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September 8, 2014
Glenn Brooks
County Engineer
Albemarle County Community Development Department
401 McIntire Road
Charlottesville, Virginia 22902
RE: Cascadia— VSMP-Comment-Response Letter(WPO 201300032)
Dear Glenn,
Enclosed please find two (2) sets of the revised Final Erosion and Sediment Control Plan and Stormwater
Management Plan and computations. The plans have been revised based on your comments dated September
2, 2014 as follows:
ENGINEERING COMMENTS DATED 9-2-14:
D. VSMP: SWPPP and Pollution Prevention Plan (WPO2013000032)
(The Virginia stormwater management program, storm water pollution prevention plan application and
documents)
1. Please provide the DEQ coverage letter.
RESPONSE: The DEQ coverage letter will be provided under separate cover.
E. VSMP: SWPPP: Stormwater Management Plan (WPO20130000032)
1. Show vehicle access to all facilities with easements. Include easement to pond 1 from Delphi or an
internal road. Include access to the biofilters and water quality swale.
Rev.A: Access to BF-1 and the Water Quality Swale was not found. It is not clear how vehicles
get to the facility itself, or how the proposed access road gets beyond BF-2 and outfall. All
accesses need to be a minimum 10' wide. Please update the other sheets of the plan to match.
The erosion control sheets do not match.
RESPONSE: As discussed at our meeting on September 4, 2014, we have revised the access
route width to 10'. Also, we have extended the access road to the grassed swale to be able to
access the outfall as discussed.
Regarding the water quality swale:
12. Provide accurate details for the water quality swale. Show soil mixture, underdrain, minimum
bottom width, maximum slope, side slopes and top width.
Rev.A: The soil mixture and underdrain were not shown. The grassed swale option does not
appear to obtain the needed removal rate.
Page 1 of 2
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RESPONSE: As discussed at our meeting on September 4, 2014, the grassed swale is
adequate to meet the water quality requirements for the subject drainage area. Simple 4
sheets have been included as an attachment to this submission.
13. Provide computations to show hydraulic adequacy per standard spec. 3.13.
Rev.A: The calculations appear to show depths greater than the weirs.
RESPONSE: The calculations have been revised such that the depths are not greater than the
weirs. Refer to Sheet SW15.
F. VSMP: SWPPP: Erosion and Sediment Control Plan (WPO2013000032)
1. The erosion and sediment control plan is approved. Comments have been addressed.
G. Mitigation Plan (WPO2013000032)
(A mitigation plan is a plan of buffer disturbances, and replanting or restorative measures)
1. The mitigation plan is approved. Buffers and easements for mitigation areas will need to be
shown on final plats.
RESPONSE: The buffer and easements for mitigation will be shown on the final plats.
H. Bond Estimate Request for VSMP plans (WPO2013000032)
1. The bond estimate request will be processed when all VSMP plans are approved.
We trust the above adequately addresses your comments. Please let me know if you have any questions or
require additional information.
Sincerely,
Michael Myers, P.E.
Cc: Keith Lancaster
Page 2 of 2
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August 22, 2014
Glenn Brooks
County Engineer
Albemarle County Community Development Department
401 McIntire Road
Charlottesville, Virginia 22902
RE: Cascadia— VSMP-Comment-Response Letter(WPO 201300032)
Dear Glenn,
Enclosed please find two (2) sets of the revised Final Erosion and Sediment Control Plan and Stormwater
Management Plan and computations. The plans have been revised based on your comments dated August 5,
2014 as follows:
ENGINEERING COMMENTS DATED AUGUST 5,2014:
D.VSMP: SWPPP and Pollution Prevention Plan (WPO2013000032)
(The Virginia stormwater management program, storm water pollution prevention plan application and
documents)
1. The swppp does not appear to give operator information.
RESPONSE:The SWPPP has been updated to include operator information.
2. Please provide the DEQ coverage letter.
RESPONSE: As of today,the DEQ coverage letter has not yet been issued. However,the 2014 permit
registration statement and fee have been submitted and are included in the SWPPP.
3. Please provide a pollution prevention plan. A specific plan was not found in the SWPPP document.
Please consult the EPA guidance and templates in preparing your plan;
http://water.epa.gov/polwaste/npdes/stormwater/Stormwater-Pollution-Prevention-Plans-for-
Construction-Activities.cfm
RESPONSE: The SWPPP has been updated to include a PPP in accordance with the EPA guidance.
E.VSMP: SWPPP:Stormwater Management Plan (WPO20130000032)
Regarding the pond;
1. The footing for the gabion basket wall is inadequate. There is no way to key the baskets in a gravel
base of unknown dimensions as shown. A similar wall to this, constructed at Hollymead Town Center
has failed repeatedly. It was undermined by scour and sunk in a soft foundation. The foundation will
depend on the underlying bearing capacity of the soil, and on the scour action from the incoming flow.
It will need to be more substantial, and deep or keyed to rock.
RESPONSE: Due to the excessive height of the gabion basket wall (9'),we have revised the pond to
include an earthen spillway in between the forebay and the main pond. The forebay spillway is earthen
Page 1 of 4
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and the check storms will cause the water surface elevation in the pond to increase such that there will
be no erosive action over the forebay spillway. The detail has been updated on Sheet SW14. Please
note that the forebay is to be constructed at such time as the sediment basin is converted to a
permanent pond facility.
2. A planting plan for the aquatic bench was not found.
RESPONSE: We have added 3 different planting species to be used on the aquatic bench with an
appropriate hatch pattern.These species have been taken from the VA SWM handbook standard 3.05. A
note has been added that aquatic bench planting is to conform to spec 3.05.
3. The computation package contains only routings and drawdown. Please provide water quality checks
for volume according to standard spec. 3.06, and pool depth zones per 3.06-2.
RESPONSE: We have added computations to sheet SW14 and to the computations booklet that indicate
the pool depth zones. Please note that we also added a shelf below the forebay to provide additional
surface area for the depth zone from 1.5'to 2'. Also, note that the total surface area for the depth zones
0'to 2'are equal to over 30%,even though the 1.5' to 2' depth zone is below 15%. We believe that the
proposed depth zones meet the intent of 3.06.
3. All details and sections must be drawn to scale, including the dam and structures.
RESPONSE: We have revised all of the details and sections relating to the pond to be drawn to scale.
5. Show vehicle access to all facilities with easements. Include easement to pond 1 from Delphi or an
internal road. Include access to the biofilters and water quality swale.
RESPONSE: We have included a SWM access road and easement to pond 1 from Delphi Drive as shown
on Sheet SW6. Sheets 13A and 13B have been added to indicate the addition of a SWM access road in
between lots 78 and 79 off of Boulder Hill Road. This access road leads to the existing access road
traversing the eastern edge of the site running parallel to the sanitary sewer. From there,we have
provided vehicle access to both biofilters and the water quality swale. A shared trail, SWM maintenance
and access and stream buffer mitigation easement has been added as shown on these sheets and as
will be indicated on the final plat.
Regarding the biofilters;
6. The biofilters are too small. Provide sizing to 4%of impervious areas, allowing some small increase
for upstream 2:1 slopes and compacted soils. I get approximately 1000sf for biofilter 1, and 550sf for
biofilter 2.
RESPONSE: Biofilter 1 provides 105%of the required storage,while Biofilter 2 provides 162%of the
required storage. The computations indicate that the sizing complies with the requirement to provide
5%of the impervious area in the drainage shed.
7. Provide sections of the dams. Each needs an impervious core, minimum top embankment width of 8ft,
and the downstream slope needs to be 3:1 or flatter.
RESPONSE: A section through the dam is indicated on Sheet SW15. An impervious core has been
indicated,the top-width to be 8 feet and the downstream slope to be 3:1. The plan and details have been
revised to facilitate the grading.
Page 2 of 4
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8. Computations need to be provided for the 1 Oyear and 100yr storm to ensure operation of spillways.
RESPONSE: Computations for sizing of the spillways have been added to Sheet SW15.
9. The dimension appear incorrect in the spillway.With a bottom width of 5' and sides slopes of 2:1, a
1'depth requires 9'total width. The dimension downstream beyond the dam would be different.
