HomeMy WebLinkAboutWPO200800045 Review Comments Erosion Control Plan 2008-06-13� OF AL
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COUNTY OF ALBEMARLE
Department of Community Development
401 McIntire Road, Room 227
Charlottesville, Virginia 22902 -4596
Phone (434) 296 -5832 Fax (434) 972 -4126
Project: Blue Ridge Cohousing [SDP200800031, WP0200800018]
Plan preparer: Kevin Conner, Gay and Neel Inc. [email: kconner @gayandneel.com]
Plan received date: 29 Apr 2008
Date of comments: 15 May 2008 (SRC Final Site Plan comments)
13 June 2008 (Road Plans, SWM Plans, ESC Plans)
Reviewer: Jonathan Sharp
A. Final Site Plans (comments from 15 May 2008)
1. Please provide copies of federal and state permits for stream disturbance (Army Corps, VDEQ,
etc.).
2. Please provide a completed copy of the standard stormwater maintenance agreement and fee for
recordation for the proposed stormwater management facilities.
3. Please provide the FEMA map and date references labeled for the FEMA floodplain.
4. Please provide all copies of necessary offsite easements. For example, easements to construct
water and sewer, road improvements, offsite construction and access easements, drainage
easements, etc.
5. The proposed adjacent subdivision and boundary line adjustment must be recorded prior to final
site plan approval.
6. Please provide traffic generation figures for the proposed site and proposed roadway
improvements.
7. Curb and gutter and treated surfaces based on VDOT regulations and standards are required for all
travelways and parking areas. As proposed, the plan requires a waiver of curb and gutter and
parking /travelway surface requirements. If you want to pursue a waiver of the requirements, please
provide a waiver request which includes the items requesting to be waived and a justification in
accordance with the Code Sections provided below:
Curb and gutter waiver request:
Curb and gutter can be waived administratively for stormwater management purposes by the
County Engineer according to Code Section 18.4.12.15g. For all other purposes, a curb and gutter
waiver can be administratively waived by the Zoning Administrator in conjunction with the
County Engineer according to Code Section 18.4.12.2c2.
Parking and travelway surface waiver request:
Parking and travelway surface requirements can be waived by the County Engineering according
to Code Section 18.4.12.15a.
8. The proposed plan is showing stream buffer disturbance. Stream buffer disturbance should be
minimized. Engineering recommends minimizing stream buffer disturbance along Parkview Drive
and eliminating all stream buffer disturbance shown on site, except for any necessary ditches to
convey the outletting drainage of the facilites to the streams below. Any stream buffer disturbances
will need approval from the Program Authority, and require an approved Mitigation Plan prior to
Final Site Plan approval.
9. The grading plans show proposed slopes steeper than 2:1. Please revise the grading plans so that
all proposed slopes are 2:1 or flatter. Some of the proposed spot elevations are very confusing. For
example, the spot elevation 651.9 near the existing barn/shed is very close to the existing 650
Albemarle County Community Development
Engineering Review Comments
Page 2 of 8
contour, creating very steep slopes in this area. There are other proposed spot elevations which
create very steep proposed slopes.
10. For SWM facilities with embankments 3 feet or higher, the downhill face of the embankment must
be a minimum of 3:1. Several of the proposed embankments are only 1.5:1.
11. All proposed slopes steeper than 3:1 must have low maintenance (not grass) ground cover
specified on the plans (site plan and road plans).
12. Safety railing must be specified for retaining walls over 4 feet high.
13. Adequate access must be provided to all of the SWM facilities. The requirements are: 10 feet wide
access not exceeding 20% in grade. For grades in excess of 10 %, graveled access is required.
Access must be provided to the embankment, any outlet structures, and any forebays.
14. All entrances must be shown with a VDOT designation.
15. Please show the sight distance lines at the entrance of the site on Parkview Drive.
16. VDOT approval is required for any work affecting the public right -of -way.
17. Parking areas cannot exceed 5% in grade, in any direction.
18. The proposed parking area configuration does not meet County requirements. In order to maintain
9 foot wide parking spaces, a 24 foot wide travelway must be provided. If a 20 foot wide travelway
is provided, parking spaces must maintain 10 feet in width.
