Date
Monday, September 9, 2024
Time
11:00 AM - 11:30 AM
Location Name
M111
Name
Modifications to Increase Reliability and Operability: Kingsport WTP High Service PS Case-Study
Track
Water Supply
Description

The City of Kingsport owns and operates a conventional water treatment plant (WTP) with filter capacity of 29 million gallons per day (mgd); this plant is the only water plant for the City. The WTP has only N+1 reliability (i.e. a single standby pump), and all clearwell volume is required for disinfection (i.e. the existing clearwell cannot be taken out of service). The existing High Service Pump Station (HSPS) was constructed in 1970 with a single vertical turbine wet pit pump; the second and third pumps were installed in 1980 and 1990, and all three pumps were replaced between 2019 and 2021. Kingsport’s WTP Master Plan includes improvements to the HSPS and finished water storage. The Master Plan includes an additional 1.5 million-gallon clearwell and adding a fourth high service pump to provide N+2 reliability. The improved HSPS will provide 24 mgd firm capacity with one pump out of service and 22 mgd with two pumps out of service. Peak hour demand (estimated 31.3 mgd for 2030) in excess of HSPS capacity will be provided by distribution system storage. There is not room for expansion in the existing wet well; therefore, the proposed fourth pump will be located outside the existing pump station and will be a vertical turbine pump installed in a can. The proposed pump will be hydraulically compatible with the existing high service pumps but will be installed with a larger impeller and larger motor for future capacity. Due to Hydraulic Institute (HI) requirements, the proposed pump suction bell will be approximately 3 feet lower than the suction bell of the three existing pumps. However, the resulting minimum water surface elevations (WSE) required to meet HI standards are not significantly different between the existing pumps in the wet well and the proposed can pump. A physical model study of the proposed can pump and the existing wet well was conducted to ensure there are not adverse hydraulic conditions that could impact pump performance. Maintenance of plant operations is a primary concern for the wet well penetration. The existing HSPS will be cored to connect piping for the new pump, but shutdown of the existing wet well during construction and startup needs to be minimized or eliminated. During design, we evaluated constructing a new wall attached to the exterior of the existing wet well to support the applied loads with a large core taken from the wall, but this would require shutdown of a few days to a week. Ultimately, design included building a vault adjacent to the existing wet well. This would allow the proposed pump to be installed and then placed in service prior to taking the existing wet well out of service. Construction is scheduled to be complete in August 2025.