HomeMy WebLinkAboutWPO201800017 Review Comments 2019-07-17 ,
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608 Preston Avenue P 434.295.5624
T I M M O N S GROUP Suite 200 F 434.295.8317
YOUR VISION ACHIEVED THROUGH OURS. Charlottesville,VA 22903 www.timmons.com
July 17, 2019
David James
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County of Albemarle
Dept. of Community Dev.
401 McIntire Rd.
Charlottesville, VA 22902
RE: Lighthouse Instruments—VSMP Permit Plan Review—WP0201800017-Comment
Response Letter
Dear Mr. James:
We have reviewed all of your comments from June 11, 2019 (Rev.4) and made the necessary
revisions. Please find our responses to the comments below in bold lettering.
A. General
1. (Rev. 2) Remove signature panel from cover sheet.
Signature Panel has been removed.
(Rev.3) Addressed.
(Rev.4) Not addressed.
The signature panel has now been removed from the cover sheet.
B. Stormwater Pollution Prevention Plan (SWPPP)
The SWPPP content requirements can be found in County Code section 17-405. A SWPPP
must contain (1) a PPP, (2) an ESCP, (3) a SWMP, and (4) any TMDL measures necessary.
1. (Rev. 1) Please complete item 12. Certification on the Registration Statement.
Sections will be completed by contractor before preconstruction meeting.
(Rev. 2)Acknowledged.
2. (Rev. 1) Insert copy of General Permit coverage when obtained.
Acknowledged.
(Rev. 2) Acknowledged.
3. (Rev. 1) There's impaired waters immediately downstream of site with a TMDL. Please
include this report in swppp:
CIVIL ENGINEERING I ENVIRONMENTAL I SURVEYING I GIS I LANDSCAPE ARCHITECTURE I CONSTRUCTION SERVICES
http://www.deq.virginia.gov/FS2016/FactSheets.aspx?id=VAV-
H28R MSCO1A00&style=1 .
TMDL fact sheets for Moores Creek has been Included.
(Rev. 2)Addressed.
4. (Rev. 1) Please complete section 9. Signed Certification & 10. Delegation (if needed).
Sections will be completed by contractor before preconstruction meeting.
(Rev. 2/3/4) Acknowledged.
5. (Rev. 3) Submit (2) copies of the SWPPP with updated plans for sections 4, 5 & 6 of the
County's template.
The SWPP has been updated and 2 copies have been included in the submittal
(Rev.4) Addressed.
11 (Rev. 3) Update Registration Statement under section 3 stating name/location of off-site
activity.
The registration Statement has been updated
(Rev.4) Fill out and submit the new DEQ Registration Statement.
The new DEQ registration statement has been filled out and added to the SWPPP.
B. Pollution Prevention Plan (PPP)
The PPP content requirements can be found in County Code section 17-404.
1. (Rev. 1) Update the PPP with the ESC changes. Show proposed staging, stockpile,
borrow, fueling, waste disposal areas on the PPP.
The PPP plans have been updated with proposed staging,stockpile,fueling, and disposal
areas. If borrow or waist is necessary, it will use an offsite source permitted separately.
(Rev.2)Addressed. Operator to update in the field as required.
C. Stormwater Management Plan (SWMP)
VSMP Regulation 9VAC25-870-108 requires the VSMP authority to approve or disapprove a
SWMP. This plan is disapproved, and the reasons are provided in the comments below. The
stormwater management plan content requirements can be found in County Code section 17-
403.
1. (Rev.1) CO.0—Add WPO number WP0201800017 to cover sheet title.
The WPO number has been added to the cover sheet title,sheet CO.0.
(Rev.2) Addressed.
2. (Rev. 1) C2.0—Show boundaries of existing predominant vegetation. Show areas of site
to be protected from disturbance. Identify/Label the adjacent rivers/streams that have
impaired water.
The boundaries of existing vegetation have been shown and the impaired waterway, Moore's
Creek, has been labeled in sheet C2.0.
(Rev.2) Addressed.
3. (Rev.1) USACE to verify if any conservation areas (i.e. wetlands) exist at downstream
location(s) of proposed storm/sewer lines. Provide USACE permit prior to plan
approval.
Acknowledged.