19. Guardrail is required for the stream crossing along Parkview Drive.
20. It appears that the concept for Stormwater Management is not capturing as much proposed
impervious area as practicable. It appears that parking areas and structures may bypass the facility.
Typically, roof drains of structures tie into the proposed stormwater management facilities, and
parking areas /travelways are directed to the SWM facilities through use of curb and gutter, piping,
or ditches and swales. Any concentrated discharges flowing into a SWM facility require forebays.
21. Please indicate the outlet locations of the proposed SWM facilities. Also, show the required
improvements in order to provide adequate channels for the outlets of the facility to the streams
below.
22. We received a copy of your SWPP permit. This should be sent directly to DCR. Please contact Mr.
Matthew Grant, DCR, at 804.225.3068 for more information. This does not affect your
review /approval of this plan.
23. Engineering has not yet been able to complete the review of the ESC plans. However, after a quick
look at the plans, it appears that the plans are inadequate. Use of only silt fence as ESC protection
is inadequate. For adequate perimeter control, please provide diversion dikes which convey
drainage to sediment traps and basins.
24. The ESC plans appear to indicate that the SWM facilities will be constructed during the same time
that grading /site construction occurs. SWM facilities cannot be constructed or retrofitted from
sediment traps to biofilters until after final stabilization has occurred.
25. The road plans, drainage plans, ESC plans, SWM plans, and mitigation plans, any easement plats,
subdivision plats, and boundary line adjustments must be approved and/or recorded prior to final
site plan approval.
26. More comments may be necessary upon resubmittal.
B. Road Plans
27. Adequate conveyance of drainage must be provided for Parkview Drive. The ditch shown opposite
the development ends at contour 646. An adequate channel must be provided to the channel
below. There does not appear to be any adequate ditches or conveyance on the roadside directly
adjacent to the development (from the high point —16 + 00 to the channel below the culvert). It
appears drainage may spill into the street.
28. Please provide pavement design calculations.
29. A traffic generation and distribution summary (ADT's) and design speed limit are needed for
Albemarle County Community Development
Engineering Review Comments
Page 3 of 8
design of Parkview Drive (for road width, K values, pavement design, etc.)
30. Please show all existing and proposed signs for traffic control (speed limit, stop signs, etc.)
31. Please show all existing and proposed street name signs.
32. Please provide the Albemarle County general construction notes, and notes for streets on the plans,
verbatim (It appears old notes are provided. A copy of the latest notes is provided at the end of this
comment letter.
33. Please show cross drain locations labeled with VDOT designations (CD -1,2) at every major cut
and fill transition or sag curve on the road profile sheet.
34. The pavement crown must be specified at 1 /a ":1' slope.
35. The roadway shoulder must be a minimum of 4' width.
36. Proposed slopes steeper than 3:1 must have low maintenance (not grass) groundcover specified.
37. Guardrail must be specified over all fill slopes and culverts, with 3' additional shoulder, using
VDOT designations. Guardrail end sections must be labeled.
38. Ditches must be dimensioned at 1' depth min., and 4' min. width from shoulder to ditch
centerline.
39. Please provide a profile for the roadway culvert.
40. Please provide culvert calculations.
41. Please provide ditch calculations.
42. Please provide outlet protection and outlet protection calculations for the roadway culvert.
43. Please show the drainage area drainage to the proposed culvert.
C. Stormwater Management Plan
44. Stormwater Management drainage area maps (proposed and existing) must have the acreage,
coefficient, and time of concentration labeled for each drainage area on the maps.
45. It appears that not all impervious areas drain to the SWM facilities. See comment #20.
46. Please provide ditch calculations for all proposed ditches conveying flow to SWM facilities.
47. The Stormwater Management facilities must not be located within the stream buffers.
48. Flow in the facilities must not be short- circuited. The flow path must be 2:1 or greater in all water
quality facilities.
49. Cross - section details of each facility must be provided, including: embankments, principle and
emergency spillways, sediment forebays, and biofilter floor dimensions. See the County
Engineering design manual checklist for all cross - section detail requirements.
