HomeMy WebLinkAboutWPO201800007 Review Comments WPO VSMP 2018-01-17COUNTY OF ALBEMARLE
Department of Community Development
401 McIntire Road, Room 227
Charlottesville, Virginia 22902-4596
Phone (434) 296-5832 Fax (434) 972-4126
VSMP Permit plan review
Project title:
Rivanna Village — Amendment 1 and Phase II
Project rile number:
WPO201800007
Plan preparer:
Scott Blossom [Scott@blossomconsulting.net]
Owner or rep.:
Tim Culpepper [tulpepper@robinsondevelopment.com]
Plan received date:
December 81' 2017
Date of comments:
January 171' 2018
Reviewers:
Bobby Jocz
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 denied. The
rationale is given in the comments below. The application may be resubmitted for approval if all
of the items below are satisfactorily addressed.
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. Amend project title to state: "Rivanna Village — Amendment 1 and Phase II".
2. Amend title sheets to state: "WPO/Stormwater Plans", "WPO/Erosion and Sediment Control
Plans", and "WPOBuffer Mitigation Plan".
3. Registration statement project name should be updated to be "Rivanna Village: Phase II"
4. Provide date for sourced topography. Topography should be field verified by engineer within the
past year.
B. Pollution Prevention Plan (PPP)
The PPP content requirements can be found in County Code section 17-404.
No Objection
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. NOTE: All BMPs must be placed within a Stormwater Management Facility Easement with SWM
maintenance agreement.
2. NOTE: 26.09 acres indicated as Forest/open space for VRRM spreadsheet compliance must be
protected within a SWM Forest and Open Space easement. Please provide exhibit indicating areas
which may already be conserved within an easement within phase I, and areas within Phase II that
are to be placed under "SWM Forest and Open Space" easement for VRRM water quality
compliance. Conserved areas must be platted along with deed of dedication and SWM
maintenance agreement.
Engineering Review Comments
Page 2 of 6
3. Proposed grading contours should be shown with a different line weight/opacity/type than existing
contours.
4. Please provide the storage and routing calculations for each basin. This can be provided as a
supplemental document digitally or in hard copy.
5. Provide elevations for 100yr, IOyr, and 2 yr WSE for each BMP. Elevations are shown on the
plans, but the numerical elevation is not provided.
6. Maintenance access roads should be provided for each structural BMP with maintenance access
easement. Please provide, or present more clearly, BMP maintenance access roads. Proposed
access road grading should be provided.
7. [Sheet SWM-4] Notes regarding on and off site TP removal for I1 show inconsistencies between
Supplemental Water Quality Compliance Documentation, Notes on Plan view, and notes within
Treatment Volume calculations shown on the left side of Sheet SWM-4. Please correct.
8. [Sheet SWM-20] long term maintenance notes should be provided for SWM forest and open
space, and compost amended soils.
Blocks G and F
1. Provide a detail/cross section for permanent diversion identified at the northeast property boundary
for block G. Provide proposed grading contours. Detail OP for channel where it discharges into
existing stream channel. Provide related stormwater calculations.
2. [BMP G1] DS Outlet invert indicated for BMP G1 does not appear to match contours on plans.
US invert cannot be lower than DS invert. Positive drainage must be maintained.
3. [Detail for BMP G1] show outfall pipe on cross section view.
4. [BMP G2] Please provide water quality orifice elevation.
5. [Detail for BMP G2] Please show riser structure and outfall pipe on cross section, and slope of
side slopes In addition, correct issues with biofilter layers (don't seem to match elevations,
additional layers added and not identified).
6. [BMP G3] Provide US and DS outfall invert elevations.
Block I
1. [BMP I2/I3] Please show riser structure and outfall pipe on cross section
2. [BMP I2/I3] Please show sub -drainage areas for BMP in order to show DA's don't exceed 2.5
acres/cell.
3. [BMP I2/I3] For level 2 designs the SFP/L ratio must be 0.8 or greater. As shown, the SFP/L for
BMP I2/I3 is 0.45 which is not adequate. This is especially the case since the inlet discharging
stormwater from the largest drainage area is the inlet with the shortest flow path to the outlet
structure.
4. [BMP I1] show contributing sub -drainage areas to each pond inlet, or provide acreages.
5. [BMP I1] Please show more clearly the location of 84" riser structure associated with pond on plan
views.
6. [Sheet SWM - 10] Provide elevations for high flow spillways associated with forebay #2. Provide
cross section detail of high flow channel.
Block J (East and West)
1. [BMP J1 and J2] cross sections reference "Low flow spillway weir crest" for both the low flow
and high flow channels. Please correct.
2. [BMP J1 and J2] For cross sections, please more clearly indicate the channel elevations for the low
flow and high flow channels. Currently the channel elevations are indistinguishable from the WSL
elevations.
3. [BMP J1] Check elevations or weir crests for high and low flow, as indicated the low flow weir
crest is indicated as sitting higher than the "high" (mislabeled) flow weir crest.