RESPONSE: The spillways dimensions have been revised to accurately reflect the bottom width and
side slopes. Please note that we have updated the design of biofilter#2 spillway to allow vehicle access
across the spillway and embankment.
10. It is not possible to achieve a 1'facility ponding depth with a rip-rap channel spillway. The rip-rap is
going to be deeper than that, and irregular enough to negate any computation. Revise the spillway
liner, remove the bio-filter schematic, and provide an accurate depiction of the facility.
RESPONSE: The spillway has been revised to a grass spillway.
11. Continue the underdrains beyond the center of the facility, and provide actual planting plans. Remove
the generic schematic and provide an accurate depiction.
RESPONSE: The biofilter details have been updated to show an accurate depiction of the underdrains.
We have left the schematic on the plans since it provides information about how the underdrains are
connected and extend beyond the bio filter with a non-perforated pipe.
Regarding the water quality swale:
12. Provide accurate details for the water quality swale. Show soil mixture, underdrain, minimum bottom
width, maximum slope, side slopes and top width.
RESPONSE: The proposed water quality feature has always been intended to be a grassed swale as
discussed at our earlier engineering meetings. Therefore,we are not indicating soil mixture or
underdrains. However,we have expanded the design and detail to incorporate the design requirements
of standard spec.3.13.
13. Provide computations to show hydraulic adequacy per standard spec. 3.13.
RESPONSE: The detail includes computations to verify hydraulic adequacy.
14. Detail proper check dams per standard spec. 3.13,with spacing planned according to the planned
slope. Show proper dimensions of check dams to ensure flow over the center. The detail provided is
incorrect in every aspect.
RESPONSE: The detail has been updated to be in accordance with 3.13.
15. Standard spec. 3.13 requires 3:1 or flatter side slopes.
RESPONSE: 3:1 side slopes have been provided.
16. Provide a better, to scale and dimensioned, detail of the channel transition, pipe under the access road,
Page 3 of 4
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stilling basin, and level spreader at the end of the water quality swale.
RESPONSE: The detail has been revised. We have updated the plan to remove the level spreader and
are providing a standard outlet protection. The attenuation of runoff that is provided by the revised
grassed swale made the level spreader superfluous and be a maintenance concern whereas the
standard outlet protection provides adequate protection of the stream.
F.VSMP: SWPPP: Erosion and Sediment Control Plan (WPO2013000032)
1. The erosion and sediment control plan is approved. Comments have been addressed.
G. Mitigation Plan (WPO2013000032)
(A mitigation plan is a plan of buffer disturbances, and replanting or restorative measures)
1. The mitigation plan is approved. Buffers and easements for mitigation areas will need to be shown on
final plats.
RESPONSE: A shared trail, SWM maintenance and access and stream buffer mitigation easement has
been added as shown on these sheets and as will be indicated on the final plat.
H. Bond Estimate Request for VSMP plans (WPO2013000032)
1. The bond estimate request will be processed when all VSMP plans are approved.
We trust the above adequately addresses your comments. Please let me know if you have any questions or
require additional information.
Sincerely,
Michael Myers, P.E.
Cc: Keith Lancaster
Page 4 of 4
Glenn Brooks
From: Mike Myers [mmyers @dominioneng.com]
Sent: Wednesday, July 30, 2014 9:48 AM
To: Glenn Brooks
Cc: Charlie Armstrong; Keith Lancaster
Subject: Cascadia- Early Grading Permit Responses-WPO 2013-00032
Attachments: Cascadia-Sediment Basin Exhibit.pdf; early grading plan submittal timeline.pdf
Glenn, Thanks very much for your quick turnaround on the Early Grading Permit Plan review following our Engineers
meeting on July 17 to discuss outstanding issues. We submitted our bond request form and fee, final WPO plans and
VSMP permit documentation yesterday. We look forward to your calculation of the bond amounts and then the issuance
of an early grading permit after the bonds are posted. The developer is eager to get started with early grading as soon as
possible and they also believe the early grading permit plan should have been approved prior to July 1, 2014 since the 45-
day time limit had expired on April 24, 2014 (see attached calendar). However, we are appreciative of your efforts to work
with us to approve the Early grading plan and to ultimately issue the early grading permit. Below I have responded to your
reservations on the plans:
COMMENT 1: One reservation is the details surrounding SB-1, the existing basin in Fontana. There are computations for
structures as if this were a new basin, when it already exists, and it is not clear if the existing structures are being
replaced. The drainage area on the plan also appears incorrect, significantly. I know we have discussed this in meetings,
and you have indicated that field conditions bear this out, but the plans are contradictory.
RESPONSE: I have attached a drainage area map and a detail of the riser structure to address your concerns.
The maximum drainage area to the Fontana basin (pond#1) is 19.55 acres as shown. During the early phases of
construction,the drainage area will be less (approximately 16.3 acres). Then,when the ditch to convey offsite
runoff from Fontana is installed,the maximum amount of area will flow to the basin. The existing riser structure,
dam and emergency spillway are to remain largely intact,with the only modifications being plugging of the
existing orifice and adding a new orifice.
COMMENT 2: The other reservation is stormwater management. As you have noted in your response letter to the last
review, many of the comments refer to revisions to come later with a stormwater management plan. It is
noted in the responses that this plan is meant to be an early grading plan. It would appear the stormwater
management component may be necessary for the VSMP.
RESPONSE: As stated above,we submitted the VSMP package to you yesterday. The 2014 VSMP permit request
has been mailed in to DEQ and we are simply awaiting their formal permit. The submittal to you yesterday
includes the SWPPP (which contains the completed registration statement and the check stub for the$6,100.00
review fee)and the revised WPO plans with all comments on SWM addressed. In any event,the SWPPP contains
all of the required information for both E+S and SWM.
We thank you again very much for working with us on this plan as we all negotiate through the new process. Please let
me know if you need anything else from us, Mike
Michael F. Myers, P.E., C.F.M.
Director of Engineering
Dominion Engineering and Design, LLC
172 South Pantops Drive
Charlottesville,VA 22911
434.979.8121 ext. 2 (office)
434.906.3161 (mobile)
Please visit our website at: www.dominioneng.com
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July 28, 2014
Ms. Megan Yaniglos,ASLA
Senior Planner
Albemarle County Department of Community Development
401 McIntire Road
Charlottesville, Virginia 22902
RE: Cascadia Final Site Plan andelliala-Comment-Response Letter-SDP2013-00025 and
Dear Megan,
Enclosed please find three (3) sets of the revised Final Site Plan and two (2) sets of the revised Road Plans.
Please note that we have revised the site plan to address Engineering and ARB comments and we have revised
the road plans to address VDOT comments. Please note the following plan approval status:
Site Plan
Planning 5-6-14
Inspections 5-13-14
Fire and Rescue 5-13-14
E911 5-13-14
ACSA—5-10-14
Engineering—pending
ARB—pending
Road Plans
Engineering—approved 5-5-14*
VDOT—pending
*NOTE: We will provide engineering with two revised set of road plans with phasing lines added once we
received approval from VDOT.
ENGINEERING COMMENTS ON SITE PLAN DATED MAY 12,2014
A. Application Information
1) Owner is required to provide a completed copy of the standard stormwater maintenance agreement and fee
for recordation for any stormwater management facilities.
[Revision 1] Acknowledged by applicant.
2) Please submit a separate set of road plans including proposed drainage and profiles for all proposed public
and private roads.This submittal appears to include road plan elements; however a standalone application and
fee is required for road plan review.
[Revision 1] Partially addressed. Please remove all road plans from the site plan.
[Revision 2] Please remove all road plans from the site plan.
Page 1 of 7
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RESPONSE: The road plans have been removed from the site plan. Two sets of the road plans have
been provided to be submitted to VDOT. Once VDOT approves the road plans,we will provide the
County with two complete road plan sets with phasing lines
3) Per ZMA2002-0004 proffer#5, please submit an overlot grading plan showing existing and proposed grading
for this project. This could coincide with a road plan or site plan submittal but is needed for proposed
subdivision.
