Gwinnett County’s Aging Stormwater Infrastructure Pipe Rehabilitation Program: An Owner’s Perspective

Abstract Only - The mission of the Gwinnett County Department of Water Resources is to provide the best possible service to the residents and ratepayers of Gwinnett County for water, sewer, and storm water; to earn the public trust through customer responsiveness; and to responsibly administer the uses of the public’s funds in fulfillment of this mission. Gwinnett County continues to be a fast growing community with an average of 700 new building permits issued monthly. With new development, infrastructure such as roads, water, sewer, and storm drainage systems are constructed and donated to the County for operation and maintenance.
Corrugated steel pipe (CSP) remains the most used pipe material for new development storm drainage infrastructure because it’s initial construction cost is less expensive than that of concrete (RCP) or high-density polyethylene pipe (HDPE). However, based on previous research, the estimated material life span of CSP is in the range of 20 to 30 years, less than RCP (100 years) or HDPE (50 years minimum). In June 2001, Gwinnett County successfully banned the use of zinc galvanized CSP (estimated 20 year material life), but continued to allow the use of aluminized CSP (estimated 30 year material life) in certain applications for storm drainage infrastructure. Nevertheless, CSP makes up almost 80% of the estimated 4,000 miles of storm drainage pipe in the County with over 600 miles of CSP past its estimated material life. By 2011, it is estimated that over 1,000 miles of CSP will be past its estimated material life.
In response to this pending liability, in 2005 Gwinnett County initiated a pilot program which included 7 projects and approximately 1,860 linear feet of cured in place pipe (CIPP) rehabilitation. The conduits rehabilitated varied in diameter from 18 inches up to 36 inches. For fiscal period 2006 to 2007 approximately $4 million was spent rehabilitating 20,000 linear feet of pipe. For fiscal period 2007 to 2008, approximately $6.5 million has been budgeted for rehabilitation of 33,000 linear of pipe.
In 2006, under Gwinnett County’s new Stormwater Utility program, dam structures were adopted as part of the stormwater infrastructure and the County rehabilitated it’s first principal spillway pipe system. This work was completed to bring the structure into compliance with the Georgia Rules for Dam Safety for a Category I, high hazard dam. Additional dams are expected to follow.
This presentation will discuss the owner’s perspective of aging stormwater pipe infrastructure rehabilitation. The rehabilitation of the Category I dams will be discussed in additional detail.