HomeMy WebLinkAboutWPO201400014 Correspondence 2015-07-02 Jonney Otto
From: Michelle Roberge
Sent: Thursday, July 02, 2015 8:23 AM
To: vfort @rivanna.org
Cc: Jonney Otto
Subject: RE: Airport parking lot expansion project
Thanks Victoria!
-Michelle
From:Victoria Fort [mailto:vfort @rivanna.org]
Sent:Wednesday,July 01, 2015 2:49 PM
To: Michelle Roberge
Cc: Dennis Seale
Subject: RE:Airport parking lot expansion project
Michelle,
There is sufficient cover over the water line at the location shown to allow the contractor to cross it with equipment
until the site plan is approved. Let me know if you have any questions.
Thank you,
Victoria
Victoria Fort, P.E.
Civil Engineer
Rivanna Water and Sewer Authority
695 Moores Creek Lane
Charlottesville,VA 22902
(P):(434)977-2970 ext. 205
(F):(434)295-1146
From: Michelle Roberge [mailto:mrobergeC@albemarle.orq]
Sent: Wednesday, July 1, 2015 2:16 PM
To: Victoria Fort; Dennis Seale
Subject: Airport parking lot expansion project
Hi Victoria,
We have issued the applicants a notice to comply to work outside the RWSA waterline. Since the waterline cuts their site
in half, they have asked if it is okay to cross the waterline near Dickerson road with their equipment. The sketch is an
approximate location only to explain the crossing. I mentioned that this will be RWSA's call. My guess is no, but let me
know what you think?John Johnson keeps mentioning the cover at this spot is 42".
Dennis, since the site is cut in half they are also proposing more than one construction entrance.Let me know what you
are okay with. We typically only ask for one, but this is your call since this in the VDOT ROW.
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Michelle Roberge
Department of Community Development
County of Albemarle,Virginia
401 McIntire Road 1 Charlottesville,VA 22902
434.296.5832 ext.3458
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DELTA AIRPORT
CONSULTANTS, INC.
December 19, 2014
Ms. Michelle Roberge
County of Albemarle
Department of Community Development
401 McIntire Road, Room 227
Charlottesville, VA 22902
Subject: Response Comments WP0201400014
Parking Lot Expansion
Charlottesville-Albemarle Airport
Charlottesville Albemarle Airport Authority
Dear Ms. Roberge:
Delta Airport Consultants is in receipt of your comments dated November 12, 2014 regarding the
referenced project. We offer the following responses to your comments, as well as four copies of the
revised plans, calculations and SWPPP.
Responses to your comments are itemized below:
A. Stormwater Pollution Prevention Plan (SWPPP)
The SWPPP content requirements can be found in County Code section 17-405.A SWPPP must contain
(1) a PPP, (2) an ESCP, (3) a SWMP, and (4) any TMDL measures necessary.
Comment: 1) Include the registration statement in the SWPP booklet.
For future submissions, please use the Albemarle County SWPP template. In can be
found in the following link:
http://www.albemarle.org/deptforms.asp?department=cdengwpo
Response: The registration statement has been inserted in the revised SWPPP booklet. The
SWPPP has been revised using the Albemarle County SWPP template.
B. Pollution Prevention Plan (PPP) : c tolItfrc , e ?ivy, ® snE
The PPP content requirements can be found in County Code section 17-404.
Comment: 1) Include an 11"x 17" Pollution Prevention Plan map showing concrete washout, porta-
johns, fueling stations, and trash containers.This will be marked up by the contractor as
construction of site progresses.
Response: A Pollution Prevention Plan Map has been completed and inserted in the revised
SWPPP booklet.
9711 FARRAR COURT, SUITE 100, RICHMOND, VIRGINIA, 23236
P. (804) 275-8301 F. (804) 275-8371 WWW.DELTAAIRPORT.COM
Ms. Roberge
December 19, 2014
Page 2
C. Stormwater Management Plan (SWMP)
VSMP Regulation 9VAC25-870-108 requires the VSMP authority to approve or disapprove a SWMP. This
plan is disapproved, and the reasons are provided in the comments below. The stormwater
management plan content requirements can be found in County Code section 17-403.
Comment: 1)The LOD area is 5.9 acres on the title page. Please include a note that 1.5 acres is
resurfacing. This is to clarify the 4.4 acres on the registration statement and that the 1-5
acres application fee applies.
Response: A note referencing the 1.5 acres of resurfacing has been added to the title page.
Please see Cover, Sheet 1 of 27.
Comment: 2) In VRRM spreadsheet, use 43" for annual rainfall. This is the accepted value for
central VA.
Response: The VRRM spreadsheet has been revised to use the 43"annual rainfall. Please see the
revised calculations.
