HomeMy WebLinkAboutWPO201400077 Review Comments WPO VSMP 2015-03-11� OF AL
,. vIRGINIP
COUNTY OF ALBEMARLE
Department of Community Development
401 McIntire Road, Room 227
Charlottesville, Virginia 22902 -4596
Phone(434)296 -5832 Fax(434)972 -4126
Project title:
Project rile number:
Plan preparer:
Owner or rep.:
Plan received date:
Date of comments:
Reviewers:
VSMP Permit plan review
Rivanna Village Phase 1
WP0201400077
Santec
RIVANNA VILLAGE LLC
3 December 2014
19 December 2014
Max Greene, Glenn Brooks
[scott.blossom@ stantec.com]
[ANDREW.BONINTI@ CBRE.COM]
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. No additional fee is required for resubmittal. 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 ESOP, (3) a SWMP, and (4) any TMDL measures necessary.
The registration statement appears to be in error. The land development is listed as 94.66 acres and
disturbed area as 40.93. The plans submitted show 58.8 acres "project limits" and 36.5 acres
disturbed. The registrations statement and SWPPP will only be permitted for areas with approved
plans.
Rev. 1: Comment addressed with 32.61 acres total permitted disturbed area.
2. Plans included with the SWPPP must be approved plans. The SWPPP includes a "Preliminary
Stormwater Concept" plan. This does not appear to have been included with ZMA201300012 or
earlier plans, and so does not appear to have any official standing. It should not be part of the SWPPP.
Rev. 1: Comment addressed.
3. Include an explanation of the staging and phasing in the SWPPP. The concept of a stage 3, in which
the ultimate development is not considered per 9VAC25- 870 -72, presents some difficulties, and we
will have to run this by DEQ personnel for guidance.
Rev. 1: Not found.
4. Please follow the standard Albemarle County SWPPP template. Including more is fine, but it should
at least have the template items.
Rev. 1: Not addressed. The template was included in an appendix, not followed. One of the purposes
of this template is to make the document somewhat readable for county inspections. Please remove all
the boilerplate restatements of permit regulations and state manuals, as well as the overcomplicated
Engineering Review Comments
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numerical index system. The length of the documents is simply too difficult to sift through on -site, to
find the actual useable parts. Please make an honest attempt to use the county template.
B. Pollution Prevention Plan (PPP)
The PPP content requirements can be found in County Code section 17 -404.
Please provide a pollution prevention plan as part of the SWPPP. Label it clearly, and provide a site
layout plan with pollution prevention measures located on it to start.
Rev. 1: Addressed.
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.
Provide the VRRM spreadsheets for each section of the site. A full review could not be completed, as
these were not included in the submittal. Please ensure that the areas used in the computation, both for
drainage to each facility, and for disturbed area load computations of turf, forest, and impervious,
appear on a plan sheet or map.
Rev. 1: The spreadsheets were received. Thank you. The areas used in the spreadsheet computations
were not received. As an example, for AS3A, the 1.34 acre and 6.84 acre areas in the spreadsheet are
not shown on sheets 4 or 5. Instead, 1. 14, 6.2 and 0.84 acres are shown on these sheets. Also, the
spreadsheet indicates only turf and forest areas, when the plan clearly shows part of Glenmore Way in
the drainage area.
2. Where preserved /forested areas are credited in the computations, there must be temporary physical
barriers and permanent easement measures provided to ensure they remain undisturbed.
Rev. 1: Not addressed. There are no barriers on the plan, and no easements, and no definitive way of
measuring the preserved areas to assure they remain undisturbed. Limits of disturbance are not
enough, and plastic safety fence is typically insufficient. Thin strips of wooded area are unlikely to be
viable at all.
3. The "project limits" shown on plans are confusing. It is unclear what they represent, as the limits of
disturbance, parcel boundaries, and drainage areas appears to provide what is necessary.
Rev. 1: Please remove project limits. Most plans use a bold line for parcel boundaries.
4. The stormwater plan seems to have temporary measures still shown, like construction entrances,
temporary stream crossings, silt fence, haul roads, and diversions. Notes even indicate temporary
perimeter measures to remain. Temporary measures should be finished, removed, and the site fully
stabilized /vegetated for the stormwater management phase. Grading and formal channels should be
provided to direct drainage if necessary rather than temporary diversions.
