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February 13, 2015
Justin Deel
Albemarle County Community Development
401 McIntire Road
Charlottesville, Virginia 22902
RE: Whittington Phase B—(WPO 2014-00094)Comment-Response Letter
Dear Justin,
Enclosed please find two (2) sets of VSMP Plans that have been revised based on your comments in
accordance with the following:
A. Stormwater Pollution Prevention Plan (SWPPP)
1. Please use the standard template from the County website. You are presenting this as a revision to expand
an existing SWPPP. Your registration statement was for 184.1 acres, 75.4 of which was disturbed. The new
plans indicate phase A was 29.9 acres and phase B is 154 acres. Please clarify the actual acreage disturbed,
and all acreages on the documents. Please incorporate the active SWPPP document, which this will replace in
large part.
RESPONSE: The SWPPP contains the entire acreage of the project, but only the disturbed area of
Phase B. There will be one SWPPP for Phase A and one SWPPP for Phase B. The contractor will be
responsible for maintaining the two separate SWPPPs. This method is being used since the VSMP
permitting was completed in two phases for the project. The county template has been used for the
SWPPP.
2. Include only items in template and/or County Code Section 17-405.
RESPONSE: The SWPPP contains all items listed in section 17-405.
3. Provide any necessary TMDL measures.
RESPONSE: The TMDL study for the wasteload allocation established for the South Fork Rivanna River
will not be completed until 2022. A note has been added to the notes on the left hand side of Sheet E2.
B. Pollution Prevention Plan (PPP)
1. Please address all items listed in section 17-404 of the County Code.
RESPONSE: The PPP contains all items listed in section 17-404.
C. Stormwater Management Plan (SWMP)
1. It is unclear to us, and warrants further discussion, as to how your proposed stormwater management plan
stays within the approved ZMA plan. This may not be essential for the grandfathering provisions in the state
code, as DEQ already issued a permit for this activity. However, the stormwater management needs to meet the
IIC criteria, and at least provide the coverage intent of the approved ZMA plan. There do not appear to be
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enough of the roadways and houses captured by treatment. The original plan showed rain gardens in the cul-
de-sacs and intersections, and large ponds, with the intent to capture all of the roads, and the majority of lots
central to the development. The new plan leaves large stretches of road and lots untreated, with grading that is
problematic in providing permanent capture to the BMP facilities. Please revise to provide follow the natural
drainage of the topography. Coordinate to provide adequate sediment trapping for erosion and sediment control,
along natural topography, outside limits of final lot and road grading, and coordinated for conversion to
permanent stormwater management.
RESPONSE: Whittington Phase B meets the IIC Criteria for Virginia Stormwater Management Plans.
Documentation and calculations, including all hydraulic and hydraulic computations and runoff
characteristics,verifying compliance with the water quality and quantity requirements have been
provided with this submission. As discussed at the post-submission conference, some impervious
areas are not required to be treated for water quality since the percent imperviousness in these sheds
are less than 16%. This is indicated on the attached BMP worksheets. With respect to adequate outfall,
the plans have been updated to indicate no increase in 2 and 10-year runoff volume at each outfall point.
Also, analyses has been provided of onsite and offsite outfall ditch cross sections to indicate that the
post-development 2-year velocity is non-erosive. Refer to Sheet E47 and attached channel cross-
sections.
2. Please provide proposed mapping and plans, showing drainage areas for proposed stormwater management
facilities, at a legible scale (preferably at least 1" = 50').
RESPONSE: Drainage areas for proposed stormwater management facilities are shown at a legible
scale.
3. Show stream/wetlands buffer at SWM-3/SB-1 and add mitigation accordingly.
RESPONSE: The stream buffer has been shown at SWM-3/SB-1. A note has been added to sheet E42
"100'stream buffer on ephemeral stream is based on current Albemarle County mapping of project in
Rural Area. This stream buffer will be removed with the adoption of the 2015 Comprehensive Plan that
will place this site in the Development Area. Refer to final plat for stream buffer location. As discussed
at Engineering Meeting on February 12, 2015, no grading permit will be issued for this area until the
development is added to the development area.
4. Provide sediment forebays in all SWM facilities [VSMH Vol. 1, 3.04].
RESPONSE: Sediment forebays have been provided with this submittal.
5. Provide measures to avoid short-circuiting in SWM-3 and SWM-7 [VSMH Vol. 1, 3.06-12-13]. The basins
should meet the flow and shape design parameters. (Baffles should not be a part of permanent designs.)
RESPONSE: For many of the facilities,the addition of a sediment forebay has effectively prevented the
short-circuiting. Where this is not possible, one-foot high earthen embankments have been added to
avoid short-circuiting of the incoming runoff.
6. Provide facility access per VSMH Vol. 1, 3.06-18.
RESPONSE: Access to the SWM facilities has been provided.
7. Existing topography is not labeled on some SWM facility details, please correct.
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RESPONSE: Existing topography has been labeled for all SWM facilities.
8. Show accurate existing topography for SWM-4.
RESPONSE: Accurate existing topography has been shown for SWM-4.
9. Provide scaled cross sections for SWM facilities, including biofilters, in place of old typical details (E43).
RESPONSE: The scaled cross sections have been provided for the sediment basins and the SWM
facilities.
10. Please remove Proffered Overlot Grading Plans. They appear to be largely redundant in this plan set.
Grades should be shown anyway as part of an E&S/SWM plan package. The overlot grading plan is a zoning
requirement as part of the proffers, which are not enforced through the VSMP program.
RESPONSE: The Proffered Overlot Grading Plan has been removed and has been added to the Road
Plan as discussed at the January 15, 2015 Engineers meeting.
11. The County BMP spreadsheet is no longer acceptable. Designs must follow the state IIC or IIB criteria.
RESPONSE: Whittington Phase B meets the IIC Criteria for Virginia Stormwater Management Plans.
Documentation and calculations, including all hydraulic and hydraulic computations and runoff
characteristics,verifying compliance with the water quality and quantity requirements have been
provided with this submission.
D. Erosion and Sediment Control Plan (ESCP)
1. Please explain how your phasing plan (E3)will be implemented. It appears as though the installation of the
sanitary sewer line will warrant E&SC measures that will not occur until subsequent phases.
RESPONSE: The phase lines that were originally shown on Sheet E3 have been removed. It is
anticipated that the developer will bond the overall project E+S/SWM Controls and then submit phased
road plans/plats following approval of the overall plan. Please note that for the E+S Plans have been
prepared in two phases. Phase one consists of rough grading for the roads and E&S measures
associated with the land disturbing activity. Phase two consists of grading for the houses and utility
installation and E&S measures associated with land disturbing activity.
2. Mitigation for disturbance to stream buffers should occur within the affected stream buffer, please correct
[Albemarle Co. Code 17-604 C.5]. Mitigation can occur in other stream buffer areas, but mitigation is not valid
outside stream buffers unless it is additional stormwater treatment for discharging into buffers.
RESPONSE: The mitigation for disturbance to the stream buffer will be satisfied by planting of the
stream buffer at the Westlake Hills subdivision in Crozet.
