City of Milton, Washington uses Fusible PVC® Pipe for Water Line under I-5

The City of Milton needed a new water line to cross under Interstate 5 to connect two potable water zones, while also meeting fire flow requirements. The City turned to Gray & Osborne to engineer the project. Gray & Osborne was interested in using Fusible PVC® pipe, but the initial bore path design exceeded the recommended bend radius of the casing. In order to use common materials, the design proceeded with HDPE for both the casing and carrier.

When the project came to bid, Advanced Boring Specialists, a local driller, noted the bend radius in the final design would now accommodate Fusible PVC® pipe. Advanced Boring then suggested Fusible PVC® pipe to the low bidding contractor, Rodarte Construction, as a reduced cost and lower risk (smaller borehole) alternative to HDPE. Rodarte agreed and presented the recommendation to Gray & Osborne for consideration. After vetting with the client and seeking approval from WSDOT, Gray & Osborne approved Fusible PVC® pipe for use as both the casing and carrier.

Pipeline Details and Project Summary
Project: Water Main in Casing Under I-5
Location: Birch Street, Milton, WA
Length: 590 LF of 12" pipe and 580 LF of 20" casing
Pipe Size: 12" DR18 Fusible C-900® 20" DR25 FPVC® Green
Pressure Test: 250 PSI for 2 Hours
Installation: Horizontal Directional Drilling
Owner: City of Milton, WA
Engineer: Gray & Osborne
Contactor: Rodarte Construction/Advanced Boring (HDD)
UGSI Contact: William H Reilly & Co. (503) 223-6197 MReilly@whreilly.com

Jared Rodarte, Project Manager for Rodarte Construction, stated: "Fusible PVC® pipe for both the 20-inch casing and the 12-inch water carrier worked very well on the project. We changed the design from 24-inch HDPE to 20-inch FPVC® casing to accommodate a smaller borehole and also give us more space in the casing to install our conduit and the 12-inch Fusible PVC water main. We were able to save money on this change. Underground Solutions worked very well with us in the field and gave us all the support that we needed."

Owner Jim Downing and Manager Dusty Downing of Advanced Boring Specialists, the directional drilling contractor for the project, said: "This was a high-risk job crossing Interstate 5 just south of Seattle. The Fusible PVC® pipe product worked great during pullback, especially in the glacial till, cobbles, sand, and clay conditions. The 20-inch FPVC® casing has very high pull force values, so we were able to pull to the max to get through those tough ground conditions."

Glen Baker, Utility Supervisor and Pipeline Inspector for the City of Milton, added: "Underground Solutions performed a fantastic job for us. They delivered on time. Their service was great, and we are very happy with the Fusible PVC® pipe installation. We have two additional future I-5 crossings that we are working on. We will be using the Fusible PVC® pipe for those projects once funding becomes available."



Pipe Layout


HDD Clevis Hook-up


Ready for Pull-in


Insertion Pit with Vac Truck


Under a Boat and the I-5


Drill Side Set-up