HomeMy WebLinkAboutWPO202200011 Correspondence 2022-05-09f 608 Preston Avenue
P 434.295.5624
Suite 200 IF434.295.1800
T I M M O N S GROUP
Charlottesville, VA 22903 www.timmons.com
May 9, 2022
John Anderson, PE
County of Albemarle
Community Development
401 McIntire Rd
Charlottesville, VA 22902-4579
RE: WP02022-00011 Rio Point —VSMP Permit Plan Review —Comment Response Letter
Dear Mr. Anderson:
We have reviewed all of your comments from March 31, 2022 and made the necessary
revisions. Please find our responses to the comments below in bold lettering.
County Code section 17-410 and Virginia Code §62.1-44.15:34 requires the VSMP authority to
act on any VSMP permit by issuing a project approval or denial. This project is disapproved for
reasons listed below. The VSMP application content requirements can be found in County Code
section 17-401.
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.
SWPPP:
1. Revise SWPPP cover to include ref. to WP0202200011.
Number has been added.
2. Complete and include CGP (VAR10) permit registration, SWPPP, Sec. 1.
The GCP has been included.
3. Sec.1, SWPPP; Sec. III: If unbalanced cut/fill requires material export, identify off -site
waste site prior to pre -construction (notify county of waste site to receive a Grading
permit, or state VAR10 permit).
Acknowledged.
ENGINEERING I DESIGN I TECHNOLOGY
4. Sec. 3 /Nature of activity: Reconcile 18.86 Ac. LOD with plan LOD, 18.44 Ac.
Limits of clearing and grading has been updated accordingly to plan changes.
5. Sec. 4/5: ESC-SWM—Revise consistent with revised WPO plan.
Revisions have been applied.
6. Sec. 6.A.: PPP Exhibit: Please show initial location of:
a. Rain gauge.
Rain gauge located north of construction entrance near construction trailer.
b. Portable sanitary facilities (porta-john), as required.
Porta-john located north of construction entrance near construction trailer.
c. Covered non -hazardous waste dumpster, if required.
Not required.
d. Vehicle wash waters, draining to trapping measure (Not a sediment trap
design, per se, but shallow depression —1-2 backhoe buckets. Avoid direct
drainage to Ex. storm system, or pond/s.)
The concrete washout will have a water tank that may be used to wash
vehicles. Located adjacent the construction entrance.
e. Concrete wash -out.
Concrete wash -out is located at construction entrance.
f. On -site fuel, if required.
On -site fuel container is located between the construction entrance and
the contractor trailer.
g. Paint, stucco, chemical storage, if required.
Container located next to chemical storage.
7. Sec. 6E: List named individual responsible for PPP measures.
Will be provided.
8. Sec. 8: List named individual responsible for ESC inspections /compliance with
VESCH, 3rd Edition, 1992.
Will be provided.
9. Sec. 9: Ensure Signed Certification is signed and dated.
Will be provided.
10. Sec. 12: Furnish [blank] inspection log /form.
Inspection log has been included with this submission.
B. Pollution Prevention Plan (PPP) —see SWPPP item 6., above
The PPP content requirements can be found in County Code section 17-404.
C. Stormwater Management Plan (SWMP)
VSMP Regulation 9VAC25-870-108 requires the VSMP authority to approve or
disapprove a SWMP. This plan is disapproved for reasons listed below. The stormwater
management plan content requirements can be found in County Code section 17-403.
1. Revise VSMP plan title sheet to include ref. to WPO202200011.
Cover revised.
2. C1.3 may be removed from the WPO plan set.
Sheet has been removed.
3. Across plan, on every sheet that depicts existing contours, please provide sufficient
existing contour labels. Additional review comments relating to existing or proposed
contours are possible.
Contour labels have been added.
4. C2.0, C2.5, C2.6, C3.16-C3.18, C4.0, C5.4, C5.5, C6.1, C7.0, C7.1, and C8.0-C8.2
display as portrait; please use landscape format. Please ensure WPO plan
consistency (landscape /correct orientation).
Landscape format was used. Unclear why uploading the plans changed the
orientation. A separate download link with the plans can be provided in addition
to the County View upload.
5. C7.4 indicates 3.82 remaining TP load reduction (lb./yr.) required, while calculation
packet, p. 16 (of .PDF) indicates 2.54 lb./yr. Please reconcile.
The remaining TP load reduction has been updated.
6. Provide wet pond design; please include this information (or design elements) from
BMP Clearinghouse VA DEQStormwater Design Specification No. 14:
a. Fig. 14.1: Please incl./revise Clearinghouse figure to include project -specific
elevations, datum.
