HomeMy WebLinkAboutWPO202200040 Correspondence 2023-03-10 (2)® COLLINS ENGINEERING
March 3, 2023
Emily Cox, PE
Department of Community Development
401 McIntire Road
Charlottesville, VA 22902
RE: Brookhill Archer Avenue Extension VSMP Plan (WPO 202200040)
200 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 dated November 1, 2022 on the above referenced project. Below are our
detailed responses to your comments. Should you have any questions during your review and approval of
this project, feel free to contact Graham Murray at graham@collins-engineering.com or Scott Collins at
scott@collins-engineering.com .
A. Stormwater Pollution Prevention Plan (SWPPP)
1. Yes, this project wants it's own DEQ permit.
2. An updated Brookhill permit coverage map is included with this submittal in the SWPPP report.
3. Acknowledged.
4. The registration statement and certification have been signed by the operator.
B. Pollution Prevention Plan (PPP)
1. PPP exhibits are included with this submittal in the SWPPP report for each ESC phase.
C. Stormwater Management Plan (SWMP)
1. The Applicant kindly requests this comment be reconsidered. A proposed road plan has been
submitted corresponding to this WPO plan. It's the Applicant's understanding a WPO plan can be
submitted with a rezoning plan and that the submitted road plan does not require a preliminary
plat, though it does require a WPO plan.
2. This comment is acknowledged. Once VDOT has narrowed their comments further, and the
Applicant feels limited revisions will be forthcoming to the proposed road plan, this information will
be provided to the board of supervisors.
3. This comment is acknowledged. Please also see the response above to SWM comment #2.
4. This comment is acknowledged. Please also see the response above to SWM comment #2.
5. The existing VDOT stormwater management (SWM) facility is not being utilized with the
construction of the Archer Avenue extension. Minor adjustments are proposed however in the
vicinity of the VDOT SWM facility, as shown with the fence relocation in places and the road's tie-in
grades adjacent to the facility. This information, as depicted in the Archer Avenue Extension Road
SUB 202200142 plans, was submitted to VDOT on September 6, 2022. Following this submittal, on
October 5, 2022, VDOT issued comments on the road plans. These comments gave no indication
that VDOT would object to the proposed modifications adjacent to their SWM facility.
6. A letter of availability has been provided with this plan. Please note, the proposed SWM plan
requires a nutrient credit purchase of 1.00 Ibs/yr of phosphorous and the letter of availability is for
1.10 Ibs/yr. This 10% overage is intentional to provide some flexibility should the removal rate
required change in subsequent submissions, though the actual amount of credits purchased will
equal the WPO plan's final approved removal rate prior to the issuance of a land disturbance permit.
7. The Microsoft Excel spreadsheet used to create the data shown on sheet 13 has been provided with
this submittal.
8. Sheet 1 has been revised to include a note prohibiting the contractor from installing the 72" culvert
beneath Archer Avenue's extension until VDOT has approved it. This is located in the bottom -center
portion of the page.
9. A sheet flow analysis for the roadway's embankment has been added to the attached SWM
calculations packet dated 3/3/23. This 2-page sheet flow analysis can be located within the ' 9VAC
25-870-66 Channel & Flood Protection Analysis 'section. This analysis is consistent with the general
guidance provided to Collins Engineering in a meeting held on March 2, 2023 between Ms. Cox of
County Engineering and Graham Murray of Collins Engineering.
10. Sediment trap #3 was revised and its bottom elevation (438') is now 2' higher than the detention
basin's bottom elevation (436').
11. Sheet 10 has been revised to more clearly show the recorded forest and open space easement areas
from blocks 9-11. The labels on this sheet for these areas were also updated to reference the
instrument number 202200001747.
12. The name for Detention Basin 4 has been revised to be Detention Basin V. Similarly, Level Spreader
4 and has been renamed Level Spreader 'C' for consistency.
13. The proposed structure A5, best viewed on sheet 11, has been revised to be 15" in diameter to
address this comment. Please note, the drainage pipes conveying the water quality treatment
volume (structures AS and A3) continue to be restricted to a 6" diameter (structure A3) to prevent
overburdening the filter strip and Level Spreader V. In other words, this comment has been
addressed with the diameter increase in structure AS without compromising the SWM design.
