Bear Creek Valley Sewage Authority Saves Money and Time with Flo-Dar

When the Bear Creek Valley Sanitary Authority, (BCVSA), located in Medford, Oregon had a requirement to upgrade a number of flow monitoring stations in their wastewater interceptor system, the two most important criteria for flowmeter selection included:

• Purchase flowmeters with verifiable accuracies and
• Reduce current flowmeter maintenance costs associated with site visits required to clean submerged sensors and manually collect flow data.

The BCVSA was created in 1966 to help protect the health of the Rogue Valley by solving wastewater disposal problems.  Approximately 25 employees provide and maintain sewer and storm drain systems for over 18,000 businesses and households.  Other services performed by the Authority include operating heavy equipment to dig trenches and lay pipe, billing, customer service and engineering.  BCVSA is also part of the regional sewer system along with the cities of Jacksonville, Medford, and Phoenix.  Most areas outside of cities, including White City, Talent, Eagle Point and Central Point are also served by the BCVSA.

The Authority had previously monitored some of their wastewater flows using area/velocity flowmeters with submerged sensors.  Due to sensor fouling in these debris-laden flows, data reliability was a major concern.  Site visits to clean the fouled sensor became labor intensive and in turn a costly endeavor for the Authority.  In addition, personnel were routinely scheduled for site visits to download collected flow data from the instruments for later data analysis back at the main facility.  The flowmeter maintenance costs were becoming a burden to the Authority, however, there appeared to be no solution available in the marketplace.

In 1999, Larry Cooper, Information Systems Manager for the BCVSA, became aware of a possible solution for their flow monitoring challenge.  The Authority was introduced to a new non-contact flowmeter that was capable of measuring flow from above the flow medium without the need for submerged sensors.  This new meter appeared to be just the solution the Authority needed for their wastewater flows.  The sensor combines digital doppler radar velocity sensing technology with ultrasonic pulse echo level to remotely measure open channel flow.  The 'Above the Flowä installation eliminates maintenance and lost data that can occur because of submerged sensor fouling.  The sensor can be re-installed and removed from street level eliminating the manpower and equipment requirements for confined space entry. 

The eight flowmeters specified for BCVSAâs project were to be 12 VDC powered units with three 4-20 mA outputs (one each for velocity, level and flow). The meters would be installed in separate sewer flow monitoring stations within their wastewater interceptor system.  The proposal also included a requirement for a remote telemetry system to be supplied by another vendor.  The completed project would enable BCVSA personnel to access flow data from remote sites within their wastewater interceptor to a centralized base station located at their main office.

At the time of the proposal, a 12 VDC version of the Flo-Dar meter was not yet available (it is now a standard product within in Flo-Dar family of products).  After discussing the project with the Authority, Marsh-McBirney proposed a customized solution to meet the power and output specification and was awarded the flowmeter portion of the contract.  The flowmeters were installed by BCVSA personnel in the spring of 2000.  Due to exorbitant costs to bring power to these remote monitoring sites, solar power was used at all but two locations.  In addition, the Authority purchased six portable Flo-Darâs to be used for their Inflow & Infiltration (I&I) studies.

The illustrations below show the two screens that are most often displayed by the Authority.  Both screens update within 5 minutes of the sensor readings.  The data is received by a Data-Linc 900 Mhz radio modem connected to a Windows 2000 PC.  RSView^¨ from Rockwell Software is the monitoring software. The data analysis is done in Microsoft^¨ Excel from raw data downloaded from both the Flo-Darâs and the RSView database.  There is also a future plan to add a remote server system that will allow monitor screens to be viewed on the internet.

Experience has shown that the Flo-Darâs are very reliable and require minimal maintenance.  Looking back, Cooper admits that he took a chance on the Flo-Darâs as the radar velocity/area technology was still fairly new in the marketplace.  Fortunately it was a chance he now says he was glad he took.  'The Flo-Darâs are providing flow data that we can hang our hat on.ä