Rev. 1: Please remove temporary construction (erosion control, haul roads, etc) measures on the
stormwater management plan.
5. Uncollected areas will need to be accounted for in the load computations.
Engineering Review Comments
Page 3 of 11
Rev. 1: This is commented on per area in later comments.
6. Provide planting plans, or typical areas to be repeated when planting within each facility. It is unclear
how the tables are to be implemented.
Rev. 1: Mostly addressed. See facility comments below.
7. Keep to standard engineer scales. (i.e. not 70)
Rev. 1: Standard engineer scales are 10,20,30,40,50,60 feet per inch. Please do not use 1" =150' or
1"=250'.
The site seems to be divided into four main areas, outlined in the graphic below, and only limited detailed
review could be provided without the load and load area computations. Facility sizing and removals
could not be checked at this time.
Area 1: (Block A)
1. The wet Swale needs a water source for the new wetland. The existing wetlands have the stream. The
proposed wet swale appears to sit 6 feet above on constructed fill.
Rev.l: Changed to bioretention basin AS3B.
Engineering Review Comments
Page 4 of 11
2. Bioretention basins have a maximum drainage area of 2.5 acres. Please adhere to the guidelines in the
state specification. The proposed bioretention has 8 acres drainage to it, which is too large.
Rev. 1: Comment addressed. I agreed to the expansion of contributing drainage area for AS3a with the
understanding that no impervious areas are present (which is not quite true as mentioned in general
comment 1), and alternative design will be provided for further development. At full development the
drainage area should not exceed 2.5 acres total.
3. Grass channel AS3a -1 is too steep and not wide enough. Please adhere to the guidelines in the state
specification.
Rev. 1: The slope is 4.4% and should be 4% max. The side slopes are 2:1 and should be 3:1 max.
The grading does not allow for the full top width. These channels should be revised to simple
conveyance only, and water quality computations removed.
4. Provide sections and details for each grass Swale.
Rev. 1: Sheet #21 is essentially a hidden detail. Please include relevant details in the block/section
drawings. This block plan is sheets 5 -7. Please include details for each channel on these sheets, with
correct dimensions and channel linings shown.
5. Contributing drainage areas to the swales appear incorrect. The full drainage area cannot simply be
split with half going to each grass swale, as much of the area appears to drain directly to the basin.
Please adhere to the guidelines in the state specification; 5 acres maximum.
Rev. 1: Please show drainage areas which work with the final contours.
6. Remove the haul road which goes directly over the ditch and diversion on the east side of the basin.
This is unmanageable.
Rev. 1: A culvert has been shown, and this is theoretically acceptable. However, if the haul road is a
temporary measure, it should not be on the stormwater management plan.
7. Biofilter/basins should have forebays and energy dissipation/spreaders at concentrated inflows.
Rev. 1: Addressed.
8. The proposed grading does not appear to tie in correctly at points on this plan, and clearly goes outside
limits of disturbance. Correct the grading.
Rev. 1: Please correct grading shown outside limits. There is still grading outside limits, and a low
spot in the wooded area along Glenmore Way.
9. Label and dimension the facilities on the cross sections.
Rev. 1: addressed
10. Provide riser details and dimensions on the cross - sections, and provide anti - clogging measures.
Rev. 1: No controls found, and no computations provided. The details on sheet 19 do not agree with
Engineering Review Comments
Page 5 of 11
the sections.
11. The dam should be 3:1 or flatter on the downstream face. Dimension heights and top widths.
Rev. 1: The sections do not appear correct. The scales are so skewed it is hard to tell, but the cross -
sections are drawn at an angle to the slopes, so the slopes should appear flatter than the noted 2:1 or
3:1. It would be better to choose cut - sections perpendicular to the dam, so that slopes measure
accurately.
12. The underdrains need to be installed in the gravel layer below the media in any biofilters, and
cleanouts must be provided.
Rev. 1: Show cleanouts.
13. Sheet 14 standard details are confusing, as they don't match the cross - section details. If the specific
sections and plans are done correctly, these generics should not be needed.
Rev. 1: I think this is sheet 19 now.
14. On the cross - sections, remove the sub - surface EC -2 matting. This should be a surface application for
stabilization.
Rev. 1: addressed.
15. Rev. 1; Facility AS 3B; Show the underdrain layout, so it is clear not all the pipes go through the dam,
as seems to be drawn on the cross - section.
