HDD — Cartridge Method and 24-Inch (610mm) Ductile Iron Pipe Key to Minimizing Surface Disruption in Hillsborough County

Abstract

In the past two decades, the Hillsborough County Water Resource Service Department (HCWRS) has been actively expanding its reclaimed water system in the South-Central service area, both as an effluent disposal method and as a potable water saving mechanism. Currently the HCWRS reclaimed water customer base is comprised of golf course users, industrial users, commercial and residential customers. To meet increasing demands in the south-central service area and pressure requirements during the peak hours, HCWRS has identified the need for additional Reclaimed Water Transmission Main (RWTM) capacity along Lithia Pinecrest Road and Bloomingdale Avenue. To serve high demands of the fast growing communities in Hillsborough County, Florida, HCWRS is challenged with designing new transmission mains within highly congested and restricted right-of-way. For each project the Water Department designers must be conscious of the impact of surface disruption and the associated socio-economic costs to the general public, as well as the project's overall cost. The design for the 24” (610mm) transmission main in Lithia-Pinecrest Road, a two-lane thoroughfare, was no different. This project was complicated by the volume of traffic in combination with portions of the alignment transitioning through a very congested right of way. The line begins at the intersection of Lithia Pinecrest Road and Bloomingdale Avenue, an east-west arterial highway and proceeds in a southeasterly direction for approximately 12,500’ (3.6 km) on an alignment that takes it past schools, businesses, and residential areas, and terminates at the entrance to River Hills Country Club. After a thorough analysis of the route studies and cost of open-cut construction versus horizontal directional drilling (HDD) methods, HCWRS project management chose to install the line using both open-cut and HDD construction methods. The 6,000’ (1.8 km) of water line installed by HDD construction would be a series of seven separate pulls using 24” (610 mm) flexible restrained joint ductile iron pipe manufactured by American Ductile Iron Pipe in 20’ (6.1 m) joint lengths. This paper will discuss in detail the comparison of the costs of the different routes and the two (2) methods of construction. It will then detail that portion of the line installed using HDD technology and address the flexible restrained joint ductile iron pipe and how using the cartridge method minimized disruption to the general public.