1997-09-15_REVISION - M1981302 ‎(9)‎

• Permit No: M1981302
• IBM Index Class Name: Revision
• Doc Date: 9/15/1997
• Doc Name: RATIONAL FOR APPROVAL OF TR-06 WESTERN MOBILE BOULDER INC DEEPE FARM PIT PN M-81-302
• From: DMG
• Type & Sequence: TR6
• Media Type: D
• Archive: No

Rationale for TR-06 Approval-Western Mobile Page 4
Deepe Farm Pit, Permit No. M-81-302
September 15, 1997
are adequate to satisfy the adequacy concerns related to the maps that were provided
with the initial TR-06 application.
2. On May 27, 1997, the Division staff met with the operator's consultants who described
the various flood plain studies that have been conducted for South Boulder Creek.
The Division subsequently reviewed numerous flood plain studies that are available
for South Boulder Creek and made the following determinations:
a. The area behind the Deepe Farm Pit perimeter levee is excluded from the
special flood hazard area (that area subject to flooding during the one percent
annual chance flood) on the current Flood Insurance Rate Maps adopted by the
Federal Insurance Administration, the Federal Emergency Management
Administration (FEMA), and Boulder County. This exclusion of the area
behind the levee has been in place since 1988, so the adopted special flood
hazard area for the past 9 years was modeled and mapped based on the
assumption that the Deepe Farm Pit perimeter levee would hold during the
one percent annual chance flood. The modifications to the levee proposed in
TR-06 could only serve to increase the level of assurance that the levee would
hold during a one percent annual chance flood. Therefore, these modifications
to the levee, by themselves, would not result in a change to the extent of the
special flood hazard area and thus would not result in a disturbance to the
prevailing hydrologic balance.
b. As described above, the area behind the levee has been excluded from the
special flood hazard area for a number of years. Recent studies of the South
Boulder Creek flood plain correctly point out that exclusion of the area behind
the levee was the result of a regulatory error. Title 44 of the Code of Federal
Regulations specifies that areas behind levees may only be excluded from the
special flood hazard area if the levee has been certified by FEMA, and the
Deepe Farm Pit perimeter levee has not been certified. Even if certification of
a levee is obtained, the area excluded from the special flood hazard through
such certification would still be depicted as an area of moderate flood hazard
(Zone B) on National Flood Insurance Program Maps; the area behind the
Deepe Farm Pit perimeter levee is not shown in Zone B, moderate flood hazard,
on the current maps. Even though a regulatory error has occurred in excluding
the area behind the levee on current flood plain maps, it does not necessarily
mean that the levee would fail to protect this area during the one percent
annual chance flood. The current crest elevation of the levee is such that using
the most conservative (highest)water surface elevations yet developed through
hydrologic analysis of South Boulder Creek, the levee has a minimum of 1.6
feet of freeboard during a one percent annual chance flood. The operator's