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Reservoir storage water as a back up for ditch supplies currently used to irrigate City parks and <br />open spaces. The Union delivery system will extend as far west as the new potable treatment <br />plant currently under construction. <br />Union Reservoir is a natural lake in an incised channel. The reservoir is nominally held back by a <br />28-foot earthen dam that was constructed in 1902. Specifics regarding the reservoir in include <br />the following: <br />• 12,768 ac-ft active capacity <br />• Maximum surface area of 717 acres <br />• Maximum inlet capacity of 100 cfs, which is currently being expanded to allow storage of <br />500 cfs <br />• Maximum outlet capacity of 95 cfs <br />An elevation-capacity curve for Union Reservoir was provided by the City of Longmont and is <br />included in Table 2. <br />Table 2 <br />Union Reservoir <br />Stage -Area - Ca acit Curve <br />Elev. Area Capacity <br />(ft) (Acres) (Ac-Ft) <br />4929 NA 124 <br />4931 NA 466 <br />4933 NA 907 <br />4935 NA 1451 <br />4937 NA 2096 <br />4939 NA 2815 <br />4941 NA 3597 <br />4943 NA 4458 <br />Elev. Area Capacity <br />(ft) (Acres) (Ac-Ft) <br />4945 NA 5393 <br />4947 NA 6416 <br />4949 NA 7523 <br />4951 NA 8698 <br />4953 NA 9958 <br />4955 NA 11310 <br />4957 717 12768 <br />Source: City of Longmont from 1986 hydrographic survey <br />Note: N/A -not available <br />HydroBase Data <br />The monthly data available in HydroBase over the 1950-2002 period of record pertaining to <br />Union Reservoir include the following: <br />End-of--month contents <br />• Complete record (see Figure 5), except for data missing in water year 1953 and sporadic <br />months over the period of record. The City provided copies of its available storage <br />content records for these periods. <br />City of Longmont Operating Memorandum.doc Page 9 of 21 March 2, 2005 <br />