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Author      Title/Abstract      

Extending the Boundaries of Wastewater Force Main Inspection Methods
Author: Henry R. (Kelly) Derr
Date: 6/311
Preprint, WEF Collection Systems Conference, June 12-15, 2011, Raleigh, NC

The Hampton Roads Sanitation District (HRSD) in Virginia Beach, Virginia, collects wastewater from fourteen area localities and conveys the wastewater to their thirteen regional treatment facilities. The conveyance system operated and maintained by HRSD consists of 430 miles of pressure mains and 50 miles of gravity mains. Over 890 local pumping stations discharge into the HRSD system at locations distributed throughout the system. The pressure mains are strongly interconnected to allow flexibility in the distribution of the wastewater flows amongst the treatment facilities. The low lying terrain, the many valves and interconnections and the random nature of the inputs to the system, make for a complex and difficult system to operate and maintain. To compound matters, the USEPA issued a unilateral administrative order (UAO) in August 2007 requiring, among other items, that HRSD conduct a condition assessment program to locate assets that presented a “material risk of failure”. In September 2007 HRSD entered a state consent order with the Virginia Department of Environmental Quality (DEQ) and then a federal consent decree in February 2010 with USEPA. Both these orders and the UAO require condition assessment. When the adminstrative order was issued (August 2007) there were only a few technologies suitable for the inspection of wastewater force mains and very little practical experience in their use. All of the available technologies for pressure pipeline inspection originally had been developed for use in the oil and gas industry or in the potable water industry. In order to begin the work of inspecting their wastewater force mains, HRSD and their engineer, Brown and Caldwell, had to develop a program of pilot testing and evaluation of technologies for adaptation and use in a wastewater pressure system. Much of this work was taking place for the first time in a wastewater system and involved considerable challenges.