Project specific details are provided on Sheet C7.6.
b. Installation, maintenance, and periodic inspection notes.
Notes are provided on Sheet C7.6.
c. Pretreatment forebay details. If overlooked, please direct reviewer to details.
A gabion basket forebay is being utilized on both the wet pond and the
bioretentions. The detail is provided on Sheet C7.7 but applies to both
types of facilities.
7. Please incorporate ISP (SDP202200009) Engineering review comments (3/24/22) in
revised WPO plan.
Comments have been included.
8. Although C6.0 and C6.1 show bioretention facilities and wet pond, depiction is
incidental to inlet or drainage area information and does not provide adequate level
of SWM facility plan -view detail.
a. Distinct SWM plan sheet/s, sheet title: Stormwater Management. In plan
view sheet/s, label each SWM facility identical with profile information
shown on C7.6, C7.7., C7.8 (Wet pond, Bio 1A, 113, 1C, 1D, 2A).
The stormwater management facilities are labeled on Sheets C4.2, C4.3,
C4.5, C5.2, C5.3, C5.5, and C7.0-C7.3.
b. Label floor w x d dimensions (ea. SWM facility) to aid review, bond estimate,
construction, and compliance (this information currently displays on layout
sheets).
Width and Depth dimensions has been provided to each stormwater
management facilities on Sheets C4.2, C4.3, C4.5, and U.S.
c. Provide distinct profiles for each biofilter; provide profile captions that
reflect plan view labels.
Individual biofilter details has been provided and reflected on plan view
with appropriate labels. Details are provided on Sheet C7.7.
d. For each biofilter profile, provide discrete elevations for:
i) base of #57 stone
Elevation has been provided in individual detail.
ii) 4" PVC underdrain
Elevation has been provided in individual detail.
iii) #8 stone
Elevation has been provided in individual detail.
iv) Filter mix
Elevation has been provided in individual detail.
v) Mulch
Elevation has been provided in individual detail.
vi) INV Nyloplast dome grate, as needed
Elevation has been provided in individual detail.
vii) 15" HDPE INV out, as needed
Elevation has been provided in individual detail.
9. Multiple impervious area inlets /pipes are proposed to route directly to the wet
pond without encountering forebays. Pg. 8, VA DEQ Stormwater Design Specification
No. 14, 6.4, Pretreatment Forebay, states: 'A forebay must be located at each major
inlet to trap sediment and preserve the capacity of the main treatment cell.' Note,
for example, all areas upstream of pipes 301, 225, and 203 collect parking lot
/rooftop runoff and discharge directly to the floor of the main treatment cell.
Provide forebay at each major inlet.
A forebay is provided within the wet pond. The gabion wall location and top
elevation are provided on Sheet C5.5.
10. C5.4, C6.1: Wet pond (plan view) proposed floor elevation is shown as 413' while
INV out is given as 418'. This appears inconsistent with C7.6 profile view (INV out
=417', profile view). Please reconcile.
All pond elevations are provided in details on Sheet C7.6. The bottom of the pond
is 413' but the lowest orifice in the riser structure is 417' for 4' of ponding. The
invert out of the outfall pipe is 410.74'. A scaled vertical profile is also provided on
Sheet C8.0.
11. Provide required geotechnical testing: Please see p. 8, VDEQ specification No. 14.
Underdrains are provided so no further testing is provided at this time.
12. Please provide pond drain. Please see Pond drain, p. 9, VDEQ specification No. 14.
A pond drain has been added.
13. Provide Landscaping and planting plan: Please see p.11, VDEQ specification No. 14.
A landscape plan has been provided with this submission.
14. Provide Water balance analysis: p.7, VDEQ Spec No. 14. to account for routing
significant runoff thru bioretention; concern being possible insufficient runoff to
support a wet pond.
The water balance analysis is provided in the BMP calculations on sheet C7.8.
15. Label wet pond side slopes. Please see p. 10, 6.6 Internal Design Geometry, side
slopes: 4H:1V or 5H:1V (mild side slopes).
Slope labels of 4:1 for wet pond has been included, please see Sheet C5.2 — C5.5.
16. Wet pond floor should be lower than SB1 floor elevation; please revise (see p. 16,
Spec. No. 14).
The sediment basin elevation has been raised to be above the wet pond bottom
elevation.
