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SECTIONIl STUDY AREA DESCRIPTION McCLELLANDS BASIN Bordering the Mail Creek Basin on the north, the McClellands Basin shares with Mail Creek similarities of land use. topography, soils and manmade features which affect drainage. Upstream of Timberline Road, the basin is long and narrow in shape. It is 2.37 miles in length and 6,400 feet wide at its broadest point. It drains 1.75 squaremiJes more or less. The basin originates at an elevation of 5,025 feet above MSl and falls 89 feet to an elevation of 4,936 feet above MSL at Timberline Road. On the southern boundary of fort Collins, Colorado, the adjacent Mail Creek and McClellands Drainage Basins originate in Section 34, 35, and 36, Town- ship 7 North, Range Sg West, and drain to the southeast through Section 1, Town- ship 6 North, Range 69 West and Section 6, Township S North, Range 68 West. Mail Creek is a tributary to Fossil Creek; McClellands is also a tributary to Fossil Creek, but this study does not include tributary areas of the McClellands Basin east of Timberline Road. Development in the uplands of the basins has changed the drainage patterns in the basins in recent years. To assess the im- pacts of these changes, three (3) basin conditions have been examined. These are described in the following paragraphs and illustrated on Figures 11-1, 11-2 and 11-3 (located in the rear pocket). MAil CREEK BASIN The historic McClellands Basin (seeFigurelI-l,in back pocket) drained app~oximately 1,117 acres west of Timerline Road. land uses were predominately agrlcultural. West of College Avenue, there are few places where there is a dis- tinct drainage channel. The basin is intersected by the Pleasant Valley and lake and the New Mercer Irrigation Canals, which were built in the late 1800's and carry approximately 30 cfs and 80 cfs respectively in the vicinity of Harmony Road. There are no wasteways or spill structures in McClellands, so it is highly probable that most storm runoff originating upstream of these canals was diverted to Mail Creek since the construction of the canals. The historic Mail Creek Basin is long and narrow in shape. It is appro- ximately 3.57 miles in length and 7,200 feet wide at its broadest point; it drains 2.47 square miles more or less. Originating at an €levation of 5,185 feet above mean sealevel (MSL),MailCreekfalls291feettoanelevationof 4,894 feet above MSL at the confluence with Fossil Creek. The historic Mail CreekBasinandsubbasinsareshownonFigurelI-l (located in the rear pocket}. Mail Creek has long been used to transport irrigation waters. TheP1ea- ,ant Valley and Lake Canal traverses the upper area of the Mail Creek Basin and Mall Creek receives waste irrigationwaterfrornthe laterals in this ar ea. Fur. ther downstream, the New Mercer Canal and Larimer County Canal No.2 Waste DitCh discharge directly into Mall Creek. Irrigation water flows in Mail Creek and is either div~rt€d out of the creek at the Man Creek ditch headgatc or contim':C$ to flow downstream to Fossil Creek and eventually to Fossil CreekN:!servoir. Other ma~de features directly affecting the drainage characteristics of Mail Creek are th€ Colorado & Southern Railroad, College Avenue, Harmony Road, and two (2) private on.stream lakes in Larimer County. Approximately l,lg5 acres of the existing Mail Creek Basin are in the City of Fort Collins, nortn of Harmony Road. Drainage patterns in the basin have been affected in recent years principally by development occurring in the City. Essen- tid.i1y, d~v~lOI!IIl~nt Ilf previously agricultural 1an~ in Sect~o;1 3S has d~./~rted runoff from the uplands of the McClellands Basin to Mail Creek via the New Mercer Canal, and new storm sewer. The McClellands Drainage Basin has been experiencing steady development in recent years in the subbasins north of Harmony Road in the City of Fort Collins. Most of the development has been done in accordance with the drainage criteria of Fort Collins, and considerable on-site detention is being created. Development is forthcoming in the section south of Harmony Road, portions of which have been annexed into the City, however, existing land uses in the lowerre achesarestlJl agricultural. Manmade f€atures affecting drainage patterns in the McClellands Basin are the Union Pacific and ColoradO & Southern Railroads, College Avenue, Harmony Road and the Larimer County No.2 and New Mercer Canals. The existing and future ~cClel1ands Sasi:'! are illustrated in Fig~res rI-2 and 1!-3 (back pocket). Mail Creek reaches inc1uded in this study begin at the confluence with fossil Creek and extend approximately 3.3 miles upstream to the center of Sec- tion34. For analysis, study reaches (Figure 11-4) were broken out into the following homogeneous segments: Reach lA Mail Creek from confluence with Fossil CreeK to Mail Cree~ Lane. Mail Creek Lane to Palmer Drive. Palmer Drive to U.S. 287 (College Avenue). U.S. 287 to C & S Railroad. C & S Railroad to Shields Street. Shields Street to upstream study limits. New Mercer Canal between Mail Creek and McClellands tributary. McClellands of Section McClellands Street. McClellands tributary from Shields Street to upstream study limits. ReachlB ReachlC Reach 10 Reach2A Reach2B Reach 3 The lower portions of the Mail Creek Basin in Larimer County are also being developed. Land use patterns arelowdens1ty residential and agricultural. The increased area of the Mail Creek Basin and existing and future drainage pat- terns are shown in Figures 11-2 and 11-3(located in the back pocket). Reach 4A ReaCh 4B Reach 5 II-l MAIL CREEK STUDY REACHES tributary 34. tributary from New Mercer Canal to center frOlll center of Section 34 to ShieldS 11-2