Project Location: Treatment and reclamation plants, remote and local reservoirs, and distribution/collection systems.
Project Description: There are two similar and related projects each with multiple phases. The two projects are PLC replacements and RTU replacements. The RTU’s and the PLC’s both communicate to the same SCADA control system, iFix, the BOPU’s graphically based Human Machine Interface. The CPU’s in both RTU’s and PLC’s perform very similar functions. The two types of controllers, PLC’s and RTU’s, have become so comparable that it is possible to have a PLC replace and RTU replacement and vice versa. In the RTU replacement project, PLCs are the likely replacement for the existing RTU’s. The key difference is the physical locations. Most of the PLC’s are located in the plants and the RTU’s are located at more remote locations like pump stations and reservoirs.
PLC Replacement Project:
lncludes replacing 55 obsolete Programmable Logic Controllers (PLC's) at Sherard Water Treatment Plant (5 major & 11 minor), two reclamation plants (2 major & 25 minor), and (12 more) at sewer lift stations, water pump stations and Granite Reservoir. Project includes reusing existing PLC I/O hardware, upgrading central processing units and adding new l/O interface modules.
Three phases are planned. PLC’s at the Sherard Water Treatment plant will be replaced in the first phase. The second phase will replace PLC’s at the Crow Creek and Dry Creek water reclamation plants. The final phase will replace PLC’s at other locations like lift stations and pump stations. Each phase will include design and construction within a single fiscal year by contract resources.
RTU Replacement Project:
Remote Terminal Units (RTU’s) at both water and sewer sites will be replaced. A total of 82 RTU’s will be replaced with PLC’s. An Ethernet based communications system is planned. Ethernet communications is less proprietary than the existing Motorola system. Communications equipment will include Ethernet radios, Ethernet cell modems, and Ethernet based satellite modems. The replacement product for the existing Motorola RTU’s will be small “micro” PLC’s or midsize PLC’s. A pilot replacement PLC and associated modems will be assembled by June 2020. If the pilot PLC is unsuccessful, the Motorola ACE RTU product will be reconsidered.
Projects to be completed in four annual phases beginning in FY 2021. Each phase will include construction within a single fiscal year by contract resources. Design for the RTU replacements will be done by BOPU staff.
Justification: There are 55 existing PLC's. Many are obsolete and unsustainable. Allen Bradley intends to end production and customer support for the major PLC's in the next two years.
Technology in the MOSCAD-version of the Motorola RTUs is no longer supported by the manufacturer. RTUs at Rob Roy, Hog Park, Lake Owen, Crystal, and Granite use an obsolete land line communication technology. Replacement parts are difficult to obtain and lost communication/control at these sites would cause significant impact to operations and data collected for decision making. Replacement of the Granite RTU in FY2021 will extend the longevity of the other four land line sites until a viable satellite system is identified. Once a satellite technology is chosen, the other four land line sites will be upgraded. The order of upgrades of other RTU sites will be based criticality.
PLC's and RTU's are integral to the remote operation of the water and sewer systems. Systems are being maintained with spare parts from unreliable, third party, private sources, Risk associated with obsolete technology is no longer acceptable.