17. (C3.2, C6.1) Q 2-yr=37.00cfs at outlet 200 in floor of wet pond. Str. 200 design
directs energy toward the inner far wall of the pond. Energy of 37.00cfs (not to
mention higher -energy, less -frequent storm events) may cause near -immediate
destabilization of inner wall of wet pond. Revise design to attenuate energy of 2-yr
event prior to discharge to pond floor to protect interior fill slopes/walls of pond
against erosive force.
The geometry of the pond has changed and outlets 200 and 300 are no longer so
close together and to the opposite wall of the pond. Outlet protection has been
provided and designed in accordance to the Virginia Erosion and Sediment Control
handbook to prevent erosion at the outfalls into the pond.
18. Outfall 300 should be revised to avoid alignment with /toward outfall 200. Erosion
/undermine of outfall 200 is a concern with current alignment.
The geometry of the pond has changed and outlets 200 and 300 are no longer so
close together and to the opposite wall of the pond.
19. It is unnecessary to include Drainage Area A and B VaRRM.xIs excerpt data on the
plan, but if it remains, please also include VaRRM.xIs summary site data.
The Drainage area tabs from the VRRM spreadsheet have been removed from the
plan sheet but are included in the Calc book.
20. C5.1
a. Evaluate increased volume of sheet flow at proposed graded slope along Rio
Road East for stormwater quantity compliance. Provide pre- /post -
development calculations for this area, or direct reviewer to pp. in calc.
packet that consider increased volume of sheet flow at this location.
Pre/Post quantity compliance has been provided for concentrated flow for
Outfall 2.
b. Area does not qualify as exempt from quantity controls, but rather,
represents increased volume of post -developed sheet flow /runoff at this
location.
Pre/Post quantity compliance has been provided for concentrated flow for
Outfall 2.
c. Post -developed runoff at this location may not cross either existing or future
sidewalk at this location or skip curb into Rio Road East.
A channel has been added prior to the proposed trail to capture runoff. A
new inlet is proposed to tie into the existing storm drain system.
d. Capture runoff at base of proposed slope along Rio Road East, and convey to
SWM facility (see 9VAC25-870-66.D.)
A channel has been added prior to the proposed trail to capture runoff. A
new inlet is proposed to tie into the existing storm drain system.
21. Furnish stormwater quantity and quality narratives on the plan.
Narratives are provided on C7.0.
22. Bioretention (1A, B, C, D, 2A):
a. Provide design that meets Level 1 or 2 design criteria listed at Table 9.3, VA
DEQ Stormwater Design Specification No. 9; for example:
All bmp calculations are provided on Sheet C7.8. Both bioretention
calculations meet Level 2 specifications.
i. Level 2:
1. A pretreatment cell plus one of the following: a grass filter
strip, gravel diaphragm, gravel flow spreader, or another
approved (manufactured) pre-treatment structure.
Both bioretentions utilities a sediment forebay and a gravel
diaphragm as pretreatment measures.
2. Planting plan
A planting plan has been provided with this submission.
3. Overflow for on-line bioretention (p. 22, VA DEQ Spec. No. 14)
Both biorentions provide overflow with a nyloplast drainage
basin. The 10-yr storm is contained within each bioretention.
4. Show underdrain which appears in C7.7 Level 2 typical in plan
view/s.
Underdrains are shown and labeled on Sheet C5.1 and C5.2.
ii. Level 1:
1. Planting plan
Both bioretentions are level 2.
2. Overflow
Both bioretentions are level 2.
3. Show underdrain in plan view/s.
Both bioretentions are level 2.
b. Provide bioretention (Clearinghouse) installation, maintenance, periodic
inspection notes.
Please see sheet C7.7.
23. Calculations should include explicit ref. to wet pond forebay volume provided by
biofilter 113, 1C, 1D forebays. Biofilter sediment forebays are not a forebay for the
wet pond but are sized for areas draining to each biofilter. Compare biofilter
sediment forebay total with design criteria at VA DEQ Stormwater Design
Specification No. 14. Revise wet pond forebay design, as needed.
Each biofilter forebay was sized for just the area draining to the biofilter and not
for the entire wet pond drainage area. The wet pond has its own forebay that is
sized for the entire drainage area to the pond and does not utilize the
bioretentions as forebays. All forebay calculations are provided on the BMP
calculation sheet, C7.8.
24. Revise calculation packet title sheet to include ref. to WPO202200011.
WPO number has been added.
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 for reasons listed, below. The erosion control plan
content requirements can be found in County Code section 17-402.
1. C3.2 sediment basin design table indicates L/ We = 8.1 (baffles required if>2), then
states, No baffles. Please provide, label, and dimension SB baffles, since baffles
appear to be required.
The calculations have been corrected. No baffles are required.
