HomeMy WebLinkAboutWPO201700019 Certified Engineer's Report 2019-10-03TIMMONS GROUP
YOUR VISION ACHIEVED THROUGH OURS.
October 3, 2019
David James
Albemarle County
Department of Community Development
401 McIntire Road
Charlottesville, VA 22902
608 Preston Avenue P 434.295.5624
Suite 200 F 434.295.8317
Charlottesville, VA 22903 www.timmons.com
Scottsville Pond As -built and updated calculations —Scottsville Elementary School Security and
Improvements (WP0201700019)
Dear Mr. James:
We received an as -built survey from JL Surveying, LLC titled "Drawing Showing Storm Pond Scottsville
Elementary School' and dated 7/29/2019. We have compared this with the approved SWM Plan C6.0
from the May 3, 2018 approved VSMP plan. The pond size and shape appear to be in general
conformance with the design.
Item of note: The volume at elevation 392 of 3,884 SF seemed too high to be reasonable. Per an email
with Jeffrey Lavelle of JL Surveying on 8/2/2019 it was found to be a typo and corrected to be 2,884 SF.
This is shown in the markup of the as -built provided in the record drawings.
Notable discrepancies between the as-builts and the design are as follows, the volumes from the survey
vary slightly from the design and the top of the riser structure was a few inches higher than the design.
The storm calculations were rerun accounting for these discrepancies and the changes in 2- and 10-year
flows and pond elevations are marked up in red on record drawing version of sheet C6.0. As those
markups show and per the summary below the 1-year and 10-year routed flow are still less than the
required maximum allowable flows required by the Channel and Flood Protection regulations.
Post Developed Maximum allowed 1-year flow = 3.83 CFS
As -built post developed flow = 3.81 CFS
Post Developed Maximum allowed 10-year flow = 13.07 CFS
As -built post developed 10-year flow = 11.65 CFS
Therefore, the pond functions to meet the Channel and Flood Protection regulations in the as -built
condition.
Sincerely,
Jonathan Showalter, PE
CIVIL ENGINEERING I ENVIRONMENTAL I SURVEYING I GIs I LANDSCAPE ARCHITECTURE I CONSTRUCTION SERVICES