1988-89 | 1990 | 1991 | 1992 | 1993 | 1994 | 1995 | 1996 | 1997 | 1998 | 1999 | 2000

1988-89

  • Horsetooth Reservoir's four dams (Horsetooth, Soldier Canyon, Dixon and Spring Canyon) and dike (Satanka) are each raised from 3 to 8 feet in elevation, increasing the reservoir's ability to store large flood flows, and addressing concerns that water in the reservoir could potentially overtop one or more of the dams during a major storm event.

1990

  • October - Wet spot #1 develops on the downstream side of Horsetooth Dam at an elevation of 5,355 feet above sea level.

1991

  • Wet spot #2 develops above the left toe drain exit of Horsetooth Dam at elevation 5,317.
  • U.S. Bureau of Reclamation and Northern Colorado Water Conservancy District staffs increase monitoring of seepage at Horsetooth Dam.
  • First drill holes and piezometers installed downstream of left dam abutment.

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1992

  • June - The left toe drain at Horsetooth Dam begins to flow for the first time.
  • Additional drill holes and piezometers installed downstream of left dam abutment.

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1993

  • April - Reclamation's Safety Evaluation of Existing Dams (SEED) inspection team completes inspections of Horsetooth Reservoir and Soldier Canyon outlet works, and issues a favorable report. The team consists of personnel from the State of Colorado, Reclamation, and the District.
    Reclamation and District personnel continue to monitor piezometer readings and flow rates at Horsetooth Reservoir.

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1994

  • Reclamation's SEED inspection team completes inspections of toe drains and measuring stations at Horsetooth Reservoir, and issues a favorable report.

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1995

  • June 28, 1995 - Horsetooth Reservoir's surface water elevation reaches a record high of 5,429.38 feet above sea level.
  • Reclamation and District personnel continue to monitor piezometer readings and flow rates at Horsetooth Reservoir.

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1996

  • Wet spot #3 develops on the downstream side of Horsetooth Dam at elevation 5,316.
  • Piezometer readings and flow rates slowly increase between 1990 and 1996. These readings coincide with higher than average storage levels at Horsetooth Reservoir.

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1997

  • Wet spot #4 develops on the downstream side of Horsetooth Dam at elevation 5,338.

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1998

  • February -- The aerial extent of wet spot #4 expands significantly.
  • June -- An independent technical consulting team completes a full review of safety activities and releases its report to the public.
  • August -- Reclamation begins drilling test holes and installing new monitoring equipment at all four of the reservoir's dams to determine foundation conditions.
  • August -- Reclamation releases its Comprehensive Facility Review of Horsetooth Dam.
  • August 31 -- First public meeting is held to update citizens on current investigations and future plans at Horsetooth Reservoir.
  • Reclamation and District personnel continue to monitor piezometer readings and flow rates at Horsetooth Reservoir.

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1999

  • January-March -- Test drilling at Horsetooth Reservoir's four dams continues.
  • Reclamation and District officials meet regularly to discuss test results and plan future course of action.
  • December 7-9 -- A consultant review board meets for a detailed discussion of studies and to consider a plan of action for Horsetooth Reservoir.
  • December 10 -- A decision memorandum is signed authorizing Reclamation to move forward with plans to modernize the dams at Horsetooth Reservoir.
  • December -- Reclamation publicly announces that modernization of Horsetooth Reservoir's dams will likely begin in the fall of 2000.

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2000

  • January 18, 24 -- Reclamation and District officials host public meetings unveiling plans to modernize Horsetooth Reservoir's four dams.
  • April -- Reclamation officials begin seismic-refraction testing to determine the depth of bedrock below Horsetooth's four dams.
  • April -- District staff ask irrigators to assist in maintaining water levels at Horsetooth Reservoir until late summer.
  • March-April -- Horsetooth Reservoir water levels drop approximately 5 feet over seven weeks due to dry weather conditions and heavy demand.
  • May 3 -- Reclamation and the District announce they are hopeful that remediation and modernization work on the dams at Horsetooth Reservoir will begin in the fall of 2000. The $110-130 million project awaits funding by Congress.
  • Early June -- The draft Environmental Assessment is released. It analyzes the alternatives to address the safety of Horsetooth Reservoir's dams.
  • July -- Continued hot, dry weather conditions make it difficult to maintain water levels at Horsetooth Reservoir despite the cooperation of irrigators utilizing local reservoir supplies.
  • July 15 -- Reclamation and the District officials pledge to maintain high water quality in the reservoir during construction on the dams. Fort Collins officials voice concerns with the project and water quality issues.
  • August 3 -- Reclamation officials estimate the need for as many as 50 trucks per day to transport rock, sand and gravel to Horsetooth Dam during the construction project.
  • August 4 -- The final Environmental Assessment is released.
  • August 18 -- The last usable boat ramp at Horsetooth Reservoir goes dry at elevation 5,359 due to falling water levels.
  • October 3 -- Crews working at Horsetooth Reservoir find a sinkhole near the left upstream toe of Horsetooth Dam.
  • October 17-18 -- Reclamation and District crews begin working around the clock to test the sinkhole near Horsetooth Dam. The District and Reclamation conclude the sinkhole is the main source of water seepage at Horsetooth Dam.
  • October 23 -- Contractors begin filling the sinkhole near the left toe of the dam with grout. District and Reclamation crews then install a 100-square foot cap and thousands of cubic yards of clay and rock.
  • October 23 -- The District begins lowering the reservoir's surface level, allowing Reclamation geologists and engineers to examine anomalies at the bottom of the reservoir near Horsetooth Dam.
  • October 24 -- Reclamation and the District announce water levels at Horsetooth Reservoir will be drawn down to dead storage, below elevation 5,295. At that point, the reservoir is essentially drained except for pools of water behind the three east-facing dams - Soldier Canyon, Dixon and Spring Canyon.

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