Comment: 3) Increase the surface area for the forebay per the new standards in Virginia DEQ
Stormwater Design Specification No 9. It should be 15%of treatment volume.
Recompute the treatment volume for the project site limits only. The VRRM you
submitted also applies for the whole site and adjusts the CN when looking at channel
protection. Also, I recommend using a portion of the biofilter as the forebay. You have
sized the biofilter larger than the required treatment surface area. This will work better
for the forbay instead of the 5' tall gabion basket shown at the slope. See a quick
description shown below. Please show for both biofilters.
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Response: Forebays have been enlarged to contain 15%of the treatment volume, and have been
lowered to the filter bottom and are separated from the biofilter by a one foot tall
gabion basket as recommended. Please see Grading and Drainage, Sheets 8 and 9 of
27 and Drainage Details,sheet 21 of 27.
<<aidec4. 11 -To 6-c �°` -Arekaj
Ms. Roberge
December 19, 2014
Page 3
Comment: 4) Provide outlet protection at the end of structure E202 and structure E405. The riprap
should extend to toe of slope with gravel diaphragm level spreader to prevent scouring.
Show detail with filter fabric lining at base. See figure 9.8, Virginia DEQ Stormwater
Design Specification No 9. See image in comment#3.
Response: Outlet protection has been added and now extends to the toe of slope in each
biofilter. Gravel diaphragms have been added with a filter fabric lining at the base.
Please see Grading and Drainage, Sheets 8 and 9 of 27. Also see Drainage Details,
Sheet 21 of 27.
Comment: 5) Per new biofilter standards, please meet the level 2 requirements.The soil media is
now 36" and stone depth below the underdrain is 12". See the standards.
Response: The biofilter materials depths have been increased to 36"soil media and 12" stone
depth below the underdrain. Please see Drainage Details, Sheet 21 of 27.
Comment: 6) Please move the spillway on southern biofilter to western portion of biofilter.
Response: The spillway for the southern biofilter has been relocated to the western portion of
the embankment. Please see Grading and Drainage,Sheet 8 of 27.
Comment: 7) Biofilter should be drawn to scale and show the spillway to the toe of slope. Also,
label the crest elevation on stone weir for both biofilters. Remove the 2%cross slopes
on embankment.
Response: Biofilter weir cross section details have been added to show the elevations and slopes
to scale. The spillway has been extended to the toe of the slope. References to 2%
cross slope have been removed. Please see Grading and Drainage Details,Sheets 8
and 9 of 27 and 21 of 27.
Comment: 8) Revise the Tc for D400-E405 in stormsewer calcs. On paved parking Tc of 15 minutes
is too high. I recommend 5-6 minutes.
Response: The time of concentration for D400 has been revised to 6 minutes. The hydrologic
data and inlet times are included in the stormsewer computations. Please see the
T revised calculations.
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'— Response: Dl-7 calculations have been revised to reflect the 6 minute time of concentration.
Please see the revised calculations.
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Ms. Roberge
December 19, 2014
Page 4
Comment: 10) You have shown a detail of SWM structure on sheet 9. Please show a detail of entire
cross-section to show riser and grate also. Remove the filter fabric inside riser structure.
Response: The temporary sediment trap detail for E401 has been revised. Required volumes and
elevations have been added to the detail. Please see Erosion and Sediment Control
Details, Sheet 13 of 27.
Comment: 11) Please include details of both risers in existing extended detention ponds to be
modified.
Response: Details of the basin riser structures have been added. Please see Drainage Details,
Sheet 21 of 27.
Comment: 12) Prove the energy balance method to meet channel protection.
Response: The energy balance method was used to determine adequate channel protection as
detailed in Virginia DEQ's draft Stormwater Management Handbook, Chapter 11,
Section 6, Equation 11.4, using a 20% reduction in runoff.
The pre-development data for both basins was collected from the TR-55 watershed
routing model. The peak volume and flow rate data was identified at the outfall of
each existing detention basin.
The post-development data was collected from the TR-55 model using modified CN
values. The modified CN values for ground cover were identified in the VRRM
worksheet for the entire drainage area contributing to the existing detention basins.
The VRRM worksheet accounts for the existing and proposed BMP facilities and
assigns appropriate volume reduction by adjusting the CN values attributed to each
facility. No modifications to the time of concentration, basin volumes,or other
drainage features were made from previous submittals.
The results of computations are that the proposed development meets the
requirements of the VSMP Channel Protection Criteria via the Energy Balance Method.
Please see the calculations.
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DELTA AIRPORT
CONSULTANTS, INC.
October 6, 2014
Mr. Glenn Brooks, P.E.