(Rev.2) Comment still valid. Also, Provide ASACE permit for constructing proposed outlet in
stream. See comment C24 below.
Outlet is being permitted through the Army Corps of Engineers.
(Rev.3) Comment still valid.
The storm design has been revised to outlet from the open channel to the ex. riprap armored
bank of Moores Creek which is sufficient to convey runoff to Moores Creek. Therefore, no
stream disturbance is necessary. Please see plan sheet C5.0 for the updated layout plan. The
design has been revised so that no disturbance of the Moores Creek is required. No wetlands
were found during delineation.
(Rev.4) See County Engineer's responses to the FDP201800019 and need for maintaining riprap
outfall. Permit required if improvements are below stream normal water level.
Per Frank Pohl's comments, a note has been added to the plans on Sheet C5.0 calling out that
the existing riprap must meet VESCH specification 3.19.A riprap detail has also been provided
on Sheet C3.0. It is not anticipated that the riprap will need to be improved below the stream
normal water level. If this becomes necessary during construction a permit will be obtained
before any disturbance takes place.
4. (Rev.1) Show and label the 'Limits of Disturbance' to include all the clearing, grading,
excavating, transporting, and filling of land.
See sheet C3.2 and sheet C3.3.
(Rev.2) Partially addressed. Include &show area past Matchline#2,shown on C4.0, on the E&SC
sheets in your LOD.
An additional viewport has been added showing the limits of disturbance past match line#2.
See sheets C3.2 and C3.3
(Rev.3) Has the LOD area changed with the additional area added?
The LOD net area has remained the same with the revision of the storm and sanitary lines
(Rev.4)Acknowledged.
5. (Rev.1) Show any areas outside of property line to be disturbed in an easement.
Areas has been shown in easements.
(Rev.2) Provide evidence that neighboring property owner is in agreement with this offsite work
in the easement or record an easement plat.This can be a letter of agreement signed by
neighboring property owner or record an easement plat. [DSM,Sect. 8C, 3F]
Owner is currently acquiring easements and evidence will be provided before plan approval.
(Rev.3/4)Acknowledged—comment still valid.
Owner is in the process of acquiring easements. Evidence will be provided before plan
approval.
6. (Rev. 1) Show proposed easements for drainage.
Area has been shown in easements.
(Rev. 2)A minimum 20' drainage easement will be needed for the drainage pipes from VDOT
right-of-way.The drainage easement width should follow the calculation shown on pg. 15 of the
DSM. Label easement as "Drainage Easement" and "dedicated to public use". Easements shall
be platted and recorded with deed prior to final site plan approval.
A drainage easement has been added as required above.See sheet C4.0
(Rev.3) Addressed.
7. (Rev.1) Label the property line.
The property line has been labeled. See sheet C2.0.
(Rev.2) Addressed.
8. (Rev.1) Show/label location of floodplain/floodway limits.
The floodplain limits have been labeled. See sheet C2.0.
(Rev.2)Addressed.
9. (Rev.1) Show/Label location of WPO buffer.
The WPO buffer has been shown and labeled. See sheet C2.0.
(Rev.2) Addressed.
10. (Rev.1) Show direction arrows for stormwater flow through pipes &flow paths onsite.
Flow arrows have been added to pipes. See sheet C5.0.
(Rev.2) Addressed.
11. (Rev.1) Show/Indicate approximate slopes after major grading activities.
Design slopes have been shown through contours and spots.
(Rev.2)Acknowledged.
12. You're proposing a series of storrnwatcr structures (downstream of str„ct„re non)
through preserved slopes and into the floodplain. I do n^ e411-c use is permitted
Alternatively, you can relocate outside of preserved slopes.
Comment removed.
13. (Rev.1) Please submit a floodplain development application / plan to the county. A
floodplain development permit is required prior to floodplain disturbance.
Floodplain development application has been provided.
(Rev.2)Acknowledged. Permit required prior to plan approval.
Floodplain development application has been resubmitted along with this plan.
(Rev.3) Not addressed.As of 1-08-2019 the application has not been received.
Flood plain application has been included with this submittal
(Rev.4)Addressed.
14. (Rev.1) You are disturbing land in the WPO buffer &floodplain. A mitigation plan is
required.
