2016-09-02_HYDROLOGY - M1992069 - Laserfiche WebLink

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Mr. Roger Schmidt September 2, 2016 Page 15 Street agricultural field would be expected to cause localized surficial erosion and possible deposition, but any erosion would not have resulted in the headcut and associated mass wasting of soil material that occurred in 2014. • Physical features that likely altered the flow in the Cache La Poudre River and may have introduced contributing factors to the amount of water flowing over the field during the - runoff event in June 2014 included the configuration of the Iverson/Martin Marietta gravel pit (located to the west, between the Cache La Poudre River and the concrete bike path) and the Great Western Railroad bridge that crosses the Cache La Poudre River (located to the north). During flood events, the backwater effect from the railroad bridge would be expected to cause more water to spill on to the F Street agricultural field than if the bridge was not present. However, the backwater condition caused by the railroad bridge existed for many years prior and did not result in a headcut across the field until the Al pit provided a mechanism for cascading flow into it. • Both the Al Pit and Iverson/Martin Marietta Pit are permitted gravel pit operations, approved by Weld County(documentation reviewed for Al Pit)and the State of Colorado Division of Reclamation and Mining Safety, or its predecessor agencies (documentation -- reviewed for Al Pit and Iverson/Martin Marietta Pit). Pit construction and reclamation requirements include measures to provide stabilized topography and to not adversely affect the stability of any significant, valuable, and permanent man-made structure(s) -' located within two hundred feet of the affected land. REFERENCES Documents reviewed for the preparation of this report include the following, organized by agency and date: Weld County Documents Aggregate Industries • Weld County Planning Commission Approval, Case 4USR-978 (August 4, 1992) • Approval of Site Specific Development Plan and Special Review Permit for an Open Pit Mining Operation, 83rd Joint Venture Resource (October 21, 1992) Division of Reclamation, Mining& Safety Documents General Guidance • Title 34 Mineral Resources Article 32 Colorado Mined Land Reclamation Act (1/29/2009)