16. Rev. 1; Facility AS 313; Revise the section to show structural fill as noted, and not rip -rap. Show the
emergency spillway properly. Please revise to match controls. You cannot control storm flows in
inches with a spillway of large jagged stones.
17. Rev. 1; Please include the soil specifications called out in the sections.
18. Rev. 1: The VRRM spreadsheets for this block do not have the grass swales, and still provide adequate
removal. If the grades and details are not working, grass swales could be removed at this stage, and
converted to conveyance channels only.
19. Rev. 1; Facility AS 3A; It is not clear what the outlet will look like for this facility. The section shows
an outlet invert 2.5ft below grade, which is not appropriate. The plan seems to show a rip -rap apron
on grade into the preserved area.
20. Rev. 1; Please address adequate channel outfalls for both basins.
21. Rev. 1; Please provide the routing computations for each basin to verify water elevations shown on
plans. The results on sheet 26 do not provide enough detail to be independently verified. (We cannot
read proprietary pondpack files provided on the disc, unless you want to provide a copy of the software
to the county.)
Area 2: (Block B)
Engineering Review Comments
Page 6 of 11
1. The basin contributing area is too large. Please adhere to the guidelines in the state specification.
Rev. 1: Most of the contributing drainage area to basin BS3a appears to drain naturally to BS3b. It
would make sense to make BS3b the larger basin. But, with 5.15 acres total, there is no reason the
haul road, as the dividing line, cannot be moved to make these drainage areas about equal and more in
line with the guideline. As it is now, BS3a has most of its CDA shunted to one high maintenance
RWD, and short circuiting BS3a. In addition, the drainage areas appear to be in error around the
periphery.
2. The wet Swale does not appear to have a water source.
Rev. 1: The Swale has been lowered. However, this wet swale still does not appear to have a source
without being contiguous with the stream like adjacent wetlands. This should be revised per comment
1 to be a biofilter.
3. See cross - section comments for Area 1. Most apply here.
Rev. 1: Not addressed. This should be revised per comment 1 and previous comments.
4. Rev. 1: The VRRM spreadsheets for this block do not match plans. In addition, there are uncontrolled
areas of graded slopes not captured by facilities which must contribute to load computations.
5. Rev. 1; Please address adequate channel outfalls for both basins.
6. Rev. 1; Please provide the routing computations for each basin to verify water elevations shown on
plans. . The results on sheet 26 do not provide enough detail to be independently verified. (We
cannot read proprietary pondpack files provided on the disc, unless you want to provide a copy of the
software to the county.)
Area 3: (Block C and E)
1. The wet swale does not appear to have a water source.
Rev. 1: This does not appear to be a viable design without a water source. It is graded more of a basin
anyway, and less of a swale, and does not appear to be in the spirit of Design Spec. No. 11.
2. CS3a contributing drainage area is too large, and the other 2 channels are too narrow, and too steep in
sections. Please adhere to the guidelines in the state specification.
Rev. 1: Not addressed. With the VRRM spreadsheets provided with this revision, it is evident that
these channels are not necessary to meet water quality compliance. They should be conveyance only
if they cannot meet design guidelines and specifications, and references and computations for water
quality should be removed.
3. Please adhere to the guidelines in the state specification for the wet pond. The wet pond does not have
the minimum contributing area and appears to be excavated next to a stream. Physical testing of the
groundwater table is required for design. If it interferes, the pond may not achieve adequate water
quality removal according to the spec. 3:1 slopes on downstream faces must be provided uniformly.
The wet pond does not meet the type 2 criteria. It must have multiple cells and wetlands. Slopes
leading to the water should be 3:1 or flatter and a safety shelf provided. The geometry is not adequate
Engineering Review Comments
Page 7 of 11
for shortest flow path. Provide an emergency spillway or adequate freeboard.
Rev. 1: Not addressed. Plan notes and computations indicate this is intended to be a level 2 design
under Design Specification No. 14. It does not meet this specification. To make matters worse, the
large fluctuation in water levels during smaller storms, combined with steep side slopes and no
benches, could make it a safety hazard. With the VRRM spreadsheets provided with this revision, it is
evident that it could be a level 1 design and meet requirements. A level 1 design can have a single cell
with forebay, standard aquatic benches, and the shape should be redesigned to provide adequate flow
path (rather than using flimsy temporary baffles).
