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I I I I I I I I I , I I I I I I I . " CHAPTER II GENERAL STUDY AREA DESCRIPTION B. History The urbanization of the Grange Hall Creek basin essentially began in the latter portion of the 1950 decade and has continued to date. Fortunately, the pattern of urbanization for this basin to date has been concentrated in the upper end of the basin (adjacent to 1-25), and the lower reaches have not had extensive development infringing into the flood plain. While various serious drainage problems exist in the upper basin, the channel and flood plain east of the Union Pacific Railroad embankment is relatively free of major problems. A. Study Area The Grange Hall Creek basin lies within the northern portion of the Denver Metropolitan area, approximately two-thirds of the basin lying north and one-third south of 104th Avenue. The upper end of the basin lies west of Interstate 1-25, and the confluence with the South Platte River is located approximately one-quarter of a mile north of the 104th Avenue bridge across the South Platte River. The basin location and Prior to urbanization, some irrigated fanning was practiced in the upper basin boundary are shown on Figures II-I and 11-2. The basin description and numbering as set forth in the Project Reuse "Drainage Basin Descriptions, Sub-basin Delineation and (mostly pasture due to relatively steep slopes). The lands adjacent to the middle reaches are still being cultivated, although the primary use appears to be pasture land. The fertile Summaries" is as follows: lands east of Riverdale Road currently are being cultivated in relatively high value crops. Grange Hall Creek Project Reuse Basin Description This reach is also impacted to a degree by the South Platte River flood plain and much of the area wi II continue to be farmed. North Tributary and Central Main Stem South Tributary 1-01-3802-0 I A = 1.63 sq. mi. L = 2.54 mi. LCA = 1.17 mi. 5 = 0.0216 1-0 1-380 1-0 I A = 1.89 sq. mi. L = 4.00 mi. LCA = 2.16 mi. S = 0.0 165 The Union Pacific Railroad line has been in the present alignment for more than 80 Lower Main Stem 1-01-3800-0 I A = 2.63 sq. mi. L = 2.45 mi. LCA = 1.60 mi. 5 = 0.0074 1-01-3800-02 A = 2.79 sq. mi. L = 1.40 mi. LCA = 1.25 mi. S = 0.0103 Upper Main Stem years, although the date on the headwall of the 108 inch culvert for Grange Hall Creek indicates this structure has either been rebui It or improved within the last fifteen years. The basin is apparently named for the Riverdale Grange Hall that is located between Riverdale Road and Colorado Blvd. on 100th Avenue. A 1914 dated map of the area shows a school and church near the same location as well as another school located in the The total basin area defined by Project Reuse was 8.94 square miles. The basin northwest corner of Washington Street and 112th Avenue. The same map indicates a boundary has been defined in more detail during the process of this study and the total significant part of the basin is located within the Municipal Irrigation District. tributary area is 9.34 square miles. The basin and major sub-basin breakdown, including Co Topographic and Geophysical Features governmental or jurisdictional area definition, is presented in Table II-I. This table indicates a small percentage (2 percent each) of the basin is within the Federal Heights The Grange Hall Creek basin has a west to east aspect with the high point on the periphery of the basin along Federal Blvd. at elevation 5560 feet. The elevation of the and Westminster incorporated areas. creek at the confluence with South Platte River is approximately 5040 feet. The total length of the basin is approximately 6.6 miles or a drop of nearly 80 feet per mile. 5