HomeMy WebLinkAboutWPO202000034 Correspondence 2020-10-30®ROUDABUSH, GALE & ASSOC., Inc.
A PROFESSIONAL CORPORATION Serving Virginia Since 1956
County of Albemarle
Mr. Prank Pohl, P.E., County Engineer
Via Email
October 30, 2020
Re: Request for Waiver
Belvedere Phase 5A VSMP Submittal
Energy Balance Compliance
Stormwater Facility Orifice Size
Mr. Pohl,
Thank you for your consideration of this matter. Per Energy Balance standards of the Virginia
Stormwater Management regulations, the orifice for Dry Pond No. 1 (Conversion from Sed Basin no.
1) was developed to limit hydraulic release from the stormwater facility. That allowable flow was
reached using an orifice (bored into the riser) of approximately 1 inch diameter.
It is our recommendation that this orifice be enlarged to 3" in an effort to protect the facility from
failure due to likely clogging of the smaller orifice. In our experience, limiting such constrictions to
3" helps minimize clogging while still providing substantial attenuation to the flows.
Enlarging the orifice to 3" will increase the potential flow from some 0.14 CFS to 0.49 CFS.
Please advise on your acceptance or rejection of this waiver request. Again, we appreciate your
consideration.
Sincerely,
CZ/A
dim Taggart, P.E.
For Roudabush, Gale and associates, Inc.
®R
imy L. Taggart
No. 022841
/d• F0_2020
999 Second Street SE. Charlottesville. VA 22902. www.Roudabush.com