City of San Diego Metropolitan Wastewater Department Sewer Pump Station No. 79

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City of San Diego Metropolitan Wastewater Department Sewer Pump Station No. 79

Sewer Pump Station 79Client: Atkins (formerly PBS&J)

Location: San Diego, California

Lopez Engineering, Inc. (LEI) was subcontracted by PBS&J to design the Sewer Pump Station No.79 (SPS No.79) electrical system upgrade to accommodate the SPS No. 79 upgrade project for the City of San Diego MWWD. During field work, LEI discovered several California Electrical Code (CEC) violations and did a study of the electrical system to determine whether it could be upgraded or had to be replaced. Due to the increase in pump motor sizes, LEI determined that almost the entire electrical system had to be replaced, with the exception of the existing temporary diesel engine generator, which could be kept as long as the circuit breaker was changed.

LEI provided deliverables including a conceptual electrical study describing recommended electrical design, calculations, contract documents, cost estimate and sequence of construction. Construction documents included drawings consisting of electrical demolition, control system demolition, electrical installation, control system installation and specifications. The set included electrical and control site plans, power and signal floor plans, single line diagram, MCC elevation and Panel Schedule.

The existing SPS consisted of 40 HP submersible pumps in series with 75 HP horizontal non-clog pumps, which were replaced by 100 HP submersible pumps in series with 100 HP horizontal pumps. The 480Y/277 volt, 3 phase, 3 wire, electrical system consists of a 2 MW diesel engine generator with 1000 amp circuit breaker, 1000 amp meter main, 1000 amp automatic transfer switch (ATS), 1000 amp switchboard, 1000 amp motor control center (MCC), six 100 HP pumps (3 pairs of one 100 HP vertical pump, one 100 HP horizontal pump), feeders, branch circuits, starters, and disconnects.

The control system was too small with potentially unsafe working conditions during maintenance. Therefore it was replaced with a larger control system. Control system drawings included floor plans, site plans, ladder diagrams for each motor, pump control panel control diagrams, pump panel detailed layout with equipment call outs, PLC card layouts and a detailed SPS sequence of operation. LEI prepared all contract documents according to MWWD design criteria while meeting CEC requirements.