County of Albemarle
Department of Community Development
401 McIntire Road, Room 227
Charlottesville,VA 22902
Subject: Response Comments WP0201400014
Parking Lot Expansion
Charlottesville-Albemarle Airport
Charlottesville Albemarle Airport Authority
Dear Mr. Brooks:
Delta Airport Consultants is in receipt of your comments dated August 4, 2014 for the referenced
project review plans. We have addressed the outstanding comments and revised the plans. Four full
sized sets of the required as-built plans, four copies of the revised SWPPP, and four revised copies of
calculations are enclosed.
Responses to your comments are itemized below:
Comment 1: Include a detailed plan of the proposed stormwater management facilities - It is not
clear that this project is grandfathered under 9VAC25-870-48, and RRM computations
were not provided.
✓ Response: Runoff reduction method computations are completed and attached in the
calculations.
Comment 2: Pollution Prevention Plan satisfying the requirements of code section 17-404 is required.
V Response: The Pollution Prevention Plan is included in the revised SWPPP, in accordance with the
required EPA template.
Comment 3: Stormwater Pollution Prevention Plan satisfying the requirements of code section 17-
405 is required. — Qualified personnel identified to sign inspection reports. — The
SWPPP document was not received. Please see the EPA guidance.
v Response: The revised SWPPP is included in this submittal, in accordance with the required EPA
template. The operator has been identified and signed. The awarded contractor shall
be required to submit his conformance documents and SWPPP requirements before
construction,as stated in the SWPPP.
9711 FARRAR COURT, SUITE 100, RICHMOND, VIRGINIA, 23236
P. (804) 275-8301 F. (804) 275-8371 WWW.DELTAAIRPORT.COM
Mr. Brooks
October 6, 2014
Page 2
Comment 4: Mitigation Plan satisfying the requirements of code section 17-406 for any proposed
disturbance of stream buffers is not applicable.
Response: Confirmed. Mitigation Plan is not applicable to this project.
Comment 5: Requested Variations or Exceptions as provided in code sections 17-407 and 408, if
applicable. (SSF, MMT, etc)
Response: Confirmed. Variations and/or Exceptions are not applicable to this project.
s
Comment 6: Construction Record Drawings (as-builts) for any existing facilities in the proposal
satisfying the requirements of code section 17-422. —This plan appears to make use of
an existing facility,for which a construction record drawing was not received.
Response: Signed Record Drawings for Basin #8 and #9 are included in this submittal. The
facilities were completed as part of the relocation of SR. 606.
Please do not hesitate to contact our office regarding this matter.
Sincerely,
(A):2111/U(A .1
William Eschenfelder, P.E.
Enclosures: Design Calculations -4 copies
Revised SWPPP-4 copies
Record Drawings-4 copies
cc: William Pahuta,Charlottesville Albemarle Airport Authority
Reference: Delta Project No.12064
DELTA AIRPORT
CONSULTANTS, INC.
July 7, 2014
Ms. Michelle Roberge
County of Albemarle
Department of Community Development
401 McIntire Road, Room 227
Charlottesville,VA 22902
Subject: Response Comments WP0201400014
Parking Lot Expansion
Charlottesville-Albemarle Airport
Charlottesville Albemarle Airport Authority
Dear Ms. Roberge:
Delta Airport Consultants is in receipt of your comments dated June 18, 2014 for the referenced project
review plans. We have addressed the outstanding comments and revised the plans. Four full sized sets
of revised plans, and four revised copies of calculations are enclosed.
Responses to your comments are itemized below:
Comment 1: It appears the erosion control plan and SWM plan sheets are missing. The title page
noted in asterisks, "sheets not included in this submission." Please provide those sheets
for review.
Revision 1: Comment addressed.
Response: Noted
Comment 2: Basin # 8 does not meet current quality standards. Converting a portion of basin #8 will
further reduce treatment of existing site. It will be best if this biofilter is moved so it
does not further reduce the existing basin's treatment capability.
Revision 1: Comment addressed. The new biofilters meets the treatment requirements for the
delineated drainage areas. The existing extended detention basins also meet the
treatment requirements.
Response: Noted
Comment 3: Provide and delineate on plan the drainage area to proposed biofilters. Also, clarify the
total impervious area draining to new biofilters.
Revision 1: Comment addressed.
Response: Noted
9711 FARRAR COURT, SUITE 100, RICHMOND, VIRGINIA, 23236
P. (804) 275-8301 F. (804) 275-8371 WWW.DELTAAIRPORT.COM
Ms. Roberge stew Nor
July 7, 2014
Page 2
Comment 4: The title page should include E&S and SWM Plan in the title.