4. [BMP J5] Please clarify configuration of wester most inlet to BMP J5, as presented the inlet
appears to split between 2 outlet structures.
Engineering Review Comments
Page 3 of 6
5. [SWM-15] Planting plan indicates BMP J5 to be of L2 design, however, BMP is designed to L1
specifications. Please clarify.
6. [BMP J7] Compost soil amendment is not recommended where contributing impervious surface
area is greater than that of the surface area of compost amended soils (0.20 acres imp. > 0.11 acres
CAS). 57 stone should be used in diaphragm due to slope of contributing drainage area. In
addition, compost amended soils are not recommended where soils are to be seasonally wet. BMP
J7's proximity to wetlands and existing stream floodplain may cause issues. This design should be
re-evaluated.
7. [BMP J6 and J7] Sheet flow to preserved buffer must maintain 35 feet of 0.5-3% slope or 50 feet
of 3-6% slope past the diaphragm, please provide on plans. See note regarding forest and open
space above.
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. Provide specific callouts for elements included in the "Phase I amendment" (i.e. what elements are
being changed from the phase I approved plans).
2. Provide stage II E&S masterplan.
3. Provide existing contour elevations.
4. Identify diversion dikes conveying clean water as "clear water diversions" in replacement of a
"right of way diversion". Ensure discharge is through stabilized outlet [Per VESCH spec. 3.12].
RWD should be indicated where CWD or DV crosses travelways/construction
roadways/entrances.
5. Rearrange labels for blocks so that labels do not obstruct stormwater/E&S/proposed contour
features.
6. Existing and proposed contours should be labeled with consistent line type/weight/opacity.
Proposed contours other than those related to E&S measures are shown grayed out, making it
difficult to differentiate between proposed and existing grades and evaluate proposed measures.
7. Provide match lines or provide boarders around blocks to help differentiate between adjacent
blocks. Another option would be to reduce opacity for structures/features/grading in blocks other
than the block being represented in the current sheet.
8. Ensure consistent labeling of sheets related to blocks shown within the sheet. For instance, on
sheet ES-8, E&S/SWM features for block J are not shown but are indicated to be shown on the
label/header for the sheet. This is seen throughout the plan set.
9. Provide detail and identify areas throughout E&S plan where dust control will be utilized.
10. Show proposed grading related to construction access road construction.
11. Provide structural fill notes as indicated throughout plans. Currently not included.
12. Ensure cross section labels (i.e. Cross section D'-D') are presented consistently through phases,
blocks. Currently they are shown on all Phase I plans, but sporadically on Phase II plans.
13. Overly buffer preservation areas proposed in mitigation plan to ensure grading/clearing will not
occur in areas proposed to be preserved.
Blocks G and F
1. Provide contour elevations
2. [Phase I] Diversion dike GS3 appears to run uphill for first 200 feet. Please correct.
3. [Phase I] ROW diversion GS4 appears to run uphill for first 100 feet. Please correct.
4. [Phase I] Provide stage/storage elevations for sediment basins/traps.
5. [Phase II] Silt fence should not be installed across detention structure outlets/spillways.
Engineering Review Comments
Page 4 of 6
Blocks I and J
1. Provide contour elevations
2. [Phase I] Identify contour interval, currently defined as N/A.
3. [Phase I] For consistency, label sediment trap IS 1.
4. [Phase I] Diversion channels IS 1 a and IS 1 d are one structure, and should be calculated/labeled as
such.
5. [Phase I] Ensure silt fence is kept a minimum of 5' from top of stream banks.
6. [Phase I] Provide stage/storage elevations for sediment basins/traps. Since no emergency spillway
is provided the crest of the principle spillway must be 3' below the height of the embankment
(currently 2' is provided for basins SBI1 and S13I2). Provide Qp and the 25 year design high water
elevation to show that it is less than the peak flow from the 25 year storm.
7. [Phase I] Silt fence should not be installed across detention structure outlets/spillways as shown
across outlet of S13I2.
8. [Phase I] Minimum flow path length for S1312 appears incorrect. Baffles should be provided to
prevent short circuiting of flows. Baffles may be included but obstructed by cross section D'-D'
symbol.
9. [Phase I] Time of concentration calculation for basin IS213 references the wrong diversions, no
diversion 12a appears to exist. Please correct.
10. [Phase I1] check narrative for correct block/structure references. References made to Block G, and
non-existent structures within the block (basin CS2?).
11. [Phase I1] Remove cross section E'-E', it appears not to be related to any structure presented on the
sheet.
12. [Phase I1] Silt fence should not be installed across detention structure outlets/spillways.
13. [Phase I1] Ensure silt fence is kept a minimum of 5' from top of stream banks.
14. [Phase I1] Define E&S measure identified with the symbol RR. It is not currently defined in the
legend.
15. [Phase I1] Identify contour interval, currently defined as N/A.
16. [Cross sections] show location of barrel structure in cross section. It appears for SBI1 outfall invert
will be higher than riser barrel outlet on structure, creating a negative drainage.
