The design of the pumping station shall be coordinated with the design of the force main as appropriate. For guidelines for force main design (general design and hydraulic design), see the WSSC Pipeline Design Manual (WSSC Chapter 11.130). Minimum pipeline velocity shall be kept above two feet per second.

System head-capacity curves shall be accurately developed (in conjunction with force main sizing) in order to properly select the best wastewater pump. A Hazen-Williams C factor of between 100 and 120 shall be used.

System head curve with the pump characteristic curve superimposed showing operating points (with C = 120) and pump performance curves showing range and efficiencies, shall be submitted for review and approval. Backup data on force main sizing shall also be submitted for review. For grinder wastewater pumping stations, hydraulic calculations demonstrating that the grinder pumps are sufficiently sized to send wastewater to the nearest existing gravity sewer or force main shall be submitted for review. System head curve with pump curve superimposed shall be included in the contract drawings.

If considered necessary by the consultant and if approved by the WSSC, a surge analysis shall be done for the submersible, nonclog pumping stations to evaluate the need for incorporating a surge relief valve for waterhammer control. (Design Guideline DG-08 § 2.0, dated August 2006)