FLOOD09501

• County: Douglas
• Community: Castle Rock
• Stream Name: Unnamed Tributary to Sellers Gulch
• Basin: South Platte
• Title: LOMR - Affected Panel 080050 0301 C - Case No. 95-08-052P
• Date: 3/20/1995
• Prepared For: Castle Rock
• Prepared By: FEMA
• Floodplain - Doc Type: Historic FEMA Regulatory Floodplain Information

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Federal Emergency Management Agency
Washington, D.C. 20472

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CERTIFIED MAIL
RETURN RECEIPT REQUESTED

IN REPLY REFER TO:
Case No. : 95,.08-'052P

The Honorable Mark Williams
Mayor, Town of Castle Rock
680 North Wilcox Street
Castle Rock, Colorado 80104

Community: Town of Castle Rock, Colorado
Community No.: 080050
Panel Affected: 0301 C
Effective Date of
This Revision:

MAR 20 1995

102-D-A

Dear Mayor Williams:

This is in response to a request for a revision to the effective Flood Insurance Study (FIS) and National
Flood Insurance Program (NFIP) map for your community. Specifically, this responds to a letter dated
March 6, 1995, from Mr. Steven A. Butherus. P.E., KLH Engineering Group Greeley, Inc., regarding
the effective FIS report and Flood Insurance Rate Map (FIRM) for the Town of Castle Rock, Colorado.
With his letter, Mr. Butherus provided additional information in support of a December 15, 1994, request
for a Letter of Map Revision (LOMR) submitted by Mr. Daniel W. Bare n, P.E., Engineer m, Town
of Castle Rock, Mr. Bare requested that we revise the effective FIRM to show the effects of the Oman
Road bridge replacement and associated channelization along the Unnamed Tributary to Sellers Gulch.
The channel improvements extend from approximately 300 feet downstream to approximately 250 feet
upstream of the bridge.

All data required to complete our review of this request were submitted with Mr. Bare's December 15
letter and with letters dated February 8 and March 6, 1995, from Mr. Butherus. Because this LOMR
shows the effects of a publicly sponsored flood-control project that reduces flooding 10 existing
development, fees were not assessed for the review.

We have completed our review of the submitted data and the flood data shown on the effective FIRM,
and have revised tile FIRM to modify the elevations and floodplain and floodway boundary delineations
of a flood having a I-percent probability of being equaled or exceeded in any given year (base flood)
along the Unnamed Tributary to Sellers Gulch from just upstream of Lake Gulch Road to approximately
650 feet upstream of Oman Road. The Special Flood Hazard Area (SFHA) and floodway widths have
decreased a maximum of 150 feet along the revised reach, and the base (l00-year) flood elevations (BFEs)
have decreased a maximum of 3 feet. The SFHA and floodway are contained within the aforementioned
channelized reach. At the upstream limit of the revision, the BFE has increased 0.2 foot. as compared
to the effective FIS report and FIRM. This increase is the result of including an additional cross section
upstream of the channelization and not the result of the bridge replacement and channelization project,
as demonstrated by a HEC-2 hydraulic computer model of pre-project conditions that was submitted by
Mr. Butherus. As compared to the pre-project conditions, the BFEs have decreased along the entire
revised reach. The channel length along the revised reach has decreased approximately 50 feet as a result
of the channelization.