17. [Cross sections] Cross section for S132 indicates that stage 1 is to be a sediment trap, whereas in
the profile view and calculations it is identified as a basin. Please clarify.
18. [Cross sections] Cross section for S132 should show riser structure and barrel. Additional cross
section may be necessary.
Block J (East)
1. Provide contour elevations.
2. [Phase I] Provide stage/storage elevations for sediment basins/traps.
3. [Phase I] Please correct labeling inconsistencies. Label sediment traps. Ensure block labels are not
covering drainage area labels.
4. [Phase 1] ROW (CWD) diversion JS2a appears to convey drainage uphill. Please correct/clarify
5. [Phase I] diversions discharging into ST JS2 are labeled as ROW diversions. Since they are
conveying sediment latent water they should be indicated as DVs. Please label diversions
6. [Phase I] Silt fence extending between traps appears to cross stream section. Please correct/clarify.
Block J (West)
1. Provide contour elevations. Proposed grading contours are missing for ST JS4 and ST JS3.
2. [Phase I] Provide stage/storage elevations for sediment basins/traps.
3. [Phase I] Please correct labeling inconsistencies. Label sediment traps. Ensure block labels are not
covering drainage area labels.
4. [Phase I] Ensure silt fence is kept a minimum of 5' from top of stream banks.
5. [Phase I] Silt fence should not be installed across detention structure outlets/spillways.
6. [Phase I] Identify/label ROW diversion crossing construction roadway to the south of TSC I.
Engineering Review Comments
Page 5 of 6
7. [Phase I] ROW (CWD) diversion JS5a appears to convey drainage uphill. Please correct/clarify.
8. [Phase I] Remove roadway name from construction access roadway.
9. [Phase I] Diversion JS5a crosses drainage area delineation line. Please correct.
10. [Phase I]
11. [Phase II] Super silt fence should remain though Phase H to prevent sediment from entering stream
during Phase II rough grading of BMPs. This is shown on previous sections, but not this one.
12. [Phase I &II] Shift viewing extent to show southern portion of LOD.
13. [Cross sections] Correct label for diversion channel cross section detail. Title references the wrong
features.
14. [Cross sections] Clarify reference to structure "H". Is this the already approved ST from phase I?
Please label structure and include cross section labels on plan views.
E&S Details
1. Provide detail for pump around/stream diversion practice related to construction of BMP I1.
2. Detail for riser structure and ant vortex device related to S132 should be provided similar to that
shown for SB 1.
E. Mitigation Plan
Plan which meets the requirements of section 17-406 that describes how encroachments into a stream
buffer will be mitigated through runoff treatment, revegetation, the addition of extra buffer areas, or other
appropriate best management practices. A mitigation plan may be a component of a VSMP permit, or an
erosion and sediment control plan if the land disturbing activity is subject solely to the VESCP.
1. Provide table summarizing acres impacted and acres proposed for conservation/restoration.
The VSMP permit application and all plans may be resubmitted for approval when all comments have
been satisfactorily addressed. For re -submittals please provide 2 copies of the complete permit package
with a completed application form.
Engineering plan review staff are available from 2-4 PM on Thursdays, should you require a meeting to
discuss this review.
Process;
After approval, plans will need to be bonded. The bonding process is begun by submitting a bond estimate
request form and fee to the Department of Community Development. One of the plan reviewers will
prepare estimates and check parcel and easement information based on the approved plans. The County's
Management Analyst will prepare bond agreement forms, which will need to be completed by the owner
and submitted along with cash, certificates or sureties for the amounts specified. The agreements will need
to be approved and signed by the County Attorney and County Engineer. This may take 2-4 weeks to
obtain all the correct signatures and forms.
Stormwater Management Facilities Maintenance agreements will also need to be completed and recorded.
The County's Management Analyst or other staff will prepare the forms and check for ownership and
signature information. The completed forms will need to be submitted along with court recording fees.
After bonding and agreements are complete, county staff will need to enter project information in a DEQ
database for state application processing. At this time, the DEQ portion of the application fees will need to
be paid directly to the state. For fastest processing, this is done electronically with the emails provided on
the application. DEQ should notify applicants with instructions on how to pay fees. When DEQ approves
the application, they will issue a permit coverage letter. This should be copied to the county.
Engineering Review Comments
Page 6 of 6
After DEQ coverage is issued, via the coverage letter, the County can hold a pre -construction conference.
Applicants will need to complete the request for a pre -construction conference form, and pay the remainder
of the application fee. The form identifies the contractor and responsible land disturber, and the fee
remaining to be paid. This will be checked by county staff, and upon approval, a pre -construction
conference will be scheduled with the County inspector. At the pre -construction conference, should
everything proceed satisfactorily, a joint VSMP and grading permit will be issued by the County so that
work may begin.
County forms can be found on the county website forms center under engineering;
http://www.albemarle.org/deptforms.asp?department--cdengno
Bobby Jocz
Albemarle County
Community Development — Engineering
rjocz@albemarle.org
(434) 296-5832 ext. 3283