4. The detail on sheet 16 appears to be for a temporary riser setup. Please correct, and add these details
to the cross - section.
Rev. 1: This sheet now appears to be sheet 20. Please remove temporary measures from the stormwater
management plan. Please add permanent riser controls to the plan sections. Please show any
blankets(filter diaphragms) or cradles in the cross sections (details 5/20, 4/20).
5. It is unclear how the planting table on sheet 10 is to be incorporated on the plan.
Rev. 1: Show a typical planted area.
6. Please remove rip -rap rather than compacting into fill on dams, which appears as though it could leave
a water conduit through the structural fill if not done very well.
Rev. 1: Section D -D is still an issue, with rip -rap shown at the base of the dam. However, the wet
Swale needs to be revised anyway.
7. See cross - section comments for Area 1 -2. Most apply here.
Rev. 1: Not addressed. The cross - section appears incorrect. Sheet 14 shows a wetland shelf, but the
section does not. The top of dam must be wide enough for access, 10' typically. The two sections, of
the same facility, show difference slopes on the dam. The emergency weir must be dimensioned and
detailed..
8. Rev. 1: The VRRM spreadsheets for this block do not match the plans. The drainage area to the pond
is listed at 3.09 acres in the spreadsheet and 9.93 on plans. In addition, there are uncontrolled areas of
disturbance not captured by facilities which must contribute to load computations.
9. Rev. 1; Please address adequate channel outfalls for both basins.
10. Rev. 1; Please provide the routing computations for each basin or pond to verify water elevations
shown on plans and required volumes. The results on sheet 26 do not provide enough detail to be
independently verified.
Area 4: (Block D)
1. Please do not include off -site areas which can be diverted. These areas may change in the future,
affecting results.
Engineering Review Comments
Page 8 of 11
Rev. 1: HS3a still shows a large portion of its contributing drainage area on the fire station property.
The parking lot must be shown as impervious in the computations if this is to remain.
2. Please see comments for areas 1 -3, many apply here.
Rev. 1: see below.
3. Rev. 1: The wet Swale without a water source is not a viable option here. Please change to a biofilter.
4. Rev. 1: Show cleanouts and layout of underdrains, as the section seems to indicate all drain through
the dam.
5. Rev. 1: The rip -rap shown through the dam is still an issue, as it is lower than the biofilter(s). In
addition, the outlet elevation and flows cannot be controlled in inches with rip -rap sizes much larger.
8. Rev. 1: The VRRM spreadsheets for this block must account for the disturbed areas which are going
untreated.
9. Rev. 1; Please address adequate channel outfalls for both basins.
10. Rev. 1; Please provide the routing computations for each basin to verify water elevations shown on
plans and required volumes.
File: E2_swm_GEB_RivannaVillagePhasel - Copy.doc
C. Erosion and Sediment Control Plan (ESCP) Max Greene's comments
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. Match lines would be helpful to the inspector /contractor.
Comment appears adequately addressed at this time.
2. All proposed grade lines will be within the limits of disturbance.
Comment does not appear adequately addressed. There are lines (Contours ?) outside of LOD on sheets
5 and 7 of 26 of the SWM plan.
3. There appears to be a basin proposed on sheet 8 of 9 on the bottom of the page across from the
Glenmore entrance. There is no outlet for this sump area. Please explain.
Sheet 8 of 19 appears to show the need to fill into the proposed tree protection area or create a pounding
area that could lead to erosion across the fill area into the basin. This area is protected by the basin and
should be corrected with the site plan grading.
4. Silt fence is shown very close to the edge of stream. Please place a note on the plan sheets "Silt
Fence and Diversions will be kept a minimum 5' from top of bank. If a discrepancy occurs in
the field for silt fence and/or diversion installation then the plans will be amended to reflect the
changes required to keep the silt fence and or Diversion a minimum 5' from top of stream
bank."
Comment appears adequately addressed at this time.
5. Silt fence should follow contours. Low points in silt fence are pounding areas and tend to fail from
excessive collection of water and silt. Traps may be required "in field" should these areas show
Engineering Review Comments
Page 9 of 11
potential for failure. Project delay could occur if a new plan is required for field adjustments.
"Operator" will need to be proactive to prevent delays.
