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Request for Permit- Floodplain Development Application Y-81 Kegonsa-Sun Prairie Rerate Project Page 3 Dane County,Wisconsin g 1.4 Summary of Floodplains Three general areas were identified where planned construction activities intersect the floodplain or floodway; all three areas are in association with Koshkonong Creek. These areas include the following: • Structure 386 and associated access off CTH N: Cross section flood elevations in this area range from 903.7 feet to 903.8 feet. Structure 386 is located in the floodway. (FIRM 55025CO289H, effective 9/17/2014) • Structures 399 — 401 and associated access off CTH N and CTH T: The mapped baseflood elevation in this area is 907 feet. Structure 400 is located in the floodway. (FIRM 55025CO289H, effective 9/17/2014) • Structures 446 — 449 and associated access off Bird Street: The cross section flood elevation in this area is 920 feet. Structures 446 — 449 are located in the floodway. (FIRM 55025CO286H, effective 9/17/2014) 2.0 Construction Activities 2.1 Summary of Construction Activities Construction involves access and rerating the existing 69 kV Y-81 transmission line between the Kegonsa and Sun Prairie Substations to a thermal rating of 200°F for all seasons. Specifically, this permit application requests authorization for the following activities to occur in the floodplain and floodway of Koshkonong Creek: • Replace four (4) structures (Structures 446 — 449) in the floodway of Koshkonong Creek • Reframe two (2) structures (Structures 400 and 386) in the floodway of Koshkonong Creek. • Reframe two (2) structures (Structures 401 and 399) in the floodplain of Koshkonong Creek. • Access structure reframes and replacements across the floodplain and floodway of Koshkonong Creek; install temporary construction matting as necessary. No impacts or alterations to waterways are anticipated. New structures will be anchored in accordance with industry standards to prevent flotation, collapse, or lateral movement from hydrodynamic or hydrostatic loads. The materials will be flood-resistant and will be constructed to ensure that the utility structures will withstand flooding. Specific activities related to construction are described in Section 2.2. Plan and profile drawings of the proposed activities are included as Attachment 3. 2.2 Floodplain and Floodway Impacts All proposed floodplain and floodway activities are located in Zone AE; refer to Figure 2 for a visual depiction of proposed floodplain and floodway activities relative to the FEMA-mapped Zone AE boundaries, and to Attachment 2 for the FEMA FIRM figures. There will be no new permanent impacts to the floodplain; the proposed activities will not cause any increase in the regional flood height due to floodplain storage lost, and there will be no new obstructions to flow. Reframe activities will occur near the top of the existing poles, and will be above flood elevation. Structure replacements will be pole-for- pole, meaning that for each new pole that is installed an existing pole will be removed. • gai consultants D160245.00/March 30, 2017