2. Provide existing contour labels across all ESC sheets (all phases).
Labels have been added.
3. Depict interim mass grade phase with ESC measures, as needed, between Phase I
(initial perimeter controls (SF, diversions) and traps/basin) and Phase 11 (build -out
/final parking — buildings). Plan should depict graphically mass grading /partial utility
installation, and ESC measures needed to grade site and install pipe networks. Show
relocated traps, perimeter measures, etc. that may be needed during interim phase
of site grading /utility work. Provide graphic complement to text at Sequence of
Installation Note. 17., C3.0.
An interim mass grading phase has been added between Phase 1 and Phase 2.
4. C3.3: Provide break in SF, ST #2 at stone weir outfall.
Plan has been updated.
5. C3.09, C3.10, C3.17, C3.18: Provide existing contours in all areas of land disturbance,
including sanitary sewer corridor.
Previously proposed sanitary sewer outfall has been removed.
6. C3.11; Evaluate existing culvert pipe capacity beneath paved walk N of development
to ensure capacity adequate to convey anticipated Q 10-yr peak flow. Avoid unusual
circumstance where a new storm pipe may have a larger DIA than a downstream
storm pipe.
The pipe out of Bioretention 2A was oversized. The 15" pipe at 4.08% is only at 8%
capacity. The existing 15" culvert is at 17% slope.
7. C3.15, C3.16: Label sediment basin
Appropriate labels have been included for sediment basin.
8. CS.xx series a.
a. Label proposed TW /BW elevations for proposed retaining walls. Assign
identifiers to proposed retaining walls for ease of reference.
TW/BW labels have been added. Only one freestanding wall is proposed.
b. Establish /label proposed SWM facility easements sufficient to construct and
perform future maintenance on SWM facilities.
A Easement plan has been added to the plan. Please see sheet C7.10 for all
easements.
c. Establish /label public drainage easements downstream of storm drain inlets
that receive Rio East storm runoff, and for pipe systems located downstream
of any SWM facility.
A Easement plan has been added to the plan. Please see sheet C7.10 for all
easements.
'Next Steps' after WPO plan approval
1. Purchase Nutrient Credits (if required)
a. PLEASE coordinate with the County reviewer before working with a nutrient
bank. The reviewer must confirm if your project must follow the DEQ hierarchy
requirements.
Acknowledged.
b. Letter of availability must be provided on the WPO approved plans.
Letter of availability is provided on sheet C7.6.
c. Applicant must contact/coordinate nutrient credit purchase with Ana Kilmer,
akilmer@albemarle.org
Acknowledged.
d. Affidavit of Purchase must be provided to Ana Kilmer before a grading permit
can be issued.
Acknowledged.
2. Post WPO Bond
a. Applicant must submit a 'Request to Establish a Bond' form and fee to CDD.
i. Complete the form and email it to akilmer@albemarle.org, along with proof
of payment (see below).
Bond request will be submitted and the fee paid.
b. Payment can be made either online or with a check.
i. If paying online:
1. Go to the online payment portal.
a. Select WPO/VSMP as the application 'type.'
b. Type in the WPO number and project name in the
Notes/Details section of the form.
c. Type in the 'payment amount' as $294.34.
d. Click "Proceed to Secure Checkout" link to make
payment.
2. You will receive a receipt in an email.
ii. Email a copy of the receipt to akilmer@albemarle.org.
Acknowledged.
c. Once the bond request and payment are received, the applicant can provide the
bond estimate (completed on the County worksheet), or Engineering staff will
complete the estimate. Once the estimate is approved, Ana Kilmer will contact
and work with the applicant to post the bond.
Acknowledged.
3. Obtain DEQ Permit (if required)
After nutrient credits have been purchased and the bond has been posted:
a. County staff will register the project with DEQ.
b. Applicant/operator listed on the Registration Statement will receive an email
with instructions on how to pay the DEQ permit fee.
C. Applicant must email a copy of the DEQ receipt of payment to
charris@albemarle.org.
d. DEQ typically will issue a permit within 2 weeks of receiving payment.
Acknowledged.
4. Request pre -construction meeting:
a. Complete and email the Request for a Preconstruction Meeting and Grading Permit to
charris@albemarle.org.
A request for a preconstruction meeting and grading permit will be emailed to
charris@albemarle.orR.
b. Pay the fee via the online payment portal or a check at the pre -construction meeting. If
paid online, email a copy of the receipt to charris@albemarle.ora .
Acknowledged.
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 or email at
Jessica.denko@timmons.com .
Sincerely,
Jessica Denko, PE
Project Manager