BOARD02424

• Board Meeting Date: 9/13/2005
• Description: Flood Section - Chatfield Downstream Channel Improvement Project - Operation and Maintenance Activities
• Board Meetings - Doc Type: Memo

STATE OF COLORADO

.

Colorado Water Conservation Board

Department of Natoral Resources
1313 Sherman Street, Room 721
Denver, Colorado 80203
Phooe: [phone]
FAX: [phone]
www.cwcb.state.co.u5

MEMORANDUM

Bill Owens
Governor

To:

Colorado Water Conservation Board Members

Russell George
Executive Director

From: Tom Browning, P.E., Chief, Flood Protection Section

Rod Kuharich
CWCB Director

Date: September 2, 2005

Rick Brown
Acting Deputy Director

Re: Agenda Item 14 - September 13-14,2005 Board Meeting
Chatfield Downstream Channel Improvement Project-
Operation and Maintenance Activities

.

INTRODUCTION
The Chatfield Downstream Channel Improvement Project encompasses a multi-mile reach of the South Platte
River below Chatfield Reservoir. The flood control project was constructed by the U.S. Army Corps of
Engineers in the 1980's, and ownership and sponsorship of the project was tumed over to the Colorado Water
Conservation Board via a Memorandum of Agreement between the State of Colorado and the Federal
Government. The CWCB is responsible for maintenance of the floodplain and project lands. For many years,
the CWCB has obtained maintenance assistance from the Urban Drainage and Flood Control District (District),
but his has been on somewhat of an ad-hoc basis. Staff works directly with the District to address routine and
on-going maintenance issues along the project right-of-way. The Corps of Engineers, Omaha District (Corps),
performs annual inspections during the spring and typically invites staff members from the CWCB, District, and
South Suburban Parks & Recreation District to join the inspection. Post-flood inspections are also conducted on
an as needed basis to assess the integrity of the flood control channel and to identify any damaged features that
are in need of repair.

BACKGROUND
The annual Corps inspections are performed to ensure that the proper maintenance is being completed as
prescribed in the Operation & Maintenance (O&M) Manual for the project. Following each inspection, the
Corps provides a letter report to CWCB Staff noting satisfactory, marginal, or unsatisfactory project features.
On an annual basis, inspection items are typically corrected and repaired by the continued joint efforts of the
CWCB and District. During the spring 2005 inspection, the Corps outlined several project deficiencies and
listed the overall project as "marginally acceptable."

The first issue at hand includes "marginal" items listed on this year's inspection report that we intend to correct.
They are: 1) Repair and replace riprap/bank revetment along a 5,000 foot stretch ofthe river that has been
somewhat damaged over time, 2) Repair an undercut weir that is in need of riprap and stabilization, and 3)
clean culvert outlets and ensure proper operation of all flap gates.

.

The second issue, which is the subject of this Board memorandum, is the presence of trees and vegetation in the
floodplain. The Corps is specifically requiring that all brush and trees 2" in diameter and larger be removed
from the channel and banks. The Corps also stated that stumps should be excavated for trees larger than 2" in

Flood Protection. Water Supply Planning and Finance. Stream and Lake Protection
Water Supply Protection. Conservation and Drought Planning