01-18-2018
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01-18-2018
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7 <br /> <br />for approximately 5.5 miles and ties into existing high ground in Section 36 of Holy Cross <br />Township near Clay County Highway 50. <br />o This component reduces the acreage of newly impacted floodplain in Minnesota and was <br />recommended by TAG. It was included in all of the options that were presented. <br /> <br />• Northern Storage/Diversion Channel Alignment – In an attempt to lower the staging area <br />elevation and have more balanced impacts, the Task Force recommended storing more <br />water in the northwest portion of the flood damage reduction area. Instead of increasing the <br />size of the aqueducts to pass more water into the lower Sheyenne and Maple Rivers (which <br />would be very costly), changing the diversion alignment was evaluated. This change would <br />have the potential to preserve more existing floodplain. An alignment change that shifts the <br />project east between the BNSF Prosper Subdivision rail line and Interstate 29 was <br />considered and presented. This shift preserves approximately 1800 acres of existing <br />floodplain, but only reduces the 100-year elevation in the staging area by 0.03 feet. Other <br />options to shift the alignment further east were considered, but were not analyzed further <br />due to existing residential developments and structures and the multiple river and roadway <br />crossings in this area. <br />o The TAG was neutral on this component due to the limited reduction in the staging elevation it <br />provided and it was not included in any of the options that were presented. <br /> <br />• Additional Flows Through Town – The TAG presented information on the impacts of <br />increasing the flow through town from RS35’ to RS37’, RS38’, and RS39’. Results were <br />presented using the proposed project alignment. <br />o The TAG recommended that a flow through town that results in a RS37’ during the 100-year <br />flood event be carried forward and RS37’ was used for all of the options that were presented. The <br />communities will have to construct additional protection to manage the additional flows through town <br />associated with RS37’. <br /> <br />• Allow Downstream Impacts up to 6 inches – The TAG evaluated and presented options for <br />changing the project operation to allow up to a maximum of 6 inches of downstream impact <br />to achieve a balance between upstream and downstream interests. The 6-inch maximum <br />impact would occur on the Red River in the vicinity of the city of Climax, MN, where the <br />floodplain is relatively narrow. Analysis was performed for Options 7A, 7B, and 7C and the <br />change results in a maximum staging area reduction at the dam of 0.3’ to 0.4’, depending on <br />the option. Concerns with this component include potential impacts extending beyond the <br />U.S./Canadian border and potential downstream mitigation costs associated impacted <br />residential structures and existing community flood protection systems. It may be possible <br />to allow downstream impacts less than 6 inches without causing an impact across the <br />U.S./Canadian border. This was not an analysis that TAG completed. <br />o The TAG identified this is a policy/permit decision that will be evaluated more going forward. <br />This is an operational issue and does not directly impact design considerations. <br /> <br />• Change Location of Dam/Southern Embankment – The TAG developed and evaluated 3 <br />alignment options for the dam/southern embankment. These alignments all shift the dam <br />north (from the proposed project alignment) and added storage in North Dakota. Option <br />7A is very similar to Component 3c that was presented at the November 29, 2017 Task <br />Force meeting and shifts the alignment north to the west of Interstate 29 and adds
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