FLOOD08354

• County: Boulder
• Community: Lafayette
• Stream Name: Coal Creek , Waneka Reservoir
• Basin: South Platte
• Title: Major Basinwide Planning
• Date: 12/1/1980
• Prepared For: Boulder County
• Prepared By: Camp Dresser & McKee
• Floodplain - Doc Type: Floodplain Report/Masterplan

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II. EXISTING DRAINAGE BASIN CONDITIONS

Major Sub-Basin 1: The land ownerships in this basin includes private, Boulder
County and a right-of-way for the Chicago, Burlington and Quincy Railroad.
No drainage channels exist in this basin, and only small culverts are present
under Weld County Road, the Chicago, Burlington and Quincy Railroad and North
119th Street. Present land use is primarily agricultural.

Major Sub-Basin 3: The land ownerships in this basin include private, Boulder
County, City of Lafayette and a Chicago, Burlington and Qunicy Railroad
right-of-way, Small drainage ditches along Emma Street and Burlington Avenue
have been used to convey stormwaters from the downtown areas of Lafayette,
These ditches terminate at the intersection of Burlington Avenue and Emma
Street, where a culvert then passes the flow to a small ditch which heads east
through agricultural land, terminating in a sump area west of Coal Creek,
Debris build up in the sump area has been a common problem during storm events.
Present land uses consist of agricultural in the lower half of Basin 3, with
fully developed urban conditions in the upper half of the basin (downtown
Lafayette) ,

For the purpose of analyzing the improvements necessary for developing the
major drainageway plans for the City of Lafayette, the total basin was
subdivided into seven major drainage basins. It should be noted that the area
encompassed by these seven major basins does not include every drainage
sub-basin within the Lafayette basin; however, the outfalls for the sub-basins
not served by to the major basins directly or shown on the preliminary design
drawings and their installation is an important part of the total system, The
existing condition of each major basin depicted in Figure 2 is discussed below,

Major Sub-Basin 2: The land ownerships in this basin include private, Boulder
County, City of Lafayette and a right-of-way for the Chicago, Burlington and
Quincy Railroad. No drainage channels presently existing except for a small
irrigation ditch in the upper portion of the basin which has received some storm
flows in the past. Culverts under the Burlington Railroad, Weld County Road,
North 119th Street and North 111th Street are small and mostly ineffective due
to debris blockage. Present land use is agricultural in the lower portion of
the basin and quickly developing residential areas in the mid-sections of the
basin. Presently, the City of Lafayette Planning Department is studying a park
area from Finch Street to North 111th Street, which could be utilized as a
drainage path, without major channel improvements.

Major Sub-Basin 4: The land ownerships in this basin includes private, City of
Lafayette and Chicago, Burl ington and Qunicy Rail road right-of-way. A system of
drai nage di tches has been provided by exi sti ng commerci al and residential
developments which convey stormwaters to Coal Creek. These drainageways are
mostly overgrown and drained by culverts of less than 10-year capacity. Present
1 and uses are industrial and residential.

Major Sub-Basin 5: The land ownerships in this basin consist of private, City
of Lafayette and State highway right-of-way (US 287). Currently, no
drainageways exist for conveyance of stormflows from existing development which
is largely in the upper half of the basin. Current land uses are agricultural
in the lower portions of the basin and residential and light commercial in the
upper portions of the basin. Waneka Reservoir, which lies in the extreme
western section of Basin 5, serves as a water supply for the City of Lafayette.
The reservoir embankment is sufficiently high to store the 100-year storm event
from those areas tributary to the reservoir.

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