Revision 1: This is partially addressed.This should be clearly stated in the title as it will be shown on
the SWM agreement form. Also, remove SDP-2014-00019 from the title of this WPO
plan.
Response: The Cover has been revised to clarify the ESC and SWM Plans, removing references to
the Site Development Plan. Please see the Cover,Sheet 1.
Comment 5: Show as-builts for both basins and outlet structures on plan. Provide a cross section of
the existing pond and outlet structures as well.
Revision 1: Comment addressed.
Response: Noted
Comment 6: Also, provide existing contours and proposed contours on plan. It is missing on sheet 8
and 9.
Revision 1: Comment addressed.
Response: Noted
Comment 7: Label the type of basin on the plan.
Revision 1: Comment addressed.
Response: Noted
Comment 8: Label the drainage area, Tc, and CN within the delineated DA on plan for existing and
proposed conditions.
Revision 1: Comment addressed.
Response: Noted
Comment 9: It appears there is a grate inlet near D400 (on parking lot) that is to be removed on
sheet 8. Please remove or clarify.
Revision 1: Comment clarified on profile and plan.
Response: Noted
Comment 10: The curb opening to D400 needs to be analyzed. The two other curb opening needs to
be analyzed as well. It appears there is a paved flume to D400. I recommend removal of
paved flume and placing a Dls at those low spots instead.
Revision 1: Comment addressed.
Response: Noted
Ms. Roberge
July 7, 2014
Page 3
New Comments
Comment 11: Provide inlet protection for E-304 on Sheet 10 as a seal coat will be placed on existing
parking lot.
Response: Inlet protection has been added for structure E-304. Please see Erosion and Sediment
Control Layout, Sheet 10. Inlet protection has been added for structures E-304 and D-
201 on the Erosion and Sediment Control Layout,Sheet 11.
Comment 12: Provide a variance for the excavated drop inlet sediment trap around E-401. This inlet
protection is designed for up to 1 acres of drainage area. Since the actual drainage area
is larger, please provide a letter for this use to the County Engineer, Glenn Brooks.
Provide calcs that shows required wet volume below grate inlet and dry volume above
grate inlet is equivalent to sediment trap requirements.
Response: A variance letter with supporting calculations has been prepared and is included with
the revised calculations.
Comment 13: On sheet 11 provide inlet protection for D-400 and D-401 to avoid sediment into pipes
as north biofilter near pond#8 is constructed.
Response: Inlet protection has been added for structures D-400 and D-401. Please see Erosion
and Sediment Control Layout,Sheet 11.
Comment 14: For the two new biofilters, please address the following:
a) Provide a forebay for pre-treatment from concentrated flow from pipes.
b) Provide cleanouts at ends of underdrain.
c) Provide a cross section of each biofilter to scale.
d) On sheet 19, provide stone weir angle.
Response: Forebays for pre-treatment of each biofilter is designed and has been added to the
plans and details. Each forebay is sized at 10% of the biofilter volume in accordance
with the Virginia Stormwater Management Handbook for small stormwater facilities.
Please see the Grading and Drainage, Sheets 8 and 9, and the Stormwater
Management Details,Sheet 19.
Cleanouts have been added to the end of each underdrain branch. Please see Grading
and Drainage,Sheets 8 and 9.
Cross sections for each biofilter have been added to the Stormwater Management
Details,Sheet 19.
The stone weir angle of 2:1 has been added to the Stormwater Management Details,
Sheet 19.
Nome
Ms. Roberge 'ewe
July 7, 2014
Page 4
Comment 15: Label LOD acreage on sheet 1.
Response: The Limits of Disturbance has been added to Project Information Table. Please see the
Cover,Sheet 1.
Comment 16: Revise the Tc for D400-E405 in stormsewer calcs. On a paved parking lot a Tc of 15
minutes is too high. I recommend 5-6 min.Also revise hydraulic gradeline computations.
Response: The time of concentration for D400 has been revised. The Drainage Area Maps and
stormsewer and hydraulic gradeline computations have been revised accordingly.
It should be noted that Site Development Plan comments from VDOT required 100'
pavement taper transitions at the entrance of the new parking lot. The Drainage Area
Maps and computations have been revised to reflect these changes.
Comment 17: Please also revise the performance curve DI-7 to reflect changes from comment 16.
Response: The DI-7 performance curve has been revised to reflect the changes in the time of
concentration.
Comment 18: Sign and seal all calcs submitted.
Response: The plans and calculations have been signed and sealed.
Comment 19: Once all items above are addressed, please sign, seal and date 4 copies of the WPO plan.
Response: Four copies of the WPO plans are signed and sealed for review.