[Revision 1] Not addressed. The overlot grading plan has to be included in the site plan or subdivision
plan and not the WPO plan.
[Revision 2] Comment addressed. Overlot grading is shown on sheets SP-6 to SP12.
4) Prior to final plat approval:
water protection ordinance—erosion and sediment control and stormwater management and
subdivision—road and sewer
bonds must be calculated by the county (sewer bond is calculated by ACSA) and paid by owner after receipt of
a Bond Request Form from owner.
[Revision 1] Acknowledged by applicant.
B. Proposed Plan View Information
1) Please label all existing and proposed contour elevations including those shown on detail 1 on sheet SP8 as
well as for proposed lots 79-84 on sheet SP8.
[Revision 1] Comment addressed.
2) Please specify by area in landscape plan low maintenance ground cover for all proposed slopes steeper than
2:1. Please also note requirements of Proffer 5 from ZMA2002-00004 for low maintenance plantings.
[Revision 1] Partially addressed. Landscaping plans do not specify the type of plantings in 2:1 slope
area outside the conservation area. Please specify.
[Revision 2]The groundcover has been specified on SP34. However,the note on the plans for location
of plantings has been removed.
RESPONSE: The note on the plans for location of the 2:1 plantings has been added to all landscape
plan sheets SP35-SP41. We have also added a note to the grading plan sheets to refer to the landscape
plan for all treatment of non-paved areas.
3) Please label all entrance and intersection radii including the corner of Glissade Lane and Delphi Lane on
sheet SP10.
[Revision 1] Comment addressed.
4) Please label all proposed drainage easements including the proposed easement for pipe out of proposed
structure 7C crossing proposed lot 1 on sheet SP6.
[Revision 1] Comment addressed.
5) Proposed drainage easement for pipe out of proposed structure 7E crossing proposed lot 4 on sheet SP7
appears to be 10' wide. Please propose a minimum width of 20' for all proposed drainage easements.
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[Revision 1] Comment addressed. Per meeting, 10' wide easements will suffice for privately owned and
maintained drainage systems.
6) Please confirm proposed parking lot curb type (appears to be CG-2) on sheet SP7.
[Revision 1] Comment addressed. CG-6 is proposed.
7) Please widen sidewalk in front of proposed neighborhood center from 5' to 6' or provide bumper blocks for
adjacent parking spaces on sheet SP7.
[Revision 1] Comment addressed. Sidewalk is 6'.
8) Please include stationing for all proposed public streets at minimum 50' intervals.
[Revision 1] Comment not addressed. 50' stations can be clearly marked on plans to satisfy this
comment.The road plans should be separated from the site plan. Include the subdivision overview
sheet in road plan.
[Revision 2] Comment addressed.
9) Please label all PCs and PTs for all proposed public streets.
[Revision 1]Comment addressed.This should be included in the separated road plan set.
RESPONSE:See response to Comment 2 above.
10) Please label the maximum (not average) height for each proposed retaining wall.
[Revision 1]This is addressed, but there is a concern there will disturbance of TMP78E-H. Please
provide actual retaining wall design with safety fence.
[Revision 2]The applicant has increased the distance of walls to the adjacent property line to equal the
maximum height of the wall.The only thing left to address is to show the safety fence railing detail.
RESPONSE: The detail for the safety railing has been added to Sheet SP43.
11) A retaining wall appears to be shown on sheets SP6 and SP10. Please label all retaining walls on all sheets
on which they appear.
[Revision 1]This is addressed,but there is a concern there will disturbance of TMP78E-H. Please
provide actual retaining wall design with safety fence.
[Revision 2]The applicant has increased the distance of walls to the adjacent property line to equal the
maximum height of the wall.The only thing left to address is to show the safety fence railing detail.
RESPONSE: The detail for the safety railing has been added to Sheet SP43.
12) Sheet SP38 appears to be part of the landscape plan. Please update sheet name.
[Revision 1] Comment addressed.
13) From our meeting, we discussed capturing more runoff behind lots along Glissade Lane, Delphi Lane, and
Boulder Hill Lane. Please address.
[Revision 2]This will be reviewed with the WPO.
RESPONSE: Refer to WPO plan for capturing of more runoff behind these lots.
B. Plan Detail Information
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1) Please specify 3000 psi strength requirement and 4"stone base for all proposed sidewalks on road typical
sections.
[Revision 1] Comment addressed.
2) Please provide a typical retaining wall detail for each proposed retaining wall. Please note per code of
development p. 24, retaining walls visible from the street or other public areas (which include both proposed
retaining walls as designed)shall be of a higher material quality and shall be compatible with the adjacent
building architecture materials and/or colors.
[Revision 1]Comment partially addressed. Please show the safety fence railing detail.
[Revision 2]Comment not addressed. Please show the safety fence railing detail.
RESPONSE: The detail for the safety railing has been added to Sheet SP43.
C. Drainage Profiles
1) The following structures appear in plan view but appear to be missing in profile view: 16, 17, 19, 20, 21, 23,
24, and 44A. Please include drainage profiles for all proposed drainage structures.
[Revision 1] Comment addressed.
2) Please label existing ground and proposed ground elevation lines on all drainage profiles including profiles for
two proposed drainage structures.
[Revision 1] Comment addressed.
3) The following pipe runs appear to have utility conflicts as indicated in plan view (w= water line, s= sanitary
sewer line) but the conflicting utility pipes appear to be missing in profile view:2-3(w), 2-3(s), 3-4(s), 10-11(s),
14-15(s), 15-16(w). 22-23(s), 23-24(w), 24-25(w), 44-44A(w). Please include all utility conflicts for all proposed
drainage structures in profile view.
[Revision 1] Comment addressed.
4) Station for structure 49 appears to be missing. Recommend including this station with drainage profile on
sheet SP29.
[Revision 1] Comment addressed.
5) The following pipe run appears to have a slope > 16%: 62B-62C. Please include anchor blocks for all
proposed pipe runs with slopes > 16%.
[Revision 1] Comment addressed.
6) Please prescribe by note or on the profile that concrete Inlet Shaping (IS-1) shall be included for all proposed
drainage structures with a 4' or greater drop.
[Revision 1] Comment addressed.
7) Please prescribe by note or on the profile that Safety Slabs (SL-1) shall be included for all proposed drainage
structures taller than 12'.
[Revision 1] Comment addressed.
8) Please include scour protection for all outlets in profile view. corresponding to computations and protection
shown in plan view.
[Revision 1] Comment addressed.
E. Drainage Computations
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1) Due to overwhelming VDOT comments, it is assumed the drainage will be re-worked for this project at
resubmittal. Conceptual review includes the following missing items which county engineering will be looking for
at resubmittal:
a) Please ensure principal access (proposed structures 66&67) is free from flooding during a 100 year storm
event.
[Revision 1] Comment addressed. Per sheet SP31,there is an analysis for the 25 year storm,but the
response letter states a 10 year storm. Please clarify if response letter is incorrectly stating 10 yr.
[Revision 2]Comment addressed.
b) Spread for all inlets need to be checked for 4 in/hr intensity per VDOT Drainage Manual Table 9-1.
[Revision 1] Comment addressed.
c) Inlet efficiency needs to be checked for 6.5 in/hr per note 4 attached to VDOT Drainage Manual Table 9-1.
[Revision 1]Comment not addressed. Please check for DI 4,4A,66 and 67.Also,4A is bypassing runoff,
which should be taken into account when analyzing DI 67.The efficiency/capture should be increased
for DI 67.
[Revision 2] Add the 6.5 in/hr check storm analysis to the final site plan.Also, please add another inlet
right before 4A.The idea is to capture 100%by the time it gets to 4A and to direct that runoff to the
proposed pond and not to the existing pond.
RESPONSE: The 6.5 in/hr check storm has been added to Sheet 31A. Another inlet has not been added
right before 4A because 4A now has 100%efficiency for both the design and check storm. This is due
to offsite water being directed away from 4A by the addition of a ditch behind the sidewalk.
d) Pipe capacities for proposed enclosed drainage (including proposed yard drains which feed into street
trunkline systems) need to be checked for a 10-year storm event at duration equivalent to time of concentration
(this appears to be included for currently proposed system on sheet SP31 pending comment F1e below).