3. Your wetlands report shows a wetland in the areas of SB-1 and SB-3. Please provide a stream buffer for
these areas and include in your mitigation plan.
RESPONSE: The stream buffer has been shown at SWM-3/SB-1. A note has been added to sheet E42
"100'stream buffer on ephemeral stream is based on current Albemarle County mapping of project in
Rural Area. This stream buffer will be removed with the adoption of the 2015 Comprehensive Plan that
will place this site in the Development Area. Refer to final plat for stream buffer location. As discussed
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at Engineering Meeting on February 12, 2015, no grading permit will be issued for this area until the
development is added to the development area.
4. Grading for SB-3 affects a stream/wetland that is not within your stream buffer. Please explain why this is not
included in the buffer.
RESPONSE: See above response.
5. Please explain why the northwesternmost stream on the property is excluded from your shown stream buffer.
RESPONSE: This area is an isolated wetland area and therefore does not require a buffer.
6. Please adjust your limits of disturbance to include all affected areas, not just the areas that are to be graded.
RESPONSE: The limits of disturbance have been adjusted to include all affected areas. Areas not
included in the limits of disturbance are surrounded by tree protection.
7. Provide staging/stockpile area(s).
RESPONSE: Staging/Stockpile areas have been provided with this submission.
8. Show dust control and temporary/permanent stabilization.
RESPONSE: Dust control,temporary and permanent stabilization have been provided with this
submittal.
9. Please do not show silt fencing going down/up hill. Silt fencing should be"stepped down".
RESPONSE: The silt fence has been adjusted to use the stepped down method requested.
10. Silt fencing should not be used in place of diversion dikes. Please provide diversion dikes and/or sediment
traps where needed (Ex.: the silt fence traversing the southern portion of Sheet E21).
RESPONSE: Sediment traps and diversion dikes have been designed in places where there are natural
low points for the site.
11. Provide legible drainage areas on E&SC plans. The provided drainage area maps are unclear and several
are unrealistic(Ex.: Drainage area for ST-12).
RESPONSE: The drainage area maps have been revised to be at a larger scale and are therefore more
legible. Diversion dikes have been placed in situations where the drainage area appears unrealistic.
12. Please show topography for the entire drainage area at ST-16. It appears as though the ridgeline may be
beyond your drainage area.
RESPONSE: The entire drainage area for ST-16 has been shown with this submittal.
13. Culvert designations vary on E&SC plans and drainage plan (E31), please correct.
RESPONSE: The culvert material designation have been revised so that they match throughout the plan
set.
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14. Please show realistic shapes for sediment traps and basins (Ex.: ST-1).
RESPONSE: Sediment traps are designed to adhere to the natural topography of the site and reduce the
overall Limits of Disturbance. As discussed at the January 15, 2015 engineers meeting,these shapes
are acceptable.
15. Provide a construction entrance that drains to a sediment trap or basin [VESC Handbook, 3.021
RESPONSE: The construction entrance drains to SB-2.
16. Show critical slopes on E&SC plans.
RESPONSE: Critical slopes have been shown on Sheet E4.
17. Show proposed Phase 1 topography as existing topography on Phase 2 plans. Ideally, phase N1 areas are
already graded, and topography should be resurveyed in these areas.
RESPONSE: Phase A topography is shown as existing on Phase B plans.
18. Show existing topography for Phase A.
RESPONSE: The existing topography is shown for phase A.
19. Please provide an explanation for your"Phasing Plan", Sheet E3.
RESPONSE: The phase lines that were originally shown on Sheet E3 have been removed. It is
anticipated that the developer will bond the overall project E+S/SWM Controls and then submit phased
road plans/plats following approval of the overall plan. Please note that for the E+S Plans have been
prepared in two phases. Phase one consists of rough grading for the roads and E&S measures
associated with the land disturbing activity. Phase two consists of grading for the houses and utility
installation and E&S measures associated with land disturbing activity.
20. Include proposed sediment basin at Phase B entrance in your limits of disturbance. Please show existing
topography and provide a designation for this basin.
RESPONSE: Proposed sediment basin SB-2 has been added to the limits of disturbance.
21. Provide detail for CWD, these are not a part of the VESC Handbook.
RESPONSE: A clean water diversion detail has been provided on Sheet E29.
22. The CWD above the cut on Sheet E14 should follow limits of disturbance to avoid high velocity flow into
wetland, please adjust.
RESPONSE: The clean water diversion follows the limits of disturbance to avoid high velocity flow into
the wetland.
23. Anywhere silt fence or diversions are coming to a point at a natural drainage low spot, a sediment trap or
basin must be provided. As an example, provide a sediment trap for the fill slope between STA 21+00 and
20+00 on Sheet E5.
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RESPONSE: Sediment traps and diversion dikes have been designed in places where there are natural
low points for the site.
24. Provide sediment trapping measure in front of Lot 26.
RESPONSE: A sediment trap has been provided in front of lot 26.
25. Provide more effective E&SC measures at stream crossings.
RESPONSE: Mud traps have been provided below sediment traps to provide more effective E&S
measures at stream crossings.
26. Provide a sediment trap for the fill slope at the end of Kentra St., Phase 1.
RESPONSE: A sediment trap has been provided at the end of Kendra St.for Phase 1. In order to make
this trap effective,we utilized a 1:1 slope as appropriate and as allowed by the VESCHB.
27. Show how drainage on Sheet E12 will reach ST-7.
RESPONSE: The drainage will reach ST-7 using a diversion dike.
28. Please show access easement for Singleton Lane.
RESPONSE: The access to Singleton Lane is contained within an onsite stormwater management
easement. The connection is being made directly to the Singleton Lane right-of-way.
29. Provide scaled details (sections)for basins.
RESPONSE: Scaled cross sections for basins have been shown on Sheets E23-E25 and on the
permanent stormwater management facilities on Sheets E38-E40.
30. Please clarify what you are proposing at ST-14, Phase 2.
RESPONSE: Sediment traps and diversion dikes have been designed in places where there are natural
low points for the site. The sediment trap is to be cut into the hill before grading for lot 26 is done.
31. Please provide adequate E&SC measures to protect WPO buffer. More than silt fencing will be required to
protect WPO buffer in many areas.
RESPONSE: One of the lots has been relocated to the top of Cottontail Way in an effort to reduce the
overall impact near the WPO buffer.
32. Provide E&SC measures, other than silt fencing, beneath fill slopes east of Kendra St., especially lot 39.
RESPONSE: A sediment trap has been designed beneath the fill slope east of Kendra St.
33. Ensure that all sediment basins outfall into an adequate channel.
RESPONSE: An adequate channel analysis has been added to the plans that indicate all basins outfall
into an adequate channel. Refer to Sheet E47 and the attached computations booklet.
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34. Is ST-13 not included in Phase 2? It appears as though it is needed and is included in Phase 2 drainage
area map, but not in Phase 2 plan.
RESPONSE: ST-13 will remain in place until stabilization of the surrounding area. Final grading will
take place once the upper reaches of the drainage area are stabilized.
