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<br />H:\LKELMN\N15110350\Highpointe Crossing\Correspondence\110350 Draft Stormwater Comments HighPointeCrossing Development <br />2024-06-25.docx <br /> <br />MEMORANDUM <br /> <br />Date: 06/25/2024 <br />To: Cara L. Geheren, P.E. <br />From: Brent Johnson, P.E. <br />Subject: High Pointe Crossing Development Plan Review <br /> City of Lake Elmo, MN <br /> Project No.: N15.110350 <br /> <br />This memo summarizes the review of stormwater related documents submitted by James R. Hill, Inc., <br />received 06/18/2024. The submittal included plans, stormwater narrative, and storm sewer design <br />information: <br /> <br />• 02-Highpointe Crossing-Preplat Submittal 2024-06-06.pdf <br />• 03a-Highpointe Crossing – Stormwater Narrative 06-05-24.pdf <br />• 03b – Existing Drainage 06-05-24.hcp <br />• 03c – Proposed Drainage 06-05-24.hcp <br />• 03d-Highpointe Crossing – Existing HydroCAD 06-05-24.pdf <br />• 03e-Highpointe Crossing – Proposed HydroCAD 06-05-24.pdf <br />• 03f -Highpointe Crossing – 10Yr Storm Design 06-03-24.pdf <br />• 03g- Highpointe Crossing – 10Yr Storm Map 06-03-24.pdf <br />• 03h- Highpointe Crossing – NURP 1P 06-05-24.pdf <br />• 03i- Highpointe Crossing – NURP 2P 06-05-24.pdf <br />• 03j- Highpointe Crossing – VBWD Calculator 06-05-24.pdf <br />• 10 - 23-01-13-Highpointe Crossing WCA Delineation – Notice of Decision. Pdf <br />• 12 – 22-03-26 Highpointe Crossing – Haugo Geo Report Bundle Final.pdf <br /> <br />1. Curve Numbers: Existing ag cropland areas are modeled in HydroCAD with a curve number of 72 <br />(for conditions of small grain, straight row and crop residue (SR + CR), good condition, HSG B). <br />Proposed conditions pervious areas are generally modeled with a curve number of 61 ( for <br />conditions with greater than 75% grass cover, good condition, HSG B). These existing and <br />proposed conditions pervious area curve numbers don't quite comply with Valley Branch <br />Watershed rule requirements: <br />“The runoff curve number for existing agriculture areas shall be less than or equal to the <br />developed condition curve number.”1 <br />Please adjust the HydroCAD curve numbers to comply with the watershed district rule or explain <br />the reasoning. <br /> <br />1 Valley Branch Watershed District Rules, Rule 2 Stormwater Management Standard 5, 2-9-2023