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4. CMSCWD Permit 18-007 ER_052418Emmons & Olivier Resources, Inc. - 1 - 5/24/18 Carnelian-Marine-St. Croix Watershed District Permit Application Number 18-007 Applicant: Pat Reicherts Big Marine Lake Store 19261 Manning Trail N Marine on St. Croix, MN 55047 614-557-4475 twincitie@yahoo.com Consultants: Todd Shoemaker Wenck Associates 1802 Wooddale Drive Woodbury, WI 55125 651-294-4580 tshoemaker@wenck.com Purpose: Land Disturbance Plan for additions to existing building, expanded parking, and stormwater improvements for Big Marine Lake Store in Marine on St. Croix, MN. Location: 19261 Manning Trail N, Marine on St. Croix. District Rule: 2 & 3 Recommendation: Conditional Approval pending receipt of the following items related to: Stormwater Management 1. Soil boring at the proposed infiltration basin location with a minimum depth of 5-feet below the basin final grade and grainsize (and hydrometer analysis if SM or tighter soils are encountered) for each soil layer. 2. Revised HydroCAD model, and stormwater management plan as necessary, per the following: a. Revised existing conditions model with a CN of 30 for all proposed disturbed areas given onsite soils are HSG A, per Rule 2.5.3(b). b. Revised proposed conditions model with a CN of 44 for disturbed areas proposed to be pervious, per Rule 2.5.3(d). c. Revised existing and proposed conditions models with a distributed CN-value approach; per Rule 2.5.3(c) (i.e. composite curve numbers are not accepted). 3. Field inspection by District Engineer and evaluation of existing stormwater management features given history of Permit 03- 044 and no apparent resolution of deficiencies noted in the file. Permit Application No. 18-007 Big Marine Lake Store Improvements Emmons & Olivier Resources, Inc. - 2 - 5/24/18 4. Revised plan, if necessary, addressing any deficiencies identified in existing stormwater BMPs. Administrative 5. Completion of a draft Declaration for Maintenance of Stormwater Facilities for access to and maintenance of proposed stormwater features (see attached District template). 6. Performance surety in the amount of $4,200 (in cash form). 7. Final Plans signed by Professional Engineer. Stipulations: 1. Contact information for the responsible erosion control contractor/site manager must be provided to the District Administrator prior to initiating work. 2. Notify District Administrator after erosion control is installed but prior to start of construction. 3. All work shall be in accordance with the approved design, plans, computations and specifications on file with the Carnelian- Marine-St. Croix Watershed District and any stipulations identified in this permit. Any proposed revision to grading drainage, landscaping and erosion control plans shall be submitted to the District for prior approval. 4. Applicant is responsible for obtaining all other required permits and approvals for construction of proposed project. 5. Install and maintain silt fence down-gradient from all proposed disturbed soil prior to start of any construction. 6. Upon approval by the District of the draft maintenance agreement, the document shall be executed and recorded at the County on the deed. Submit certified copy to District within 60 days of notice of District approval of draft agreement. Permit Application No. 18-007 Big Marine Lake Store Improvements Emmons & Olivier Resources, Inc. - 3 - 5/24/18 7. Seed and mulch all disturbed soil within 14 days of the end of construction activities. 8. Notify District Administrator after completion of work for final inspection and return of surety. 9. The permittee shall supply an as-built survey within 35 days of project completion. The District shall review this survey as a part of the certificate of completion for the project. Exhibits: 1. Permit Application dated 5/8/18, received 5/8/18. 2. Permit Application fee ($2,500) received from Pat Reicherts, on 5/8/18. 3. Preliminary Plan Set (7 sheets) prepared by Wenck Associates, last revised April 2018, received 5/3/18. 4. Technical Memo prepared by Wenck Associates, dated 4/26/18, received 5/3/18. 5. Soil Profile & Location Map prepared by Wenck Associates, dated 5/10/18 and 5/14/18, respectively, received 5/14/18. 6. CMSCWD Permit File 03-044. Findings: 1. Description – The proposed project entails constructing additions to the existing building, replacing an existing driveway with permeable pavers, expanding the parking lot, and additional stormwater improvements. The site is 2.13 acres in size, with 0.91 acres of existing impervious. The proposed project would result in 0.32 acres of additional impervious surface and disturbance of 0.57 acres. 2. Stormwater Management – It does not appear that the calculation of impervious surfaces followed the definition provided in the CMSCWD Rules in that, by definition, gravel is an impervious surface. Regardless, it is clear less than 50 percent of the existing impervious is disturbed such that the redevelopment criteria is not triggered and the stormwater management criteria apply only to the new and reconstructed impervious surfaces. Stormwater management will be provided through the use of permeable pavers in the northwest corner of the site, which drain to an existing raingarden; and an infiltration basin, which will be graded in the northeast corner of the site and overflows into an Permit Application No. 18-007 Big Marine Lake Store Improvements Emmons & Olivier Resources, Inc. - 4 - 5/24/18 existing dry pond. A 3-foot buffer strip around the edge of the proposed parking lot provides pretreatment for the new lot. The pervious pavers provide pretreatment for runoff from the roof of the new building. Stormwater calculations were developed in HydroCAD, while the buffer strip was analyzed using a P8 model. It appears the stormwater management plan is consistent with District stormwater management standards; however, modeling revisions noted in the pending items are required for review and verification. 3. Erosion & Sediment Control – A satisfactory erosion and sediment control plan has been submitted. 4. Floodplain – The EOF of the proposed infiltration basin and existing dry basin is approximately 976, well below the low entry elevation of the store thereby satisfying District freeboard requirements. 5. Wetlands – Based on the District’s CWPMP wetland inventory, there are no known wetlands on site; District Rule 8.0 does not apply. However, it should be noted that the site drains to a Category 1 wetland (82-211W) east of the site. This wetland is a groundwater- dependent natural resource. Board Action: