FLOOD05061

• County: Boulder
• Community: Boulder
• Stream Name: Twomiel Canyon Creek
• Basin: South Platte
• Title: LOMR - Affected Panel 395F - Case No. 04-08-0494P
• Date: 1/1/2004
• Prepared For: FEMA
• Prepared By: FEMA
• Floodplain - Doc Type: Historic FEMA Regulatory Floodplain Information

CHANGES ARE MADE IN DETERMINATIONS OF BASE FLOOD ELEVATIONS FOR THE CITY
OF BOULDER AND THE UNINCORPORATED AREAS OF BOULDER COUNTY, COLORADO,
UNDER THE NATIONAL FLOOD INSURANCE PROGRAM

On June 2, 1995, the Department of Homeland Security's Federal Emergency Management Agency
identified Special Flood Hazard Areas (SFHAs) in the City of Boulder and in the unincorporated areas of
Boulder County, Colorado, through issuance of a Flood Insurance Rate Map (FIRM), The Mitigation
Division has determined that modification of the elevations of the flood having a I-percent chance of
being equaled or exceeded in any given year (base flood) for certain locations in these communities is
appropriate, The modified Base Flood Elevations (BFEs) revise the FIRM for the communities,

The changes are being made pursuant to Section 206 of the Flood Disaster Protection Act of 1973 (Public
Law 93-234) and are in accordance with the National Flood Insurance Act of 1968, as amended
(Title XIII of the Housing and Urban Development Act of 1968, Public Law 90.448), 42 U.S,C.
4001-4128, and 44 CFR Part 65,

A detailed hydraulic analysis was performed to incorporate more detailed topographic information for
Twomile Canyon Creek from approximately 530 feet upstream to approximately 1,040 feet upstream of
Lake Bri,ar Drive, This has resulted in an increase in SFHA width and the establishment of a regulatory
floodway and BFEs for Twomile Canyon Creek, The table below indicates existing and modified BFEs
for selected locations along the affected lengths of the flooding source(s) cited above.

Location

Existing BFE
(feet)*

Modified BFE
(feet)*

I Approximately 560 feet upstream of Lake Briar Drive
I Approximately 700 feet upstream of Lake Briar Drive
2 Approximately 880 feet upstream of Lake Briar Drive
2 Approximately 1,020 feet upstream of Lake Briar Drive

None
None
None
None

5,638
5,649
5,659
5,670

*National Geodetic Vertical Datum, rolUlded to nearest whole foot
ICity of Boulder
2Unincorporated areas of Boulder County

Under the above-mentioned Acts of 1968 and 1973, the Mitigation Division must develop criteria for
floodplain management. To participate in the National Flood Insurance Program (NFIP), the community
must use the modified BFEs to administer the floodplain management measures of the NFIP, These
modified BFEs will also be used to calculate the appropriate flood insurance premium rates for new
buildings and their contents and for the second layer of insurance on existing buildings and contents,

Upon the second publication of notice of these changes in this newspaper, any person has 90 days in
which he or she can request, through the Chief Executive Officer of the community, that the Mitigation
Division reconsider the determination, Any request for reconsideration must be based on knowledge of
changed conditions or new scientific or technical dala. All interested parties are on notice that until the
90-day period elapses, the Mitigation Division's determination to modify the BFEs may itself be changed,