[Revision 1] Comment addressed.
e) Please include time of concentration of drainage area maps shown on sheets SP32 & SP33 (this information
appears to be on calculations shown on sheet SP31 A).
[Revision 1] Comment addressed.
ARB COMMENTS DATED MAY 6,2014
1.A fence detail was requested;a photo was added to the plan. Please supplement the photo with a traditional
detail drawing that specifies height,sizes, material and color.
RESPONSE: A fence detail has been added to Sheet SP34 to indicate height,size, material and color.
2. An increase in the number of shrub species was requested so that no single shrub species exceeds 25%of
the total number of shrubs proposed for the site. Abelia, Boxwood, Forsythia,Winter jasmine, and Viburnum are
proposed for a total of 284 shrubs. 25%of that total is 71 shrubs.The 84 Abelia exceed 25%of the total. Please
revise the plan so that no single shrub species exceeds 25%of the total number of shrubs proposed for the site.
RESPONSE: The landscape schedule has been updated accordingly so that no single shrub exceeds
25%of the total number of shrubs provided.
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3. Clarify on the plan the reason for the two different plant schedules shown on sheet 34 and sheet 35.The
plant sizes on Sheet 34 cannot be approved for the ARB.
RESPONSE: The plant schedule on Sheet 34 indicates compliance with the tree cover canopy
requirements only. This schedule has been updated to include the proper plant sizes for EC plantings
that can be approved by the ARB. The plant schedule on Sheet 35 is a plant list that the landscape
contractor will use for ordering of the planting materials. The two schedules have been coordinated and
match with respect to species, minimum planting size and quantities. The only difference is that the
schedule on Sheet 35 includes a range of plant sizes and provides some additional planting comments.
Note that the range of plant sizes on Sheet 35 has the smaller number as the minimum plant size to
ensure compliance with ARB plant size requirements.
VDOT COMMENTS DATED MAY 30,2014
1. The storm sewer profile for structure 12A to 12 indicates that the pipe length is 1'. This typo
should be corrected.
RESPONSE: This typo has been corrected on Sheet SP27.
2. It appears that storm structures 63 and 63A could be lowered so that they are installed in existing
soil.
RESPONSE: Structures 63 and 63A have been lowered so that they are installed in existing soil. Refer
to Sheet SP29.
3. The full flow capacity of lines 87 through 101 has not been included in the storm sewer
calculation table.
RESPONSE:The full flow capacities for lines 87 through 101 have been added Refer to Sheet SP31.
4. Several of the storm sewer pipes appear to be near capacity. HGL calculations need to be
provided to verify that there is not a risk of overflowing the drop inlets during a 10-year storm
event.
RESPONSE: HGL calculations have been performed and added to Sheet SP31. In no case,does the 10-
year water surface elevation in the structures overflow the drop inlets.
5. Street trees should be located at least 30 feet from the end of radius at each intersection in
accordance with Appendix B(1)of the Road Design Manual. The trees at the intersection of
Delphi Drive and Fontana Drive and at the intersection of Delphi Drive and Delphi Lane appear
to be located too close to the intersection.
RESPONSE: Street trees have been adjusted to be located at least 30 feet from the end of radius at
each intersection.
6. There appears to be a conflict between a street tree and storm structure 713.
RESPONSE: The street tree has been removed.
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7. There appears to be a street tree at the intersection of Flat Water Lane and Delphi Lane that is
within 30 feet of the end of radius.
RESPONSE: These street trees have been adjusted to be located at least 30 feet from the end of radius
at each intersection.
We trust the above adequately addresses your comments. Please let me know if you have any questions or
require additional information.
Very truly yours,
t..
'ichael Myers, P.E., C.F.M.
Attachments
Cc: Keith Lancaster
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July 28, 2014
Glenn Brooks
County Engineer
Albemarle County Community Development Department
401 McIntire Road
Charlottesville, Virginia 22902
RE: Cascadia—E+S/SWM Plan-Comment-Response Letter(WPO 201300032)
Dear Glenn,
Enclosed please find two (2) sets of the revised Erosion and Sediment Control Plan and Stormwater
Management Plan. The plans have been revised based on comments by Michelle Roberge dated May 30,
2014. Please note that comments 1-9, 19, 20 and 22 have been addressed with the early grading permit plans.
Comments 10-18 and 21 are addressed on the SWM plan as follows:
ENGINEERING COMMENTS DATED MAY 30, 2014:
1) [Comment] The application states Early Gr„i ng Permit. For this type of application, there should be no
structures shown on this plan. Please clarify how you would like to pursue application. Even though this may be
an early grading plan application, I have reviewed plans for E&S and SWM just in case it was a typo on the
application.
[Revision 1] The title should include "Early Grading Plan."Also, remove all hardscapes: proposed roads,
proposed single family homes, proposed sidewalks, etc. This early grading plan should only include E&S control
measures and grading for Phase 1 and Phase 2.
2) [Comment] On sheet SW3, please label preserved and managed slopes.
[Revision 1] Comment no longer required. The critical slopes are shown on plan. The critical slopes waiver was
already approved with the ZMA. At this point there is no need to differentiate managed slopes from preserved
slopes. Also, the ZMA was approved prior to the adoption of the new critical slopes section in the ordinance.
[Response] Comment Addressed.
3) [Comment] Temporary slope drains are not designed per VESCH standards. Typical designs show a
compacted earthen dike to divert runoff to slope drains. Please show.
[Revision 1] Comment partially addressed. DDs still need to be shown for TSD draining to SB-2.
4) [Comment] Per meeting on Feb 6, 2014, we discussed revising the existing topography. Please address. A
sewerline was installed along northern and eastern portion of the site. We discussed possibly using this road as
a means to divert runoff to a sediment trap.
[Revision 1] Comment partially addressed. Applicant has not designed sediment traps near the access road
(built for the existing sewerline). Sediment traps will need to be designed. Remove the DDs that split the site
and size the sediment traps for new drainage areas.
5) [Comment] For phase 1 (northern and eastern portion), it will make more sense to have diversion dikes at
bottom of slopes to sediment traps. Then grade up the steep slopes. These diversion dike are partially shown
for the eastern portion of site.
[Revision 1] Comment partially addressed. Diversion dikes are proposed at the bottom of fill slopes, but it
appears that the construction of the walls will be required to satisfy the proposed grades on the early grading
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plan. The retaining walls can only be built if the site plan is approved and at this time it is still under review. Also,
as previously mentioned in comment 1, an early grading plan should not show hardscapes. Please clarify how
you would like to proceed since an early grading plan will not allow you to construct the walls necessary to
grade the eastern portion to the final grades on plan.
6) [Comment]The diversion dikes which splits the site on sheet SW8 and SW13 does not appear to work for
clearing, grubbing and grading. This coincides with comment 4. I suggest removing these diversion dikes and
enlarging sediment trap 1. The diversion dikes at the bottom of the slope should be extended for more capture
to sediment trap 1.
[Revision 1]Comment partially addressed. There is still a diversion dike#3 that splits the site. This will not work
as it will be difficult to maintain as the site is being cleared, grubbed and graded. Address with comment 4.
7) [Comment]The challenge is how to address erosion control in Phase 2 once the walls on eastern side are
installed. The dd's behind homes will not work.
[Revision 1] Comment partially addressed. This is only an early grading plan. The walls need to be built to
construct the DDs at the top of the fill slope. See comment 5.
8) [Comment]The temporary slope drains on phase II erosion control on eastern portion will not work. They
should outlet into perimeter controls, such as as sediment trap.
[Revision 1] Comment partially addressed. Clarify the gravel outlet on SW 14 as no sediment shall leave the
site.
9) [Comment] SB-1 on calcs appear to be SB-2. Please revise name and note "post condition".
[Revision 1] Comment not addressed. The calcs were not submitted with this submission. Also the SB-1 on
calcs should be relabeled to SB-2 post conditions. This submittal should also show the post drainage areas in
phase 2 of early grading plan. All design of SB or ST shall be for higher DA of pre and post conditions.