A mitigation plan has been added. See sheet C8.0.
(Rev.2) Addressed.
15. (Rev.1) Show existing & proposed land cover area maps.
Land cover maps are shown on sheet C6.0.
(Rev.2) Not addressed.
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Land cover is shown on sheet C6.0 which was clarified with David by email on 11/29.
(Rev.3)Addressed.
16. (Rev.1) Label constructed ditches/channels and show channel cross-sections (w/slope &
dims), lining type, and engineering calcs.
Ditch sections and calculations have been added to sheet C5.0.
(Rev.2) Addressed.
17. (Rev.1) Please correct/update the VRRM spreadsheet. You show 2.10ac managed turf
pre-dev. On the spreadsheet, but the plan shows 1.9ac forest/open space & 0.2ac turf.
Spread sheet and plan sheet have been revised to match.
(Rev. 2) Please use the 2013 Stds&Specs VRRM version.There's 0.10ac forest/open space post-
dev. See comment C23.
2013 version has been selected at the top of the VRRM Spreadsheet.
(Rev.3) Addressed.
18. (Rev.1) Stormwater profiles-Add note to provide safety slabs (SL-1) in any structure
taller than 12'. Add note to provide concrete inlet shaping 1S-1) for any structure with a
4' or greater drop.
Notes have been added to storm profiles sheets C7.0 and C7.1.
(Rev. 2) Addressed.
19. (Rev.2) Provide pipe anchors at every other joint for pipe 111 (>16% slope).
A note has been added to the storm profiles to provide pipe anchors as required. See sheets
C7.0 and C7.1
(Rev.3) Addressed, N/A.
20. (Rev.2) Show Tc and associated flow paths.
Tc flow paths have been shown on Sheet C6.1.
(Rev.3) Addressed.
21. (Rev.2) Show the 1% area map.
A Drainage area map and report from USGS StreamStats has been added to the calculations
book showing the total Drainage area to Moores Creek at the outfall is 19,000 acres.
(Rev.3) Partially addressed.Show on the plan or state the contributing DA at the point of
analysis.-map provided in calc packet.
Callout has been added to sheet C5.0 reffencing drainage area to Moores Creek and Map in
calculations book.
(Rev.4)Addressed.
22. (Rev.2) Sheet C7.0-Add note to provide%" steel plate at the bottom of manhole
structures in "step-down" system (Str. 104 thru 112).
A note has been added to sheet C7.0. See note#4
(Rev.3) Addressed.
23. (Rev.2) Show the forest/open space area to be protected in a 'forest/open space
easement'. This area will need to be shown/recorded with a deed and plat prior to
approval. Consider protecting the additional forested space on the site in an easement
to be dedicated to offset the amount of nutrient credits needing to be purchased.
Post condition has been updated to not include any forest/open space.
(Rev.3)Addressed.
24. (Rev.2) Provide detail of outlet design at stream. Profile should show rip-rap, stream
bed, etc.
Rip Rap has been added to storm profile.See sheet C7.0
(Rev.3) Minimum standards (MS-12, MS-14, MS-15) must also be met. Show appropriate non-
erodible or armored controls& details (VAESC NB Spec. 3.22 thru 3.27) for disturbed area of
stream.
The storm design has been revised to outlet from the open channel to the ex. riprap armored
bank of Moores Creek which is sufficient to convey runoff to Moores Creek. Therefore no
stream disturbance is necessary. Please see plan sheet C5.0 for the updated layout plan.
(Rev.4) See County Engineers' responses to the FDP201800019 and need for maintaining riprap
outfall. Permit required if improvements are below stream normal water level.
Per Frank Pohl's comments, a note has been added to the plans on Sheet C5.0 calling out that
the existing Riprap must meet VESCH specification 3.19.A riprap detail has also been provided
on Sheet C3.0. It is not anticipated that the riprap will need to be improved below the stream
normal water level. If this becomes necessary during construction a permit will be obtained
before any disturbance takes place.
25. (Rev.2) Please contact Ana (akilmer@albemarle.org) regarding nutrient credit
agreement. The Owner Name, Project Name, WPO#, TMPs, # of phosphorous credits
needed, and project's HUC will all need to be provided.
Ana has been contacted and we will have the nutrient credit agreement before final approval
of plans.