35. Please make sure all existing and proposed contours are labeled on all plan sheets (Ex.: Proposed contours
on Sheet E13 are not labeled, existing and/or proposed contours are not labeled on many of the sediment
basin/trap details.
RESPONSE: All existing and proposed contours are labeled on all plan sheets.
36. Further, please ensure that all structures and embankments match permanent design for facilities to be
converted to permanent stormwater management facilities.
RESPONSE: All structures and embankments match permanent design for facilities to be converted to
permanent SWM facilities.
37. Diversion dike cannot go through home lots. As stated in the stormwater management comments, please
ensure all protection measures are outside lot and road grading where ongoing maintenance is not possible.
Perimeter protections must be on the perimeter.
RESPONSE: The diversion dike in question has been abandoned.
38. Silt fence alone is not adequate enough on and around Lot 28, please correct.
RESPONSE: Sediment traps and diversion dikes have been designed in places where there are natural
low points for the site.
We thank you for taking the time to review this revision and please let me know if you have any questions or
require additional information.
Best Regards,
Dustin Greene, EIT.
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June 5, 2015
Glenn Brooks, P.E.
County Engineer
Albemarle County Community Development
401 McIntire Road
Charlottesville, Virginia 22902
RE: Whittington Phase B—(WPO 2014-00094)
Dear Glenn,
Please consider this letter and attached exhibit as our request to use a 3.7-acre portion of the Westlake Hills
Subdivision—Phases II, Ill and IV (WPO 2014-00031)to meet the onsite mitigation planting requirements for
the Whittington—Phase B subdivision. This request is being made in accordance with Albemarle County
Zoning Ordinance 17-403(A)(9) and item A(5) of 9VAC25-870-69 for"Offsite Compliance Options"as described
below in which a letter of availability must be provided from the offsite landowner. Based on your approval of
our request,we will then work with the County Attorney's office to coordinate the form of the letter.
By way of background information,the developer is proposing to construct 79 single family lots and associated
infrastructure on Whittington—Phase B, which consists of approximately 154 acres of land. In order to
construct the lots and required infrastructure as shown on the approved PRD plan (ZMA 2006-00011) and
Preliminary Subdivision Plat(SUB 2014-00110),we require clearing for three road crossings and three
permanent stormwater management facilities that are located in the landward 50-foot portion of buffer. The total
amount of land disturbance within the onsite stream buffer is 1.75 acres. As part of the mitigation requirements
for disturbing the stream buffer with a road crossing,the developer is typically required to replant other buffer
areas onsite at a rate of 2:1, or in this case, 3.7 acres.
The Whittington Phase B site is completely wooded and there are no available buffer areas onsite in which to
provide the mitigation plantings. However,the developer, Stanley Martin, has control over the Westlake Hills
Subdivision, located in Crozet which has approximately 3.7-acres of existing cleared stream buffer area as
shown in green on the attached map. It is our intent to use mitigation plating from the Westlake Hills stream
buffer to meet the onsite mitigation planting requirements. This option is supported by Zoning Ordinance
Section 17-403(A)(9) regarding offsite compliance as follows:
Offsite compliance options. If an owner intends to meet the requirements established in section 17-502, which
implements 9VAC25-870-63 and 9VAC25-870-66, through the use of off-site compliance options, where
applicable, a letter of availability from the offsite provider.
The offsite compliance options are found in 9VAC25-870-69, particularly, item A(5),which states:
A(5)... When an operator has additional properties available within the same HUC or upstream HUC that the
land-disturbing activity directly discharges to or within the same watershed as determined by the VSMP
authority, offsite stormwater management facilities on those properties may be utilized to meet the required
phosphorus nutrient reductions from the land-disturbing activity.
The ability of a riparian buffer to provide phosphorus nutrient reduction is described in the Riparian Buffer
Modification& Mitigation Guidance Manual"published by the Chesapeake Bay Local Assistance Department
(CBLAD). The manual states, "Riparian buffers are noted for their ability to protect or enhance water quality. A
vegetated riparian zone can trap sediment and reduce nutrients and other chemicals from precipitation, surface
waters and ground waters."
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The CBLAD manual goes on to state that `Because riparian buffers can act to remove sediment from runoff, a
buffer that is effective in removing sediment should also remove the majority of total phosphorus."
Furthermore,the Westlake Hills Subdivision is located in an upstream watershed and Hydrologic Unit Code
(HUC)from the Whittington watershed. The point of confluence to both subdivisions is at the Rivanna River in
the location as shown on the below area map.
We are seeking your approval of the offsite mitigation request so that we may proceed with the formal approval
of the offsite mitigation agreement with the County Attorney's office.
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We thank you for taking the time to review this request and please let me know if you have any questions or
require additional information.
Best Regards,
Mi9nael Myers, P.E., C.F.M.
Cc: Jeremy Swink
Pete Caramanis
Attachment
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Justin Deel
Albemarle County Community Development
401 McIntire Road
Charlottesville,Virginia 22902
RE: Whittington Phase B—(WPO 2014-00094)Comment-Response Letter to Supplemental Comments
Dear Justin,
We wanted to thank you and Glenn for taking the time to meet with us on April 30, 2015 and May 7,2015 to discuss our
responses to your supplemental comments below regarding the VSMP plans. Below,please find our responses:
Stormwater Management Plan: As we discussed at our last meeting,you have really taken the hardest path to
implementing an old rezoning plan.The county has a handful of these older rezoning plans,and getting final plans
approved in accord with them is difficult.The easiest path to approval of final plans is to implement the rezoning plan. The
next alternative is to amend the zoning with a new concept plan which is easier to implement.Next,it is theoretically
acceptable to use a new plan with the new VSMP criteria,and process a zoning variation on the grounds that it is an
improvement.The last and worst option,is to try a new plan, while simultaneous trying to follow the old zoning plan,and
prove equivalency through computations.This is the option you have taken.
We are not yet able to decipher your alternative concept, and have real trouble even piecing together the complete picture.
It is essential that you provide a plan sheet showing the entire development proposal, stormwater facilities and drainage
areas used for stormwater management and water quality computations to illustrate your concept. We must be able to
compare it with the ZMA plan. Please finalize this overall approach with the county before creating detailed plans.
RESPONSE: Based on resolution reached on May 8,we are providing computations in the plans that indicate the
following information:
a) We are treating more impervious area than was treated on the zoning plan.(See Sheets E34 and E35)
b) We are reducing the phosphorus load at each outfall point of analysis.(See Sheets E36 and E38)
c) We are reducing the peak volume of runoff at each outfall point of analysis.(See Sheets E37 and E38)
The Hydrologic/Hydraulic Computations booklet also includes this information.
We also have obtained confirmation from David Benish in letter dated May 14, 2015 that the
proposed layout is in general accord with the zoning plan, and that a zoning variation is not
required as part of the plans approval process. A copy of this letter is attached to this submission
and can also be found on Sheet ES.
