HomeMy WebLinkAboutWPO202100013 Correspondence 2021-04-28® COLLINS ENGINEERING
April 23, 2021
Frank Pohl, P.E.
Department of Community Development
401 McIntire Road
Charlottesville, VA 22902
RE: Jarman's Gap Development- WPO 20210DO13
20o GARRETT ST, SUITE K CHARLOTTESVILLE VA 22902
��434.293.3719 PH 434.293.2813 FX
www.coll ns-eng ineeri ng.com
Thank you for your comments provided on April 15, 2021 on the above referenced project. Please see the detailed responses below
describing how the remaining comments have been addressed.
A. Stormwater Pollution Prevention Plan (SW PPP)
1. A SWPPP has been provided with this resubmittal.
B. Pollution Prevention Plan (PPP)
1. A PPP has been provided with this resubmittal.
C. Stormwater Management Plan (SWMP)
1. The concentrated outfall downstream from the proposed basin discharges into an existing channel. Please see the photographs in
the attached stormwater management calculations packet for evidence of this.
2. Sheet 6's'OvervieW in the'Stormwo.. _ ement Narrative' was updated to address this comment. All future impervious
areas associated with this subdivision have been accounted for in the calculations packet and the tables shown on sheet 6. The
analysis accounts for a maximum lot impervious area of 25,500 sf, roughly 5,100 sf per lot.
3. The WPO number has been added to the cover sheet, hereby addressing this comment.
4. There are no proposed onsite stormwater quality BMPs, only the onsite stormwater quantity BMP. An offsite best management
practice of purchasing nutrient credits is proposed with this plan. However in efforts to address this comment the VRRM printouts
have been included with the SWM report, inclusive of listing subarea A's managed turf and impervious areas not being treated for
water quality.
5. Sheet 6's'Water Quantity Summary' in the'Starmwater Management Narrative was updated to address this comment. Towards
the end of this subsection, the plans now read' Where proposed improvements & land cover changes occur outside of subarea A,
for example the rear portion of lot 3 & lot 4, the pervious & disconnected impervious areas shall be released in a sheet flow
manner that is not concentrated. Houses on these lots shall have splash blacks at the outlets of their downspouts to prevent
erosion, sedimentation or flooding of down gradient properties.' A detail of the splash block, or equivalent, has been added to
sheet 7 as well.
6. The basin's orientation has been revised and the emergency spillway now releases runoff from larger storm events onto the
subject property, and not directly onto the adjacent property. Furthermore, the runoff will now flow down the proposed
embankment and collect in the existing, downstream channel that is to remain. This will further protect the adjacent property.
And lastly, the revised basin has been enlarged and can now contain the 100-year design storm within the BMP while providing
12" of freeboard.
7. Please see the response above to Engineering's SWM comment 46.
D. Erosion and Sediment Control Plan (ESOP)
1. Please see the response above to Engineering's SWM comment ff6. Also, this plan complies with minimum 9VAC25-870-66 water
quantity requirements. And per 9VAC25-870-66, "Compliance with the minimum standards set out in this section shall be deemed
to satisfy the requirements of subdivision 19 of 9VAC25-840-40 (Minimum standards; Virginia Erosion and Sediment Control
Regulations)."
2. The grades (rise: run) have been added to the areas in question in ESC phases III and IV on sheets 5A and 5B.
Should you have any further questions regarding the pending approval (nutrient credits) of this project, please feel free to contact Graham
Murray at graham@collins-engineering.com.
Sincerely,
Graham Murray, PE