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Ms. Katie Larsen 12/03/2025 Page 4 7. Provide calculations demonstrating spread at the catchbasins is 10’ or less for the 3- year storm event. Hill (11/10/2025) Spread calculations will be provided with final plans. WSB (12/3/2025) Noted, remains an open comment. 8. Rational method pipe capacity calculations must be provided showing storm sewer is sized to convey the 10-year storm event and flow velocities are minimum 3 ft/s. Hill (11/10/2025) Included with this submittal as requested. WSB (12/3/2025) Capacities are demonstrated sufficient. Recommend reducing slope on pipe between STM-122 and STM-121, velocities over 10 ft/sec may cause scouring long-term. 9. Confirm constructability of connecting proposed storm outlets into the existing trunkline risers. Hill (11/10/2025) Connection design will be included with the final design. WSB (12/3/2025) Noted, remains an open comment. 10. As the proposed ACD 72 ditch realignment will no longer need to provide subsurface drainage, nonperforated pipe can be specified in order to reduce loading to the tile. Hill (11/10/2025) ACD 72 is no longer required; the draintile will be abandoned in- place and/or removed. 11. Pending anticipated development, flows from area 41X/S can be eliminated as proposed drainage on that site is planned to route to the southeast rather than the west. 12. Impervious area calculations should be based on actual site impervious, not the percentages in HydroCAD land use types. Hill (11/10/2025) Revised as recommended. a. Confirm the source of the 1,398,711 square feet of impervious in the SWMP. 13. Pond areas 2.5a and b should each be sized for NURP dead storage volumes separately according to their tributary areas. Pond flows only combine through Wetland 10 so undersized dead storage may contribute pollutant loading to the wetland. Hill (11/10/2025) Each dead storage cell has been sized for its receiving area. Pond 3, which is down stream of Pond 4, has dead storage to accommodate the drainage area to both Ponds 3 & 4. 14. Please include node summary sheets on future HydroCAD reports so total modeled areas can be confirmed in existing and proposed conditions. Hill (11/10/2025) Included in the report appendix as requested. 15. The 4.1X and 4X existing conditions HydroCAD subcatchment areas do not match the drainage area map. 16. The culvert modeled as 2XP/2P is a 21” CMP, not 18” RCP. Hill (11/10/2025) Revised as recommended. WSB (12/3/2025) The 21” pipe is modeled with an 18” orifice. Please clarify if this is an existing feature or intended to be constructed. 17. The outlet for 41XP/41P should be modeled with a pipe outlet, not just an orifice. Peltier Ponds Development - Engineering Review