HomeMy WebLinkAboutWPO201800030 Correspondence 2018-07-24a4a4*,*0
TIMMONS GROUP
YOUR VISION ACHIEVED THROUGH OURS.
WW Associates
County of Albemarle
Dept. of Community Dev.
401 McIntire Rd.
Charlottesville, VA 22902
608 Preston Avenue P 434.295.5624
Suite 200 F 434.295.8317
Charlottesville, VA 22903 www.timmons.com
RE: Charlottesville Albemarle SPCA — VSMP Permit Plan Review — WP0201800030 -
Comment Response Letter
Dear WW Associates:
We have reviewed all of your comments from June 1, 2018 and made the necessary revisions.
Please find our responses to the comments below in bold lettering.
A. Stormwater Pollution Prevention Plan (SWPPP)
The SWPPP content requirements can be found in County Code section 17-405. A SWPPP
must contain (1) a PPP, (2) an ESCP, (3) a SWMP, and (4) any TMDL measures necessary.
1. Please add WP0201800030 to the cover sheet of the SWPPP, plans, and stormwater
management calculations pacl<age.
WPO# has been added to Plans, SWPPP, and calculations.
2. SWPPP Section I — Please provide a registration statement that is completed to include
the certification. Please delete instruction for completing the registration statement.
Registration statement has been sent to the owner for signature. We
acknowledged that a signed registration statement is needed for the SWPPP
prior to plan approval.
3. SWPPP Section 2 — Please provide a copy of the DEQ coverage letter when obtained.
DEQ coverage letter will be added when obtained.
4. SWPPP Section 7 — Impaired water status cannot be verified as registration statement is
not completed.
Acknowledged.
S. SWPPP Section 8 — Please provide the information requested.
Qualified personal shall be provided once a contractor has been selected.
6. SWPPP Section 9 — Please complete and sign the certification.
Certification has been sent to the owner for signature. We acknowledged that a signed
certification is needed for the SWPPP prior to plan approval
CIVIL ENGINEERING I ENVIRONMENTAL I SURVEYING I GIs I LANDSCAPE ARCHITECTURE I CONSTRUCTION SERVICES
7. SWPPP Section 10 — Per 9VAC25-880-70 Part K, please provide the person with the
authority to sign inspection reports or to modify the stormwater pollution prevention
plan.
This information will be provided once a contractor has been selected.
8. Please note that additional comments may be generated based on responses to these
comments.
Acknowledged.
B. Pollution Prevention Plan (PPP)
The PPP content requirements can be found in County Code section 17-404.
1. SWPPP Section 6 PPP meets Albemarle County Code section 17-404.
Acknowledged.
C. Stormwater Management Plan (SWMP)
VSMP Regulation 9VAC25-870-108 requires the VSMP authority to approve or disapprove a
SWMP. This plan is disapproved, and the reasons are provided in the comments below. The
stormwater management plan content requirements can be found in County Code section 17-
403.
1. Please provide Owner's phone number and email address for the Owner to receive
correspondence.
This information has been added to the cover sheet.
2. Please provide closed conduit storm drain pipe and drop inlet or curb drop inlet
calculations using VDOT LD229 and LD204 worksheets (see VDOT Drainage Manual
and Section 6 Drainage Systems of the Albemarle County Design Standards Manual).
Albemarle county design standards manual calls for stormwater calculations to
presented in a tabular format. We feel that the calculations as prevented provide the
pertinent information for the pipe/inlet design.
3. The drainage area divides on the Phase 2 E&SC plan does not address where roof runoff
from the existing building and the northern most and southern most new building
additions enters the closed conduit storm drain system. It appears that roof drainage is
directed to existing structure "A". Please provide closed conduit storm drain calculations
from existing structure "A" to existing structure "G" and reroute the existing
underground detention system.
Roof drainage drains to structure `A'. See Sheets C6.2 & CS. 1.
4. It appears that structures "C" and "2F" are stormceptors and appears to be of the inlet
type. It appears that an OSR model is proposed as based on Figure 3 presented in the
design calculation booklet. Please provide sizing calculations and Stormceptor Model
No. to demonstrate that proper size unit is being provided as based on the flow directed
to the unit. Also, provide the proper inlet/outlet drop per the stormceptor technical
data sheet for the selected unit (or denote custom design).
Stormceptor sizing information as well as details have been added to Sheet C5.1.
S. Please provide the numeric identifier on each underground detention facility to match
that indicated in the Model Schematic (Figure 4 of the design calculation booklet) and
show on plan sheet (C4.2) and detail sheet (C5.1).
Detention facilities have been numbered to match the calculations. See Sheet C4.2.
6. Please provide soil group and soil surface description to facilitate verification of weighted
CN for each subbasin's input data in the design calculation booklet.
