Boca Dam


 Boca Dam and Reservoir

Boca Dam and Reservoir are within an intermountain basin flanked on the west by the 9,000-foot-high Sierra Nevada and by the 10,000-foot-high Carson Range on the east. The basin is underlain by Tertiary lavas and pyroclastics north of latitude 39.5 N. and by Pliocene and Pleistocene basalts and latite flows to the south.

The Cenozoic volcanic rocks are in turn underlain by Jurassic granite bedrock at some undetermined depth. As determined from logs of exploration, Boca Dam is founded on predominantly volcanic tuff with subordinate interlayers of tuff breccia, andesite, basalt, and diabase.

Alluvial deposits of interbedded silt, sand, gravel, and cobbles were encountered to 20 feet thick in Little Truckee River channel, to 90 feet thick in the left abutment area, and to 66 feet thick in the right abutment area. Exploration extended approximately 100 feet below stream grade and approximately 200 feet deep in the abutment areas.

No information is available discussing faulting at the damsite, in the dam foundation area, or in the diversion tunnel. However, ground surface rupture occurred during the September 12, 1966 earthquake along a possible fault trace bearing approximately N. 20 E. only 5 miles northwest of Boca Dam.

After the earthquake, widely spaced cracks were observed over a ±9-mile-long distance. A concealed, pre-Quaternary fault is mapped about 2 miles east of Boca Dam trending about N. 20 W. A ±1-mile-long branch of the fault appears to traverse the left abutment area a few hundred feet east of the dam.


RegionFacilities in Mid-Pacific | Mid-Pacific Home Page
ProjectTruckee Storage
Dam Type
WatercourseLittle Truckee River
Original Construction1937-1939
Modified Construction
National ID NumberCA10135
Hydrologic Unit Code

Structural Height93.0 ft
Hydraulic Height (Normal Operating Depth at Dam)
Top Parapet (Elevation)
Spillway Crest Elevation5589.00 ft
Crest Elevation5615.0 ft
Crest Length1629.0 ft
Crest Width
Base Width
Volume of Dam Construction Materials
Streambed at Dam Axis5512.00 ft
Top of Exclusive Flood Control Pool (Elevation)
Top of Joint Use Pool (Elevation)5605.0 ft
Top of Active Conservation Pool (Elevation)5596.37 ft
Top of Inactive Conservation Pool (Elevation)
Top of Dead Storage Pool (Elevation)5521.00 ft

Hydraulics & Hydrology
Total Water Storage at Elevation
Maximum Water Surface Elevation
Normal Water Surface Elevation5596.37 ft
Spillway Type
Auxiliary SpillwayNo
Spillway Capacity at Elevation8000 cfs at 5605.0 ft
Auxiliary Spillway Capacity at Elevation
Uncontrolled Spillway Capacity at Elevation
Outlet Works Capacity at Elevation900 cfs at 5605.0 ft
Diversion Capacity at Elevation
Drainage Area36.0 sq mi
Hydrometeorological Report (HMR)HMR 36
Probable Maximum Flood (PMF) Report

Contact Information
TitleArea Office Manager
OrganizationLahontan Basin Area Office
Address705 N. Plaza Street, Room 320
CityCarson City, NV 89701
Phone (Office)775 882-3436
OrganizationWashoe County Water Conservation District
Address295 Holcomb Ave. Suite A
CityReno, NV 89502
Phone (Office)775 322-9139

Last updated: Apr 07, 2009