Sincerely,
William Eschenfelder, P.E. 1
Enclosures: Design Calculations -4 copies
Revised Plans-4 full copies
cc: William Pahuta,Charlottesville Albemarle Airport Authority
Reference: Delta Project No.12064
DELTA AIRPORT
CONSULTANTS, INC.
July 7, 2014
Mr.Glenn Brooks, P.E.
County Engineer
County of Albemarle
Department of Community Development
401 McIntire Road, Room 227
Charlottesville,VA 22902
Subject: Design Variance WP0201400014
Parking Lot Expansion
Charlottesville-Albemarle Airport
Charlottesville Albemarle Airport Authority
Dear Mr. Brooks:
Delta Airport Consultants is preparing construction documents for the construction of a new employee
parking lot at the Charlottesville-Albemarle Airport. The project is currently under review of the
Stormwater Management and Water Protection Ordinance by Albemarle County Department of
Engineering. The purpose of this letter is to provide explanation and documentation to support our
request for of a design variance for contributing area exceeding one acre to a proposed excavated drop
inlet sediment trap.
The excavated drop inlet sediment trap is a variant of Standard 3.07 of the Virginia Erosion and
Sediment Control Handbook (1992). The handbook states that the facility is "applicable where l'eavy
flows are expected and where overflow capability and ease of maintenance is desired." Excavation of
storage volume beneath the grate provides sediment laden runoff to settle. This volume is 134 CY per
contributing area. The standard maximum contributing area per Section 3.07 is one acre.
The application of the excavated drop inlet sediment trap for this project is proposed based on the
existing conditions and space constraints of the project site. The existing site is a previously developed
area adjacent to the main airport entrance.The site is mostly level and will require minimal grading.The
estimated earthwork is approximately 1,000 CY, of which most is excavation for the proposed pavement
box.
97M FARRAR COURT, SUITE 100, RICHMOND, VIRGINIA, 23236
P. (804) 275-8301 F. (804) 275-8371 WWW.DELTAAIRPORT.COM
•
Existing Structure E-401
•
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Project Site
As a result of being a previously developed area, existing drainage is handled by the storm sewer
system. The existing median drop inlet, structure E-401 on the plans, is the primary drainage outfall to
the north of the proposed parking lot. This structure is proposed to be removed, the existing storm
sewer extended, and replaced with two new median drop inlets, identified as D-400 and D401 in the
plans. The geometric footprint and grading criteria of the proposed parking lot do not provide adequate
space for traditional sediment trap configurations.
The proposed excavated drop inlet sediment trap is designed in accordance with the Virginia Erosion
and Sediment Control Handbook, less the one acre requirement. The proposed configuration is
designed to accommodate 1.85 acres of contributing runoff. The existing structure will be raised 12" to
an elevation of 599.57 and the storage volume excavated to an elevation of 597.57. The volume in the
trap below the proposed inlet elevation exceeds the 134 CY per Acre requirement. An inlet filter bag is
proposed to be installed within the inlet for extra protection from sediment overflow.
If sediment is still able to enter the storm sewer, the runoff of the contributing drainage area is routed
to the existing basin #9. The structure at basin #9 is proposed to be modified by raising the inlet grate
and adding a perimeter of stone gabions in accordance with minimum standard 3.07 "Extended
Detention Basin" of the Virginia Stormwater Management Handbook. These modifications provide
additional means to prevent sediment leaving the project site.
Should you have any questions regarding this matter, please do not hesitate to contact our office.
Sincerely,
John D. Borgie, P.E.
TEMPORARY SEDIMENT TRAP CALCULATIONS STAGE 1
SEDIMENT TRAP#1
Charlottesville-Albemarle Airport
Charlottesville,Virginia
Delta Project No.VA 12064
NOTE: THIS IS AN EXCAVATED DROP INLET SEDIMENT TRAP(SEE PLATE 3.07-4)
Drainage Area (ac) = 1.85
Total Storage Req'd (CY) = 248 (134 CY/AC)
Elevation Area (SY) Incremental Volume (CY) Cumulative Volume (CY)
597.57 0 0 0
598.00 330 47 47
599.00 430 143 191
600.00 540 180 371
Bottom Elev= 597.57
Wet Storage Elev= 599.57
Volume(CY) = 272 Wet Storage Volume is: ok
Dry Storage Elev= 600.00
Volume(CY) = 98
Total Storage Provided = 371 CY
vim,INI , E KOSI ON & 5 1 M f C tiROL
1992 N AN Dk
STD & SPEC 3.07
STORM DRAIN
INLET PROTECTION iP
Definition
A sediment filter or an excavated impounding area around a storm drain drop inlet or curb
inlet.
