Arnold Air Force Base (TN) Remotely Monitors Wastewater Flows with Flo-Dar and SCADA-Flo Meters

Arnold Air Force Base (AFB), home of the worldâs premier aerospace testing facility, is situated on 44,000 acres in the heart of Tennessee.  Dedicated in 1951 by President Harry Truman, the facility was named after 5-star Air Force General Henry 'Hapä Arnold.  The mission of Arnold AFB is to support the development of aerospace systems by testing hardware in facilities that simulate flight conditions.  Arnold AFBâs Arnold Engineering Design Center (AEDC) conducts a research and technology program to develop advanced test techniques and instrumentation as well as supporting the design of new test facilities.  AEDC has contributed to the development of nearly every national aerospace program since the 1950s.

Aerospace Center Support (ACS), a joint venture of Computer Sciences Corporation, DynCorp and General Physics, is the support contractor for this $7-billion complex that includes approximately 58 testing facilities.  ACS supports the facility with a multitude of services, one of which is environmental management.  The goal of the Environmental Management Program is to ensure that all activities and operations meet federal, state, local and Air Force regulatory requirements for preventing damage to the environment. This program includes compliance in the areas of air emissions quality, drinking water quality, wastewater discharges, solid waste management, hazardous waste management, hazardous materials management, noise abatement, and storage tank management.

The Tennessee Department of Environment and Conservation and the U.S. Environmental Protection Agency permit AEDC to discharge cooling water, storm water, remediated groundwater, and sanitary wastewater from the main base and Arnold Village (military family housing area) area through a National Pollutant Discharge Elimination System (NPDES) permit and two multi-sector storm water permits. Wastewater is treated by an on-site wastewater treatment plant before being discharged to the retention basin.

An aging sewer system, originally constructed in the early 1950âs, as well as appendages to the existing system, and large pipe sizes in excess of 12 feet, presented challenges for ACS personnel involved in on-going Inflow and Infiltration (I&I) studies at the facility.  I&I is a result of groundwater or stormwater that flows into a sanitary sewer system due to leaky sewer lines or manholes or from situations where stormwater can flow into the sanitary sewer system. Limiting I&I is important in order to maximize current capacity at the wastewater treatment facility, to limit public health and safety problems, for environmental benefit, and to minimize the cost of treatment. The reduction of I&I at the facility would not only offer a significant operational cost savings but would provide the benefit of lower operational risks by deferring or cutting down the need for emergency repairs in the future.

As part of an on-going effort to prioritize necessary sewer system upgrades and repairs discovered during I&I work, flow monitoring as well as video inspection were utilized.  SCADA-Flo Open Channel Electromagnetic Flowmeters manufactured by Marsh-McBirney (MMI) were initially purchased for the task.  The SCADA-Flo meter was designed for use in applications where it is desirable to have 4-20 mA outputs fed directly to a data collection system. SCADA-Flo incorporates a submerged style sensor that measures both the velocity and level of the fluid, a critical requirement for accurate flow rate determination. Collected flow data is then sent remotely to the plant via a base licensed RF-link system for further data analysis. These battery powered units are charged by solar panels installed by ACS. Temperature data is also being collected at each monitoring site to be compared against wet and dry weather flows.

Shortly after the release of MMIâs latest flowmeter innovation - Flo-Dar - MMIâs local representative, Chris Paris of Southeastern Automation Group, called on ACS personnel. Flo-Dar provides a revolutionary approach to open channel flow monitoring by combining digital Doppler radar velocity sensing technology with ultrasonic pulse echo level sensing to remotely (above the flow) measure open channel flows. Paris felt that the Flo-Dar meter would be a genuine problem solver for ACSâ I&I work.  Maintenance problems were becoming an expensive and time consuming issue at some of the bases heavier debris-laden flows. In addition, confined space entry to install and maintain submerged sensors was not only a costly and time consuming endeavor, but safety was a major concern.  Flo-Dar had the ability to eliminate both of these concerns for ACS personnel.

Six Flo-Dar Model 464 flowmeters have been ordered by ACS with installation of the first meter beginning in the Spring of 2002. The Model 464 is a permanent AC or DC powered version of the Flo-Dar flowmeter.  Two different Flo-Dar sensor mounts (pictured above), available from MMI, are being used for ACSâ short-term and long-term I&I monitoring applications. In addition, customized mounts are also being developed by ACS personnel for some of their unique sewer and creek installations.  The Flo-Dar units have also been connected to the radio-link system along with the SCADA-Flo meters.