Erosion and Sediment Control Plan:At our last meeting, we spoke extensively about the proposed phasing on the
erosion control plan. However, with this revision,we are still not in agreement with the phasing.This seems to be the
primary source of difficulties in the county review.This set of plans is Phase B.It is a different geographic location than
phase A,which is already approved and under construction. This phasing works.The phases 1 and 2 of phase B plans
appear to be trying to the reduce sediment trap and basin sizes.This does not work.Phase I will essentially be removed
from the plan set or ignored. Phase 2 will be the effective erosion control plan.All facilities must be sized for the full
drainage area and disturbance, which appears to be shown in phase 2. Care should be taken not to grade such that
drainage carries through more than three lots.
RESPONSE: We have revised the plans to provide a significantly more robust erosion and sediment control plan
that provides trap/basin control in every location practical. We have also provided stepped silt fence for any areas
that are not treated by traps/basins. In order for this design to be functional,it is necessary that we obtain approval
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of our variation request to allow clean water diversions and mud traps. Please refer to attached variation request
that is provided with this submission. We have also added storm sewer where appropriate in any locations where
overlot drainage crosses more than three lots. We have also added a sequence of construction on Sheet Ell which
provides detailed information on how to implement the E+S plan.
Mitigation Plan:If you are trying something other than the usual mitigation,please run it by the county before submitting
plans. The usual mitigation is;(1)avoidance, (2)plantings in the project buffers, (3)stream restorations within the project,
or(4)additional water quality measures. Use the CBLAD Buffer Guidance Manual.
RESPONSE: Please refer to attached request to utilize mitigation on an offsite parcel that was prepared in
accordance with Albemarle County Zoning Ordinance 17-703(A)(9)and 9VAC25-870-69. Approval of this request
will be subject to drafting of a letter of agreement that is suitable to the County Attorney.
Again,thank you for meeting with us, and we look forward to working with you towards approval of the VSMP plans.
Please call me with any questions or if you require additional information.
Best Regards,
cifi r
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Mi,fiael Myers,P.E.
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June 12,2015
Justin Deel
Albemarle County Community Development
401 McIntire Road
Charlottesville,Virginia 22902
RE: Whittington Phase B—(WPO 2014-00094)Comment-Response Letter
Dear Justin,
Enclosed please find two(2)sets of VSMP Plans,SWPPP and Hydrologic/Hydraulic Computations that have been revised
based on your comments in accordance with the following:
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 use the standard template from the County website. You are presenting this as a revision to expand an existing
SWPPP. Your registration statement was for 184.1 acres,75.4 of which was disturbed.The new plans indicate phase A was
29.9 acres and phase B is 154 acres.Please clarify the actual acreage disturbed,and all acreages on the documents.Please
incorporate the active SWPPP document,which this will replace in large part.
(Rev. 1)Comment partially addressed.The County template has not been used,please do.
RESPONSE: We have updated the SWPPP to follow the County template.
2.Include only items in template and/or County Code Section 17-405.
(Rev. 1)Comment not addressed.Stormwater calculations should not be a part of the SWPPP document,please remove.
RESPONSE: We have removed the stormwater calculations and included only items in the County template.
3.Provide any necessary TMDL measures.
(Rev. 1)Comment partially addressed.Your response to the comment needs to be incorporated into the SWPPP
document.
RESPONSE: The note regarding TMDL measures has been incorporated into the SWPPP.
B.Pollution Prevention Plan(PPP)
The PPP content requirements can be found in County Code section 17-404.
1.Please address all items listed in section 17-404 of the County Code.
(Rev. 1)Comment partially addressed.Please follow the template.Use the index and numbering system,so our
inspectors know where to find items,and follow the instructions on the template for content.
RESPONSE: We have updated the SWPPP to follow the County template.
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. It is unclear to us,and warrants further discussion,as to how your proposed stormwater management plan stays within
the approved ZMA plan.This may not be essential for the grandfathering provisions in the state code,as DEQ already
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issued a permit for this activity.However,the stormwater management needs to meet the IIC criteria,and at least provide
the coverage intent of the approved ZMA plan.There do not appear to be enough of the roadways and houses captured by
treatment.The original plan showed rain gardens in the cul-de-sacs and intersections,and large ponds,with the intent to
capture all of the roads,and the majority of lots central to the development.The new plan leaves large stretches of road and
lots untreated,with grading that is problematic in providing permanent capture to the BMP facilities.Please revise to
provide follow the natural drainage of the topography.Coordinate to provide adequate sediment trapping for erosion and
sediment control,along natural topography,outside limits of final lot and road grading,and coordinated for conversion to
permanent stormwater management.(Rev.1)Comment not addressed.An overall stormwater management plan is not
found in this plan set.In order to approve what you are proposing in your response,an overall stormwater management
plan(s)must be provided showing each SWM facility with its respective clearly defined drainage area. We need to see what
areas you are proposing to treat and what areas will be left untreated.We need to see that you are in general accord with the
rezoning plan.Specifically,an attempt must be shown to capture and treat the areas that are shown as being treated in the
rezoning plan.
Please refer to supplemental comments provided by the County Engineer.
RESPONSE: We have met with Engineering on April 30,2015 and May 7,2015 to discuss the overall stormwater
concept plan and how it treats as much impervious area as was treated on the zoning plan. We reached agreement
on May 8,2015 of the overall concept. The plans have been updated to include updated sheets that clearly indicate
the overall SWM plan and updated computations and details. Also,we have updated the E+S plans to include one
phase only to ensure that perimeter controls are in place prior to road/mass grading.
2.Please provide proposed mapping and plans,showing drainage areas for proposed stormwater management facilities,at a
legible scale(preferably at least 1"=50').
(Rev.1)Comment addressed.
3.Show stream/wetlands buffer at SWM-3/SB-1 and add mitigation accordingly.
(Rev.1)Comment addressed.
4.Provide sediment forebays in all SWM facilities [VSMH Vol. 1,3.04].
(Rev.1)Comment not addressed.SWM 5&8.
RESPONSE: Sediment forebays have been provided in all SWM facilities.
5.Provide measures to avoid short-circuiting in SWM-3 and SWM-7 [VSMH Vol. 1,3.06-12-13].The basins should meet
the flow and shape design parameters. (Baffles should not be a part of permanent designs.)
(Rev.1)Comment partially addressed.The one-foot earthen embankments will not be adequate or practical in avoiding
short-circuiting and cannot be used.There is room to grade differently and reposition the primary spillway.
RESPONSE: The pipe inlets and outlets have been revised to avoid short-circuiting.
6.Provide facility access per VSMH Vol. 1,3.06-18.
(Rev.1)Comment partially addressed.Show access to SWM-4.
RESPONSE: An access road has been provided to SWM-4. Since this facility is located awkwardly on the sheet,we
have provided an inset map on Sheet E10 for clarity.
7.Existing topography is not labeled on some SWM facility details,please correct.
(Rev. 1)Comment not addressed.
RESPONSE: Additional existing topography labeling has been added to all SWM facility details.
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8. Show accurate existing topography for SWM-4.
(Rev. 1)Comment addressed.
9.Provide scaled cross sections for SWM facilities,including biofilters,in place of old typical details(E43).
(Rev.1)Comment partially addressed.Show crest elevations on all SWM details.Provide note concerning dam core and
compaction on sections.The old typical biofilter details and sections cannot be used,please remove these and provide only
actual details and sections.