14. Structure A4 has been revised to be a MH-1 (48" I.D. manhole) to assist with maintenance and
access.
15. Sheet 11 has been revised to better depict the level 10' wide top of dam surrounding 2 of the 3 sides
around Detention Basin V. The fence already surrounding the VDOT SWM Facility, which is already
being relocated with the proposed plans, has been adjusted with the resubmitted plans. This
adjustment now borders the third side of Detention Basin V. In the aforementioned March 2""
phone conversation, it was determined this fence realignment and the flat top of dam surrounding
much of Detention Basin C's perimeter was an acceptable method for addressing this comment.
16. The staking of the filter strip's location is being set up. Once the location has been staked the
Applicant will contact County Engineering for a meeting onsite.
17. This comment is acknowledged. Also, sheet 11 shows and labels the'Proposed Conserved Open
Space Easement.
D. Erosion and Sediment Control Plan (ESOP)
1. Collins Engineering field verified the site on March 2, 2023. The 'Topography & Survey' note shown
on sheet 1 has been updated accordingly.
2. Sheet 2's labels for Blocks 9-11 and Block 9's pond and drainage system have been updated
accordingly to address this comment.
3. Sheet 14 of the plans has been added to this set to show all applicable buffers, in accordance with
the code of development 2.4.2, page 19.
4. The years in the Erosion Control Notes & Narrative 'Project Description' subsection, shown on sheet
3, were updated to address this comment.
5. The erosion and sediment control (ESC) and SWM plan sheets have been updated to label the
acreage associated with the limits of disturbance expansion.
6. The 'Culvert Installation Notes' shown on sheet 4 have been updated to include information from
sheet 3's sequences of construction notes #6 and 7. Also, the notes in sheets 3 and 4 have been
updated to further define the fill material required over the culvert for crossing with earth moving
equipment.
7. The proposed plan is not a balanced site and it will require fill. Sheet 6 has been updated in the
upper -left corner to state this, and to list the estimated cubic yards of fill and cut required.
8. The Applicant kindly requests this comment be reconsidered since the WPO 202000004 ESC and
SWIM designs are not impacted from this proposed plan. The Applicant feels the modification is
limited to the storm sewer design and that this can be handled with the proposed SUB 202200142
currently under review.
9. Sheet 4 has been revised to state the riprap size at the transition points.
10. Minimal runoff is draining to sediment trap #3 in ESC phase I. Sheet 4 has been updated to now
show and label this area.
11. The drainage area label to sediment trap #1 on sheet 4 has been updated to read 'sediment trap #1',
and not the previously incorrectly labeled 'sediment trap #2'.
12. Sheets 4-6 have been updated to include a sign and label requiring the Contractor to install a sign
reading No Construction Traffic to Enter/Exit Ashwood Blvd.
13. Sheet 7 has been revised and sediment trap #3 is now sized for a 1.47 acre watershed.
14. Sediment trap #3 has been revised. In order to address this comment, and SWIM comment #10, the
bottom of the sediment trap was raised. The wet storage shown on sheet 7's Sediment Trap #3
De 1 computations now provide a wet storage depth of 4'.
15. Baffles have now been added to all three sediment traps. Please see sheet 7's sediment trap details,
and the detail in the bottom -left corner for specific information.
16. The silt fence locations have been modified to be located a minimum of 5' from the base of the
disturbed slopes. Please note, during construction the location of the limits of disturbance, limits of
clearing, tree protection and silt fence will all coincide. However for plan production clarity
purposes, these lines are offset making the separation between the silt fence and the base of the
disturbed slopes appear closer than they will in reality. Please also note, sheet 4 has been updated
in the upper -left corner to mandate the Contractor install 2 rows of super slit fence along the
perimeter.
17. The filter strip is now shown on sheet 6, along with a note reading Proposed level spreader, filter
strip & upland storm sewer shall be installed in ESC Phase Ill. Filter strip shall be stabilized with
permanent seeding. The storm sewer immediately upland of the level spreader shall not be activated
until the SWM riser is activated, which shall only occur after complete stabilization of the site, the
stabilization of the level spreader, the conversation of ST#3 to a permanent SWM facility and ESC
Inspector approval.
Sincerely,
Graham Murray, PE