(Rev.3) Acknowledged; currently 2.43 lbs credit required.—will follow up with Ana on status.
Acknowledged please let us know if there is any information we can provide?
(Rev.4) Nutrient credit agreement required prior to VSMP plan approval.Show Letter of
Availability from nutrient credit bank.Will send follow-up email to Anna.
A letter of availability has been provided from a nutrient credit bank.
26. (Rev.2) Design Calcs packet— Page 1 Project Narrative: The areas stated don't match the
plans/VRRM.
Areas have been updated in the calculations book Narrative.
(Rev.3) Addressed.
27. (Rev.2) See Frank's email (10/10/18) regarding the relocation of the public drainage pipe
outfall location to reduce impact on preserved slopes and proposed retaining wall.
Items has been resolved through email coordinate with Frank and David. Pipes have been
moved out side of wall footprint.
(Rev.3) Addressed.
28. (Rev.3) Design Calcs/Analysis:[Rev. May 10, 2019]
a. DI Str. 124 (LD229/ LD204 worksheets) DA & C value differs from what's shown
in the plans.
(Rev.4) Not addressed.
The DA and C values have been revised to match the worksheets and the plans.
b. Routing must use NOAA's precipitation data for the site (see email sent 11/29).
{9VAC25-870-72 A}
Routing has been updated and approved by David James per emails 5-2-2019.
(Rev.4) LD-229 pipe design calls for 18" dia.for pipes 131 through 159.You're showing 15" pipes
in the profiles.The lengths are different for pipe 149. Pipe 169 not found in profiles. Provide LD-
268 calcs for the ditches. LD-347—Unable to locate.
Pipes 131 through 159 have been updated to match the pipe sizing from LD-229.The pipe
length for pipe 149 has been updated to match the plans. Pipe 169 and inlet 170 no longer
exists and has been removed from the pipe calculations. Flowmaster has been used to
calculate the 2-year velocities and can be seen on sheet C6.0.The Ditch calculations have been
run and based on velocities calculated no lining is required for the ditch parallel with Avon
Court extension.The Velocity calculated is much lower than the maximum allowable velocity.
The soil type for the site is 72C3 which is Rabun Clay.According to Table 3.18-B from the
VESCH Handbook,the permissible velocity for this soil type is 5.0 ft/s. Our calculated 2-year
velocity is 2.33 ft/s which is well below the maximum permissible velocity. For the storm
channel running into Moores Creek,the velocity calculated after the proposed riprap has also
been calculated to far less than maximum allowable velocity for the soil type on site.See
Sheet C6.0 for these flows,velocities,depths and other required information.
29. (Rev.3) LOA#1—Overland flow from site may re-concentrate before reaching channel.
Provide some sort of permanent control measure (per email 11/29).
SWM has been revised to meet Energy Balance. Due to this no down stream analysis
is required per email from David James 5-2-2019.
(Rev.4) Addressed.
30. (Rev.4) C6.0—Confirm ditch section B-B detail side slope of 10:1 (Should be 4:1? Or
shown backwards?).
The ditch section has been revised and now calls out 4:1 slopes on both sides.
31. (Rev.4) You're 2-/10-yr flow rates reported for the ditches (C6.0) don't match the flows
reported in the HydroCAD routing.
The flow rates calculated for the ditches use the rational method.The SWM plan and
HydroCAD calculates the flow using TR-55 to route a 24-hour storm. It is typical for the
flow rates to differ as shown using these two different methods.
32. (Rev.4) C6.1—You're pre-dev. (2.69 Ac) & post-dev..(2.57 Ac) DA totals don't match.
Account for the 'undetained' area(s) of runoff post-dev.
The DA's have been revised and the pre and post developed should now match at 2.60
AC.
(Emailed comment from David James 7/15)
Is any area (runoff) not being captured? If so, provide justification.
There is a small area 0.1 acres from the northern pre drainage area that is not
captured in the pipe in system in the post condition. This area will sheet flow to the
north down through the flood plain to Moores Creek as in the pre-condition. While
this area is not expected to reconcentrate before reaching Moores Creek calculations
have also been provided to show this area satisfies energy balance to match approach
shown for other areas per earlier request from engineering.
