FLOOD02900

• County: Adams
• Community: Commerce City
• Basin: South Platte
• Title: Lower First Creek and Direct Flow Area 0055 Major Drainageway Planning
• Date: 5/1/2002
• Prepared For: UDFDC
• Prepared By: Turner Collie & Braden Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

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AGEl'll>A

TumerCellie0Braden Inc.

MEETING MINUTES

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First Creek OSP and FH.ID
(Progress Meeting)
Time: 1 :00 PM
Date: August I, 2000
Location: Urban Drainage & Flood Control District

Subject:
Job No.:

Lower First Creek and Direct Flow Area 0055 Outfall Study
35-05096-040

Place: Urban Drainage and Flood Control District Offices
Date & Time: 8/2/00 I :00 PM

Introduction

Attendees: David Mallory (UDFCD)
David Krickbaum (TCB)
David Center (TCB)
Chris Gervais (Commerce City)
Wade Thornburg (RMA-Shell-MK)
Stephen Smith (RVO-RMA-USFWS)

Bill DeGroot (UDFCD)
Alan Potok (TCB)
Carl Mackey (R!vlA-Shell-MK)
Tom Browning (CWCB)
Tim Kilgannon (RVO-RMA)
Edward Stafford (Commerce City)

Review and conunents of July 3" and July 18'" Meeting Minutes

Prepared By: David Center

Date: 8/2/00

Additional Survey Proposal

The purpose of the meeting was to report on progress on the Outfall Systems Planning and Flood Hazard
Area Delineation Study for the lower First Creek watershed.

Status of FHAD Revisions

Two meetings were held: the first to review information pertaining to the Flood Hazard Area Delineation
at 1 :00 PM; and the progress meeting at 2:00 PM.

Comparison of TC&B analysis to current effective 100-year floodplain

FHAD
FEMA has adopted the ECI floodplain.

Maul Reservoir

Portions of the Birch Drainage channels are being constructed. These channels were sized using a
Mannings "n" value of 0.03. TC&B has modeled the floodplain IIsing a 0.04 for the main channel section
and 0.045 for the overbanks. With these values the floodplain is outside the channel banks. A consensus
is needed, among the project sponsors, regarding the type of channel, the level of maintenance and
appropriate un" values.

Open Discussion

Along the Arsenal North drainage some channels exist upstream of Havana Street. Commerce City will
provide as-built plans for those channels. In order to delineate the floodplain upstream of the O'Brian
Canal and Burlington Ditch the embankments will be assumed to hold. Downstream of the canal and
diteh the embankments will be assumed to fail.

Next Meeting! Adjournment

HEC-RAS does not support the split flow optimization feature that was present in HEC-2.

The effects of the First Creek floodplain on DF A 0055 will be reviewed by TCB. TCB will review the
timing of the peak flows from these two drainage systems to determine a starting water surface elevation
for the DF A floodplain delineation.

Additional information pertaining to flows and cross-sections were discussed.