HomeMy WebLinkAboutWPO201800030 Review Comments Appeal to BOS 2018-12-21a4a4*,*0
TIMMONS GROUP
YOUR VISION ACHIEVED THROUGH OURS.
December21, 2018
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 John Anderson:
We have reviewed all of your comments from November 27, 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 package.
Revision I Response: WPO# has been added to Plans, SWPPP, and Calculations.
Revision I Comment: Comment addressed.
2. SWPPP Section I — Please provide a registration statement that is completed to include
the certification. Please delete instruction for completing the registration statement.
Revision I Response: Registration statement has been sent to the owner for signature.
We acknowledge that a signed registration statement is needed for the SWPPP prior to
plan approval.
Revision I Comment: Acknowledged.
3. SWPPP Section 2 — Please provide a copy of the DEQ coverage letter when obtained.
Revision I Response: DEQ coverage letter will be added when obtained.
Revision I Comment: Acknowledged.
4. SWPPP Section 7 — Impaired water status cannot be verified as registration statement is
not completed.
Revision I Response: Acknowledged.
CIVIL ENGINEERING I ENVIRONMENTAL I SURVEYING I GIs I LANDSCAPE ARCHITECTURE I CONSTRUCTION SERVICES
Revision I Comment: Comment not addressed. The discharge is to DEQ identified
impaired waters. Please include the verbiage contained in 9VAC25-880-70(B)(4)(b) and
(c) and (B)(4)(d)(I) and (2).
SWPPP has been revised to include the requested verbiage.
S. SWPPP Section 8 — Please provide the information requested.
Revision I Response: Qualified personnel shall be provided once a contractor has been
selected.
Revision I Comment: Acknowledged. (Rev 2) As follow up: Provide a named individual.
SWPPP cannot be approved without listing an individual. Sec 10, Delegation of Authority,
may be used to transfer authority, later. Recommend list Timmons Group qualified
personnel. (Note: may amend SWPPP at pre construction, by which point GC/RLD will
be selected/known. Also, item #9 below)
We acknowledge that qualified personnel needs to be noted prior to SWPPP
being approved.
6. SWPPP Section 9 — Please complete and sign the certification.
Revision I Response: Certification has been sent to the owner for signature. We
acknowledged that a signed certification is needed for the SWPPP prior to plan approval.
Revision I Comment: Acknowledged.
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.
Revision I Response: This information will be provided once a contractor has been
selected.
Revision I Comment: Acknowledged. (Rev 2.) As follow-up: Engineering recommends
delegate authority to GC/RLD at Albemarle County -Applicant pre -construction meeting.
Acknowledged.
8. Please note that additional comments may be generated based on responses to these
comments.
Revision I Response: Acknowledged.
Revision
Comment: Acknowledged. (Rev. 2) — See item #9 below.
Acknowledged.
9. New: Provide a named individual responsible for pollution prevention practices, SWPPP,
Sec. 6.E.. This may be Timmons Group personnel; SWPPP cannot be approved without
listing an individual.
We prefer to wait until the SPCA has selected a general contractor before
providing this information. We acknowledge the SWPPP cannot be approved
until this information is provided.
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.
Revision I Response: Acknowledged.
Revision I Comment: PPP approved.
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.
Revision I Response: This information has been added to the cover sheet.
Revision I Comment: Comment addressed.
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).
Revision I Response: Albemarle County design standards manual calls for stormwater
calculations to be presented in a tabular format. We feel that the calculations as
presented provide the pertinent information for the pipe/inlet design.
Revision I Comment: Comment not addressed. The Albemarle County VSMP/ESC
Program Authority Administrator requires submission of inlet computations on VDOT
Form LD204 and storm drain on VDOT Form LD209 or a similar form that includes all
the information presented on the sited VDOT forms to include the required storm
event(s) (inlets throats 4"/hour and 10-year check storm and pipe system at the I 0-year
storm).
Forms LD204 and LD209 have been provided with this submission. See Calculations
book.
Rev. 2 Partially addressed. At sag inlet 2H: Revised inlet throat length to ensure spread less
than 6'. See Table C5.1.
Throat length has been revised to ensure spread is 6 feet.
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.
Revision I Response: Roof drainage drains to structure "A". See Sheets C6.2 and C5.1.
Revision I Comment: Comment addressed.
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).
Revision I Response: Stormceptor sizing information as well as details have been
added to Sheet C5.1.
Revision I Comment: Comment addressed.
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).
Revision I Response: Detention facilities have been numbered to match the
calculations. See Sheet C4.2.
Revision I Comment: Comment addressed.
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.
Revision I Response: This information has been added to the calculations book.
Revision I Comment: Comment addressed as based on item 2 of the storm sewer
computation notes on Sheet C5.1 and the response to Comment 10 below states the
entire site is within hydrologic soil group B.
7. Please provide stage discharge curves and routings of I and 10-year storm events for
New Det 01 and New Det 02.
Revision I Response: This information has been added to the calculations book.
Revision I Comment: Comment does not appear to be addressed. The requested
information was not observed in calculation package. Please provide requested
information.
