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Salt Lake County, Utah Manages I&I with Flo-Totes and FLO-DAR

Salt Lake City Salt Lake County is home to nearly half of all Utahns (almost 900,000 out of just over 2-million Utah residents). The county is the state's leader in trade, services, transportation, communications, finance, insurance, and construction.

The County is filled with many diverse communities from Magna in the northwest, Alta to the southeast, Herriman in the southwest and Emigration Canyon to the northeast. There are fifteen incorporated cities in Salt Lake County. About a quarter million people live in several "unincorporated" sections of the county and receive basic municipal services through their County government.

Seven of cities are located in the South Valley Sewer District (SVSD) located in Draper, UT. The SVSD serves seven cities including Bluffdale, Copperton, Draper, Herriman, Riverton, South Jordan and South Sandy.

As part of an ongoing effort to determine the need for sewer system upgrades, the District's engineering group began performing their own Inflow and Infiltration (I/I) studies in the early 1990's utilizing two different types of Marsh-McBirney flowmeters - Flo-Tote and Flo-Dar. Both flowmeters calculate flow based on the equation Q = V x A, where Q = flow, V = Average Velocity, and A = Area. The measurement of both velocity and level is critical for accurate flow rate determination. Flow data management is accomplished utilizing Flo-Ware for Windows software that is compatible with both Flo-Tote and Flo-Dar flowmeters.

The initial Flo-Tote flowmeter was purchased in the early 90's to determine upgrade requirements for pipes that were reaching capacity. The Flo-Tote portable flowmeter was the original area/velocity type flowmeter available on the market that could electronically automate data collection. The Flo-Tote flowmeter utilizes a submerged electromagnetic sensor installed on a stainless steel band that is inserted directly into the channel.

When Marsh-McBirney introduced the non-contact Flo-Dar Radar Velocity Flowmeter the District felt it would be an ideal flowmeter choice for difficult sites where high velocities and large channels made monitoring more challenging. Mike Foerster, District Engineer, was sold on the fact that the Flo-Dar flowmeter could accurately measure flow from "above the fluid" without the need for a submerged sensor and band installation.

Flo-Dar combines advanced Digital Doppler Radar velocity sensing technology with ultrasonic pulse echo level sensing to remotely measure open channel flow. The Flo-Dar sensor (shown at left) is mounted above the flow utilizing a temporary sensor mount. The temporary sensor mount (not shown) consists of a jack-bar, tension-type assembly that requires no structural modification or fastening hardware. Once the Flo-Dar sensor is installed above the flow it can be easily removed/reinstalled from street-level using a sensor installation/retrieval tool.

The District's first Flo-Dar flowmeter was purchased in 2000 to assist with the ongoing I/I project. At the time, the District had a known infiltration problem, but didn't feel that there was an inflow problem. The infiltration problem was prevalent during the months of April-October when the canals that run through the valley transported water resulting in a 3 MGD increase in flows. Shortly after the installation of the first Flo-Dar, a very large rain storm came through the valley and a huge spike in their flows indicated a problem in one basin.

A flow modeling study began in 2001 and an additional Flo-Tote and three Flo-Dar flowmeters were purchased. The meters were used to calibrate the District's model. The study indicated a need to isolate both inflow and infiltration. Starting this year, the District began an I/I study that will rotate the Flo-Dar and Flo-Tote Flowmeters through all of their system basins to isolate inflow problems.

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