HomeMy WebLinkAboutWPO202000034 Correspondence 2021-04-16 (2)ROUDABUSH, GALE & ASSOC., Inc.
A PROFESSIONAL CORPORATION Sening Virginia Since 1956
15 April 2021
Mr. Frank Pohl
Department of Community Development
401 McIntire Road
Charlottesville, VA 22902
Re: Belvedere Phase 5 VSMP
W PO-2020-00034
Amendment #1
Dear Mr. Pohl,
Amendment #1 of the WPO-2020-00034 is to address the recent discovery of bedrock during
the mass grading and excavation activities at the Belvedere Phase 5 stormwater management
pond.
To limit the amount of potential damage to nearby residences from the blasting required on -site,
the northern embankment of the pond will follow the exposed bedrock. The presence of
bedrock, reduced some 5% of the originally approved pond capacity and to regain it; the top of
dam was raised by 0.3-feet. As the additional grading encroached into the maintenance access
road near the emergency spillway, the road width was reduced to 8.8 feet at the narrowest
section.
Due to the slight loss of pond capacity, the width of the emergency spillway widened from 10-
feet to 15-feet to provide the required 1-foot of freeboard above the 100-year water surface
elevation.
Moreover, due to the bedrock, the terminal pipe run between structure #1 and storm outfall at #0
will be altered. This section has been replaced with a grouted riprap open channel. The pipe
from structure #2 to the new end -section at #1 has a pipe slope running at 0.5% and has been
revised to daylight at the northern bank of the pond. The required pipe capacity and HGL
calculations were revised to reflect the pipe change. The results remain within the design
parameters. The channel will convey water from the outfall into the forebay of the pond. The 6"
underdrain pipe running along the rear to Lots 19 — 28 will daylight into the open channel.
Thank you for your consideration in this matter.
Sinc
9
m Taggart, P.E.
For Roudabush, Gale and Associates, Inc.