#15 - Inwood 8th Add Prelim Plat, PUD & Comp Plan Amend

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Page: 4 STORMWATER MANAGEMENT 1. The proposed development is subject to a Stormwater Management Plan (SWMP) meeting State, South Washington Watershed District (SWWD) and City rules. A SWWD permit is required. 2. The Preliminary Plat/Plans include improvements that reside within the larger Inwood subdivision in which stormwater management provisions have been previously designed, permitted and constructed. The site design will create 10.06 acres of new impervious surfaces, or 52 percent impervious surfaces.  The SWMP must be revised to identify the new impervious surface to be created separately for Outlot O (west parcel) and Outlot A (east parcel) respectively, showing that each Outlot is creating less than the 75% allowable impervious surface.  The Preliminary and Final Plans must identify the existing stormwater ponds used to meet permitting requirements, labeled consistently as referenced in the SWMP. The pond bottom, normal water level and high water elevations must be labeled and identified, including the 100-year HWL contour. Ponds must be labeled as infiltration basin or wet ponds as applicable.  An overall stormwater management plan sheet must be added with a view port that clearly identifies the complete stormwater management system for the proposed Preliminary Plans from the proposed improvements to the existing pond systems. 3. Approval of the Preliminary Plat/Plans for the development is contingent upon all SWMP revisions, as required by the SWWD or other applicable permitting agency, being submitted to the City for review and approval. 4. Approval of the preliminary grading and storm sewer plans for the development is contingent upon all grading plans being reviewed and approved by the City Engineer prior to the start of any grading or construction. 5. Overland emergency overflow (EOF) elevations are required throughout the site, requiring a system of interconnecting drainage ways. Low openings for adjacent structures must maintain 1- foot above any adjacent EOF in the as-built condition.  The grading plans must be revised to incorporate several missing 100-year HWL elevations for localized low points and several missing EOF elevations. 6. Plan revisions may be required to meet City design standards and to mitigate all encroachments. 7. All storm sewer systems internal to the subdivision will be privately owned and maintained. A Stormwater Management Maintenance and Easement Agreement in the City’s standard form of agreement must be executed and recorded with the Final Plat for all privately owned stormwater facilities. Easement areas must incorporate all maintenance access roads, all 100-year high water level areas including localized low points, and to protect all overland emergency overflow locations and flow paths. Easement revisions may be necessary to reflect any revisions to the construction plans. A detailed stormwater management maintenance easement must be submitted as part of the Preliminary Plans to clearly labeled, dimension and detail the easement area. 8. The Grading Plans must be revised and detailed to demonstrate minimum 2% grade is attained throughout the site in the as-built condition, including the northwest corner of Lot 1, Block 1. 9. The Grading Plans must be further detailed by labeling all existing contours and adding spot elevation call-outs at each tie-in location along the public right-of-way for 5th Street and Island Trail. Plan notes must also be added to require all grading work to match into the existing public right-of-way grades. All silt fence and tree protection fence must be noted to be field staked and placed at least 1-ft. inside of the right-of-way to eliminate right-of-way impacts. 10. Revise the Grading Plans along the south property line of the east parcel to maintain the existing drainage swale at the property line.