HomeMy WebLinkAboutWPO201700058 Review Comments WPO VSMP 2018-04-19 PROJECT ME sHimp CIVIL ENGINEERINGNAGEMNT
LAND PLANNING
ENGINEERINGa
April 19, 2018
Mr. David James
Department of Community Development
401 McIntire Road
Charlottesville,VA 22902
Regarding: WPO 2017-00058—Sparrow Hill VSMP Amendment Comment Response
Dear David,
Thank you for your review of the third revision of the VSMP Plan for Sparrow Hill. We have revised the
plan per the your most recent comments emailed April 18, 2018. See below for detailed responses to each of your
comments.
SWMPA
1. It appears that the culvert crossing(SC) and the utility crossing (USC) are happening in the same
location. How do you plan to perform trenching operations while the culvert crossing is in place?
The culvert crossing will be constructed first as the sanitary sewer is built uphill from the RWSA
connection. This requires vehicles to first cross the stream using the temporary culvert crossing.
However, per your comment we have amended the utility installation crossing type to achieve less
linear disturbance this location.The utility installation shall now utilize a flume type crossing so that the
sanitary can be installed under the 48" culvert crossing. We believe this is the most direct and reliable
strategy for the utility crossing.
2. Show the length & slope of culverts,width of the channel crossing,and alignment,
Information added to plans
3. Include the Construction Specifications& Maintenance for the Temp. Culvert Crossing on the plans
(E&SC HB 3.24, III-226).
Information added to plans.
4. Include the Construction Specifications& Maintenance for the Cofferdam Utility Crossing on the plans
(E&SC HB 3.25, III-235).
Information added to plans.
5. Certify calculations
Calculations are now certified. RECEIVED
APR 2 0 2018
COMMUNITY
Page 1 of 2 DEVELOPMENT
Included with this letter you will find 2 copies of the Amendment and 2 copies of the calculation packet. If
you have any questions or concerns about these revisions please feel free to call me at (434) 227-5140 ext. 3 or
email Justin Shimp at Justin@shimp-engineering.com and we can discuss any questions that you may have in
further detail.
Best Regards,
Keane Rucker, E.I.T.
Shimp Engineering, P.C.
Page 2 of 2
Sparrow Hill
Stream Crossing Flow Calcs
Impervious C 0.9
Pervious C 0.3
To Crossing Area (sf) Im 8 ervious C A
A C TOC Intensity 10-Yr Flow
(ac) (min) (in/hr) (cfs)
3 4 7 8 9
. ' 1+� 4
1 ,. .ter �' ;,.-' .; �V s ._ .a...- .:. 7097407*
Note:TOC taken from Site Runoff Calculation for conservative design.
Drainage Area Calculated from County GIS topo.
SPARROW HILL VEHICULAR STREAM
CROSSING 10 YEAR CULVERT SIZING
Chapter 8-Culverts
Appendix 8C-1 Inlet Control,Circular Concrete
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Keane:
Based on your submitted drawing (excerpted below),the use of self-tapping screws on the Contech
ALT2 Perforated CMP system shown will not present a significant structural problem, provided these
self-tapping screws are spaced no closer than every 2' along the lower circumference of the pipe and
spaced no closer than 2' along the length of this pipe. NOTE also that this pipe should be 12 gauge in
thickness.
I would be happy to discuss Contech options for pretreatment of infiltration systems at our meeting next
week. Attached are a few choices, with our HDS units being the best.
PRETREATMENT CELL FILTER Se i . _ Tip(''",
FABRIC DETAIL MM
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I,.
Glen Payton, CPSWQ
Stormwater Consultant, western VA, GA &AL
Contech Engineered Solutions LLC
804-937-3228
cipayton(c�conteches.com
www.ContechES.com
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