1997-06-13_REVISION - M1981302 (49)

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81-10- Deepe Farm Pit). The constructed dike and diversion channel were included as integral part of the mi yy� 4 and reclamation plans. The Special Use was approved by the Boulder County Board of County Commie ionms an January 11, 1982. Because the dike and diversion channel were not proposed to remove any property from the floodplain, were not necessary to protect any permitted structures or facilities from flooding (sand and gravel mining was and dill is■ permitted use in the 100-year floodplain not requiring special 'floodproofing' mean=), and had bees determined to not cause an undue adverse effect on flood flow characteristics, they were not inspected by Boulder County during or after construction. There had been a complaint this last year about truck noise and speed, however that was resolved when the investigation showed no violation. The operation is in compliance with the approved SU and we have received no complaints,other than the one cited, in recent years Our understanding is there is about two more months of raining left. The reclamation plan M-81-302 and M-78-064 for the mining area are governed by the State. The end use listed is open agriculture. The dike is not discussed specifically in these plans and, based upon conversations with the State, the dike can remain but the use of the dike, in its present condition, cannot be used for flood control. South Boulder Creek Floodnlain At the time that Flatirons applied for the Special Permit to construct the dike, the adopted (and initial)flood study for South Boulder Creek was prepared by the U.S. Corps of Engineers in 1969. In 1973 Urban Drainage and Flood Control District(UD&FCD)commissioned a Major Drainageway Planning Study for South Boulder Creek by R.W. Back and Associates. The R.W. Back study incorporated proposed floodplain improvements to mitigate flooding, including an emwntimwt levee located on the north end of the Deepe property which was designed to prevent flood water from flowing west along the U.S. 36 •mba.,l- n t The R.W. Back study, however, was never formally adopted by Boulder County. In March of 1995.Boulder County and the Urban Drainage and Flood Control District contracted with Greenhorns and O'Mara. Inc., Consulting Engineers, in cooperation with the Colorado Water Conservation Board, to restudy and delineate the South Boulder Creek floodplain and floodway. After a lengthy review and public hearing process the new study was adopted by Boulder Cotmty in November of 1987. In March of 1987, the Greenhorn and O'Mara study was submitted to the Federal Emergency Management Agency (FEMA) and in December of 1987, FEMA notified Boulder County that the study and technical information had been reviewed and the Flood Insurance Study and Flood Insurance Rate Map had been revised to incorporate the new study. With respect to the FLttirons property, the largest chaage from the 1969 Corps of Engineers study was the removal of the am west of the Flatiron dike and diversion channel from the 100-year floodplain. In the Greenhorns and O'Mara flood study report it states that: •Areas landward of the embankment were assumed ineffective for flood conveyance.' It don not appear therefore that the dike and diversion channel were considered and reviewed as needing to meet the FEMA requirements for a flood control levee. Since the duke u deigned would not appear to meet all of the FEMA requirements, there have been recent discussions that the Greenhorne and O'Mara study may have been in error in removing the am west of the dike from the floodplain. It should be noted however, that the study was reviewed by engineers at Boulder County, the Colorado Water Conservation Board, the Urban Drainage and Flood Control District,and FEMA prior to adoption, with all these agencies apparently accepting the Grecabome and O'Mara conclusion that the area west of the embankment was ineffective for flow conveyance(and therefore resulting in approximately 90 acre being removed from the floodplain).