Pump Station Considerations for a Simple Duplex Station

Pump Station Considerations for a Simple Duplex Station Discharging into a Combined Regional Force Main Rachel Rausch, EIT

Site Location Bluffton, SC

Project Background • Private development client • Development includes two large retail buildings, service station, bank, and general commercial • No gravity sewer service in area

Project Background

Unique Design Considerations • Donation of project to Beaufort Jasper Water and Sewer Authority (BJWSA) • Little topographical variability on site • Deep wetwell • Site pump station will pump into 16” combined regional force main Unknown conditions in regional force main

Design Solution: Data Collection • BJWSA Standards • Force main record drawings • Force main operating conditions • Operating pressure • Flow

Design Solutions: Calculations • Wastewater Flow Estimate • Site Storage Volume • Force Main Operating Conditions • Choosing Pumps

Design Solutions: Calculations Wastewater flow from site: Peaking Factor=4 Qpeak=92. 4 BJWSA storage volume requirement: Storage volume in site MH and pipes > 24 hour volume from site

Pump Selection Existing force main conditions analyzed • Regional Force Main Pump station on • 1, 000 gpm @ 70’ TDH • Regional Force Main Pump Station CP-67 off • No flow in regional force main • Two C factors analyzed for each system curve

System Curve-Pumps On System Curve-Regional Force Main Pumps On 250 Hazen-Williams C Factors: C 1=110 C 2=130 200 Design Point: 310 gpm at 102’ TDH (ft) 150 100 50 0 0 200 400 600 800 1000 Flowrate (gpm) TDH C 1 MIN [FT] TDH C 1 MAX [FT] TDH C 2 MIN [FT] PUMP CURVE #1 PUMP CURVE #2 PUMP CURVE #3 PUMP CURVE #4 PUMP CURVE #5 PUMP CURVE #6 TDH C 2 MAX [FT] 1200

System Curves-Pumps Off System Curve-Regional Force Main Pumps Off 350 Hazen-Williams C Factors: C 1=110 C 2=130 300 250 Design Point: 410 gpm at 96’ TDH (ft) 200 150 100 50 0 0 200 400 600 800 1000 Flowrate (gpm) TDH C 1 MIN [FT] TDH C 1 MAX [FT] TDH C 2 MIN [FT] PUMP CURVE #1 PUMP CURVE #2 PUMP CURVE #3 PUMP CURVE #4 PUMP CURVE #5 PUMP CURVE #6 TDH C 2 MAX [FT] 1200

Pump Selection

Other Calculations • Buoyancy Calculations • High groundwater table • Deep wetwell, approximately 24 feet deep • Cycle time

Final Pump Station Layout

Project Status • BJWSA Approval • Construction Status

Questions?

Lessons Learned