33. (Rev.4) C7.0:
a. Show profile of ditch/channel and improvements to receiving stream (walls, EG-
1, transitions, pipe crossings).
b. Show profile of ditch to 130: DI-1.
Ditch and channel profiles have been added and can be found on Sheet C6.3.
D. Mitigation Plan (MP)
The mitigation plan requirements can be found in Country Code Chapter 17-406.
(Mitigation plan not required anymore. Stormwater runoff now proposed to be directed to an
existing channel that is being improved.)
1. (Rev.1) Submit a mitigation plan & pay fee of$150. Resubmit VSMP application form.
{Rev.2)Addressed.
also include removal of invasive plants.
{Rev.3) Provide deed/page of temporary easement.
3. (Rev.3) Mitigation required (-1.4e--vegctation) for disturbance. Mitigation: for channel
restoration, 1' of restored channel for every 100sf of disturbed buffer.
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4 (Rev 3) n\Afner to s bmit' �"and requ lift for W1itig''�ion
Ede.E. 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.
1. (Rev.1) C1.0- You're showing duplicate general construction notes. Please remove one.
One copy of general construction notes has been removed.
(Rev.2) Not addressed.
Acknowledged and notes have been removed.
(Rev.3) Addressed.
2. (Rev.1) C2.0—
a. You're showing the steep slopes differently. Use the County's GIS overlay for
steep slopes.
(4/19 SRC meeting follow-up) — If you are claiming slopes are less than 25%
where the County's GIS steep slopes are you must demonstrate better accuracy,
based on newer survey data. Please provide an exhibit sheet comparison of the
site showing the county's steep slope overlay versus your surveyed topo.
Label/highlight areas you claim are less than 25%slope. Please have licensed
surveyor sign & date exhibit sheet. Frank Pohl, the county engineer, will make
the final determination.
Exhibit sheet sealed by a licensed surveyor and approved by Frank Pohl has been
included with resubmission
(Rev.2) Sign seal; Need original signature.
Update exhibit sheets were submitted with original signatures 10/12tn
(Rev.3)Addressed.
b. (Rev.1) Ensure that all existing easements with deed book references, locations
& dims are being shown.
All existing easements with deed book references, locations & dims are shown. See
sheet C2.0.
(Rev.2) Addressed.
3. (Rev.1) C3.2 —
a. You are showing DD symbols along the road ditchline, and they should be CD for
check dams & spaced according to the specs.
DD symbols have been replaced with CD where appropriate. See sheets C3.2 and
C3.3.
(Rev.2) Sheet C3.1—Show CD details.
CD detail has been added.
(Rev.3) Addressed.
b. Add baffle at the upper inlet sediment trap to prevent runoff shortcutting to the
inlet.
Inlet is in the center of the trap and flow from the diversion will enter the trap at
either end maximizing the flow paths.
(Rev.2) Addressed; N/A.
4. (Rev.1) C3.2/C3.3 — Add OP symbol at outfall end of pipe & detail. Provide OP shape &
stone size calcs (see VADEQ ESC HB Spec. 3.18).
Outlet Protection calculations have been added to the calculations book.
(Rev.2) Addressed.
5. (Rev.1) For grass stabilization on constructed slopes, the maximum steepness is 3:1.
Slopes steeper than 3:1 must be permanently stabilized with landscaping vegetation
hardier than grass, which will not require mowing [DSM].
See landscape plan for plantings.
(Rev.2) Partially addressed. Move seed mix spec from site plan to the E&SC plan. Confirm if
recommended seed mix doesn't conflict with permanent seed mix table on sheet C3.1.
Seed spec mix has been added to the E&SC plan. It has been confirmed that the seed mix
doesn't conflict with permanent seed mix table on sheet C3.1
(Rev.3) Addressed.
6. (Rev.1) A building permit is required for walls. Please refer to the Building Official
[DSM].
Acknowledged.
(Rev.2)Acknowledged. See SDP201800070, SUB201800044 plan comments for the walls.
Acknowledged.
We have included 2 copies of the plans and calculations for your review. If you have any
questions or comments, please feel free to give me a call at 434.295.5624.
Sincerely,
yz v 4 to
Jonathan Showalter, PE
Project Engineer
j^ .q
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