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Two of the double 10'.-10' X 4' con'~rete box culverts under north bound Interstate Highway 25 would be E~xtended underneath the planned east to north [(Imp. The existing 24 inch diameter corrugated metal pipe culvert which drains irrigation flows under the existing frontage road and north bound Interstate Hi9hway 25 to the median ditch would be maintained. A 24 inch diameter reinforced concrete pipe culvert would be ext<e,nded undE~r both the planned north to east interchange ramp and the relocated frontage road to drain irrigation return flows from the area northeast of the planned interchange. The existing 24 inch diameter cross culvert under the Larimer County Road 50 embankment Illest of Interstate Highway 25 would be extended to the north to drain the area bounded by the south to west ramp and south bound Interstate Highway 25 to the south. A 24 inch diameter reinforced concrete pipe cross culvert would be provided under the west to soul:h r.~mp to drain storm runoff from the area bounded by the w,~st to south ramp and south bound Interstate Highway 25 to the south west to the roadside ditch along the west side of Interstate Highway 25. A 24 inch diameter reinforced concrete pipe cross culvert would be provided under the north to east ramp to drain storm runoff from the area bounded by nQrth bound Interstate Highway 25 and the north to east ramp tQ th,e south east to the roadside ditch between north bound Interstate Highway 25 and the existing frontage road. 6. .cQN.cL.!.!.sIQNS_ANLLE~.cQMM~Nj;)AnQnS Under existing conditions, during the lOO-year spill frClm Boxelder Creek of 3320 CFS, approximately 1261 CFS would flow to the south via the 1-25 median ditch, 1303 CFS would flow to the south via the existing frontage road and norhbound lanes of 1-25 and 756 CFS would overtop Larimer County Road 50 east of 1-25 and flow to the south. The anticipated 100-year 1-25 median ditch flow of 1261 cfs is the sum of 30 cfs from the 24 inch diameter culvert beneath the emergency vehicle median turna.round located nor th of Larimer County Road 50, approximately 1100 CFS from the existing concrete box culverts under northbound 1-25 and approximately 131 CFS from overtopping of northbound 1-25. Under conditions associated with the planned interchange, during the 100-year spill from Boxelder Creek of 3320 CFS, approximately 1130 CFS would flow to the 1-25 median di1:ch by means of the existing concrete box culverts (extended) 19