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TETRA TECH <br /> January 11, 2017 <br /> Ms. Connie Davis <br /> Aggregate Industries-WCR, Inc. <br /> 1687 Cole Blvd., Ste. 300 <br /> Golden, CO 80401 <br /> RE: Colorado Division of Reclamation and Mining Safety Facility Inspection on July 12, 2016 <br /> (signature date December 14, 2016) and Wright Water Engineers, Inc. Letter to City of <br /> Greeley dated September 2, 2016 <br /> Dear Ms. Davis: <br /> As you requested we have performed and review and evaluation of the above reference documents. Our <br /> work focused on the"Problem/Possible Violation"and "Corrective Actions" presented in the Division of <br /> Reclamation and Mining Safety Inspection Report: <br /> • PROBLEM/POSSIBLE VIOLATION:Problem: The City of Greeley submitted a report titled <br /> "Engineering Evaluation of Nature and Causes of Erosion in Agricultural Field Adjacent to Boyd <br /> Irrigation Company Pipeline and Damage to Pipeline"by Wright Water Engineers, Inc. (WWE) <br /> dated September 2, 2016. A copy of the report was forwarded to the Operator on September 7, <br /> 2016. Aggregate Industries(Al) and their consultant are reviewing the WWE report and are <br /> preparing a response to the report. <br /> • CORRECTIVE ACTIONS: The Division awaits a response from the Operator to the WWE report <br /> and has imposed a 30-day deadline for receipt of the Operator's response. <br /> We began our work by reviewing the Al permit for the facility, specifically looking at the grading and <br /> revegetating of the pit slope in the area of the breach. The permit stipulates that the reclaimed slope shall <br /> be graded to a slope no steeper than 3 horizontal to one vertical (3:1). Topographic data is presented on <br /> Sheet 9 of the Anderson Consulting Engineers March 2011 Preliminary 90% Design Documents for the <br /> Boyd Freeman Ditch...Improvements (2011 Ditch Improvements). The contours indicate a graded slope <br /> no steeper than 3:1 and the topographic elevations of the top of the slope are consistent with the land west <br /> of the pit. Consequently the grading plan is in compliance with the permit. Observations in the field also <br /> indicate reclamation slopes flatter than 3:1. The permit also requires revegetating of the slopes. Reviews <br /> of aerial photograph ground level photos and field observations indicate that the slopes in the area of the <br /> breach were well vegetated prior to the breach. <br /> The WWE report documents that the northwest portion of the pit and the area of the breach is within the <br /> 100-year flood plain. We agree with their delineation of the 100-year flood plain and Al was aware of the <br /> condition. The pit is no closer to the Cache la Poudre River than approximately 1,200 feet. Consequently, <br /> there was no requirement in the permit for armoring of the slopes of the pit or construction of spillways. <br /> The WWE report concludes that sheet flow across the F-Street Agricultural Field became concentrated in <br /> the area of the breach. The concentrated flows resulted in erosion that began with the 2013 flood and was <br /> reactivated in the 2014 flood. We agree that the increased flow velocities led to the erosion of the <br /> reclamation slope, hence the breach of the pipeline and erosion of the F-Street Agricultural Field. <br />