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Ms. Rachel Juba <br />December 1, 2022 <br />Page 3 <br />S:\Users\R_Juba\DEVELOPMENT PROJECTS\Oneka Prairie\Preliminary Plat\Engineers Memo <br />and Red-lined Comments\LTR-r juba-Oneka Prairie Preliminary Plat - 120122.docx <br /> <br /> <br />Wetlands <br /> <br />The Oneka Prairie development requires wetland impact replacement approval to move forward. <br />Based on a Technical Evaluation Panel meeting held on 11/21/22 to review proposed impacts, <br />we anticipate approving wetland impact replacement and boundary and types for Oneka <br />Parkway, but need the applicant to address technical comments provided below. <br /> <br />17. A revised wetland replacement plan has not been provided that accurately reflects the <br />amount of impact for the development nor the construction of Oneka Parkway. <br /> <br />18. The wetland boundaries and types have been approved for the area within the confines of <br />parcel 0703121420001, and a MN Joint Application requesting approval for <br />sequencing/sequencing flexibility and wetland replacement using bank credits for impacts <br />due to the development itself has been noticed (10/27/22) with a 60 day deadline of 12/27/22. <br /> <br />19. A series of wetland impact exhibits have been submitted by the applicant’s team . A figure <br />dated 11-18-22 was submitted on 11-18-22 by Anderson with the correct wetland boundaries <br />drawn. This exhibit was distributed to the Technical Evaluation Panel (TEP) and used for the <br />TEP meeting held on 11/21/22. The most current wetland impact exhibit is dated 11-29-22 <br />and was used for this review. <br /> <br />20. A revised wetland replacement plan identifying all impacts as discussed at the 11/21/22 TEP <br />meeting needs to be submitted in a timely fashion to allow for review; no submittal has been <br />received to date. The 11/29/22 wetland impact exhibit does not include impacts for rip-rap <br />and grading within wetland D/E, outlot A in the northwest corner. <br /> <br />21. A determination needs to be made in regard to the use of retaining walls near wetlands. The <br />TEP indicated that it would be OK to not use retaining walls to prevent additional wetland <br />impact due to the quality of the wetlands. The TEP is requesting a table that shows the <br />amount of impact with and without retaining walls to see the difference it would make. <br /> <br />22. The wetlands on site are most likely a combination of surface water and groundwater fed. <br />Proposed grading and development will alter surface hydrology which may result in regulated <br />impacts to on site wetlands. The TEP would like to see a figure showing existing hydrology <br />(surface flow), the size of existing and proposed watersheds (catchments), and the volume of <br />hydrology routed to wetlands under existing and proposed conditions. <br /> <br />23. Stormwater ponds adjacent to wetlands need to be lined to ensure no horizontal flow from the <br />wetland to the pond resulting in wetland drainage. <br /> <br />24. Initial modeling shows a reduction in the hydrology elevation in some wetlands. This would <br />be considered and impact and would need to be mitigated for. Adding this additional impact <br />may put the amount of wetland impact for the development over the 0.5 acre threshold for the <br />US Army Corps. <br /> <br />25. All stormwater/point hydrology needs to have pretreatment (quality not volume) prior to <br />discharging to any wetland. FES 108 and 309 appear to direct untreated stormwater to <br />wetland D/E. <br /> <br />26. All inverts need to be above the defined wetland boundary elevations so as not to cause <br />drainage of the wetlands.