RESPONSE: The crest elevations have been added to all SWM details. Geotechnical Engineering notes for dam
construction have been added to Sheet E2 with a reference on each facility. The old biofilter details have been
removed and replaced with actual details and cross-sections.
10.Please remove Proffered Overlot Grading Plans.They appear to be largely redundant in this plan set.Grades should be
shown anyway as part of an E&S/SWM plan package.The overlot grading plan is a zoning requirement as part of the
proffers,which are not enforced through the VSMP program.
(Rev.1)Comment addressed.
11.The County BMP spreadsheet is no longer acceptable.Designs must follow the state IIC or IIB criteria.
(Rev.1)Comment addressed.
Revision 1 Comments:
12. Slopes leading in to your basins are too steep. Any basin should have maximum 3:1 slopes for maintenance and safety
[VSMH Vol. 1,3.01-13].Please reflect this on your plans,details,and sections.
RESPONSE: We have added aquatic benches to all SWM facilities for safety. We are continuing to show 2:1 slopes
above the ponds in order to match the existing topography.
13.Please provide SWM facility type in your details(Basin 1,II,Bio-Retention).
RESPONSE: The SWM facility type has been added to each detail.
14.Show all facility structures in plan details,see riser in SWM-6 detail.
RESPONSE: All facility structures are shown in plan details.
15.Show proposed contours west of retaining wall at SWM-3.
RESPONSE: The proposed contours have been shown.
The computation package, included as an appendix to the SWPPP, could not be reviewed adequately, because it could not
be correlated to the plan set, and we anticipate changes to the overall concept.
RESPONSE: The computations package has been updated to reflect the approved overall concept.
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.
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1. Please explain how your phasing plan(E3)will be implemented.It appears as though the installation of the sanitary
sewer line will warrant E&SC measures that will not occur until subsequent phases.
(Rev.1)Comment addressed.
2.Mitigation for disturbance to stream buffers should occur within the affected stream buffer,please correct[Albemarle
Co.Code 17-604 C.5]. Mitigation can occur in other stream buffer areas,but mitigation is not valid outside stream buffers
unless it is additional stormwater treatment for discharging into buffers.
(Rev. 1)Comment not addressed.Mitigation should occur within the WPO buffer within this subdivision.
RESPONSE: We have included a formal request to utilize mitigation planting from the Westlake Hills subdivision
subject to a separate letter of agreement,the form of which is to be coordinated with the County Attorney. We have
also updated the mitigation areas and added mitigation notes to the plan sheet.
3. Your wetlands report shows a wetland in the areas of SB-1 and SB-3. Please provide a stream buffer for these areas and
include in your mitigation plan.
(Rev.1)Comment addressed.
4.Grading for SB-3 affects a stream/wetland that is not within your stream buffer.Please explain why this is not included
in the buffer.
(Rev.1)Comment addressed.
5.Please explain why the northwesternmost stream on the property is excluded from your shown stream buffer.
(Rev.1)Comment addressed.
6. Please adjust your limits of disturbance to include all affected areas,not just the areas that are to be graded.
(Rev.1)Comment partially addressed.There are still"gaps"in your limits of disturbance that will receive sediment.
Tree protection alone will not leave these areas unaffected by erosion and sediment.
RESPONSE: The limits of disturbance have been revised to include all affected areas.
7.Provide staging/stockpile area(s).
(Rev.1)Comment partially addressed.These areas require E&SC measures.
RESPONSE: Additional E&SC measures have been provided around the staging and stockpile areas.
8.Show dust control and temporary/permanent stabilization.
(Rev.1)Comment addressed.
9.Please do not show silt fencing going down/up hill. Silt fencing should be"stepped down".
(Rev.1)Comment partially addressed.The stepped down silt fencing looks good in some areas but other areas require
more adequate steps.
RESPONSE: The stepped down silt fence has been adjusted in the areas in question.
10.Silt fencing should not be used in place of diversion dikes.Please provide diversion dikes and/or sediment traps where
needed(Ex.:the silt fence traversing the southern portion of Sheet E21).
(Rev.1)Comment partially addressed.There are still several areas(see Revision 1 comments below)that need diversion
dikes leading to traps or basins.
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RESPONSE: The plans have been revised to add many more diversion dikes and sediment traps,especially
adjacent to the stream buffer.
11.Provide legible drainage areas on E&SC plans.The provided drainage area maps are unclear and several are unrealistic
(Ex.:Drainage area for ST-12).
(Rev. 1)Comment addressed.
12.Please show topography for the entire drainage area at ST-16.It appears as though the ridgeline may be beyond your
drainage area.
(Rev.1)Comment addressed.
13.Culvert designations vary on E&SC plans and drainage plan(E31),please correct.
(Rev.1)Comment addressed.
14.Please show realistic shapes for sediment traps and basins(Ex.: ST-1).
(Rev. 1)Comment not addressed.Our recollection of the discussion was that the shapes of the sediment traps and basins
should be realistic;ST-1 &ST-15,for example,are not.Realistic shapes are close to a square,circle or equilateral triangle,
and do not have narrow protrusions or turns,which tend to not be constructed,or to collect sediment unevenly,harming
functionality. Also,you are showing multiple proposed grading lines in several sediment traps,please clean this up(Ex.
ST-11,-19,-20).
RESPONSE: The contours have been cleaned up and the shapes of traps/basins have been revised to be more
realistic.
15.Provide a construction entrance that drains to a sediment trap or basin [VESC Handbook,3.02].
(Rev. 1)Comment not addressed.How are you proposing that the CE will drain to SB-2?Is there an existing cross drain
that is not shown?Otherwise,there should be a RWD.Also,the CE is not shown in Phase 2,please correct.
RESPONSE: Spot elevations have been added to indicate how the CE will drain to SB-2. Since the CE is located
across several match lines,we have provided an inset map on Sheet E10 for clarity.
16.Show critical slopes on E&SC plans.
(Rev.1)Comment not addressed.
RESPONSE: The critical slopes have been added to the E+S sheets.
17.Show proposed Phase 1 topography as existing topography on Phase 2 plans.Ideally,phase A/1 areas are already
graded,and topography should be resurveyed in these areas.
(Rev.1)Comment addressed.
18.Show existing topography for Phase A.
(Rev.1)Comment addressed.
19.Please provide an explanation for your"Phasing Plan",Sheet E3.
(Rev.1)Comment addressed.
20.Include proposed sediment basin at Phase B entrance in your limits of disturbance.Please show existing topography and
provide a designation for this basin.
(Rev.1)Comment addressed.
21.Provide detail for CWD,these are not a part of the VESC Handbook.
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(Rev.1)Comment addressed.
22.The CWD above the cut on Sheet E14 should follow limits of disturbance to avoid high velocity flow into wetland,
please adjust.
(Rev.1)Comment not addressed.This diversion has not been changed,rather the wetland is now being shown as
ephemeral stream.I see that this reflects the provided updated report by TNT Environmental.However,high velocity flow
should be avoided here whether this is wetland or ephemeral stream.Please correct. Perhaps the diversion should lead to
ST-11,which would need to be resized.