Low points and pockets are still proposed in the silt fence alignment with this submittal. Potential fines
and delays may occur from run -off producing storm events. This office recommends correcting the silt
fence alignments to remove the low- points /pockets.
6. Silt fence installed down a slope is essentially a diversion and tend to cause erosive velocities and
blow -outs in low points of silt fence. If silt fence must be utilized down slopes then check dams
should be installed to slow the velocities and to force the stormwater through the filter fabric. (See
note #3) Diversions are recommended for down slope installations.
No comment
7. Temporary Stream Crossings do not appear to be adequately addressed.
a. Please Refer to VESCH Std. & Spec. 3.24 Temporary Stream Crossing (SC) Design Criteria
Page III -221 note d for diversion requirements.
b. Please add VESCH Std. & Spec. 3.24 Temporary Stream Crossing (SC) Construction
Specifications "Temporary Bridge Crossing" to the plan.
Detail on sheet 14 of 19 appears adequate at this time.
8. Please place a note on the plans: "Silt fence will NOT be installed across the outlet of any
stormwater detention structure. Pipe Outlet: Silt fence shall be installed over the outlet of pipes.
Stone Weir: Silt fence shall be turned up slope on either side of weir outlet.
Comment appears adequately addressed at this time.
9. Limits of disturbances appear to include sanitary sewer installation limits. Early grading does not
allow for the installation of sanitary sewer lines or other hardscape. Please remove the limits of
construction for infrastructure such as sanitary or storm sewer line installation.
Clearing for sanitary installation is not approved with this plan.
10. Proposed silt fence appears to have an existing swale intersecting perpendicular to the silt fence. The
silt fence directs the storm flows to the low point in the corner adjacent to the wetland area. A
diversion and trap should be shown in this location instead of silt fence.
This may remain a problem area on sheet 10 of 19.
11. Sediment basin AS 1 a is missing the outlet structure and riser pipe on plan view. (Page 7 of 19)
Comment appears adequately addressed at this time.
12. Proposed diversion AS1a appears to have an existing swale intersecting perpendicular to the diversion
and is also the low point of the diversion. Stormwater will not make it to the basin as shown until the
fill material is placed. Please show a temporary trap in this location. (Pages 7 of 19)
Comment appears adequately addressed at this time.
13. Silt fence and fill material appear to encroach on existing swale at the top of page 10 of 19. Swales
should not be blocked with silt fence. A sediment trap is recommended in this area; otherwise, pull
the proposed grading toe of slope back to top of 2 year storm elevation for swale to prevent erosive
undermining of silt fence.
Comment appears adequately addressed at this time.
14. Erosion control measures are not shown for East side of sediment trap BS2b along limits of
disturbance. (page 10 of 19)
Silt fence does not appear to meet the minimum requirements of Std. & Spec. 3.05. the length of
disturbance appears to exceed the capacity of silt fence capabilities.
15. Silt fences and diversions on Stage 2 plans sheets have all most disappeared from view like the
existing contours. Please make sure the shading of E &SC measures that are to remain are clearly
recognized on the plan sheets.
Existing contour lines are still too lightly shaded to follow. Please darken the existing contour lines.
16. Proposed travel ways that cross over a diversion will require a pipe or other State approved method
designed for the 10 year storm event.
See comment #21 below.
New comments due to changes on submittal:
Engineering Review Comments
Page 10 of 11
17. Proposed grading is shown under and below silt fence on sheet 8 of 19. Please move the silt fence to
capture the proposed disturbance.
18. Existing conditions /topography is not legible on several of the plan sheets. Please make the plans
legible. Adequate review was not possible for vague pages.
19. Silt fence shown in /across the proposed fill/grading is allowed and will be bonded and inspected for
compliance. This office recommends removing the internal silt fence across construction site.
20. Sheet 8 does not appear to match to sheet 10 and sheet 10 does not appear to match up with sheet 12
and sheet 12 does not appear to match to sheet 13, etc. Please make plans match/overlay.
21. The right of way diversions appear to be labeled (DV) instead of (RWD).
22. Please label all baffles in basins.
Additional comments and /or conditions may be forthcoming due to requested changes to plan.
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 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. DEQ will review the application information based on local VSMP
authority approval. 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.
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;
httD://www.albemarle.or2/deDtforms.asD?deDartment=cden2WDO
File: E1_vsmp_review_projectname.doc
Engineering Review Comments
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