighborhoods and communities, feasibility, and cost effectiveness. The number of potential routes were narrowed to those with the greatest potential, which were then reevaluated in greater detail to determine the final pipeline route. Ultimately, the final route would require construction through a mixture of wooded areas, established neighborhoods, town streets, and North Carolina Department of Transportation highways. This thorough process of evaluation and elimination resulted in a route selection that minimized impacts while providing OWASA with a raw water transmission main that would service the community for the next 50 years.

Product Details

Edition:

Vol. - No.

Published:

01/01/2002

Number of Pages:

9

File Size:

1 file , 150 KB