RESPONSE: The CWD has been extended to the bottom of the slope to avoid the high velocity flow. The use of
clean water diversions is critical to the design of the project to limit the amount of runoff treated by onsite E+S
facilities. It is also a beneficial practice in that it prevents clean runoff from mixing with construction runoff,which
reduces the potential volume of water that may contribute to downstream sedimentation. In order to use CWD's,
we have included an E+S variance request letter and fee.
23.Anywhere silt fence or diversions are coming to a point at a natural drainage low spot,a sediment trap or basin must be
provided.As an example,provide a sediment trap for the fill slope between STA 21+00 and 20+00 on Sheet E5.
(Rev.1)Comment partially addressed.Additional sediment traps and diversions are need throughout the site, see
Revision 1 comments below.
RESPONSE: Additional traps and diversions have been added throughout the site. The traps have been designed
to treat the maximum amount of runoff anticipated to reach the facility. As construction progresses,the amount of
runoff entering each facility may be reduced.
24.Provide sediment trapping measure in front of Lot 26.
(Rev.1)Comment addressed.
25.Provide more effective E&SC measures at stream crossings.
(Rev. 1)Comment partially addressed.Sediment traps at stream crossings should be moved further out of WPO buffers.
In most cases,the sediment traps will need to be moved into the proposed home lots.There should be a note on the plans
saying that the building permit for these lots cannot be issued until E&SC until a County inspector authorizes removal of
E&SC measures.
RESPONSE: The sediment traps have been moved outside of the buffer. Also,a note has been added to Sheet Ell
of the plans stating which lots can not receive a building permit until a County inspector authorizes removal of
E&SC measures.
26.Provide a sediment trap for the fill slope at the end of Kentra St.,Phase 1.
(Rev.1)Comment partially addressed.This trap needs to remain in place for Phase 2.Additional E&SC measures
(sediment traps)are needed at lots 39 and 40 as well.
RESPONSE: The trap at the end of Kendra Street has been adjusted to treat the upstream area from the road
construction. The diversion dike also intercepts a portion of runoff from Lot 39. Please note that the other portion
of runoff from Lot 39 will be protected by three layers of super silt fence as it was not feasible to construct another
sediment trap on the steep slope in that location.
27.Show how drainage on Sheet E12 will reach ST-7.
(Rev.1)Comment addressed.
28.Please show access easement for Singleton Lane.
(Rev. 1)Comment addressed.
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29.Provide scaled details(sections)for basins.
(Rev.1)Comment partially addressed.Please provide both existing and proposed grades on sections.
RESPONSE: Both existing and proposed grades have been added.
30.Please clarify what you are proposing at ST-14,Phase 2.
(Rev.1)Comment addressed.
31.Please provide adequate E&SC measures to protect WPO buffer.More than silt fencing will be required to protect
WPO buffer in many areas.
(Rev.1)Comment partially addressed.Please see Revision 1 comments below.
RESPONSE: Additional traps and diversions have been added throughout the site.
32.Provide E&SC measures,other than silt fencing,beneath fill slopes east of Kendra St.,especially lot 39.
(Rev. 1)Comment not addressed.See comment 26.
RESPONSE: Additional traps and diversions have been added beneath fill slopes east of Kendra Street. Also,see
response to comment#26 above.
33.Ensure that all sediment basins outfall into an adequate channel.
(Rev.1)Comment addressed.
34.Is ST-13 not included in Phase 2?It appears as though it is needed and is included in Phase 2 drainage area map,but not
in Phase 2 plan.
(Rev. 1)Comment addressed.
35.Please make sure all existing and proposed contours are labeled on all plan sheets(Ex.: Proposed contours on Sheet El3
are not labeled,existing and/or proposed contours are not labeled on many of the sediment basin/trap details.
(Rev.1)Comment not adequately addressed.See proposed contours on Sheet E22.Additional contour labels are need
throughout these plans,existing and proposed.
RESPONSE: Contour labels have been added throughout the plan set for both existing and proposed.
36. Further,please ensure that all structures and embankments match permanent design for facilities to be converted to
permanent stormwater management facilities.
(Rev. 1)Comment addressed.
37.Diversion dike cannot go through home lots.As stated in the stormwater management comments,please ensure all
protection measures are outside lot and road grading where ongoing maintenance is not possible. Perimeter protections
must be on the perimeter.
(Rev.1)Comment addressed.
38.Silt fence alone is not adequate enough on and around Lot 28,please correct.
(Rev.1)Comment not addressed.There are no E&SC measures to prevent stream buffer disturbance from the grading of
this lot.
RESPONSE: A diversion dike has been added to prevent stream buffer disturbance from the grading of Lot 28.
Revision 1 Comments:
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39.Ensure that sediment traps/basins in Phase 1 are designed for drainage areas increase with Phase 2.
RESPONSE: All traps and basins have been designed for ultimate drainage areas. This has been clarified on the
drainage divides sheets E21 and E22.
40.Many of your sediment traps and basins need diversions leading to them(SB-1,SB-4,ST-12,and others).
RESPONSE: Diversions have been added where appropriate.
41.The limits of disturbance around the CWD at around elevation 620' (Sheet E5)are unrealistic and need to be adjusted.
Is this being removed in Phase 2?Please clarify.
RESPONSE: The limits of disturbance have been adjusted in this location. The clear water diversions are to
remain in place permanently.
42.The diversions leading to ST-19 should remain in place in Phase 2,please correct.
RESPONSE: This has been addressed since the plans indicate only one phase of E+S controls.
43. More sediment traps and diversions are needed to protect the WPO buffer on both sides of Cottontail Way. Silt fencing
alone is not adequate.For example,Lot 23 needs diversions leading to a trap in the swale,as does the open space between
Lots 27&28.
RESPONSE: Additional traps and diversions have been added on both sides of Cottontail Way.
44. Silt fencing is needed to protect the stream buffer east of SB-1.Tree protection alone will not leave this area
undisturbed.
RESPONSE: A silt fence has been added at the bottom of the slope and a right-of-way diversion has been added to
direct runoff from the area east of the basin to the basin.
45.Diversions leading to a sediment trap are needed between Lots 43&44,please provide.
RESPONSE: Diversions have been added.
46.Provide silt fence and/or diversions behind Lots 11 & 12.
RESPONSE: The lots on the west side of Kendra Street have been adjusted,but the area in question is actually a
cut section,so disturbed area will not be untreated in this location and it will indeed flow to ST-7. A diversion has
been added where appropriate behind lots 7-9.
47.Drainage should not traverse more than 3 home lots without a sediment trap(Ex.Most of Kendra Street),please correct.
RESPONSE: As discussed at the engineer's meeting this comment refers to the need to pick up drainage in a storm
sewer system once it crosses three home lots. Storm sewer has been added where appropriate.
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48.Diversions and more silt fence are needed to protect WPO buffer at the back of the lots along Kendra St.