10) [Comment]On SW-5, SB-1 is an existing pond. Please correct label. This should not be used as a
sediment pond. What is the benefit of reducing the amount of drainage area to existing pond 1 when both
ponds are owned by Dr Hurt.
[Revision 1] Comment partially addressed. Before the SCC and ditch (for Fontana development) can be
fully functional, final grading will need to be completed. Then ditches will be constructed. I recommend
showing a designed berm greater than 18"with SCC to divert water to SB-1 and SB-2 as a perimeter control
measure in Phase 1 and Phase 2. SCC to SB-2 can be designed with SWM plan.
RESPONSE: The SCC design to SB-2 is shown on Sheet SW6.
11) [Comment]Also, it appears that the ponds proposed does not match the approved ZMA2002-04 plans.
Please clarify. This may have been discussed already while Michael Koslow was the reviewer.
[Revision 1] Applicant has stated the proposed pond design has been approved by Engineering Review the
ARB. This was previously coordinated with original plan reviewer, Michael Koslow.
RESPONSE: This issue has been addressed with Michael Koslow. The resolution was to require the
applicant to obtain ARB approval of the pond design, which has been obtained.
12) [Comment] On SW24, the pond labels do not match report. Please revise.
[Revision 1] This is an early grading plan. Applicant will revise on SWM plans.
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RESPONSE: The pond labels have been updated to match the report. Please note that the drainage
map sheets have been provided on Sheet SW17 and 18.
13) [Comment] It appears that the target phosphorous removal is 43%, not including the future development.
Please take the future development into account. The current proposed development shows the retention
pond to be sized to treat 4* WQV (Retention Pond II), 275,880 cu-ft. When you add the future development,
the BMP choice may change. Page 6 on your report reflects the correct impervious areas, but this is not
reflected in removal rate calcs. Please revise removal rate calcs.
[Revision 1] This is an early grading plan. Applicant will revise on SWM plans.
RESPONSE: We have provided a simple 4 sheet on SW14 that indicates compliance with the target
phosphorus removal,which is calculated to be 44%. To this end,we have accounted for a conservative
300,000-sf of impervious area for future development as indicated on the spreadsheet. Based on a total
impervious surface of 748,276 sf draining to Pond 2,we are required to provide 125.293 cubic feet of
storage to meet the 4*WQV requirement where the WQV is equal to 1/2" of storage per impervious acre.
Please also note that the simple 4 spreadsheet and the impervious areas reflected on Page 7 of the
report match.
14) [Comment] Once 13 is addressed, please meet all three below if site has inadequate channels:
a) Detain the WQV (1" runoff) and release over 48 hours.
b) Detain the 1 year 24-hour storm and release over 24 hours.
c) Detain and reduce the peak flow for a 1.5, 2 and 10 year 24-hour storm, to the following level; peak flow
<=Of (Vf/Vpost), where Qf is flow from the site in a well forested condition (C = 0.25, or CN = 51), and Vf is
volume from the site in a well forested condition.
[Revision 1]This is an early grading plan. Applicant will revise on SWM plans.
RESPONSE: The project complies. Please refer to the stormwater management computations booklet
for additional information.
15) [Comment] Show detail of emergency spillway.
[Revision 1]This is an early grading plan. Applicant will revise on SWM plans.
RESPONSE: A detail of the emergency spillway has been added to Sheet SW14.
16) [Comment] It appears that a majority of the eastern portion is untreated. I recommend increasing the size of
the biofilter on the north and addressing more treatment on eastern portion of site.
[Revision 1] This is an early grading plan. Applicant will revise on SWM plans.
RESPONSE: The biofilter to the north has been increased in size and we have added Biofilter 2 behind
lots 76 and 77. As currently designed,we are treating all of the eastern portion of the site with the
exception of the rears of lots 50-57.
17) [Comment] Please provide SCC calculations.
[Revision 1] Comment partially addressed. I recommend a new SCC on western boundary of site in
conjunction with proposed DD#8. The velocity was higher than 4 f/s. Please show appropriate grass lining
on detail.
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The proposed ditch on southern boundary should also state acreage on calcs. The velocity was higher than
4 f/s. Please show appropriate grass lining. SCC to SB-2 can be designed with SWM plan.
RESPONSE: The SCC's associated with the E+S plan have been provided on the early grading permit
plan. The SCC design to SB-2 has been provided on Sheet SW6.
18) [Comment] All plans and calculations shall be signed, sealed and dated when it is ready to approve.
[Revision 1] Comment not addressed. No calcs for E&S has been submitted. Applicant will submit calcs for
SWM with appropriate swm plans.
[Response] All calculations are provided with this submittal.
RESPONSE: Signed and sealed calculations have been provided.
New comments:
19) On SW-5, one of the new excavated sediment traps is missing. Please add.
[Response] Sediment trap has been designed and is in place.
20) On SW-12, show the silt fence behind the DD.
(Response] Silt fence has been shown behind the DO on sheet SW-12
21) On SW-13, the rip-rap ditch appears to be part of the SWM facility design. Please confirm. This can be
shown later with the SWM facility design. Also, please note there is a proposed pedestrian trail crossing this
ditch. A culvert should be proposed.
RESPONSE: The rip rap outfall channel below lots 82 and 83 will be provided when the sediment trap
there is converted to a bio-filter. At this time, a pedestrian bridge will be provided for the trail crossing.
Also, refer to final grading plan Sheet SP8 for the rip rap channel and pedestrian bridge location. Notes
to this effect have been added to Sheet SW15.
22) DD6 will not work. This splits the site also. I recommend removing DD and sizing excavated sediment trap to
work with drainage area.
[Response] DD has been removed and a sediment trap is capturing the resulting water.
We trust the above adequately addresses your comments. Please let me know if you have any questions or
require additional information.
Sincerely,
3i
Michael Myers, P.E.
Cc: Keith Lancaster
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June 16, 2014
Michelle Roberage
Albemarle County Community Development Department
Engineering Department
401 McIntire Road
Charlottesville, Virginia 22902
RE: Cascadia— Early Grading Plan (WPO 201300032)
Dear Michelle,
Enclosed please find two (2) sets of revised Early Grading. The plans have been revised based on
your comments dated May 30 , 2014 in accordance with the following:
1) [Comment] The application states Early Grading Permit. For this type of application,there should be no
structures shown on this plan. Please clarify how you would like to pursue application. Even though this may be
an early grading plan application, I have reviewed plans for E&S and SWM just in case it was a typo on the
application.
[Revision 1] The title should include"Early Grading Plan."Also, remove all hardscapes: proposed roads,
proposed single family homes, proposed sidewalks, etc. This early grading plan should only include E&S
control measures and grading for Phase 1 and Phase 2.
[Response] All hardscapes have been taken off of both phases of the Early Grading Plan. The rectangles
you see on the plan are not buildings,they represent building pads and are used for grading purposes
only. A note has been added to each plan sheet of the Early Grading Plan.
2) [Comment] On sheet SW3,please label preserved and managed slopes.
[Revision 1] Comment no longer required. The critical slopes are shown on plan. The critical slopes waiver was
already approved with the ZMA. At this point there is no need to differentiate managed slopes from preserved
slopes. Also,the ZMA was approved prior to the adoption of the new critical slopes section in the ordinance.
[Response] Comment Addressed.
3) [Comment] Temporary slope drains are not designed per VESCH standards. Typical designs show a
compacted earthen dike to divert runoff to slope drains. Please show.
[Revision 1] Comment partially addressed. DDs still need to be shown for TSD draining to SB-2.
[Response] Temporary slope drains have been designed with Diversion Dike's for this submittal.
4) [Comment] Per meeting on Feb 6, 2014,we discussed revising the existing topography. Please address. A
sewerline was installed along northern and eastern portion of the site. We discussed possibly using this road as a
means to divert runoff to a sediment trap.
[Revision 1] Comment partially addressed. Applicant has not designed sediment traps near the access road(built
for the existing sewerline). Sediment traps will need to be designed. Remove the DDs that split the site and size
the sediment traps for new drainage areas.
