Sustainable Replacement of Aging Drinking Water Lines Using Horizontal Directional Drilling Technology

Background: Due to deterioration from aging, the City of Yuma, Arizona undertook the replacement of approximately 5800 L.F. (1767 m) of existing aging and undersized asbestos cement water lines in the vicinity of the downtown core to reduce maintenance and repairs and improve water service levels. Installed between 1938 and 1940, six line segments of existing 2-inch (50 mm) to 6-inch (150 mm) asbestos cement water lines were replaced by 6-inch (150 mm) diameter PVC pipe. Methods: To study advantages and disadvantages of traditional open-cut construction compared to Horizontal Directional Drilling (HDD), the City separated the project into approximately 2000 L.F. (609 m) of HDD and 3800 L.F. (1158 m) of open-cut. Analyzing the same project provided an opportunity to study a true head-to-head comparison of the two methods. PVC C900 DR18 was installed using open-cut, while Fusible PVC (FPVC) DR18 was installed by HDD. Data was collected in the field over a two-month period with factors analyzed including comparison of: (1) environmental impacts; (2) traffic impacts; and (3) productivity. Results: The results found HDD to have inherent advantages in all three areas when compared to traditional open-cut. The HDD option emitted approximately 23% of airborne emissions compared to open cut. Traffic was restricted in the sections involving open-cut construction, while the HDD sections had continuous traffic flow due to the closure of only one lane. HDD achieved an average productivity of 1.91 L.F./min (0.58 m/min) compared to traditional open-cut, which achieved an average productivity of 0.43 L.F./min (0.13 m/min). This translates to HDD achieving a production rate greater than four times that of open-cut. Conclusions: The adoption of trenchless technologies such as HDD will continue to increase as municipalities turn to sustainable solutions for replacing and/or rehabilitating their existing water pipe line infrastructure. HDD has proven to be superior to open-cut construction in environmental, traffic control and productivity.