RESPONSE: ST-7 has been added to treat lots 7-12. Additional stepped silt fence has been added to treat lots 5 and
6. Also,the runoff from the existing culvert at station 21+75 is to be redirected to SB-4.
49.A sediment trap(s)is needed at Lots 38&39,and 68&69,please provide.
RESPONSE: Sediment traps have been provided. Also,see response to Comment 26 above.
50.Diversion dikes leading to a sediment trap are needed along the back of the proposed lots on the south side of Warbler
Way,please provide.
RESPONSE: Additional sediment traps and diversions have been added along the backs of the lots on Warbler
Way.
51.More than silt fence is needed to protect the WPO buffer at Lot 73.
RESPONSE: A sediment trap with diversions has been added.
52. ST-13 needs to be at the base of the slope with diversions leading to it.
RESPONSE: ST-13 has been removed and replaced with SB-5 with diversions.
53.Provide silt fence between SB-3&4 and the WPO buffer,there are labels in place but not drawn.
RESPONSE: Silt fence has been added.
54.Provide silt fence at SB-2.
RESPONSE: Silt fence has been added.
55.Please clarify SB-5 grading on Phase 1 &2 plans.Also,you are showing the basin outfalling into a sediment trap in
Phase 2.The basin should be located where this trap is located.Please correct and clarify this.
RESPONSE:Pine Knot Road E+S has been updated to provide three traps at the low end of the road to treat the
existing drainage sheds. SB-5 has been shifted to Lot 89,along with a temporary culvert to treat the upper half of
the roadway until the site is stabilized. Also refer to Sequence of Construction on Sheet Ell.
56.The riser/outfall at SB-1 should be placed in a location that would avoid short-circuiting.
RESPONSE: Acknowledged. The plans have been corrected.
57.Your sediment trap spillways are too small and are unrealistic,please correct.A practical limit with rip-rap is about 6
feet.
RESPONSE: The trap spillways have been revised accordingly.
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58.The diversion dike around ST-11 is unrealistic in that we feel it will be impractical to construct and inadequate,please
address.This ties in with the italicized comment below concerning your phasing approach.
RESPONSE: ST-11 has been removed in favor of providing a trap on the other side of the street. A diversion will
be provided until such time as the storm system is extended to this location. Also refer to Sequence of Construction
on Sheet Ell.
59.A variance is required for each proposed MT and CWD.
RESPONSE: A variance has been requested with this submission.
60.There are multiple proposed contours for ST-11, 19,&20,please clarify.
RESPONSE: The contours have been revised.
61.Please be consistent with DD/CWD line weights. Some are enormous while others are difficult to see. See Sheet E5.
RESPONSE: The line weights have been normalized.
We thank you for taking the time to review this revision and please let me know if you have any questions or require
additional information.
Best Regards,
77-.s
Mi;;hael Myers,P.E.
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August 13, 2015
Justin Deel
Albemarle County Community Development
401 McIntire Road
Charlottesville, Virginia 22902
RE: Whittington Phase B—(WPO 2014-00094)Comment-Response Letter
Dear Justin,
We wanted to thank you and Glenn for taking the time to meet with us on August 6, 2015 to discuss our
responses to your comments dated July 30, 2015 and Glenn's variation response letter dated July 15, 2015.
For your convenience, we have provided responses to only the "open"comments from your August 6 letter:
A. Stormwater Pollution Prevention Plan (SWPPP)
Revision 2 Comment:
4. Incorporate below requested changes in to SWPPP upon resubmission.
RESPONSE: Updated SWPPP information has been coordinated with the reviewer.
C. Stormwater Management Plan (SWMP)
4. Provide sediment forebays in all SWM facilities [VSMH Vol. 1, 3.04].
(Rev. 1) Comment not addressed. SWM 5 &8.
(Rev. 2) Comment not addressed. Provide detail for the 1'gabion basket walls that you are proposing to use as
sediment forebays. These need to be entrenched to avoid scouring underneath.
RESPONSE: Gabion basket/sediment forebay details for SWM-5 and 8 have been added to Sheet E28.
6. Provide facility access per VSMH Vol. 1, 3.06-18.
(Rev. 1) Comment partially addressed. Show access to SWM-4.
(Rev. 2) Comment not addressed. The access road should clearly show access to the facility structures.There
is no grading being shown for this access road and it is not clear that the facility can be accessed from this road,
as it does not directly tie in to the dam. Please correct.
RESPONSE: Access to SWM-4 has been clarified in plan on Sheet E9 and on Sediment Basin/SWM
Details on Sheets E14 and E26.
Revision 1 Comments:
12. Slopes leading in to your basins are too steep. Any basin should have maximum 3:1 slopes for maintenance
and safety[VSMH Vol. 1, 3.01-13]. Please reflect this on your plans, details, and sections.
(Rev. 2) Comment not addressed. Although aquatic benches have been added, your slopes are still 2:1. Please
address this.
RESPONSE: The plans have been revised to provide a maximum 3:1 slope to the basins.
13. Please provide SWM facility type in your details (Basin I, II, Bio-Retention).
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(Rev. 2) Comment not addressed. SWM-5, 8, 9, & 10. Please label these on details.
RESPONSE: The facility type has been labeled on the details.
Revision 2 Comments:
16. Please adjust storm sewer pipes so that they are no steeper than 16%.
RESPONSE: Storm sewer pipe runs have been adjusted to be no steeper than 16%.
17. Provide a sediment forebay in western corner of SWM-7.
RESPONSE: A sediment forebay has been added. See sheet E25.
18. SWM facility dams need to be 10'wide for access, please correct SWM-6.
RESPONSE:The access for SWM-6 has been revised to 10'-wide.
19. Please remove Sheets E19 & E39. These will be reviewed with the Road Plan set.
RESPONSE: Sheets E19 0 and E39 0 have been removed.
20. Provide a more clear detail of structure 24A.
RESPONSE: A more clear detail has been added to Sheet E27.
D. Erosion and Sediment Control Plan (ESCP)
2. Mitigation for disturbance to stream buffers should occur within the affected stream buffer, please correct
[Albemarle Co. Code 17-604 C.5]. Mitigation can occur in other stream buffer areas, but mitigation is not valid
outside stream buffers unless it is additional stormwater treatment for discharging into buffers.
(Rev. 1) Comment not addressed. Mitigation should occur within the WPO buffer within this subdivision.
(Rev. 2) Comment partially addressed. Offsite mitigation plan concept is approved per County Engineer's 15
July 2015 letter. A mitigation plan must be submitted, approved, and bonded. Referencing WPO201400031,
alone, on the plan will not adequate.
RESPONSE: As discussed at our August 6 Engineers meeting,we are providing a separate mitigation
plan to address the offsite mitigation that is being provide on Westlake Hills Subdivision.
6. Please adjust your limits of disturbance to include all affected areas, not just the areas that are to be graded.
(Rev. 1) Comment partially addressed. There are still "gaps" in your limits of disturbance that will receive
sediment. Tree protection alone will not leave these areas unaffected by erosion and sediment.
