Westport’s Pump Station No. 2 Force Main Replacement Project using HDD: A Case Study

摘要

Pump Station No. 2 is a submersible station located on the western shore of the Saugatuck River that provides service to 25% of the customers on the western side of the Town of Westport, Connecticut. The force main is a 10” cast iron pipe that crosses the river to connect the station to the Westport Water Pollution Control Facility (WWPCF). The force main was originally constructed in 1959 by floating it across the river and sinking the pipe to the river bottom, crossing the river at a point where it is tidally influenced. The pipe is also located within the right-of-way for I-95. The Town of Westport has experienced several force main breaks on pipe of similar age/material and decided to proactively replace this main to avoid the catastrophic environmental impacts that would result from a force main break below the river. Horizontal directional drilling was selected as the preferred installation method. The new 14” HDPE force main was designed to be installed via directional drilling entirely within bedrock to minimize the potential for the frac-out of drilling fluid within the river. This paper will focus on:1. Unique technical challenges associated with accessing/evaluating subsurface conditions in a tidal river, and designing the drill entirely in hard and abrasive rock, with limited site access2. The extensive permitting efforts required during the design phase3. Coordination efforts between the town, commuter rail riders, local businesses, and Connecticut Department of Transportation (CTDOT)4. Benefits achieved by having the Town take an active role in both the permitting and construction phases of the project.