Nevada Irrigation District
Nevada County, CA
2015 – 2018
The Bear River Siphon project is located on the Bear River approximately 1.5 miles downstream of Combie Dam, within both Nevada and Placer Counties. The project involved design and construction of approximately 850 feet of siphon with 45 feet elevation difference between the inlet and outlet. The main section of the existing siphon is steel pipe supported on a cable suspension type structure with two towers that span approximately 250 feet across the Bear River. The replacement included connections to existing canal facilities.
Blackburn Consulting provided geologic and geotechnical design services, as well as construction support. Geologic/geotechnical challenges included:
- determination of suitable foundation,
- access onto steep slopes,
- stability of slopes in areas with significant soil cover,
- rock slope stability,
- hard rock excavation,
- generation of large boulders during excavation,
- foundation and trench excavations into hard rock,
- drainage and erosion control along the pipeline,
- and naturally occurring asbestos (NOA) minerals.