Introduction

Since 1890 there have been at least 130 dam incidents and failures in Colorado. In recent years the failure rate has remained significant while the resulting costs have escalated. This it due in large part to the propensity of people to settle and develop lands downstream from dams, within those areas which would be inundated in the event of a dam failure. Accepting this as fact, large scale losses are an inevitable result of future dam failures.

In a general sense, the seriousness of the threat of dam failure is based on many variables: flash flooding, inadequate size of spillways, mechanical failure of valves and other equipment, rodent activities in earthen dams, freezing and thawing cycles and earthquakes. Old age and neglect can intensify vulnerablity to these same influences.

In reviewing the history of dam failure in Colorado, the failure to cost ratio (life and property costs) has been surprisingly favorable. Levels of awareness vary across Colorado. Some people are fully aware of their exposure to this hazard while many do not even realize that they reside in one of the 236 inundation zones for high hazard dams. Some counties have only one or two high hazard dams while Larimer County has 45! It comes as no surprise then that Larimer County is high on the list of the 19 counties most in need of dam safety planning.

The Horsetooth Reservoir Dams specifically are rated as high hazard dams. The use of the term "high hazard" means that should the dam fail even though this possibility is remote, the failure could cause loss of life to downstream residents. On the positive side, these dams have a satisfactory rating when it comes to a structural assessment. Satisfactory is the highest of the three structural assessment ratings. The state of repair assessment has four ratings: excellent, good, poor, and unacceptable. The Horsetooth Reservoir Dams are rated in the good category. The excellent rating is only given to those dams which are maintained in essentially new or original condition.

Definitions and Introduction | Horsetooth Reservoir | What Emergency Plans are Already in Place? | Where Would All That Water Go?