50. For facilities with embankments 3 feet or higher, the 10 yr and 100 yr high water elevations must
be shown on the cross - section details. With an emergency spillway, 1 foot of freeboard for the 100
yr storm must be provided. Without an emergency spillway, 2 feet of freeboard for the 100 yr
storm must be provided.
51. Areas of sheet flow draining into biofilter facilities must be protected from erosion by appropriate
scour protection stone or energy dissipation measure.
52. Plants must be shown and labeled with height or caliper in the biofilters. Three species of trees and
three species of shrubs are required in each biofilter.
53. The minimum depth of sand/soil media in biofilters is 2.5 feet.
54. The outlet of the facilities must be shown on the plans and cross - sections, matching the
computations.
55. Biofilter underdrains and cleanouts must be shown on the plans. Clean-outs are required at each
junction and 50'.
56. Please provide the Albemarle County general stormwater notes on the plans. Notes are provided at
the end of this comment letter.
57. The 100 yr storm elevations are shown at a lower elevation than the 2 and 10 year storm. This does
not make sense. The critical duration storm must be used for the 100 yr storm. Detention
Albemarle County Community Development
Engineering Review Comments
Page 4 of 8
requirements are for the 2 and 10 yr storm only, the 100 yr storm does not need to be detained. The
routings for the 100 yr storm are required to show that freeboard requirements are met for facilities
with embankments 3 feet and high and above.
58. A SWM bond will be computed by the County once the plans have been approved.
D. Mitigation Plan
59. A mitigation plan is required for any stream buffer disturbance. Please provide a mitigation
application, plan, and fee.
60. A Mitigation bond will be computed by the County once the plans have been approved.
D. Erosion and Sediment Control Plan
61. It appears that inadequate perimeter control is provided. See comment #24.
62. Silt fence must not be used across contours in place of diversion dikes. Silt fence is limited to areas
of sheet flow with 1/a acre per 100 ft of level on -grade silt fence.
63. Please provide ESC measures for the road improvements and sewer line improvements.
64. Stream crossings and diversions must be provided at all stream crossings. A detailed sequence of
construction must be provided for the replacement of the existing culvert and work within the live
stream.
65. The County Erosion Control notes must be shown on the plans. Notes are provided at the end of
this comment letter.
66. The limits of clearing and grading encompassing all disturbances must be shown on the plans.
67. Please graphically show the construction entrance on the plans.
68. Please show existing drainage divides.
69. Please show existing soil boundaries with labels.
70. Pleas show a stockpile location.
71. Please show a staging and parking area.
72. Please show outlet protection at all outlets.
73. All ESC measures must remain outside of stream buffers.
74. Adequate channels (MS -19) are required at each facility outlet and at the outlet of all ditches and
culverts.
75. A paved construction entrance detail is required for the plans. A copy of the detail is attached
following the comments.
76. An ESC bond will be computed by the County once the plans have been approved.
Albemarle County Community Development
Engineering Review Comments
Page 5 of 8
ALBEMARLE COUNTY
FINAL PLANS NOTES
General Construction Notes
1. Prior to any construction within any existing public right -of -way, including connection to any
existing road, a permit shall be obtained from the Virginia Department of Transportation (VDOT).
This plan as drawn may not accurately reflect the requirements of the permit. Where any
discrepancies occur the requirements of the permit shall govern.
2. All materials and construction methods shall conform to current specifications and standards of
VDOT unless otherwise noted.
3. Erosion and siltation control measures shall be provided in accordance with the approved erosion
control plan and shall be installed prior to any clearing, grading or other construction.
4. All slopes and disturbed areas are to be fertilized, seeded and mulched.
5. The maximum allowable slope is 2:1 (horizontal:vertical). Where reasonably obtainable, lesser
slopes of 3:1 or better are to be achieved.
6. Paved, rip -rap or stabilization mat lined ditch may be required when in the opinion of the County
Engineer, or designee, it is deemed necessary in order to stabilize a drainage channel.
7. All traffic control signs shall conform with the Virginia Manual for Uniform Traffic Control
Devices.
8. Unless otherwise noted all concrete pipe shall be reinforced concrete pipe — Class Ill.
9. All excavation for underground pipe installation must comply with OSHA Standards for the
Construction Industry (29 CFR Part 1926).
