FLOOD10493

• County: Adams
• County: Arapahoe
• Community: Aurora
• Stream Name: Upper Box Elder Creek
• Basin: South Platte
• Title: Upper Box Elder Creek Outfall Systems Planning Study - Alternative Evaluation Report
• Date: 12/1/1994
• Prepared For: Aurora, Arapahoe County, Adams County, UDFCD
• Prepared By: CH2M Hill
• Floodplain - Doc Type: Floodplain Report/Masterplan

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Estimate existing and future development condition peak discharges
volumes for the 2-, 5-, 10-, 50-, 100-, and 500-year storm events.

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Evalua.te the existing channel for stability and maintenance needs under
future discharge conditions.

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Section 1.0

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Develop alternative concepts and, with participation by the advisory
committee, refine the concepts into alternative plans.

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Authorization

1.1

Evaluate the advantages and disadvantages of the alternative plans with
consideration for capital and maintenance costs, flood control benefits,
implementation issues, open space, recreation, riparian areas, water quality,
land use, and legal issues.

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This study was authorized by the Urban Drainage and Flood Control District (UDFCD),
the City of Aurora, Arapahoe County, and Adams County under UDFCD Agreement
No. 92-11.06 dated October 7, 1993. CH2M HILL was retained to complete the scope of
work summarized in Subsection 1.3.

The scope of work was modified on July 12, 1994 (Agreement 92-11.06A) to include a
Letter of Map Revision (LOMR) and FHAD on a portion of Box Elder Creek starting at
its confluence with Coyote Run and extending approximately 11 miles upstream. A reach
of Cardboard Draw extending approximately 3 miles upstream of its confluence with Box
Elder Creek is also included.

Purpose

The purpose of the study is to provide local jurisdictions with drainage and flood control
guidance in the form of an "Outfall Systems Plan" for dealing with land development
activities. Land development pressure is increasing in the area because of the construction
of Denver International Airport. This Alternative Evaluation Report will be followed by a
Preliminary Design Report, which will outline the design of the selected plan.

1.2

Mapping

The UDFCD provided I-inch to 200 feet, 2-foot contour interval mapping of the FHAD
study areas. This mapping was produced by Landmark Mapping under a separate
agreement with UDFeD. Mapping for the remainder of the study area consisted of
United States Geological Survey (USGS) quadrangles.

Summaries of alternative plans

Comparisons of alternative plans

Background Information

1.5

Background information provided by the sponsors and others was used to develop the
hydrology and alternative analyses. Information provided is identified below and is listed
in Section 8, References.

1987) (COE, 1989)
1990) (Aurora, 1993)

Urban Drainage and Flood Control District (CCWCD,
City of Aurora (Aurora, 1989) (Adams County, et al.,
Arapahoe County (FEMA, 1993)
Adams County (FEMA, 1989)
Colorado Water Conservation Board (WRC,

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1.3 Scope of Work

The scope of work includes a hydrologic and alternative analysis of the study area shown
in Figure 1-1. The scope also includes a Flood Hazard Area Delineation (FHAD) for the
Coyote Run Tributary.

1979)

is a summary of the scope of work:

Meet periodically with the project sponsors to exchange information and
discuss project progress and direction.

1.4

the following:

and storm

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A recommended plan

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Following

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includes

Existing and future development condition peak discharges
volumes

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The drainage and flood control guidance documented in this report

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Project Advisory Committee

A project advisory committee was formed at the outset of the study to obtain input from
as many interested organizations as possible. In addition to the project sponsors, the

1.6

Complete a review of all relevant data.

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1-1

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Complete a field reconnaissance.

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