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[Response] Sediment traps have been designed in the areas where we have abandoned the Diversion
Dike's crossing the site. Sediment trap#2 uses the existing access road to direct water to the trap.
5) [Comment] For phase 1 (northern and eastern portion), it will make more sense to have diversion dikes at
bottom of slopes to sediment traps. Then grade up the steep slopes. These diversion dike are partially shown for
the eastern portion of site.
[Revision 1] Comment partially addressed. Diversion dikes are proposed at the bottom of fill slopes, but it
appears that the construction of the walls will be required to satisfy the proposed grades on the early grading
plan. The retaining walls can only be built if the site plan is approved and at this time it is still under review.
Also, as previously mentioned in comment 1, an early grading plan should not show hardscapes. Please clarify
how you would like to proceed since an early grading plan will not allow you to construct the walls necessary to
grade the eastern portion to the final grades on plan.
[Response] The retaining walls have been taken out of the Early Grading Plan. The fill slopes have been
regraded and the Diversion Dike's have been moved back as a result.
6) [Comment] The diversion dikes which splits the site on sheet SW8 and SW 13 does not appear to work for
clearing, grubbing and grading. This coincides with comment 4. I suggest removing these diversion dikes and
enlarging sediment trap 1. The diversion dikes at the bottom of the slope should be extended for more capture to
sediment trap 1.
[Revision 1] Comment partially addressed. There is still a diversion dike#3 that splits the site.This will not
work as it will be difficult to maintain as the site is being cleared, grubbed and graded. Address with comment 4.
[Response] Diversion dike#3 was shortened so that site is not split. Sediment tap#1 has been designed to
capture the resulting water.
7) [Comment] The challenge is how to address erosion control in Phase 2 once the walls on eastern side are
installed. The dd's behind homes will not work.
[Revision 1] Comment partially addressed. This is only an early grading plan. The walls need to be built to
construct the DDs at the top of the fill slope. See comment 5.
[Response] The retaining walls have been taken out of the Early Grading Plan. The fill slopes have been
regraded and the Diversion Dike's have been moved back as a result.
8) [Comment] The temporary slope drains on phase II erosion control on eastern portion will not work. They
should outlet into perimeter controls, such as as sediment trap.
[Revision 1] Comment partially addressed. Clarify the gravel outlet on SW 14 as no sediment shall leave the
site.
[Response] Per conversations with Michelle the gravel outlet will have a 'j' hook so that a large rain event
✓will not blow through Diversion Dike#6. Please note that the naming of the Diversion Dike's have
changed due to the removal of one. See sheet SW5 for DD naming.
9) [Comment] SB-1 on calcs appear to be SB-2. Please revise name and note"post condition".
[Revision 1] Comment not addressed. The calcs were not submitted with this submission. Also the SB-1 on
calcs should be relabeled to SB-2 post conditions. This submittal should also show the post drainage areas in
phase 2 of early grading plan. All design of SB or ST shall be for higher DA of pre and post conditions.
[Response] Calculations are provided with this submission. DA's for Phase 2 are shown on sheet SW10.
Page 2 of 4
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10) [Comment] On SW-5, SB-1 is an existing pond. Please correct label.This should not be used as a sediment
pond. What is the benefit of reducing the amount of drainage area to existing pond 1 when both ponds are
owned by Dr Hurt.
[Revision 1] Comment partially addressed. Before the SCC and ditch(for Fontana development)can be fully
functional, final grading will need to be completed. Then ditches will be constructed. I recommend showing a
designed berm greater than 18"with SCC to divert water to SB-1 and SB-2 as a perimeter control measure in
Phase 1 and Phase 2. SCC to SB-2 can be designed with SWM plan.
./ [Response] A SCC with a 24" berm has been designed in the location suggested.
11) [Comment] Also, it appears that the ponds proposed does not match the approved ZMA2002-04 plans.
Please clarify. This may have been discussed already while Michael Koslow was the reviewer.
[Revision 1] Applicant has stated the proposed pond design has been approved by Engineering Review the
ARB. This was previously coordinated with original plan reviewer, Michael Koslow.
12) [Comment] On SW24,the pond labels do not match report. Please revise.
[Revision 1] This is an early grading plan. Applicant will revise on SWM plans.
[Response] Comment will be addressed with the SWM Plan.
13) [Comment] It appears that the target phosphorous removal is 43%, not including the future development.
Please take the future development into account. The current proposed development shows the retention pond to
be sized to treat 4* WQV(Retention Pond II), 275,880 cu-ft. When you add the future development,the BMP
choice may change. Page 6 on your report reflects the correct impervious areas, but this is not reflected in
removal rate calcs. Please revise removal rate calcs.
[Revision 1] This is an early grading plan. Applicant will revise on SWM plans.
[Response] Comment will be addressed with the SWM Plan.
14) [Comment] Once 13 is addressed, please meet all three below if site has inadequate channels:
a) Detain the WQV (1"runoff)and release over 48 hours.
b) Detain the 1 year 24-hour storm and release over 24 hours.
c) Detain and reduce the peak flow for a 1.5, 2 and 10 year 24-hour storm,to the following level; peak flow<_
Qf(VfNpost), where Qf is flow from the site in a well forested condition (C =0.25, or CN= 51), and Vf is
volume from the site in a well forested condition.
[Revision 1] This is an early grading plan.Applicant will revise on SWM plans.
Comment will be addressed with the SWM Plan.
15) [Comment] Show detail of emergency spillway.
[Revision 1] This is an early grading plan.Applicant will revise on SWM plans.
Comment will be addressed with the SWM Plan.
16) [Comment] It appears that a majority of the eastern portion is untreated. I recommend increasing the size of
the biofilter on the north and addressing more treatment on eastern portion of site.
[Revision 1] This is an early grading plan.Applicant will revise on SWM plans.
Comment will be addressed with the SWM Plan.
17 [Comment] Please provide SCC calculations.
17
1] Comment partially addressed. I recommend a new SCC on western boundary of site in conjunction
with proposed DD#8. The velocity was higher than 4 f/s. Please show appropriate grass lining on detail.
Page 3 of 4
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The proposed ditch on southern boundary should also state acreage on calcs. The velocity was higher than 4 f/s.
Please show appropriate grass lining. SCC to SB-2 can be designed with SWM plan.
[Response] SCC calculations are provided with this submittal on sheet SW5 in Diversion Dike/SCC
Calculations. EC-3 has been noted on the plan to ensure soil stabilization for a velocity higher than 4 ft/s.
18) [Comment] All plans and calculations shall be signed, sealed and dated when it is ready to approve.
[Revision 1] Comment not addressed.No calcs for E&S has been submitted. Applicant will submit calcs for
SWM with appropriate swm plans.
[Response] All calculations are provided with this submittal.
New comment
z19)On SW-5, one of the new excavated sediment traps is missing. Please add.
[Response] Sediment trap has been designed and is in place.
J O)On SW-12, show the silt fence behind the DD.
[Response] Silt fence has been shown behind the DD on sheet SW-12.
21)On SW-13,the rip-rap ditch appears to be part of the SWM facility design. Please confirm. This can be
shown later with the SWM facility design. Also, please note there is a proposed pedestrian trail crossing this
ditch. A culvert should be proposed.
[Response] Rip-rap ditch has been taken out of the Early Grading Plan. Pedestrian crossing culvert to be
proposed with SWM Plans.
22) DD6 will not work. This splits the site also. I recommend removing DD and sizing excavated sediment trap
to work with drainage area.
[Response] DD has been removed and a sediment trap is capturing the resulting water.
Best Regards,
Dustin Greene, EIT
Page 4 of 4
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May 13, 2014
Ms. Michelle Roberge
Albemarle County Department of Community Development
401 McIntire Road
Charlottesville, Virginia 22902
RE: Cascadia WPO Plan- Comment-Response Letter— WPO 2013-00032
Dear Michelle,
Enclosed please find two (2) sets of revised Erosion and Sediment Control and Stormwater Management Plans.
