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HomeMy WebLinkAboutWPO201900051 Correspondence 2023-03-10.00000� 0 T I M M O N S GROUP suit00 Preston Avenue F 434.295.8317 YOUR VISION ACHIEVED THROUGH OURS. Charlottesville, VA22903 www.timmonscom January 12, 2023 Dan Ratzlaff Albemarle County Department of Community Development 401 McIntire Road Charlottesville, VA 22902 Scottsville BMP and Pond As -built Certification —Scottsville Elementary School Addition (WP0201900051) Dear Mr. Ratzlaff: We received the attached as -built survey performed by Draper Aden Associates, seal date 10/14/2022 by Cheryl Stockton. We have compared this with the approved Plans from the September 13, 2021. The pond and Bioretention size and shape appear to be in general conformance with the design. The elevations of the bottom of the Biorentetion and dry pond and their risers and control structures were compared to the plan and the appear to be in general accordance with the approved plan and design. For Bioretention Facility 1 while the floor of the basin's ponding area is higher than plan the riser has been set higher as well so that the required 0.73' of ponding is achieved. For Bioretention Facility 2 there is at least 0.5' of ponding provided from the floor of the Bioretention ponding area to the top of the riser to provide the required ponding. For the Dry Pond the invert out of the structure and the 1-year outflow orifice have been set about 2" lower than the plan which will give more room for detention of smaller storms before the 10-year notch in the structure is engaged. The rectangular notch for the 10-year storms is about 0.5" lower than the plan with the correct width. Given the width of the notch being correct and the 1-year orifice being set lower as well we expect this pond will function in general accordance with the approved plans and design. Please let me know if you have any questions or concerns. Sincerely, Jonathan Showalter, PE Timmong Group 608 Preston Avenue, Suite 200 Charlottesville, VA 22903 ionathan.showalteraa timmons.com 434.327.1681 CIVIL ENGINEERING I ENVIRONMENTAL I SURVEYING I GIs I LANDSCAPE ARCHITECTURE I CONSTRUCTION SERVICES