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Ms. Katie Larsen 3/4/2026 Page 2 nd Stormwater management for the Otter Crossing South 2 Addition development is proposing to use the existing City stormwater pond south and east of the project area to provide rate control and water quality treatment. There is a conservation easement for a wetland bank that exists over the existing City pond. Analysis includes a proposed City th roundabout on Otter Lake Road south of 70 Street. Runoff will be routed via the existing storm sewer system along the roadway. nd Future phases of development will provide onsite stormwater management. 2 Addition flows ultimately discharge to the west for a small northern portion of the site and the rest discharges south to Clearwater Creek from the City pond. Additional lots and a future roundabout in Otter Lake Road are included in the drainage area to the existing stormwater pond. These areas were included in the original study prepared by TKDA with 1998 Otter Lake Road improvement project. This pond has capacity to provide stormwater management for the development. The pond existing and proposed discharge rates are summarized below. Pre- and Post- Development Discharge Rates (cfs) 2-10-Day Condition10-Year100-Year YearSnowmelt Existing - Creek15.0023.2456.26N/A Proposed - Creek10.3513.6640.14N/A Existing - West5.5910.1527.00N/A Proposed - West3.976.5120.40N/A Existing – 8.7218.6941.10N/A Southeast (wetland) Proposed – 8.7218.6941.10N/A Southeast (wetland) Comments: 1.Clarify the extents of what will be constructed as part of the 2nd Addition and what will be constructed as part of the individual lot developments. 2.Applicant to verify through RCWD existing City pond use in the conservation easement, see below. 3.Per the 2024 RCWD rules, stormwater ponds designed in accordance with NURP criteria satisfy stormwater management requirements. The proposed filtration bench is not needed and should be removed to simplify future maintenance of Pond 2P. a.While implied in the details, show the location of the proposed riprap- stabilized spillway for the pond in the plan view. 4.Without the proposed filtration bench, the new proposed outlet through OCS-2 shall be removed. Rate control should be achieved for the updated design via alterations to the existing outlet structures. The NWL of 900 must be maintained. 5.Applicant to confirm if storage curves of Pond 2P in HydroCAD are based on as-built or surveyed depths. If surveyed, include bathymetry linework in SWMP for verification. 6.Original permitted drainage areas and stormwater calculations for Pond 2P shall be included as an appendix to the SWMP. nd Otter Lake South 2 – Engineering Review