FLOOD01452

• County: Larimer
• Community: Fort Collins
• Stream Name: Fossil Creek Drainageway Basin
• Title: Master Drainageway Planning Study
• Date: 8/1/1982
• Prepared For: Larimer County
• Prepared By: Simons Li & Associates Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

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2.2.8 Smith Creek, Reach 8

The land use along Smith Creek is predominantly grazing. One residence

exists near Shields Street. The channel follows a wide swale and has low

banks. The flood plain is wide upstream of Shields Street due to ponding

behind the road embankment. The Trilby Lateral crosses the upstream portion

of the basin and terminates near Smith Creek.

2.2.9 Burns Tributary, Reach 9

The land along Burns Tributary is undeveloped, with grazing activity the

most common land use. There is some very low-density residential development

north of the tributary. The Pleasant Valley and Lake Canal discharges into

Burns Tributary upstream of Shields Street. The flood plain is narrow and

well defined along the valley channel. Where the water ponds upstream of

Shields Street, the flood plain widens.

2.3 Irrigation Ditches, Reservoirs, Roads and Railroads

The Fossil Creek drainage system is used to transport irrigation water.

Flows from Portner Reservoir enter Fossil Creek from a channel along the south

bank upstream of Lemay Avenue (County Road 13). Flows are also diverted

across Fossil Creek towards Portner Reservoir through a pond located

downstream of Highway 287. Louden Ditch runs parallel with Highway 287 from

the south end of the basin for about three miles, then turns east and carries

its flows to portner Reservoir. The Pleasant Valley and Lake Canal runs north

and parallel to Shields Street, and discharges into Burns Tributary at the

north bank upstream of Shields Street.

The Trilby Lateral starts from the west bank of the Pleasant Valley and

Lake Canal about half a mile south of Harmony Road. Trilby Lateral winds

across Burns Tributary basin, Fossil Creek basin, and Smith Creek basin. It

crosses Taft Hill Road just south of the Fossil Creek crossing at Taft Hill

Road. As development occurs upstream of existing canals, care should be taken

to ensure storm water runoff reaches natural drainages.

Numerous ponds exist throughout the basin. For flood routing purposes

they were assumed full due to lack of storage. Major reservoirs in the study

area are portner Reservoir and Robert Benson Lake. Tributary areas to these

reservoirs were assumed to be noncontributing to the Fossil Creek system.

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Several major roads criss-cross the study area. Included among them are

Lemay Avenue (County Road 13), Highway 287 (College Avenue), Shields Street

and Taft Hill Road, all running north and south. The major roads traversing

east and west are Harmony Road and Trilby Road. Often the culverts at these

crossings are undersized, and during high runoff water ponds causing the roads

to be overtopped.

Two railroads cross north and south through the basin. The Union Pacific

Railroad crosses Fossil Creek 1-1/2 miles east of Highway 287. The Colorado &

Southern (C&S) Railroad is located between Highway 287 and Shields Street.

The C&S Railroad crosses Lang Gulch four times and Fossil Creek once.

2.4 Soil~

Soils in the watershed are divided into five general soil associations

with thirteen different soil series defined in the area. The characteristics

of each soil series are variable, but generally the soils may be divided into

two areas. The first are the areas dominated by warm soils on plains. These

soils are usually deep, well drained and composed of sandy, fine or clay

loams. Most often the soils are formed in alluvium and in materials weathered

from shale or sandstone on fans or terraces. The second general soil area is

dominated by warm soils on foothills. These soils may range from shallow to

deep and are often on steep slopes. The soils are well drained clay, silt or

stony sandy loams that formed in material weathered from sandstone, limestone

or rock outcrop. They are found on uplands and some alluvial fans.

2.5 Water Quality

The effects of urbanization on the quality of storm water runoff is to

transfer more pollutants to other areas of the basin, and in particular to

larger bodies of water such as streams and lakes. The transfer of urban

pollutants such as sediment, trash, salts, fertilizers and oils may be detri-

mental to streams, lakes and areas subject to flooding by storm water.

Urbanization with decreased areas of vegetation and permeable surfaces will

contribute larger amounts of pollutants due to increased storm water flow

rates and volumes. The U.S. Environmental Protection Agency, EPA), under

Section 208 of the 1972 Amendments to the Water Pollution Control Act (P.L.

92-500), has required public officials in all metropolitan areas to develop

area-wide plans for controlling and reducing pollution from storm water. Non-