Purpose
To prevent sediment from entering storm drainage systems prior to permanent stabilization
of the disturbed area.
Conditions Where Practice Applies
Where storm drain inlets are to be made operational before permanent stabilization of the
corresponding disturbed drainage area. Different types of structures are applicable to
different conditions (see Plates 3.07-1 through 3.07-8).
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1992 3.07
Planning Considerations
Storm sewers which are made operational prior to stabilization of the associated drainage
areas can convey large amounts of sediment to natural drainageways. In case of extreme
sediment loading, the storm sewer itself may clog and lose a major portion of its capacity.
To avoid these problems, it is necessary to prevent sediment from entering the system at the
inlets.
This practice contains several types of inlet filters and traps which have different
applications dependent upon site conditions and type of inlet. Other innovative techniques
for accomplishing the same purpose are encouraged, but only after specific plans and details
are submitted to and approved by the appropriate Plan-Approving Authority.
Care should be taken when choosing a specific type of inlet protection. Field experience
has shown that inlet protection which causes excessive ponding in an area of high
construction activity may become so inconvenient that it is removed or bypassed, thus
transmitting sediment-laden flows unchecked. In such situations, a structure with an
adequate overflow mechanism be should utilized.
The following inlet protection devices are for drainage areas of one acre or less. Runoff
from larger disturbed areas should be routed to a TEMPORARY SEDIMENT TRAP (Std.
& Spec. 3.13) or a TEMPORARY SEDIMENT BASIN (Std. & Spec. 3.14).
The best way to prevent sediment from entering the storm sewer system is to stabilize the
site as quickly as possible, preventing erosion and stopping sediment at its source.
Stone is utilized as the chief ponding/filtering agent in most of the inlet protection types
described in this specification. The various types of"coarse aggregates"which are depicted
are able to filter out sediment mainly through slowing down flows directed to the inlet by
creating an increased flow path for the stormwater (through void space in the respective
stone). The stone filtering medium by no means slows stormwater flowrate as does filter
cloth and therefore cannot provide the same degree of filter efficiency when smaller silt and
clay particles are introduced into stormwater flows. However, as mentioned earlier,
excessive ponding in busy areas adjacent to stormwater inlets is in many cases unacceptable
- that is why stone must be utilized with many installations.
Fortunately, in most instances, inlet protection utilizing stone should not be the sole control
measure. At the time that storm sewer inlet and associated appurtances become
operational, areas adjacent to the structures are most likely at final grade or will not be
altered for extended periods; this is the time when TEMPORARY SEEDING (Std. & Spec.
3.31) and other appropriate controls should be implemented to enhance sediment-loss
mitigation. In addition, by varying stone sizes used in the construction of inlet protection,
a greater degree of sediment removal can be obtained. As an option, filter cloth can be
used with the stone in these devices to further enhance sediment removal. Notably, the
potential inconvenience of excessive ponding must be examined with these choices,
especially the latter.
III - 32
?IdI*( 3.07
1992 r O o ra Ao se
Design Criteria 4t
1. The drainage area shall be no greater than 1 acre.
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2. The inlet protection device shall be constructed in a manner that will facilitate clean-
out and disposal of trapped sediment and minimize interference with construction
activities.
3. The inlet protection devices shall be constructed in such a manner that any resultant
ponding of stormwater will not cause excessive inconvenience or damage to adjacent
areas or structures.
4. Design criteria more specific to each particular inlet protection device will be found
on Plates 3.07-1 through 3.07-8. SEE E P1 AT „ 4O7
5. For the inlet protection devices which utilize stone as the chief ponding/filtering
medium, a range of stone sizes is offered; VDOT #3, #357, or #5 Coarse Aggregate
should be used. The designer/plan reviewer should attempt to get the greatest
amount of filtering action possible (by using smaller-sized stone), while not creating
significant ponding problems.
6. In all designs which utilize stone with a wire-mesh support as a filtering mechanism,
the stone can be completely wrapped with the wire mesh to improve stability and
provide easier cleaning.
7. Filter Fabric may be added to any of the devices which utilize "coarse aggregate"
stone to significantly enhance sediment removal. The fabric, which must meet the
physical requirements noted for "extra strength" found in Table 3.05-B, should be
secured between the stone and the inlet (on wire-mesh if it is present). As a result
of the significant increase in filter efficiency provided by the fabric, a larger range of
stone sizes (VDOT #1, #2 or #3 Coarse Aggregate) may be utilized with such a
configuration. The larger stone will help keep larger sediment masses from clogging
the cloth. Notably, significant ponding may occur at the inlet if filter cloth is utilized
in this manner. nu/ FILTER PbtosE.
