Conditional Letter of Map Revision (CLOMR)

This section of the Authority Website provides access to the Conditional Letter of Map Revision (CLOMR) mapping completed by Ayres Associates before construction of the Authority’s regional improvements consisting of the East Side Detention Facility (ESDF) and the Larimer-Weld Canal Crossing Structure (LWCCS).  This mapping includes the effects to the floodplain from the downstream drainage improvements under I-25 and on Prospect Road completed by the City of Fort Collins and the Town of Timnath in 2016.  This mapping is very close to the Letter of Map Revision (LOMR) mapping which will be submitted and reviewed by FEMA.  Please note, however, that there could be slight variations between the two sets of mapping and FEMA may require changes to certain areas based on their review of the modeling and mapping.  This mapping is provided as a general reference to interested parties and could be subject to change after review and approval of the LOMR by FEMA.

You can view the CLOMR maps here: Conditional Letter of Map Revision (CLOMR) mapping

Based on the above statement, here is an explanation of the mapping provided in the file above:

  1. Sheet 2 of the PDF provides an overall index of the C200 sheets from the CLOMR submittal. The C200 sheets provide the clearest depiction of the FEMA Effective Floodplain and the adjusted Existing Conditions Floodplain before construction of the above-referenced improvements and the Proposed Floodplain after construction of the same improvements.  All three floodplain boundaries are based on 100-year recurrence interval storm events.
  2. Sheets C201 through C221 depict the limits of the following floodplains in more detailed maps:
    • The Effective Floodplain boundary is the legally-binding floodplain depicted on the current FEMA mapping through the area (shown as a light blue line).  This reflects conditions BEFORE construction of the regional improvements, and without any corrections based on the pre-project ground surface such as construction projects by others.
    • The Existing Floodplain boundary is the more accurate current floodplain based on revised modeling and topographic mapping available since the FEMA mapping was originally done (shown in green lines). This reflects actual ground conditions BEFORE construction of the regional improvements.
    • The Proposed Floodplain boundary is based on the effect of the construction of the regional improvements completed by the Boxelder Authority, City of Fort Collins and Town of Timnath (shown in dark blue lines).  This reflects the anticipated condition AFTER construction of the regional improvements.  Construction was completed in accordance with the design, and we expect that any variances between the CLOMR and the LOMR will be very minor.
  1. As a general note, properties shown in Sheets C215 through C221 are in an area referenced as the Boxelder Creek Overflow, and should be taken out of the Boxelder Floodplain entirely as a result of the regional improvements.

Please contact the Authority Manager if you have any questions about the CLOMR or LOMR.