General Construction Notes for Streets (This list is in addition to the General Construction Notes)
1. Construction inspection of all proposed roads within the development will be made by the County.
The contractor must notify the Department of Community Development (2965832) 48 hours in
advance of the start of construction.
2. Upon completion of fine grading and preparation of the roadbed subgrade, the contractor shall
have CBR tests performed on the subgrade soil. Three (3) copies of the test results shall be
submitted to the County. If a subgrade soil CBR of 10 or greater is not obtainable, a revised
pavement design shall be made by the design engineer and submitted with the test results for
approval.
3. Surface drainage and pipe discharge must be retained within the public right -of -way or within
easements prior to acceptance by the County. All drainage outfall easements are to be extended to
a boundary line or a natural watercourse.
4. Guardrail locations are approximate. Exact length, location and appropriate end treatments will be
field verified at the time of construction. Additional guardrail may be required at locations not
shown when, in the opinion of the County Engineer, or designee, it is deemed necessary. When
guardrail is required, it shall be installed four (4) feet offset from the edge of pavement to the face
of guardrail, and roadway shoulder widths shall be increased to seven (7) feet.
5. Where urban cross sections are installed, all residential driveway entrances shall conform to
VDOT CG -9(A, B or Q.
6. Where rural cross sections are installed, all residential driveway entrances shall conform to VDOT
standard PE -1.
7. Compliance with the minimum pavement width, shoulder width and ditch sections, as shown on
the typical pavement section detail, shall be strictly adhered to.
8. Road plan approval for subdivisions is subject to final subdivision plat validation. Should the final
plat for this project expire prior to signing and recordation, then approval of these plans shall be
null and void.
Albemarle County Community Development
Engineering Review Comments
Page 6 of 8
9. All signs or other regulatory devices shall conform with the Virginia Manual for Uniform Traffic
Control Devices and the Albemarle County Road Naming and Property Numbering Ordinance and
Manual.
10. Traffic control or other regulatory signs or barricades shall be installed by the developer when, in
the opinion of the County Engineer, or designee, they are deemed necessary in order to provide
safe and convenient access.
11. The speed limits to be posted on speed limit signs are 5 mph below the design speed, or as
determined by VDOT for public roads.
12. VDOT standard CD -1 or CD -2 cross - drains under to be installed under the subbase material at all
cut and fill transitions and grade sag points as shown on the road profiles.
13. A video camera inspection is required for all storm sewers and culverts that are deemed
inaccessible to VDOT or County inspections. The video inspection shall be conducted in
accordance with VDOT's video camera inspection procedure and with a VDOT or County
inspector present.
General construction notes for Erosion and Sediment Control plans
1. The plan approving authority must be notified one week prior to the pre - construction conference,
one week prior to the commencement of land disturbing activity, and one week prior to the final
inspection.
2. All erosion and sediment control measures will be constructed and maintained according to
minimum standards and specifications of the Virginia Erosion and Sediment Control Handbook
and Virginia Regulations VR 625 -02 -00 Erosion and Sediment Control Regulations.
3. All erosion and sediment control measures are to be placed prior to or as the first step in clearing.
4. A copy of the approved erosion and sediment control plan shall be maintained on the site at all
times.
5. Prior to commencing land disturbing activities in areas other than indicated on these plans
(including, but not limited to, off -site borrow or waste areas), the contractor shall submit a
supplementary erosion control plan to the owner for review and approval by the plan approving
authority.
6. The contractor is responsible for installation of any additional erosion control measures necessary
to prevent erosion and sedimentation as determined by the plan approving authority.
7. All disturbed areas are to drain to approved sediment control measures at all times during land
disturbing activities and during site development until final stabilization is achieved.
8. During dewatering operations, water will be pumped into an approved filtering device.
9. The contractor shall inspect all erosion control measures periodically and after each runoff -
producing rainfall event. Any necessary repairs or cleanup to maintain the effectiveness of the
erosion control devices shall be made immediately.
10. All fill material to be taken from an approved, designated borrow area.
11. All waste materials shall be taken to an approved waste area. Earth fill shall be inert materials
only, free of roots, stumps, wood, rubbish, and other debris.