Construction Specifications
1. Silt Fence Drop Inlet Protection
a. Silt Fence shall conform to the construction specifications for "extra strength"
found in Table 3.05-B and shall be cut from a continuous roll to avoid joints.
b. For stakes use 2 x 4-inch wood (preferred) or equivalent metal with a
minimum length of 3 feet.
III - 33
1992 3.07
b. Wire mesh shall be placed over the outside vertical face (webbing) of the
concrete blocks to prevent stone from being washed through the holes in the
blocks. Wire mesh with 1/2-inch openings shall be used.
•
c. Stone shall be piled against the wire to the top of the block barrier, as shown
in Plate 3.07-3.
d. If the stone filter becomes clogged with sediment so that it no longer
adequately performs its function, the stone must be pulled away from the
blocks, cleaned and replaced.
r 4. Excavated Drop Inlet Sediment Trap
a. The excavated trap shall be sized to provide a minimum storage capacity
calculated at the rate of 134 cubic yards per acre of drainage area. A trap
shall be no less than 1-foot nor more than 2-feet deep measured from the top
of the inlet structure. Side slopes shall not be steeper than 2:1 (see Plate
3.07-4).
b. The slope of the basin may vary to fit the drainage area and terrain.
Observations must be made to check trap efficiency and modifications shall
be made as necessary to ensure satisfactory trapping of sediment. Where an
inlet is located so as to receive concentrated flows, such as in a highway
median, it is recommended that the basin have a rectangular shape in a 2:1
(length/width) ratio, with the length oriented in the direction of the flow.
c. Sediment shall be removed and the trap restored to its original dimensions
when the sediment has accumulated to one-half the design depth of the trap.
Removed sediment shall be deposited in a suitable area and in a manner such
that it will not erode.
5. Sod Drop Inlet Sediment Filter
a. Soil shall be prepared and sod installed according to the specifications in Std.
& Spec. 3.33, SODDING.
b. Sod shall be placed to form a turf mat covering the soil for a distance of 4
feet from each side of the inlet structure, as depicted in Plate 3.07-5.
6. Gravel Curb Inlet Sediment Filter
a. Wire mesh with 1/2-inch openings shall be placed over the curb inlet opening
so that at least 12 inches of wire extends across the inlet cover and at least 12
inches of wire extends across the concrete gutter from the inlet opening, as
depicted in Plate 3.07-6.
III - 37
4
1992 3.07
EXCAVATED DROP INLET
SEDIMENT TRAP
FLOW '-
\ /
��\\�\11cJ/��� FLOW
r
C Y(C----\ N<_
II
FLOW
a�
SEDIMENT-LADEN RUNOFF
AS DEPTH BELOW TOP OF INLET:
REQUIRED MIN. 1'- MAX. 2'
III-1II-111=1. `i1�� -III
—T 1I
-T-T T_ II—III ITI-TIC
—III 11= 1 �- -L..i .I I- 1 I I
'I-111— =I �- �. -I- • 1 -III: _I-
'1=1=1 I I. -i , .L.. 1.I I ` ` � 'i I ICI i
�—lT P - 1 1 1 ,;:,.._::;:::.rr.,.:.:,< :.: — IIII
-
MAX. s o P E z: I 111—I 11-111- --�—IITIiTf--I_T- Il STORM WATER WITH . 11 . LARGER PARTICLES
LARGER PARTICLES -11 HOLES :iii.-- SETTLE OUT
REMOVED II FOR 11. 11
momeit, 81i -Qp DEWATERING
� I
PORK ula
7g yo IECEI
DRAIN INLET _11Wi', ' • arr11�u Tr-
X11. TT
— 1=1 =111=II 1 I -it=
I m-I I it L1 1 1=11
SPECIFIC APPLICATION
THIS METHOD OF INLET PROTECTION IS APPLICABLE WHERE HEAVY FLOWS
ARE EXPECTED AND WHERE AN OVERFLOW CAPABILITY AND EASE OF
MAINTENANCE ARE DESIRABLE.
Source: Michigan Soil Erosion and Sediment
Control Guidebook, 1975, and USDA-SCS Plate 3.07-4
III - 39 641,
•
Neve *woo
1992 3.07
b. A 2-inch x 4-inch stud shall be cut and placed through the outer holes of each
spacer block to help keep the front blocks in place.
c. Concrete blocks shall be placed on their sides across the front of the inlet and
abutting the spacer blocks as depicted in Plate 3.07-8.
d. Wire mesh shall be placed over the outside vertical face (webbing) of the
concrete blocks to prevent stone from being washed through the holes in the
blocks. Wire mesh with 1/2-inch openings shall be used.
e. Coarse aggregate shall be piled against the wire to the top of the barrier as
shown in Plate 3.07-8.
f. If the stone filter becomes clogged with sediment so that it no longer
adequately performs its function, the stone must be pulled away from the
blocks, cleaned and/or replaced.
