Reliable Data in Rochester, Minnesota

In the year 2000, Rochester, Minnesota, a rapidly growing community and the stateâs third largest city, was faced with a $50 million infrastructure investment that would take place over a 15-year period. A portion of the investment was slated for upgrading the cityâs sewer system, a project considered necessary to accommodate the cityâs future growth plan. The recommendation for the upgrade was based on flow data collected during Inflow and Infiltration (I&I) studies performed over a prior number of years. However, once faced with the ultimate decision to move forward with the expansion plan, the city began to question the flow data upon which the decision was based. Public Works Department personnel were faced with the dilemma that the flow data they possessed was limited in scope due to its short-term monitoring periods that did not include significant rainfall events nor adequate sampling periods necessary to accurately portray the current status of the cityâs sewage flows. The city felt that an infrastructure upgrade of this magnitude needed to rely on flow data that could only be provided by implementing a long-term, real-time monitoring program. At this juncture in the process, the cityâs Public Works Department made a commitment to investigate the implementation of such a system. The required system would allow for a fully integrated data acquisition system based on a long-term monitoring program that would also eliminate the need for site visits to collect flow data.

Rochester awarded ProAcq, Inc. (Winona, MN) with the contract to provide the city with a new fully integrated data acquisition system in combination with Marsh-McBirney (MMI) flow sensors. ProAcqâs PDAWAREú System would provide the continuous collection of critical flow data within the sanitary sewer system. With the addition of ProAcq Web Services software, the city also had the desired ability to retrieve and monitor real-time flow data from any office location through the use of an internet browser.

Fourteen Remote Terminal Units (RTUs) were placed at strategic locations throughout the city. The RTUâs were connected to ten Marsh-McBirney flow sensors including the revolutionary Flo-Dar Radar Velocity/Area Open Channel Flowmeter and the SCADA-Flo Electromagnetic Open Channel Flowmeter. The Flo-Dar radar velocity/area sensor was chosen for its unique ability to accurately monitor flow from above the fluid eliminating costly maintenance issues as well as lost data that could occur with fouled submerged style sensors. The SCADA-Flo sensors utilized a submerged style electromagnetic sensor that was placed in the pipe in order to accurately measure flow during surcharge conditions. Flow, velocity and depth information were collected for each location, as well as precipitation information provided by on-site rain gauges. A fail-safe, battery back-up system for all of the monitoring instruments involved in the project was implemented at the cityâs request, as well as the use of industrial modems.

ProAcqâs PDAWAREú Systemâs MasterPC will reside in Rochesterâs Water Reclamation Plant. The networked system will be set up and controlled from the MasterPC. Once all RTUs were on-line and the system "synchronized", data collection and sampling immediately began and began to provide an extremely accurate picture of their wastewater flows. Scott Carlson, ProAcqâs President explains, 'This important step is accomplished with just one click of the PDAWAREú System software.ä
He adds, 'Initially, an operator will adjust the RTU sample rates from the MasterPC. For example, if the forecast calls for rain, the sample rate of the RTUs can be increased. During dry periods the sample rates can be decreased. Again, these sample rate adjustments are made from the MasterPC and individual connection to each RTU is not necessary.ä

Carlson goes on to say, 'Future plans call for the system to become further automated. If a rain event occurs at one of the rain gauges (a tip event is equal to .01 inches of rain) this RTU would call the MasterPC and report the rain event. The MasterPC would then contact all the other RTUs in the system and automatically increase the sample rates to create a more detailed picture of the system.ä

Collected flow and precipitation data are stored and backed-up by the MasterPC. This data is then transferred to a ProAcq server which then serves up web pages to users requesting the information. All Rochester Public Works personnel can quickly review data from their desktop. In addition, third-party support firms can query and download data for detailed analysis from their office as well. The cost savings of these services versus manual data collection quickly becomes evident. Currently, data is being collected once per hour but is easily adjustable so as not to miss any significant events occurring within the collection system. Each flow sensor has custom designed high/low flow alarms. Additionally, the alarm generates an e-mail to pertinent Public Works staff who in turn also note the event.

John Wellner, Infrastructure Manager for the City of Rochester states, 'This project is a first of its kind for us. It is a 24/7 - 365 days a year out in the system type program. The reason we selected the Flo-Dar meters for the project was the fact that the sensor had no parts in the flow. This is not a very nice environment for any piece of equipment and we were looking for a solution to submerged sensors we have used in the past. MMIâs equipment offered that solution.ä  Wellner goes on to add, 'The equipment has been reliable and the information is going to be very helpful as we do more and more planning relating to the sewer system. Decisions on improvement to existing trunk lines adds up to a lot of money. We have also had a pretty dry year here but we are definitely going to get those storms and now we will be able to collect the flow data during the entire event.ä Commenting on the overall project, Wellner continues, 'It is a concept that is not without cost, however, the system in turn gives us the real-time data that we need to make better decisions on expensive system upgrades that may or may not be necessary.ä

With the new data acquisition system now in place for over two years, the City of Rochester at last has the continuous real-time data collection program they deemed necessary to paint an accurate portrait of their sanitary sewer flows. Decisions on expenditures for sewer system infrastructure upgrades can now be confidently made, without hesitation, now and for many years to come due to the detailed flow analysis provided by ProAcq software and MMI flow sensors.