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<br />storage capacity is also included with this supplement. Generally, the needs can be placed in one of the <br />following categories, in this order of priority: <br /> <br />1. Outlet W orl(s - Deterioration of outlet components such as pipes and gates is one of the greatest <br />safety and serviceability concerns for all dams, particularly older ones which may have un-protected <br />steel pipes. Erosion and removal of embanl(ment or foundation material along the outside or into and <br />through the pipe can result in sudden catastrophic failure even for dams that have had a long history <br />of stability. Additionally, the risl( is increased at some of the project dams which have downstream <br />control valves. Downstream valves pressurize the outlet pipe. Therefore, the proposed worl( includes <br />focusing attention on the outlet systems for all of the dams. <br /> <br />2. Seepage - Uncontrolled seepage, particularly seepage which exits on the embanl(ment, at the <br />embanl(ment/foundation contact, in the foundation slightly downstream from the toe of the <br />embanl(ment or along the outside of the outlet pipe, is of a concern. If the seepage forces or pressures <br />are great enough, material can be eroded from the embanl(ment or foundation, or the pressures can <br />de-stabilize the dam slopes. Methods to address seepage range from channeling and measuring to <br />installation of filters and drains. The proposed worl( includes identifying significant seepage areas. <br /> <br />3. Slope Stability - As experienced with the Carl Smith failure, a long history of embanl(ment stability <br />does not assure either perpetual security or adequate safety factors under all possible conditions. <br />Slope stability is affected mainly by the steepness of the slopes, the characteristics and strength of the <br />embanl(ment and foundation soils and the seepage forces and pressures. In order to adequately <br />address slope stability issues a considerable amount of worl( is needed including drilling test holes <br />through the embanl(ment and foundation and installing and monitoring piezometers. That degree of <br />effort is considered well beyond the scope of worl( needed to prepare the proposed inventory. <br />However, it is possible to perform a preliminary stability analysis using soil samples from shallow <br />hand-auger holes and based on observations of downstream surface seepage. The proposed project <br />includes this preliminary level of stability evaluation. <br /> <br />4. Spillway/Flood Hydrology - Except for transient maintenance-related issues such as debris and ice <br />accumulation, a long history of spillway adequacy can indicate some degree of spillway security. <br />Therefore, this is the lowest priority item and related aspects of the proposed study will be limited to <br />field observations of spillway conditions, identification of spillway adequacy modeling previously <br />performed by the Division of Water Resources, and research of typical means used to identify <br />spillways that are susceptible to ice damming and effective means used to control ice damming. <br />Future investigations may pursue this aspect of the facilities at a more detailed level. If, at some <br />future point, it appears appropriate to pursue spillway and flood hydrology issues in a more <br />comprehensive manner, it would be best to evaluate the entire basin rather than individual dams. <br />This is because spillway considerations can be substantially impacted by both upstream and <br />downstream dams. For example, a small dam may not pose a great breach hazard if a larger <br />downstream dam could contain the entire capacity of the smaller dam within its freeboard. On the <br />other hand, a dam which has adequate spillway capacity when considered by itself may pose a much <br />greater hazard if the breach of an upstream dam creates a cascading series of breaches in this dam <br />and, perhaps, other downstream dams. A comprehensive evaluation would lil(ely consist of creating <br />a flood hydrology model of the entire basin that could be used to evaluate the impact of a wide range <br />of precipitation events. <br /> <br />5. General Dam Condition - Overall characteristics of the dam and appurtenant features which are <br />relevant to safety and serviceability will be observed and noted. <br /> <br />2 <br />