(Rev. 2) Comment not adequately addressed. Ex.: Sheet E8, west side of Cottontail Way, first 350 feet, silt
fence has been removed here and replaced with tree protection. Open space on east side of Cottontail Way;
tree protection only, will this area not be affected by sediment from grading the road and lot 36?Another
example is lot 66. Areas such as these need to be included in your limits of disturbance, unless some other
measure(s) is taken to leave them undisturbed.
RESPONSE: Silt fence has been placed on the west side of Cottontail Way,first 350 feet. Silt fence has
also been bolstered up on the east side of Cottontail Way.The E+S controls including an extension of
the diversion dike at the rear of Lot 66 have been included within the limits of construction
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26. Provide a sediment trap for the fill slope at the end of Kentra St., Phase 1.
(Rev. 1) Comment partially addressed. This trap needs to remain in place for Phase 2. Additional E&SC
measures (sediment traps) are needed at lots 39 and 40 as well.
(Rev. 2) Comment not addressed. Please address slope on lot 37. SSF, alone, will be inadequate here.
RESPONSE: A sediment trap has been provided in this location.
35. Please make sure all existing and proposed contours are labeled on all plan sheets (Ex.: Proposed contours
on Sheet E13 are not labeled, existing and/or proposed contours are not labeled on many of the sediment
basin/trap details.
(Rev. 1) Comment not adequately addressed. See proposed contours on Sheet E22. Additional contour labels
are need throughout these plans,existing and proposed.
(Rev. 2) Comment not addressed. The sheet noted, now Sheet E13, still does not have adequate proposed
contour labels.
RESPONSE: Adequate contour labels have been added to Sheet E13.
Revision 1 Comments:
45. Diversions leading to a sediment trap are needed between Lots 43 &44, please provide.
(Rev. 2) Comment not addressed. In your comment response letter you state that diversions have been added
here. However, I'm finding only silt fence and a mud trap. Please provide diversions leading to a sediment trap,
see County Engineers 15 July 2015 letter concerning mud trap variances (Comment 4). Also, include these lots
in the list of lots that building permits will not be issued until a County inspector authorizes removal of the E&SC
measures.
RESPONSE: Diversion dikes and two(2)temporary slope drain have been added behind lots 40-44 as
discussed at our August 6 Engineers Meeting. The list of lots that building permits will not be issued
until a County inspector authorizes removal of the E+SC measures has been provided on Sheet El 1.
See detailed responses to County Engineer's Comments below.
48. Diversions and more silt fence are needed to protect WPO buffer at the back of the lots along Kendra St.
(Rev. 2) Comment partially addressed. Please clarify what you mean by"the existing culvert at station 21+75 is
to be redirected to SB-4". Also,the note "Existing 24 inch culvert and redirect runoff to roadside ditch on north
side of Kendra Street", what do you mean here? Is the culvert being removed?
RESPONSE: A more detailed note regarding the culvert has been added to Sheet E9. The culvert is to
be capped and filled with grout.
59. A variance is required for each proposed MT and CWD.
(Rev. 2) Comment partially addressed. Not all requested variances have been approved. Please see County
Engineer's 15 July 2015 letter and adjust accordingly.
RESPONSE: See detailed response to County Engineer's Comments below.
Revision 2 Comments:
62. Provide an emergency spillway for SB-5 and silt fencing below dam.
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RESPONSE: As discussed at August 6 Engineers Meeting,an emergency spillway has not been
provided since the designed SB-5 meets the freeboard requirements for a facility without an emergency
spillway per the VESCHB.
63. Label SB-4 on plans and details.
RESPONSE: SB-4 has been labeled on plan and details.
64. Provide basin sizing calculations.
RESPONSE: A basin sizing chart has been included with this submission.
65. Provide bottom dimensions for sediment traps and basins on plans and details.
RESPONSE: Bottom dimensions have been provided on plans and details for all sediment traps and
basins.
66. Provide a sediment trap at Lot 40. It appears that you are exceeding the limits for silt fencing provided in the
VESCH.
RESPONSE: As discussed at the August 6 Engineers Meeting,diversion dikes and a slope drain have
been added in this location.
67. Provide silt fence below ST-6.
RESPONSE: Silt fence has been added.
68. Where sediment traps or other E&SC measures are added to home lots, please include those lots in the list
of lots that for which building permits will not be issued until a County inspector authorizes the removal of that
E&SC measure.
RESPONSE: The list has been updated on Sheet El1.
Response to County Engineer's Comments Dated July 15, 2015:
1. Cottontail Way: This variance location is approved. The drainage areas appear suitably small
provided the right-of-way diversion is workable. If the right-of-way diversion proves unworkable, a
sediment trap will be required in the field, or the pipe can be temporary outlet into the trap.
2. Warbler Way, station 17+50: The diversions here, across ditches and the raised road sections are
unlikely to work. These should be traps.
RESPONSE: As discussed at our August 6 Engineers Meeting,the Mud Trap on the southwest side of
this crossing has been removed and replaced with a sediment trap(ST-26). Also as discussed,the mud
trap on the southeast side of this crossing remains since there will be very little drainage area flowing to
this trap and the diversion across Lot 76 will divert upstream water away from this trap without any
issues since this diversion is not located in the right-of-way
3. Warbler Way, station 23+00: On the station 22 side, the mud trap variances are approved. On the
24+00 they are not. Sediment traps should be provided. The diversion uphill across the ditches
and roadway is unlikely to work.
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RESPONSE: We have provided a temporary storm drain pipe to divert water to SB-7 in the event that
the right-of-way diversion becomes unworkable. The mud trap on the low side of the road remains
since there will be very little drainage area flowing to this trap and the diversion across Lot 73 will divert
upstream water away from this trap without any issues
4. Below lots 43 and 44 on Kendra Str.: Provide a trap here.
RESPONSE: As discussed,diversion dikes and a temporary slope drain have been provided in this
location.
5. Below lot 62 on Warbler Way: Not found on plans.
RESPONSE: No variance needed for this one.
6. Below lot 13 on Cottontail Way: This variance location is approved.
Your request for a variance for the use of clean water diversions in 4 locations has been reviewed.
Generally clean water diversion should not be internal to the site, with no danger of receiving sediment laden
waters or of eroding.
1. Above lots 59 and 61: There is a large fill slope above, and disturbed sewer clearance which
channels sediment into this diversion.
RESPONSE:This clear water diversion has been removed and SB-6 added. A small portion of CWD
remains on Lot 61 since a ridge line there makes it not feasible to direct upstream water in that location
to SB-6. The area upstream from this portion of CWD is to be protected by a diversion dike flowing to a
slope drain which does flow to SB-6.
2. Above lots 62 and 63. There is a sediment trap and sewer disturbance which dumps into this area.
Sediment trap 17 does not even meet code for drainage area. A portion of the area above 63 might
be diverted away, but the rest is compromised.
RESPONSE:This clear water diversion has been removed and SB-7 added.
3. Above lots 29 and 30. This variance location is approved.
4. Above lot 28. This variance location is approved.
Again, thank you for meeting with us, and we look forward to working with you towards approval of the VSMP
plans. Please call me with any questions or if you require additional information.
Sincerely,
/
•Mirnael Myers, P.E.
Cc:Jeremy Swink
John Kessler
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