City of Scottsdale
Valentine performed an analysis of horizontal directional drill method and eventual design for a 650 lineal foot sewer line through steep desert terrain in bedrock conditions. The horizontal direction drill (HDD) analysis reviewed the bedrock conditions, alignment, bore pit locations and tailings handling. The major factor affecting the feasibility of HDD was developing an understanding of hard rock conditions. In lieu of soil borings along the steep desert terrain (with protected plan species), our geotechnical sub consultant performed a seismic refraction geophysical survey to determine degree of bedrock and assess the bedrock hardness. As part of this initial evaluation, we partnered with a local HDD contractor who reviewed the geotechnical analysis and provided their expert opinion on the viability of drilling along the proposed alignment. After it was determined that site geotechnical conditions were conducive to HDD, we then worked with the City and the HDD contractor to determine space requirements and locations of upstream and downstream bore pits. Given the sensitive native desert and high-end neighborhood, tailings pits were not allowed and a recycle system and recycle tanks were specified to contain spoils and recycle water for drilling. Once the details regarding geotechnical conditions, bore pit locations and tailings handling, Valentine proceeded to detailed design. Valentine also acquired local permits, prepared basis of design report, and provided construction phase services. This was our first HDD project and although it was a difficult HDD project, it was a very successful project, allowing the city to decommission an existing lift station and avoid the construction of a second lift station.
Unique Project Features
HDD in Bedrock Conditions
Simplified Collection System O&M
Community Sensitive Design