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Mr. Roger Schmidt <br /> March 15, 2017 <br /> Page 8 <br /> pipeline was designed by a competent engineer with additional oversight during <br /> construction provided by the pipe manufacturer. <br /> • The removal of the 15-inch CMP that resulted in uncontrolled overtopping of the <br /> reclamation slope <br /> WWE comment: <br /> The capacity of a 15-inch diameter corrugated metal pipe (CMP) (roughly 3 to 4 <br /> cfs in this installation) is not significant compared to the flow rate across the field <br /> when the Cache La Poudre River overtopped its banks in 2013 and 2014 (likely <br /> several hundred cfs). Neither the presence nor the absence of a 15-inch CMP <br /> would have made a difference in terms of the embankment being overtopped <br /> when major flooding is occurring in the Cache La Poudre River floodplain. <br /> Tetra Tech letter,p. 2, last paragraph, last sentence: <br /> "The reclamation slope in the area of the breech should be armored to protect from future <br /> floods. " <br /> WWE comment: <br /> We agree that the reclamation slope should be armored to protect from future floods. <br /> Armoring the slopes of gravel pits for protection from erosion if susceptible to flooding is <br /> consistent with design criteria developed by the Urban Drainage and Flood Control <br /> district (UDFCD) for gravel pits located in floodplains. However, instead of limiting the <br /> armoring to the area of the existing breach, the extent of the armoring should be <br /> determined based on the projected flow rate for a specific design storm event. <br /> Consequently, the extent of the armoring on the reclamation slope may need to extend <br /> beyond the current breach opening. In addition, the areas of erosion damage on the F <br /> Street Property also need to be filled in and repaired. <br /> WWE appreciates the opportunity to provide responses to comments received regarding the <br /> nature and causes of erosion that resulted in damage to the pipeline and the adjacent agricultural <br /> field. This response letter has been prepared based on the information listed above, information <br /> gained from our field visits and discussions with City of Greeley personnel familiar with the site, <br /> and from discussing the project with the engineer responsible for the pipeline's design and <br /> construction. If additional information becomes available, we may need to update our findings. <br /> Please feel free to contact us with any information regarding this report. <br />