Please note that we have revised the plans to address your comments dated July 10, 2013, and based on
follow-up engineering meetings in accordance with the following: 9/
ENGINEERING COMMENTS U
A. Erosion & Sediment Control Plan and SWM Plan (WPO201300032)
1) The application states Early Grading Permit. For this type of application, there should be no structures
shown on this plan. Please clarify how you would like to pursue application. Even though this may be an
early grading plan application, I have reviewed plans for E&S and SWM just in case it was a typo on the
application.
RESPONSE: The enclosed plan is indeed for early grading as indicated on the cover sheet. We have
addressed the comments below that pertain to the E+S plans only. A note has been added to the E+S
Phase 2 plan sheets that no utility construction of other final construction items are to be installed with
c� ,� Y p <
these plans, only mass grading. Y ;n't,,�: PU., ?r•1...,* . �r��,� 'r ,�. _ �,.r ,r.p -� S , �. .:•.,'.
riCt,U , i teci D'. T?TLL
2) On sheet SW3, please label preserved and managed slopes. + ""
RESPONSE: As discussed at our May 1 meeting,we will not differentiate the slopes since this site is
subject to a critical slopes waiver that was previously approved with the ZMA.
3) Temporary slope drains are not designed per VESCH standards. Typical designs show a compacted
earthen dike to divert runoff to slope drains. Please show.
RESPONSE: We have revised the plans to indicate diversion dikes that divert runoff to the slope drains.
4) Per meeting on Feb 6, 2014, we discussed revising the existing topography. Please address. A
sewerline was installed along northern and eastern portion of the site. We discussed possibly using this
road as a means to divert runoff to a sediment trap.
RESPONSE: As discussed,the plans have been revised to include the field-run topography that was
established by this firm after the clearing for the Hyland Ridge offsite sewer was constructed. We have
also updated the plan to i dude thr_e excavated sediment traps that use the sewer road to diver'Fwa_ter
to t„ _h_em. Since these sediment traps are temporary and are located in recently cleared areas in a
sensitive area,we have not indicated mass clearing or full-depth excavation. Essentially,we are doing
what we can to utilize the existing topography of the site
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5) For phase 1 (northern and eastern portion), it will make more sense to have diversion dikes at bottom of
slopes to sediment traps. Then grade up the steep slopes. These diversion dike are partially shown for
the eastern portion of site.
RESPONSE: As discussed,we have revised the plan to provide diversion dikes at the bottom of these
fill slopes.
6) The diversion dikes which splits the site on sheet SW8 and SW13 does not appear to work for clearing,
grubbing and grading. This coincides with comment 4. I suggest removing these diversion dikes and
enlarging sediment trap 1. The diversion dikes at the bottom of the slope should be extended for more
capture to sediment trap 1.
RESPONSE: As discussed,we have revised the plan to move the dikes and the trap to the bottom of the
hill. As a result,trap 1 has increased in size.
7) The challenge is how to address erosion control in Phase 2 once the walls on eastern side are installed.
The dd's behind homes will not work.
RESPONSE: We have revised the design of the units on the eastern portion of the site to allow
additional space for the diversion dikes at the top of the slope. In order to install
8) The temporary slope drains on phase II erosion control on eastern portion will not work. They should
outlet into perimeter controls, such as as sediment trap.
RESPONSE: The temporary slope drains have been revised to outlet into sediment traps. On the
temporary slope drain at the northeast corner of the property,we have provided a gravel outlet to slow
the slope drain water down before it drains along the diversion dike to the sediment trap.
9) SB-1 on calcs appear to be SB-2. Please revise name and note "post condition".
RESPONSE: The word "post condition" has been added to the cacls for SB-1.
10) On SW-5, SB-1 is an existing pond. Please correct label. This should not be used as a sediment pond.
What is the benefit of reducing the amount of drainage area to existing pond 1 when both ponds are
owned by Dr Hurt.
RESPONSE: As discussed,we have provided a ditch to convey offsite Fontana water to the existing
pond. Also, as discussed at our May 1 meeting,this pond may be used as a temporary sediment basin.
11) Also, it appears that the ponds proposed does not match the approved ZMA2002-04 plans. Please
clarify. This may have been discussed already while Michael Koslow was the reviewer.
RESPONSE: As discussed at our May 1 meeting,the proposed pond design has been approved by the
ARB. This was previously coordinated with Mr. Koslow.
12) On SW24, the pond labels do not match report. Please revise.
RESPONSE: Please refer to final SWM plan for all responses to SWM comments.
Page 2 of 3
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13) It appears that the target phosphorous removal is 43%, not including the future development. Please
take the future development into account. The current proposed development shows the retention pond
to be sized to treat 4*WQV(Retention Pond II), 275,880 cu-ft. When you add the future development,
the BMP choice may change. Page 6 on your report reflects the correct impervious areas, but this is not
reflected in removal rate calcs. Please revise removal rate calcs.
RESPONSE: Please refer to final SWM plan for all responses to SWM comments.
14) Once 13 is addressed, please meet all three below if site has inadequate channels:
a) Detain the WQV(1" runoff) and release over 48 hours.
b) Detain the 1 year 24-hour storm and release over 24 hours.
c) Detain and reduce the peak flow for a 1.5, 2 and 10 year 24-hour storm, to the following level; peak flow <=
Qf(VfNpost), where Qf is flow from the site in a well forested condition (C = 0.25, or CN = 51), and Vf is volume
from the site in a well forested condition.
RESPONSE: Please refer to final SWM plan for all responses to SWM comments.
14) Show detail of emergency spillway.
RESPONSE: Please refer to final SWM plan for all responses to SWM comments.
15) It appears that a majority of the eastern portion is untreated. I recommend increasing the size of the
biofilter on the north and addressing more treatment on eastern portion of site.
RESPONSE: Please refer to final SWM plan for all responses to SWM comments.
16) Please provide SCC calculations.
RESPONSE: SCC calculations are shown for E+S ditches. Please refer to final SWM plan for all final
SCC calculations.
17) All plans and calculations shall be signed, sealed and dated when it is ready to approve.
RESPONSE: Acknowledged for E+S. Please refer to final SWM plan for all responses to SWM
comments.
We trust the above adequately addresses your comments. Please let me know if you have any questions or
require additional information.
Very truly . r
ZiOr
Michael ■ yers, P.E., C.F.M.
Attachments
Cc: Keith Lancaster
Page 3 of 3
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March 11, 2014
Ms. Michelle Roberge
Albemarle County Department of Community Development
401 McIntire Road
Charlottesville, Virginia 22902
RE: Cascadia WPO Plan - Comment-Response Letter– WPO 2013-00032
Dear Michael,
Enclosed please find two (2) sets of revised Erosion and Sediment Control and Stormwater Management Plans.
Please note that we have revised the plans to address your comments dated January 21, 2014 and based on
the follow-up engineering meeting on February 6, 2014 in accordance with the below summary. Please also
note the developer would like to pursue an early grading permit based on these WPO plans as indicated on the
cover sheet of the plans.
ENGINEERING COMMENTS
Erosion&Sediment Control: I Adequate
(Code Chapter 17,Article ll) x Not Adequate
1.dPP
Y N ?lose vat a Sri 4,44 7...4 kG vie} w.evIty ki"1 i* e14,5w s 6
X ] State standards followed,and Design Standards Manual notes and details l„rPSU tc aw a
),f Adequate limits and perimeter measures out of work areas bp, tr 3643 SW 7 8t ti et re al
All stages protected adequately ` {Q bG
Adequate channels lase.etvYPlt. 19 e^0,14 7 2/ St-� [!'�_tea 5o Mcr�le
et ret -esled Can�i an roll`' , desere� a5 a.(S, q
vs fs SC raMt I (dett.dc4 ee»d; l c1.4bUtei 5 Ao each(4t.l{,1+b Ths
vvoi*{u add.ess a¢evA‘c.t,grwels v4141 be arede4
C�nr.nmofo.•*A .non*. ,aw.►3 C rig4i0te —
RESPONSE: As discussed at our February 6, 2014 Engineer's meeting,we have added a sediment trap
and diversion dikes to treat the 2.4-acre drainage area on sheet SW8. We have also updated the plan to
modify the area being served by diversion dikes such that the maximum drainage area to any one
diversion dike is less than 5-acres (3.58-acres maximum). Also,we have provided a temporary SCC
design adjacent to diversion dikes where the longitudinal slope is greater than 2% per calculations on
Sheet SW5. Also, please note that we have added SB-4(detail Sheet SW 20A) and provided a temporary
SCC to direct site runoff to SB-2. As discussed and agreed at our meeting, since we have completed
our E+S design based on a denuded site (C=0.60), the additional MS-19 analysis during construction is
not required.
