FLOOD04661

• County: Boulder
• Community: Boulder
• Stream Name: South Boulder Creek
• Basin: South Platte
• Title: Floodplain Analyses of South Boulder Creek at Flatiron Property
• Date: 8/12/1996
• Prepared For: University of Colorado at Boulder
• Prepared By: Love & Associates, Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

I
I
I
I
I
I
I
, I
I
I
I
I
! I
I
I
,I
I
I
I

modeled from the current Reclamation Grading Plan, A second hydraulic model,
Condition 2, was generated with the assumption that the berm surrounding the property
could be certified by FEMA as a flood protection levee, This model was entitled "100-
Year Floodplain with Certified Flood Levee", These hydraulic models are provided in
the Technical Appendix of this report.

Both conditions analyze water surface elevations using the lOO-year flood peak
discharges provided in the PIS regulatory model. It is therefore assumed that flood peaks
are not attenuated by floodplain or overbank storage. It is also assumed that the Viele
Canal is flowing full and does not convey South Boulder Creek flood flows.

Condition 1 - "lOO-Year F100dDlain Model - No Levee with 200-Foot Wide
Channel:

In order to analyze the first condition (no berm), which included the construction of a
200-foot wide (bottom width) interior interceptor channel, the mining operator's most
current reclamation grading plan, which includes this channel, was utilized to
supplement the G&O topography and current as-mined topographic conditions survey
information. This Reclamation Grading Plan was prepared by Scott, Cox & Associates
dated April, 1996. The field survey data was obtained in May, 1996. The Reclamation
Grading Plan includes an approximately 200 foot wide interceptor channel along the
interior southern and eastern edges of the Property to intercept spills from the South
Boulder Creek main channel during the 100-year flood, The second condition assumed
the site perimeter berm was constructed in accordance with FEMA criteria as a flood
protection levee and could be certified as such. Additional mapping utilized for this
model was obtained from the City of Boulder's May, 1993 aerial topography,

For Condition I, a portion of the South Boulder Creek lOO-year flood waters enter the
Flatiron Property along the southern property boundary and flow to the north within the
interior interceptor channel toward D,S, Highway 36, The HEC-2 analysis indicates

-14-