FLOOD05005 - Laserfiche WebLink

Home Browse Search

3 PHOTO 1.4-3 EARTHQUAKE DAMAGE Settlement of 2.5 feet on dam crest first noted about 2 weeks after an earth- quake in the area. 1.5 LIFE EXPECTANCY OF A DAM One of the most compelling economic concerns of a dam owner is how 10 prolong the useful life of his dam. The oldest dam in the United States as shown on the National Inventory of Dams is known as Podunc Pond, located on the Podunc River near the town of Pleasant Valley, Connecticut. This 17-foot-high dam, impounding llOacrefeet, was constructed in 1730and has been in service more than 250 years. In Colorado, extensive dam building was initiated in the early 1900s, utilizing the engineering know-how and construction techniques available at that time. These dams, which were located in sparsely populated rural areas, occasionally experienced partial failure which caused little damage in the downstream flood plain. Historically, the required repairs were made as quickly as economic conditions permitted. Although these older dams were built without some of the safety- oriented features included in recently constructed dams, their useful lives can be extended greatly if the owners exercise the appropriate effort to assure the dams remain in good condition. Providing the money necessary to carry out periodic maintenance and required repairs is essential to prolong the life of the dam. The recently published costs of proposed or newly constructed water storage projects clearly indicate that making all possible effort to keep an older structure in service is preferable to attempting to build a new dam. When an owner constructs a new dam he should ensure. at the end of construction, that all portions of the structure are at the line and grade specified on the approved plans. This will allow inspection and moni- toring to be carried out with a reliability level that will help assure the safety and longevity of the new dam. PHOTO 1.5 EARLY CONSTRUCTION METHODS TYPICAL OF AN EARLIER ERA. 1.6 NEED FOR STORED WATER Colorado is a semi-arid region with average annual precipitation being less than 16 inches per year. The early settlers quickly found that natural precipitation was not adequate to support their farming efforts. Runoff from snowpack in the high mountain areas usually is finished by early July and natural precipita- tion is usually not sufficient to bring irrigated crops to maturity. Control of the runoff for future use becomes vital. since most streams receiving snow melt produce two-thirds of their annual volume of runoff in May, June and July. The critical need for stored water which can be made available on demand is present in all areas of the state. Owners of these dams playa vital role in society by making water available for the various required uses. Although the use of the stored water directly benefits the owner, a number of the secondary benefits are enjoyed by people in the community. 1.7 ROLE OF THE DAM OWNER Initially the dam owner identifies the need for the project, finds a method to finance and reimburse pro- ject costs, then contracts for the design and construc- tion work. Even before construction is complete, the owner assumes liability for any type of damage that might occur because of the uncontrolled release of stored water. Although a great number of people enjoy the benefits provided .by the dam and reservoir, the owner has total responsibility for the dam's safety, and must provide the funds and effort necessary to obtain the maximum useful life from the structure. 1.8 DAM SAFETY ROLE OF THE STATE ENGINEER Colorado statutes charge the State Engineer with responsibility for public safety in relation to dams. This responsibility is addressed by three primary areas of activity: a. Physical inspection of dams. Based on conditions identified during these inspections, the dam owners are directed to take action to correct any deficien- cies and required storage restrictions are ordered to assure the safe operation of the dam. These inspections are conducted by experienced regis- tered professional engineers in the Dam Safety Branch. Follow up of the inspection often includes