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Flatiron Afterbay Dam

Flatiron Afterbay

 


Statistics

General

  • Region (Map) : ............ Great Plains
  • State (Map) .................. Colorado
  • County .......................... Larimer
  • Project: .......................... Colorado Big Thompson
  • Dam type: ..................... Earthfill
  • Location: ...................... 8 mi SW of Loveland
  • Watercourse: ............... Chimney Hollow Creek
  • Reservoir: ..................... Flatiron
  • Construction Date: ......1951-1953
  • National ID Number .... CO01654
  • Hydrologic Unit Code ...

Dimensions


Hydraulics

  • Normal Water Surface Elev: ..............5472.8 ft
  • Hydraulic Height: .................................. 55.0 ft
  • Service Spillway Type:
  •    Uncontrolled  Crest    .............................Yes
  •    Morning-Glory ......................................... No
  •    Crest Length    ........................................ NA
  •    Gated      .................................................... No
  •    Capacity at Elev:  5480.0  ft,       23,600  cfs 
  • Auxiliary Spillway ...................................... No
  •     Capacity at Elev.   ............................... 0 cfs
  • Outlet Works Capacity at
  •     Elevation  5464.8 ft.,  ...................... 930 cfs

Hydrology

  • Drainage Area: ................................... 7.1 sq mi
  • Hydrometeorological Report           HMR 55A
  • Flood Type: ..............................Winter General
  • Storm Duration: ....................................... 72 hrs
  • Probable Maximum Flood (PMF) Report:
  •   Peak Inflow: .....................................40,000 cfs
  •   Inflow Volume: ......................... 12,700 acre-ft
  •   Flow Duration: ..................................... 6 days
  •   PMF Routing MWS Elev.: ...................... NA
  •   Initial Routing Elev: .......................5472.8.0 ft
  •   Study Date:  .......................... November 1989

 


Power Generation

 


Narration

 


Geology

The zoned and compacted earthfill-type dam provides for the retention and regulation of water discharged into Chimney Hollow from Flatiron Powerplant. It consists of an impervious central core flanked by zones of relatively free-draining material grading to pervious at the outer slopes of the dam. The upstream zone is designed to resist percolation of the afterbay water and to dissipate internal pressures exerted outwardly during rapid afterbay drawdowns. The downstream zones protects the impervious central core and stabilizes the dam by lowering the saturation line in the downstream area. The cutoff trench beneath the dam is designed to obstruct percolation along the foundation contact to prevent dangerous seepage velocities. The stability of the dam is further safeguarded by the embankment toe drains which intercept seepage along the foundation contact and surface flow from within the dam. The toe drains are designed to permit easy escape of the seepage and to lower the ground water table sufficiently to avoid the formation of boggy areas below the dam.


Links

 | Recreation |

 | Dams Located by State | USBR Colorado Dams | South Great Plains Region Dams |

 | Owner:  Bureau of Reclamation, Eastern Colorado Area Office,
                   11056 West County Road 18E, Loveland, CO 80537-9711, (970) 667-4410

 | Operator:  Bureau of Reclamation, Eastern Colorado Area Office,
                       11056 West County Road 18E, Loveland, CO 80537-9711, (970) 667-4410

 

 

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