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Blast Vibration Analysis: Proposed MMRR Quarry <br />Page 8 <br />SILVER DOLLAR METROPOLITAN DISTRICT LIGHTING <br />OPERATIONS <br />The SDMD owns, operates, and maintains highway lighting located along Colorado Highway 119 as <br />it traverses North Clear Creek Canyon between Colorado Highway 6 and the City of Black Hawk. <br />' This area is within the City of Blackhawk emergency response zone pursuant to a Consent Judgment <br />in Case No. Ol CV 15, dated December 6, 2002. Approximately five years ago, a series of citizens' <br />focus groups identified the lack of illumination along Highway 119 as a potential hazard. A traffic <br />' study conducted by the Colorado Department of Transportation concurred with this assessment and <br />highway lighting was installed9. <br />' Nationwide accident statistics show that more than 50% of fatal accidents occur during the hours of <br />darkness, a fatality rate about three times higher than during the day. Overhead highway lighting is a <br />potential countermeasure to this nighttime accident problem10. Conditions along a heavily traveled, <br />' winding canyon road such as Colorado Highway 119 only highlight the need for appropriate lighting. <br />Thus, continuous assured operation of the SDMD highway lighting is a matter of public safety. <br />RECEPTORS <br />The SDMD highway lighting consists of a series of lamp poles spaced approximately 100 feet apart <br />along Colorado Highway 119 between Colorado Highway 6 and the City of Black Hawk. The <br />physical fixtures conform to Public Service of Colorado material specifications (fixture <br />specifications aze included as Appendix A). The nomina135 feet-high tapered aluminum poles are <br />bolt-mounted into concrete bases approximately 2 feet in diameter by 5 feet long (deep). An <br />aluminlun arm extends from the light pole approximately 10 feet over the roadway. The luminaire, <br />which houses the actual lamp, is attached to the end of this arm. <br />The SDMD fixtures employ 250-watt high pressure sodium (HPS) lamps. Generically known as <br />high intensity dischazge (HID) lamps, these fixtures produce high intensity light by an electrical arc <br />source. In addition to the lamp assembly, a typical luminaire also contains the photoelectric control <br />cell and a ballast assembly consisting of an igniter/starter, capacitor, and core & coil. <br />Because HPS lamps are discharge lighting sources, theyrequire a mechanism to create and sustain an <br />azc of electricity between the two electrodes within the arc tube. The ballast system of an HPS or <br />HID lighting fixture acts as this mechanism. The ballast provides the necessary voltage required to <br />start and stabilize the lamp. Once the arc tube is ionized, and the arc strikes, the ballast also controls <br />and limits the current flow through the lamp. The ballast must also compensate for 1) variations in <br />line voltage and 2) lamp voltage change due to ageing of the arc tube. <br />e Barnes M, Silver Dollar Metropolitan District, personal communication, November 7, 2005 <br />10 U.S Departrnent of Transportation, Federal Highway Administration, Research & Technology Transporter, <br />Volume 58 No. 2, Autumn 1994. <br />~ Leonard Rice Engineers, Inc. November 10, 2005 -Job No. 1086BCS03D <br />