FLOOD00551

• County: Douglas
• Community: Douglas County and Unincorporated Areas
• Stream Name: East Plum Creek
• Title: LOMR - Affected Panel 080049 0188 C - Case No. 95-08-110P
• Date: 4/5/1995
• Prepared For: Douglas County
• Prepared By: FEMA
• Floodplain - Doc Type: Historic FEMA Regulatory Floodplain Information

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Federal Emergency Management Agency
Washington, D.C. 204-72

CERTIFIED MAIL
RETURN RECEIPT REQUESTED

IN REPLY REFER TO:
Case No.: 95-08-lIOP

The Honorable Robert A. Christensen
Chairperson, Douglas County Commissioners
101 3rd Street
Castle Rock, Colorado 80104

Community: Douglas County, Colorado
Community No.: 080049
Panel Affected: 0188 C
Effective Date of
This Revision: APR 05 1995

102-D

Dear Mr. Christensen:

This is in response to a request for a revision to the effective Flood Insurance Study and National Flood
Insurance Program (NFlP) map for your community. Specifically, this responds to a letter dated
February 28, 1995, from Mr. Daniel W. Bare II, P.E., Engineer III, Town of Castle Rock, regarding
the effective Flood Insurance Rate Map (FIRM) for the unincorporated areas of Douglas County,
Colorado. Mr. Bare requested that we revise the effective FIRM to show the effects of the construction
of the Village North Diversion Channel, which comprises a trapezoidal grass-lined channel and associated
drop structures, and more detailed hydrologic and hydraulic analyses along an unnamed tributary to East
Plum Creek. The channel improvements extend from the Atchison, Topeka, and Santa Fe Railway to
the Omni Drainageway.

All data required to complete our review of this request were submitted with Mr. Bare's February 28
letter, and with a letter dated March 21, 1995, from Mr. Richard N. Wray, P.E., Principal, Kiowa
Engineering Corporation. Because this Letter of Map Revision (LOMR) shows the effects of a publicly
sponsored flood-control project that reduces flooding to 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 the FIRM to modify the floodplain boundary delineations and zone designations of a
flood having a I-percent probability of being equaled or exceeded in any given year (base flood) along
the unnamed tributary to East Plum Creek from the Atchison, Topeka, and Santa Fe Railway to the Omni
Drainageway. The construction of the Village North Diversion Channel, which lies within the Town of
Castle Rock and Douglas County, diverts the loo-year flood discharge from its present confluence with
East Plum Creek to the Omni Drainageway. The loo-year flood is contained within the channel.
Because of map scale limitations, the loo-year floodplain with a maximum topwidth of 23 feet cannot be
shown on the FIRM. The diversion of the loo-year flood discharge removes the effective floodplain
designated Zone X (shaded), which was created by shallow flooding from the loo-year flooding event
from downstream of the Atchison, Topeka, and Santa Fe Railway to approximately 800 feet upstream of
its past confluence with East Plum Creek. The impact of the diversion on flood hazards from the Omni
Drainageway were summarized in a LOMR issued on March 10, 1994.

The data submitted in support of this revision also affect the FIRM for the Town of Castle Rock,
Colorado. A separate LOMR was issued to the Town of Castle Rock with the same date as this LOMR
to describe the changes to the flood hazard information for that community.