This information has been added to the calulcations book.
7. Please provide stage discharge curves and routings of I and 10-year storm events for
New Det 01 and New Det 02.
This information has been added to the calculations book.
8. Please provide the name of the DEQ certified facility that is intended to provide nutrient
credits. Provide VAHUC for the project site and for the nutrient credit facility.
This information has been provided with this submission.
9. It appears that the existing underground detention upstream to the existing bioretention
facilities is modeled with a Tc of 5 minutes. Please provide calculations demonstrating a
Tc of 5 minutes.
Water is conveyed to the existing detention facility via the onsite storm system. This
area is primarily asphalt and has a low time of concentration therefore the minimum
allowable Tc was used.
10. Please correct the VRRM site summary as per sheet No. C5.3 denotes a portion of the
site is in hydrologic soil group B Glenelg and a portion is within hydrologic soil group C
Elioak.
The plan sheet shown on C5.3 is from an older plan an is provided for reference only.
Current soils information is shown on Sheet C6.1, which shows that the entire site is
within soil group B.
11. Please note that additional comments may be generated based on responses to these
comments.
Acknowledged.
D. Erosion and Sediment Control Plan (ESCP)
Virginia Code 62.1-44.15:55 requires the VESCP authority to approve or disapprove an ESCP.
This plan is disapproved, and the reasons are provided in the comments below. The erosion
control plan content requirements can be found in County Code section 17-402.
1. The County's Critical Resources Plan denotes managed critical slopes throughout the
parcel. Please denote the location of the managed slopes with a symbol and add to the
legend.
Critical slopes have been added to Sheets C6.0 & C6.1.
2. Please provide a top of wall spot elevation at the northeast corner of the eastern most
new parking lot to verify that retaining wall height is not greater than six feet as it appears
that the retaining wall is located within a managed critical slope area.
A spot has been shown in the requested area. See Sheet C3.1.
3. Please address pedestrian access as it is noted that Phase I and Phase 2 CE will conflict
with sidewalk to remain.
A portion of the sidewalk where the CE is shown is to be removed as a part of this
project. A note has been added to Sheet C6.2 stating that the contractor is responsible
for maintenance of traffic (including pedestrian) during construction.
4. Please add dust control symbol to the E&SC plan sheets legend and add locations to the
plan. Provide same information for temporary and permanent seeding as well.
This information has been added to the plans. See Sheet C6.0 & C6. I.
5. A DID is shown in a portion of the area to be filled to construct a new parking lot
(eastern most new parking area). Please explain the DID status during earthwork
operations.
The DD shall remain in place, and be adjusted by the contractor during earthwork
operations.
6. Please add soil boundary to the Phase 2 E&SC plan sheet.
Soils boundaries have been added to the plans. See Sheet C6.1.
7. Please provide a stockpile and contractor's staging/laydown and parking areas to the
E&SC plan sheet.
This information has been added to the plans. See Sheet C6.0.
8. Please verify that cut or fill balances do not exceed a 10,000 cubic yard deficit. If deficit is
exceeded, an approved waste area will need to be identified.
Cut/Fill balances for the project are less than 300 cubic yards.
9. SSF is shown crossing contours at several locations on the Phase I and Phase 2 E&SC
plan. SSF is to run parallel with contours. Please place SSF on tangents or provide other
perimeter E&SC measures.
SSF locations have been revised. See Sheets C6.0 & C6. I.
10. It appears that slopes sleeper than 3:1 are proposed on the south side of the eastern
most new parking lot and the north side of the northern most new parking lot. Please
provide a symbol for slopes steeper than 3:1 and add to the legend and to the E&SC plan
sheets. These areas are to have low maintenance (not grass) ground cover specified
(what type) on the E&SC plan sheets.
This information has been added to Sheet C6. I.
11. Please provide an alpha or numeric indicator for the two excavated drop inlet traps to
facilitate reference. Provide a stage/storage volume table for each trap and identify the
wet and dry storage volumes and elevations, and a calculation verifying a 2:1 length/width
ratio for flow path in consideration of the inflow location.
This information has been added to sheet C6.0.
12. The clean water DID on the west side of the project site is to discharge to a
stable/stabilized outfall. Please provide appropriate drainage area/flow calculations and
size riprap apron or other measures to stabilize outfall.
A temporary level spreader has been added at the end of the CWD. See Sheet C6.0.
13. Please add the drainage area (0.30 acres) to the volume calculation for the eastern most
drop inlet sediment trap on Sheet No. C6.0.
Calculation has been revised to include the 0.30 acres.
We have included PDF copies of the plans and calculations for your review. If you have any
questions or comments, please feel free to give me a call at 434.295.5624.
Sincerely,
John Wilson, PE
Project Engineer