Lahontan Dam

Overview
Lahontan Dam and Reservoir are situated in the southern Carson Desert, a large intermountain basin in the northwestern portion of the Basin and Range geomorphic province.  The dam embankment and spillways are founded almost entirely on Truckee Formation rocks and sediments at a point where the Carson River has incised a 120-foot-deep canyon into an isolated butte capped by 40 to 50 feet of Lahontan Lake sediments.  The Late Miocene to Pliocene Truckee formation consists of sandstone, claystone, siltstone, conglomerate, hard sandy clay, tuffaceous sand, tuff and minor volcanic flows with most beds being 1.0 to 4.2 feet thick.  Unconformably overlying this formation are the flat-lying, unconsolidated, lacustrine beds of the Pleistocene Lahontan Valley Group.  These lacustrine beds typically range in composition from poorly graded and silty sands to silt and lean to fat clays.  The only parts of the embankment founded on the Lahontan Valley Group are the far left and right ends of the embankment.  On the right abutment the contact between the Lahontan Valley Group and the underlying Truckee Formation is projected beneath the right spillway at about station 12+20 and elevation 4139 feet (dam crest elevation is 4174.0 feet).  On the left abutment, this contact is projected to cross the centerline of the dam at about station 4+12 and elevation 4120.  An isolated minor occurrence of river alluvium was encountered at a depth of 123.8 feet in Drill Hole DH/P-8.8 drilled in the crest of the embankment at Station 8+80.  Any alluvium under the embankment is considered to be discontinuous and limited based on preconstruction, construction, as-built, and later investigation information.  The 1915 Final Construction Report stated that: "The riverbed was cleaned to either rock or clay and all sand, gravel and loam excavated and wasted." .

Typically the Truckee Formation beds at the dam site dip to the northwest, but with dips ranging from 10 to 30 degrees.  There are local changes in the dips and strikes which are generally attributed to nearby faults.  For instance, outcrops immediately upstream and downstream of the right spillway chute contain beds which strike northeast and dip 27 to 43 degrees northwest.   Indirect evidence indicates two faults are present in the foundation of Lahontan Dam.   The first fault, termed the Channel Fault, is believed to be present in the right portion of the Carson River channel, thus striking transversely under the dam at its maximum section.  The fault strikes about N 35-45oE and dips about 70oSE.  The presence of a spring and nearby artesian well along the trace of this fault prior to construction suggest groundwater moves along this fault.  The second fault, termed the Right Abutment Fault, shows up as a strong lineament, over 400 feet long, to the right and downstream of the right spillway chute.  This apparent fault strikes N 20-37o E, dips 70o southeast and is also a groundwater conduit as evidenced by clear water springs along its farthest downstream trace (about 700 to 800 feet downstream of the dam axis).  These faults are not considered to be active (see Section I.G, Earthquake Loading).

General
RegionFacilities in Mid-Pacific | Mid-Pacific Home Page
StateNevada
CountyChurchill
ProjectNewlands
Dam Type
ReservoirLahontan
WatercourseCarson River
Location
Longitude
Latitude
Original Construction1911-1915
Modified Construction
National ID NumberNV10123
Hydrologic Unit Code

Dimensions
Structural Height162.00 ft
Hydraulic Height (Normal Operating Depth at Dam)120 ft
Top Parapet (Elevation)
Spillway Crest Elevation4162.0 ft
Crest Elevation4174.00 ft
Crest Length1325 ft
Crest Width
Base Width
Volume of Dam Construction Materials
Streambed at Dam Axis4054.0 ft
Top of Exclusive Flood Control Pool (Elevation)
Top of Joint Use Pool (Elevation)4163.67 ft
Top of Active Conservation Pool (Elevation)4162.0 ft
Top of Inactive Conservation Pool (Elevation)4070.0 ft
Top of Dead Storage Pool (Elevation)4070.0 ft

Hydraulics & Hydrology
Volume
Total Water Storage at Elevation
Maximum Water Surface Elevation
Normal Water Surface Elevation4162.0 ft
Spillway Type
Auxiliary SpillwayNo
Spillway Capacity at Elevation26200.0 cfs at 4168.0 ft
Auxiliary Spillway Capacity at Elevation
Uncontrolled Spillway Capacity at Elevation
Outlet Works Capacity at Elevation2000.0 cfs at 4055.0 ft
Diversion Capacity at Elevation
Drainage Area1450.0 sq mi
Hydrometeorological Report (HMR)HMR xx
Probable Maximum Flood (PMF) Report

Contact Information
Owner
TitleArea Office Manager
OrganizationLahontan Basin Area Office
Address705 N. Plaza Street, Room 320
CityCarson City, NV 89701
Phone (Office)775 882-3436
Operator
OrganizationTruckee-Carson Irrigation District
AddressPO Box 1356
CityFallon, NV 89407-1356
Phone (Fax)702 423-5354
Phone (Office)702 423-2141


Last updated: Nov 05, 2008