Maintenance
1. The structure shall be inspected after each rain and repairs made as needed.
2. Sediment shall be removed and the trap restored to its original dimensions when the
sediment has accumulated to one half the design depth of the trap. Removed
sediment shall be deposited in a suitable area and in such a manner that it will not
erode.
3. Structures shall be removed and the area stabilized when the remaining drainage
area has been properly stabilized.
III - 44 '1,
'ter ,.nr
Michelle Roberge
From: Michelle Roberge
Sent: Wednesday, April 16, 2014 5:15 PM
To: 'beschenfelder @deltaairport.com'
Cc: Ellie Ray
Subject: RE: SDP201400019 CHO Surface Parking Expansion - Major Amendment
Bill,
I recommend submitting the old SWM agreement.This will be routed to the County Attorney for review.The County
Attorney will then determine if the old SWM agreement is okay or if a new agreement should be completed.
-Michelle Roberge
From: Ellie Ray
Sent: Friday, April 11, 2014 2:03 PM
To: William M. Eschenfelder
Cc: Michelle Roberge
Subject: SDP201400019 CHO Surface Parking Expansion - Major Amendment
Bill,
I wanted to follow up on some of the outstanding issues discussed in yesterday's SRC meeting, so here's is what I've
found:
1. The internal signs will require a sign application.
2. Michelle will send information about whether or not a new stormwater maintenance agreement will be
required.
I think this covers the remaining questions, please let me know if I've neglected anything.
Thanks,
Ellie Carter Ray, PLA
Senior Planner
Albemarle County Community Development
Planning Division
401 McIntire Road, North Wing
Charlottesville,Virginia 22902
ph: 434.296.5832 x. 3432
fax: 434.972.4126
1
DELIAIRPORT �.
_ CONSULTANTS, INC.
March 7, 2014
Albemarle County
Community Development Office
Engineering Department
401 McIntire Road
Charlottesville, Virginia 22902
Subject: E&SC and SWM/BMP Plan
Surface Parking Expansion
Charlottesville-Albemarle Airport
Charlottesville, Virginia
Delta Project No. 12064
Please find enclosed our complete Erosion and Sediment Control Plan and Stormwater
Management /BMP for the above referenced project at the Charlottesville-Albemarle
Airport. Be advised that the original signed application and review fee has been forwarded
separately by the CHO Authority. Enclosed is a copy for your reference.
If you should have any questions regarding this matter, please do not hesitate to contact
our office.
Sincerely,
William M. Eschenfelder, P.E.
WME/amf
Enclosures: 1) E&SC and Storm Drainage Design Reports—2 copies
2) E&SC and SWM/BMP Plan—2 sets
cc: Bill Pahuta, Deputy Executive Director CHO
9711 FARRAR COURT. SUITE 100, RICHMOND, VIRGINIA, 23236
P. (804) 275-8301 F. (804) 275-8371 WWW.DELTAAIRPORT.COM
Ms. Roberge
December 19, 2014
Page 5
D. Erosion and Sediment Control Plan (ESCP)
Virginia Code §62.1-44.15:55 requires the VESCP authority to approve or disapprove an ESCP. This plan
is disapproved, and the reasons are provided in the comments below. The erosion control plan content
requirements can be found in County Code section 17-402.
Comment: 1) Remove the geotextile fabric in inlet 400 shown in detail sheet. This is prone to more
clogging. I recommend showing gravel wrapped in wire mesh around base of inlet. Use
#3 or#57 stone.
Response: The temporary sediment trap detail for E401 has been revised. Geotextile fabric has
been removed. Gravel filter and wire mesh have been added. Please see Erosion and
Sediment Control Details,Sheet 13 of 27.
"Comment: 2) It appears the sediment trap does not meet the 134 cy for water quality. Please
provide more surface area. Design it according to contours shown on plan and show
detail with required capacity.
Response: The temporary sediment trap volume calculations have been revised and the size of
the trap enlarged to meet the required volume. Designed storage has been added to
the cross section detail as well. See Grading and Drainage Details,Sheet 8 of 27 and
Erosion and Sediment Control Details,sheet 13 of 27.
Signed and sealed plans and calculations have been submitted for your approval. Please contact our
office should you have any questions.
Sincerely,
William Eschenfelder, P.E.
Enclosures: Design Calculations -4 copies
Revised SWPPP-4 copies
Revised Drawings-4 copies
cc: William Pahuta,Charlottesville Albemarle Airport Authority
Reference: Delta Project No. 12064