FLOOD10405 ‎(3)‎

• County: Adams
• Community: Northglenn
• Stream Name: South Fork Grange Hall Creek
• Title: LOMR - Affected Panel 08001C0038 G - Case No. 99-08-377P
• Date: 5/9/2000
• Prepared For: Northglenn
• Prepared By: FEMA
• Floodplain - Doc Type: Historic FEMA Regulatory Floodplain Information

Federal Emergency Management Agency

Washington, D. C. 20472

MAY 09 2000

CER nFIED MAIL
RETURN RECEIPT REQUESTED

IN REPLY REFER TO:
Case No.: 99-08-377P

The Honorable Don Parsons
Mayor, City of North glenn
P.O. Box 330061
Northglenn, CO 80233-8061

Community: City of North glenn, CO
Community No.: 080257
Panels Affected: 0800 lC003 8 G
Ef~ective.~ate of AUG 23 2000
ThIS ReVISIOn:

102-I-A-C

Dear Mayor Parsons:

This responds to a request that the Federal Emergency Management Agency (FEMA) revise the effective
Flood Insurance Rate Map (FIRM) and Flood Insurance Study (FIS) report for Adams County, Colorado and
Incorporated Areas (the effective FIRM and FIS report for your community), in accordance with Part 65 of
the National Flood Insurance Program (NFIP) regulations. In a letter dated July 19, 1999, Mr. Frank D.
Casteleneto, City Engineer, City of Thornton, requested that FEMA revise the FIRM and FIS report to show
the effects of construction of the Thornton Town Center along South Fork Grange Hall Creek and updated
topographic information from approximately 950 feet downstream of Grant Streetto approximately 100 feet
downstream of Melody Drive. The construction of the Thornton Town Center included installation of a
7-foot-high by 14-foot-widereinforced-concrete box culvert (RCB) under Grant Street; a storage pondjust
upstream of Grant Street; and approximately 1,400 feet of 7 -foot -high by 10- foot-wide RCB from the storage
pond tojust upstream ofInterstateHighway 25 (1-25). The construction has resulted in a realignment of the
profile baseline for South Fork Grange Hall Creek; therefore, the stationing and letter designations of the
cross sections from approximately 800 feet downstream of Grant Street to just downstream of Huron Street
were adjusted accordingly. In addition, this Letter of Map Revision (LOMR) includes a correction to the
cross-section letter designations on the effective FIS profile panels to make them consistent with those shown
on the effective FIRM and Floodway Data Table from 1 04th Avenue to approximately 900 feet upstream
of Washington Street.

All data required to complete our review of this request were submitted with letters from . 'l
~
, P.E., Kiowa Engineering Corporation, and Mr. Casteleneto.

We have completed our review of the submitted data and the flood data shown on the effective FIRM and
FIS report. We have revised the FIRM and FIS report to modifY the elevations and floodplain and floodway
boundary delineations of the floods having a I-percentchance of being equaled or exceeded in any given
year (base flood) and a O.2-percent chance of being equaled or exceeded in any given year along South Fork
Grange Hall Creek from just upstream of 1-25 to approximately 100 feet downstream of Melody Drive. As
a result of the modifications, the base flood elevations (BFEs) for South Fork Grange Hall Creek and the
widths of the Special Flood Hazard Area (SFHA), the area that would be inundated by the base flood, and
the regulatory floodway increased in some areas and decreased in other areas. In addition, the cross-section
stationing and letter designations were revised fromjust upstream of 1-25 to just downstream of Huron