Most of the City's wastewater lift stations are comprised of a “wet well” containing two submersible pumps.
All “wet wells” are designed differently. Here’s one example from within the City.
Wastewater crew utilizing a City vacuum truck to suck-up wastewater
from a “wet well”. This is the first step in the process of cleaning the wet well.
Now, a Wastewater Maintenance Technician is using a
pressure-washer to complete the process of cleaning a
“wet well” from the top.
A few large lift stations in the City have a “dry well” that contains pumps, valves, pipes and electrical systems.
The City’s largest lift station “dry well” is equipped with three motors,
two of which are shown here, one story underground. Each motor drives a pump.
Inside the largest lift station "dry well" two stories underground.
A pump and wastewater pipe, painted blue and green respectively,
Lift station design incorporates level-sensing equipment, including ultrasonic level transmitters, bubblers, pressure transducers, and floats. At some stations, it’s necessary to control odor. The City dissipates odor through the use of activated carbon and sulfa-treat filtering systems.
The City has installed odor control systems like this one at several wastewater lift stations.
To operate efficiently wastewater lift station equipment requires higher voltage than is supplied to a residential household. Stand-by generators provide emergency power to lift stations to ensure the proper pumping of wastewater during a power outage.
This stand-by generator provides emergency power without any
perceptible noise outside the lift station where it’s installed.
If the lift station does not have onsite power generating capability, a trailer-mounted portable generator may be connected to the station. Generators will continue to supply power to the station until power service is restored.
All of the City’s wastewater lift stations are monitored for status and alarm conditions by a computer-based SCADA (Supervisory Control and Data Acquisition) system. The SCADA system consists of a PC-based central computer system located at the City’s Maintenance and Operations Center (MOC) that communicates with the remote telemetry units located at each wastewater lift station.
The SCADA system gathers information, such as a high wet well level, failed pump or generator, and relays the information back to the MOC, alerting personnel that a problem has occurred. The SCADA system affords Wastewater Division staff the ability to monitor the lift stations and make minor pumping modifications from the wastewater office.
The Wastewater Division employs a specialist skilled in troubleshooting and repair of complex electrical circuits, pumps, and equipment to ensure uninterrupted wastewater service to the residents and businesses of Redmond. This is accomplished through various maintenance and repair activities including but not limited to:
- Pump lubrication
- Visual inspection and repair of electrical and mechanical components (level controllers, check valves, motor starters, relays, phase monitors, indicator lights)
- Maintenance of automatic transfer switches
- Standby generator maintenance (weekly exercise, fluid and filter replacement)
- Grounds maintenance (landscaping, pavement, building, sprinkler systems)
- Odor control system maintenance and repair
Lift stations are designed to pump wastewater uphill from low-lying areas to the wastewater system where it can flow by gravity. The City's Wastewater System utilizes 24 lift stations to convey wastewater to a treatment plant operated by King County.