Design and Construction of the St. Rose Sanitary Sewer Phase I: Henderson, Nevada

One of the effects of explosive growth in the Southwest is the rising demand for expedited construction of major infrastructure to serve fast growing areas. As development in Henderson, Nevada extended farther from the City's central Water Reclamation Facility, the existing sanitary sewers have become overburdened, and the need for satellite treatment plants and larger diameter sewer infrastructure has arisen. In the summer of 2004, a 5,000-acre master planned community's updated Sewer Master Plan indicated the need to immediately evaluate the capacity of an existing sewer line. The flow calculations indicated that a 42-inch and 48-inch diameter sewer interceptor, which was thought to be a future pipeline, would be expedited through design and construction immediately by two major land developers and three engineering firms. Establishing the alignment of the pipeline presented many design and schedule constraints. Initially, the sewer would parallel an existing State of Nevada roadside ditch to the north and the existing overburdened sewer to the south. However, the pipeline would also need to connect flows from two existing sewers, be deep enough to allow for future upstream extensions under proposed Regional Flood Control facilities, and cross under newly constructed highway box culverts. The large diameter gravity sewer line needed to cross a newly paved 300 foot State Highway directly (St. Rose Parkway), extend into the embankment of a major unlined channel, and connect to a predetermined pipe invert at the termination of the project. Coordination with three government agencies further complicated the design of the sewer. The Nevada Department of Transportation (NDOT) would not allow the closing of any street crossings, and St. Rose Parkway (State Highway) was considered a `no cut' street. The City of Henderson would require full protection of the existing sewer during excavation of the 20-foot deep trench for the new pipeline and full protection of the pipeline located in the embankment of the unlined channel. In addition to the intricacy of agency coordination, the jurisdictional line between the City of Henderson and the County of Clark jogged across the proposed pipeline alignment at multiple locations. The design of the proposed sewer line appeared to be a standard pipeline project. However, back-to-back physical constraints coupled with a tight schedule were what made this project worthy of documentation.