- ENGINEERING INFO
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The City of Napa Water Division was faced with completing a major waterline project along Highway 221 in the winter of 2012, to resolve a bottleneck that existed in its water distribution system. An undersized section of 16-inch transmission main pipe required replacement with a larger 24-inch line to connect two segments of 24-inch pipe at either end. The project required 7,400 LF of new 24-inch water main running from Napa Valley College south to Kaiser Road. Due to the critical nature of this large main, the work had to be completed in the winter during low demand times. The location of the new waterline replacement presented other challenges, including work near the Cal Trans right of way associated with Highway 221, and working in and around Napa Valley College, Napa State Hospital, Napa Valley Memorial Park Cemetery, and the Municipal Golf Course at Kennedy Park. Additionally, there was concern regarding pipeline materials due to the corrosive soils and their impact on the new pipeline asset.
The Water Division turned to Fusible PVC® pipe to be installed via horizontal directional drilling (HDD) for the installation of a large portion of the new pipeline. The City had used Fusible PVC® pipe on two previous projects. For this project, HDD was selected as the installation method due to narrow easements, utility conflicts, surface conflicts, varied topography, and other constraints that would have made traditional open-cut pipe installation difficult, impossible, or cost prohibitive. HDD provided a small footprint at grade and could be adjusted to the site constraints on an as-needed and variable basis, minimizing impact on existing utilities and surface features due to the lack of required excavation and construction footprint. On this waterline project, HDD facilitated the completion of the pipeline without removal of the attractive trees in front of Napa Valley Memorial Park, impact to existing gravesites, or removal of the landscaping and signs in and around Napa Valley College and the municipal golf course at Kennedy Park. Importantly, the trenchless approach kept southbound Highway 221 open to traffic flow during the project. All of these items would have been compromised with a traditional direct-bury construction methodology.
|Pipeline Details and Project Summary|
|Project:||Highway 221 Water Transmission Main|
|Pipe Size:||24" DR18 PC 325 Fusible C-905®|
|Pressure Test:||175 psi|
|Owner:||City of Napa Water Division|
|Contractor:||The HDD Company, Granite Bay, CA|
City of Napa Water Division General Manager Joy Eldridge stated: "A successful project: On-time and on-budget. This approach resulted in lower change orders than would have occurred using conventional open-trench techniques for this project." City of Napa Design Engineer Megan Thomas commented: "Fusible C-900® and Fusible C-905® pipe are still new materials to the City of Napa, and we've trusted it for our few HDD projects. The more I've worked with the pipe material and the personnel at UGSI, the more comfortable I feel about using their product in our water system. UGSI helped us confirm that the design worked well with their product, and they cared that the pipe they supplied survived the whole construction process, watching its installation with us every step of the way. From our smaller projects to this one, UGSI was there the whole time (on the phone and in the field), and I'm grateful to have that kind of support from a pipe manufacturer." Neil Swope, owner of the HDD Company, said: "Fusible PVC® pipe worked well for this project. We learned that PVC pipe can provide owners with another option when it comes to HDD installations. Had we used HDPE pipe we would have had to use a larger 30-inch pipe that would have cost the owner more due to the increased size and larger boreholes that would have been required."