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Stormwater Management: d°"�q en�sthee�tthe
(Code Chapter 17,Article III) No
equate
X Not t Adequate
Y N Ac+^1'TOG s
k 1 Enough capture and treatment for on-site areas r Br t? r ILcdot's k
x ,Enough detention storage for on-site areas rltasa lwl.e4 p,c .d to c:h k*.es a.' e-stet,
A Sealed hydrologic and hydraulic computations provided a-,d i- d,a t..a)c. ett# I a Pc
Plest address 4e1n.i t;o.t' fre�4k.R,� �. T,29 Ao si„w•,d.o.'..,r '„,i Si$ Sifee,"
sces 4 SWic
RESPONSE: Sheets SW24 and SW25 have been updated to indicate proposed BMP facilities and times
of concentration on both sheets. For the 9.29-acre that is draining to the existing stream,we have
added computations that show how the 10-year peak flows have been reduced. Also as discussed,we
have added a rain garden facility for the lots on Boulder Hill Lane. We have also added a diversion dike
at the top of the slope behind lots 53-70 during E+S phase 2 so that runoff can be directed to a slope
drain to protect the slope. As discussed,we have also provided a water quality swale below these lots
with a plunge pool outfall below the proposed trail. Please refer to Sheets SW 13/14, SW 18/19 for the
grading plan and SW 22A for construction details.
Mitigation:
q
(Code Chapter 17,Article III) uate
1 Not Adequate I
Y N
Buffers and disturbed areas adequately shown
rE
X Adequate plantings at 2:1,or other mitigation provided
stil,e.t.ale./(+ la vI
rf„ease ,1,,4;>r AR., a roFf0S.ej iiltii- df tmli-igwt;ov, 04/0 fits
V RESPONSE: As discussed at our February 6, 2014 meeting,the stream buffer plan as submitted on
Sheet SW 23 is adequate. Q'1 �' .
( i' lrl's 9,s lif e.,t n,,
We trust the above adequately addresses your comments' Please let me know if you have any questioni or
require additional information.
Very truly
47i
Michael i yers, P.E., C.F.M.
Attachments
Cc: Keith Lancaster
Page 2 of 2
Mike Myers
From: Mike Myers
Sent: Friday, February 07, 2014 9:35 AM
To: Glenn Brooks; 'Michelle Roberge'; 'Michael Koslow'; Max Greene
Cc: Keith Lancaster; 'Charlie Armstrong'
Subject: Cascadia 2.6.14 Engineers Meering
Glenn, Michelle and Michael,Thanks for meeting with us yesterday to discuss resolution to the WPO comments dated
January 21, 2014. The meeting was very helpful, and I just wanted to formalize the minutes:
1) The E+S comment regarding the MS-19 analysis of pre-forested conditions has been addressed since we used a
C factor for a completely denuded site for the design of our sediment trapping facilities in accordance with
guidelines in the VESCHB.
2) With respect to the 9.29-acres at the top of the site,we are reducing the runoff after development so no
additional detention is required. However,we will provide water quality treatment of the cul-de-sac area and
we will provide a modified water quality swale and berming measures to protect the deep fill slope behind lots
56-70. These areas will not necessarily meet the water quality phosphorus removal requirements, but we will
do our best efforts in this area due to site constraints of the preservation area, stream buffer and critical slopes.
We are providing significant mitigation plantings, which will also help with the overall water quality for the site.
3) The mitigation plan is acceptable as submitted.
Again,thanks for your time yesterday, Mike
Michael F. Myers, P.E., C.F.M.
Director of Engineering
Dominion Engineering and Design, LLC
172 South Pantops Drive
Charlottesville, VA 22911
434.979.8121 x140 (office)
434.906.3161 (mobile)
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November 26, 2013
Mr. Michael Koslow, P.E.
Albemarle County Department of Community Development
401 McIntire Road
Charlottesville, Virginia 22902
RE: Cascadia WPO Plan-Comment-Response Letter— WPO 2013-00032
Dear Michael,
Enclosed please find two (2) sets of revised Erosion and Sediment Control and Stormwater Management Plans.
Please note that we have revised the plans to address your comments dated July 10, 2013, and based on
follow-up engineering meetings in accordance with the following:
ENGINEERING COMMENTS
Erosion&Sediment Control: Adequate
(Code Chapter 17,Article II) X Not Adequate
N
State standards followed,and Design Standards Manual notes and details
?4-., Adequate limits and perimeter measures out of work areas
X All stages protected adequately h
Ai Adequate channels ,�,rr �"f1 ,p`. `
V r G Pds' Br Pt.o..11 �lG S�j'L sW I46 <erul er.c
RESPONSE: We have updated the existing topography based on a field survey of existing conditions
following installation of the Hyland Ridge sanitary sewer. We have also provided sediment basins at the
SW(existing dry pond to serve as a sediment basin)and NE(new sediment basin)corners. We have
also shown the existing sediment trap adjacent to the Broadus church site that was constructed with
the Hyland Ridge sewer plan.
Stormwater Management: -
Adequate
(Code Chapter-17,Article III) X Not Adequate
Y N
A- Enough capture and treatment for on-site areas
Enough detention storage for on-site areas
X Sealed hydrologic and hydraulic computations provided WE s v c+ SAG(e
t!avu o4 dam.-foes tc,nse Cor.+r*Art vt Artie 4r@
Foal by i t ete./4—A.(' G,L ,j-e/ec4 l ti 441405
5
RESPONSE: We have clarified the drainage maps to indicate the contributing drainage areas. Final
buildout of Blocks 1-3 has been considered and is reflected on the drainage maps and calculations. We
Page 1 of 2
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41 h. Engineering Charlottesville, VA 22911
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have also shown that we have reduced undetained areas to below pre-development levels along the
eastern and northern property lines.
N Mitigation:
(Code Chapter 17,Article� Adequate
�,p....t e.u( PAT reylc.W 7c Not Adequate
Y N
Buffers and disturbed areas adequately shown
Adequate plantings at 2:1,or other mitigation provided
u 1,n ev'a - to y 61. a C..2 a fi a �f Gp��ts .
. .
p4enu. ppovtc . G.. as5eSS0-1 to i. i C ,t'g
.Pc^en�`4.)
This review attempts to encompass the larger compliance questions. County staff does not assume Q.1�,1 d
responsibility for any calculation or plan details,and cannot cover the intricacies of every plan submitted."
Each plan and calculation must have a professional seal and signature to assume these responsibilities. hINS-4 4, C
1 I .______._r ._+____ _._ _.._ r__.t a_____._ir.__.�t._n I r5)
RESPONSE: A stream buffer mitigation plan has been provided as part of the WPO plan has been provide for
review. Refer to Sheet 23.
We trust the above adequately addresses your comments. Please let me know if you have any questions or
require additional information.
Very truly yours,
4i/rr,
i
Michael Myers, P.E., C.F.M.
Attachments
Cc: Keith Lancaster
Page 2 of 2
Michael Koslow
From: Michael Koslow
Sent: Thursday, July 11, 2013 2:43 PM
To: 'Mike Myers'
Subject: Cascadia Blocks 4-7 and Riverfront Townhomes (WPO2013-000232 and WPO2012-00032)-
engineering comments
Attachments: CDDE2_ESC_SWM_MAK Riverfront_Townhomes-Final.pdf; El
_MAK_ESC_SW M_M IT_W_PO201300032.pdf
Hi Mike,
Please see attached.
Thanks, Michael
Michael Koslow, PE
County of Albemarle
Community Development Department
401 McIntire Road
Charlottesville,VA 22902
434-296-5832 ext. 3297
434-972-4126(fax)
mkoslow @albemarle.org
1