Requested information is now shown in the calculations package.
t- - -1 - -1 - - -1
Rev 2. Partially addressed. As follow-up: Please revisit/edit I-/10- pre/post development table
on C5.1. to clarify pre/post point of comparison (ditch v. Kegler's pond). Clarify channel
protection and flood protection narrative on C5.0. Please bridge statements that the post
developed flow is being reduced to be less than the pre -developed flow (channel protection) and
(flood protection) that post-devlopment flows are confined to stormwater conveyance systems,
with Fig. 4 schematic, which is somewhat difficult to interpret. It is difficult for examply to identify
keglers pond. Engineering appreciates the I % point of analysis(pond) and 110 pg. of supporting
data/graphs, but requests C5.1 and calc. package distill relevant pre/post routings at point of
discharge to manmade conveyance. Nothing between site discharge to ditch and kegler's pond
should reduce or increase peak discharge from on -site detention systems. Also, provide explicit
computations that show ditch conveys the I 0-yr event at point of site discharge to ditch.
Engineering welcomes PDF preview.
Narrative has been revised to provide more clarity. Additional tables have been added
to the calculations page titled Node Summary. This table reports the flows out of each
node, accounting for all stormwater management measures. PRE_COMB &
POST _COMB is the combined flows at the point of analysis. Ditch calculations have
been added to the calculations page.
8. Please provide the name of the VtQ certified facility that is intended to provide nutrient
credits. Provide VAHUC for the project site and for the nutrient credit facility.
Revision I Response: This information has been provided with this submission.
Revision I Comment: Comment addressed.
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.
Revision I Response: 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.
Revision I Comment: Comment addressed.
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.
Revision I Response: The plan sheet shown on C5.3 is from an older plan and 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.
Revision I Comment: Comment not addressed. No soils information is shown on Sheet
C6.1 as stated. Please turn on the soils layer to include soils boundary and soils
designation and add to the legend.
Soils information is shown on Sheet C6.1, legend has also been revised.
11. Please note that additional comments may be generated based on responses to these
comments.
Revision I Response: Acknowledged.
Revision I Comment: Please note that additional comments may be generated based on
responses to these comments.
Acknowledged.
12. New: Please revised C3.0 sheet title to read Site Layout. A WPO Plan cannot approve a site plan.
C3.0 has been renamed to Site Layout.
13. New: Copy Figs. 2 and 3 from Calculations package to WPO Plan Sheets.
This information has been added to sheet C4.4.
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.
. 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.
Revision I Response: Critical slopes have been added to Sheets C6.0 and C6.1.
Revision I Comment: Comment addressed.
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.
Revision I Response: A spot has been shown in the requested area. See Sheet C3.1.
Revision I Comment: As based on the elevations given, the height of the retaining wall
north of the terminus of the northern most new parking area exceeds 6 feet and is within
the managed steep slope overlay district. Either reduce the wall height to under 6 feet or
provide a double tiered wall system.
Retaining wall height has been reduced. See Sheet C3.1.
(Rev 2): Partially addressed. BOW spot elevation (27.87) is shown. Please provide/restore TOW
spot elevation. TOW appears to tie to elev. 534.
Spot elevation has been readded to the plans.
3. Hease aaaress peaestrian access as it is notea that Phase I and Phase 2 CE will conflict
with sidewalk to remain.
Revision I Response: 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.
Revision I Comment: Comment addressed.
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.
Revision I Response: This information has been added to the plans. See Sheets C6.0
and C6.1.
Revision I Comment: Comment addressed.
S. 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.
Revision I Response: The DID shall remain in place and be adjusted by the contractor
during earthwork operations.
Revision I Comment: Please note that the Albemarle County VSMP/ESC Authority
Administrator does not permit the placement of erosion and sediment control measures
in the way of grading during construction (see attached Engineering E&SC Plan Checklist.
Item circled on Sheet 3 of 4. Please provide E&SC controls for this area that do not
conflict with grading operations.
Addressed
6. Please add soil boundary to the Phase 2 E&SC plan sheet.
Revision I Response: Soil boundaries have been added to the plans. See Sheet C6.1.
Revision I Comment: See Part C Revision I Comment 10. Please provide the requested
information.
7. Please provide a stockpile and contractor's staging/laydown and parking areas to the
E&SC plan sheet.
Revision I Response: This information has been added to the plans. See Sheet C6.0.
Revision I Comment: Comment addressed.
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.
Revision I Response: Cut/fill balances for the project are less than 300 cubic yards.
Revision I Comment: Comment addressed.
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.
Revision I Response: SSF locations have been revised. See Sheets C6.0 and C6.1.
Revision I Comment: Comment not addressed. Please adjust super silt fence as
requested.
Silt fence locations have been revised.
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.
Revision I Response: This information has been added to Sheet C6.1.
Revision I Comment: Comment not addressed. The criterion is for slopes steeper than
3:1. Then Consultant has referenced 2:1 slopes. Please correct plan to address
comments.
Note has been revised to state 3: 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.
Revision I Response: This information has been added to Sheet C6.0.
Revision I Comment: Comment addressed.
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.
Revision I Response: A temporary level spreader has been added at the end of the
CWD. See Sheet C6.0.
Revision I Comment: Comment addressed.
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.
Revision I Response: Calculation has been revised to include 0.30 acres.
Revision I Comment: Comment addressed.
14. New: Include paved wash rack detail from ACDSM, pg 8. Albemarle County Engineer
requires this detail on all plans. Albemarle County Inspectors may, under rare
circumstance, permit construction of a stone construction entrance, but paved
construction entrance with wash rack is typical.
Paved construction entrance detail has been added to the plans.
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