12. Borrow or waste areas are to be reclaimed within 7 days of completion per Zoning Ordinance
section 5.1.28.
13. All inert materials shall be transported in compliance with section 13 -301 of the Code of
Albemarle.
14. Borrow, fill or waste activity involving industrial -type power equipment shall be limited to the
hours of 7:OOam to 9:OOpm.
15. Borrow, fill or waste activity shall be conducted in a safe manner than maintains lateral support, or
order to minimize any hazard to persons, physical damage to adjacent land and improvements, and
damage to any public street because o slides, sinking, or collapse.
Albemarle County Community Development
Engineering Review Comments
Page 7 of 8
16. The developer shall reserve the right to install, maintain, remove or convert to permanent
stormwater management facilities where applicable all erosion control measures required by this
plan regardless of the sale of any lot, unit, building or other portion of the property.
17. Temporary stabilization shall be temporary seeding and mulching. Seeding is to be at 75 lbs /acre,
and in the months of September to February to consist a 50150 mix of Annual Ryegrass and Cereal
Winter Rye, or in March and April to consist of Annual Rye, or May through August to consist of
German Millet. Straw mulch is to be applied at 80lbs /100sf. Alternatives are subject to approved
by the County erosion control inspector.
18. Permanent stabilization shall be lime and fertilizer, permanent seeding, and mulch. Agricultural
grade limestone shall be applied at 90lbs /1000sf, incorporated into the top 4 -6 inches of soil.
Fertilizer shall be applied at 1000lbs /acre and consist of a 10 -20 -10 nutrient mix. Permanent
seeding shall be applied at 180lbs /acre and consist of 95% Kentucky 31 or Tall Fescue and 0 -5%
Perennial Ryegrass or Kentucky Bluegrass. Straw mulch is to be applied at 80lbs /100sf.
Alternatives are subject to approved by the County erosion control inspector.
19. Maintenance: All measures are to be inspected weekly and after each rainfall. Any damage or
clogging to structural measures is to be repair immediately. Silt traps are to be cleaned when 50%
of the wet storage volume is filled with sediment. All seeded areas are to be reseeded when
necessary to achieve a good stand of grass. Silt fence and diversion dykes which are collecting
sediment to half their height must be cleaned and repaired immediately.
20. All temporary erosion and sediment control measures are to be removed within 30 days of final
site stabilization, when measures are no longer needed, subject to approval by the County erosion
control inspector.
General construction notes for Stormwater Management plans
1. All dams and constructed fill to be within 95% of maximum dry density and 2% of optimum
moisture content. All fill material to be approved by a geotechnical engineer. A geotechnical
engineer is to be present during construction of dams.
2. Pipe and riser joints are to be watertight within stormwater management facilities.
3. For temporary sediment traps or basins which are to be converted to permanent stormwater
management facilities; conversion is not to take place until the site is stabilized, and permission
has been obtained from the County erosion control inspector.
Albemarle County Community Development
Engineering Review Comments
Page 8 of 8
Paved construction entrance for erosion control plans
rOfdE 70' MIN.
CONSTRUCTION —\ 3" Sfu! -2,� ASPHALT TOP
COURSE EYI1 .7 NG
2 � PAVEMENT
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ACCESS —,
6" %N. 21A AGGRE(WE BASE
PROFILE
70' MIN.
—o ASPHALT PAVED
WASH RAC K
2% 1 2%
2% 12' MIN_*
I POST;VE Dew E
*DUST E}{TENd FULL w11dTH t0 SEDIMENT
OF INGRESS AND EGRESS TOAPPING pI:VIE
OPERATION
PLAN
EXISTING
PAVEMEWTJ
F;LTER CLu -II
SECTION A —A
JAGL.
IC.
A mutimmi water tap of 1 inch amst be n>u celled alth a miu -ninn 1 inch bAcock
s-butoff valve nTppt -nkg a welt Bose with a di- 7mefier of 1.5 inches for adequate
constant jAessaue. Wash Wafer must be cainled away from the enhrauce to an
approved sa ink area to U sediment shall be prevented troin
enteiiym storin drains, ditches or watercourses.
PAVED WASH RACK
NO SCALE