HomeMy WebLinkAboutWPO201500066 Review Comments WPO VSMP 2017-12-01 Emily Cox
From: Jeremy Fox <JFox@roudabush.com>
Sent: Friday, November 10, 2017 10:21 AM
To: Emily Cox
Cc: Bill Ledbetter
Subject: RE: Planning Application Review for WP0201500066 Old Trail Village, Block 15
Amendment - VSMP.
Attachments: Blockl2&15 Modified Pond Conversion-Rev.11102017.pdf
Emily,
Attached are the revised slip sheets and requested changes. Below are my comments in RED so you don't have to track
down the changes. When the comments are deemed satisfactory, I will print and submit a new set for final approval.
Thanks for the quick turnaround!
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
stonnwater management plan content requirements can be found in County Code section 17-403.
1. Update the TMP on the cover sheet.
2. On Sheet 413. you are using situation 2. but your worksheet says worksheet #3. Please revise.
3. Show how 9VAC25-870-97 & 98 (IIC)is being met for stream channel erosion & flooding.
Channel is shown on Sheet 9.and outlet protection is shown on Sheet 10.but there doesn't seem
to be a calculation showing that channel is adequate or a statement showing that 10-yr post is less
than 10-vi pre. Please clarify
•
1. The TMP has been updated on the cover sheet to read 55E-01-12-A1 as requested.
2. The worksheet has been revised to read "worksheet situation No. 2" as requested.
3. Channel adequacy calculations have been provided on sheet 4B as requested. Please refer to the added note
for the basis of my calculations and it should make sense. Please call me if not.
Thank you,
Jeremy Fox
Roudabush, Gale and Associates
914 Monticello Road
Charlottesville, Virginia 22902
Office: 434.977.0205
Fax: 434.296.5220
www.mudabush.com
From: Emily Cox [mailto:ecox@albemarle.org]
Sent:Thursday, November 09, 2017 4:41 PM
To:Jeremy Fox<JFox@roudabush.com>
1
Cc: Bill Ledbetter<BLedbetter@roudabush.com>; dave@oldtrailvillage.com
Subject: RE: Planning Application Review for WP0201500066 Old Trail Village, Block 15 Amendment-VSMP.
Ok. Let me know if you have any questions. Feel free to submit by PDF since changes are so minor.
Thanks,
Emily Cox, PE
Civil Engineer II
(434) 296-5832 Ext. 3565
4s: moi.,. u,i
4
401 McIntire Rd.
Charlottesivlle,VA 22902
www.albemarle.org
From:Jeremy Fox [mailto:JFox@roudabush.com]
Sent:Thursday, November 09, 2017 4:37 PM
To: Emily Cox<ecox@albemarle.org>
Cc: Bill Ledbetter<BLedbetter@roudabush.com>; dave@oldtrailvillage.com
Subject: Re: Planning Application Review for WP0201500066 Old Trail Village, Block 15 Amendment-VSMP.
Thanks Emily,
I'll revise and resubmit asap.
Jeremy Fox
Roudabush, Gale and Associates
914 Monticello Road
Charlottesville, Virginia 22902
Office: 434.977.0205
Fax: 434.296.5220
www.roudabush.com
On Nov 9, 2017, at 4:18 PM, Emily Cox <ecox@a,albemarle.org>wrote:
The Review for the following application has been completed:
Application Number= WP0201500066
Reviewer= Emily Cox
Review Status = Requested Changes
Completed Date = 11/09/2017
This email was sent from County View Production.
Emily Cox, PE
Civil Engineer II
(434) 296-5832 Ext. 3565
2
<image001 jpg>
401 McIntire Rd.
Charlottesivlle, VA 22902
www.albemarle.org
<El_vsmp_review_Old Trail Block 15 &PH II Block 12 EC & SWM Plan_wpo201500066
Amendment 1.pdf5
3
COUNTY OF ALBEMARLE
Department of Community Development
401 McIntire Road, Room 227
Charlottesville, Virginia 22902-4596
Phone (434) 296-5832 Fax (434) 972-4126
VSMP Permit plan review
Project title: Old Trail Village Block 15 & Ph. II, Block 12 Erosion Control & SWM
Plan Amendment
Project file number: WPO201500066 Amendment 1
Plan preparer: Roudabush, Gale & Associates, Inc. [jfox@roudabush.com]
Owner or rep.: Dave Brockman [dave@oldtrailvillage.com]
Plan received date: 18 Oct 2017
Date of comments: 09 Nov 2017
Reviewers: Emily Cox
County Code section 17-410 and Virginia Code §62.1-44.15:34 requires the VSMP authority to
act on any VSMP permit by issuing a project approval or denial. This project is denied. The
rationale is given in the comments below. The application may be resubmitted for approval if all
of the items below are satisfactorily addressed. The VSMP application content requirements can
be found in County Code section 17-401.
A. Stormwater Pollution Prevention Plan (SWPPP)
The SWPPP content requirements can be found in County Code section 17-405. A SWPPP must
contain (1) a PPP, (2) an ESCP, (3) a SWMP, and (4) any TMDL measures necessary.
1. Ensure the SWPPP is updated on site to include the latest plans. Provide 2 copies for plan
approval.
B. Pollution Prevention Plan (PPP)
The PPP content requirements can be found in County Code section 17 -404.
1. PPP is unchanged. No comment.
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. Update the TMP on the cover sheet.
2. On Sheet 4B, you are using situation 2, but your worksheet says worksheet #3. Please revise.
3. Show how 9VAC25-870-97 & 98 (IIC) is being met for stream channel erosion & flooding.
Channel is shown on Sheet 9, and outlet protection is shown on Sheet 10, but there doesn’t seem
to be a calculation showing that channel is adequate or a statement showing that 10-yr post is less
than 10-yr pre. Please clarify
Engineering Review Comments
Page 2 of 3
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 approved, 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. E&S is unchanged. No comment.
The VSMP permit application and all plans may be resubmitted for approval when all comments have
been satisfactorily addressed. For re-submittals please provide 2 copies of the complete permit package
with a completed application form.
Engineering plan review staff are available from 2-4 PM on Thursdays, should you require a meeting to
discuss this review.
Process;
After approval, plans will need to be bonded. The bonding process is begun by submitting a bond estimate
request form and fee to the Department of Community Development. One of the plan reviewers will
prepare estimates and check parcel and easement information based on the approved plans. The County’s
Management Analyst will prepare bond agreement forms, which will need to be completed by the owner
and submitted along with cash, certificates or sureties for the amounts specified. The agreements will need
to be approved and signed by the County Attorney and County Engineer. This may take 2-4 weeks to
obtain all the correct signatures and forms.
Stormwater Management Facilities Maintenance agreements will also need to be completed and recorded.
The County’s Management Analyst or other staff will prepare the forms and check for ownership and
signature information. The completed forms will need to be submitted along with court recording fees.
After bonding and agreements are complete, county staff will need to enter project information in a DEQ
database for state application processing. DEQ will review the application information based on local
VSMP authority approval. At this time, the DEQ portion of the application fees will need to be paid
directly to the state. For fastest processing, this is done electronically with the emails provided on the
application. DEQ should notify applicants with instructions on how to pay fees. When DEQ approves the
application, they will issue a permit coverage letter. This should be copied to the county.
After DEQ coverage is issued, via the coverage letter, the County can hold a pre-construction conference.
Applicants will need to complete the request for a pre-construction conference form, and pay the remainder
of the application fee. The form identifies the contractor and responsible land disturber, and the fee
remaining to be paid. This will be checked by county staff, and upon approval, a pre-construction
conference will be scheduled with the County inspector. At the pre-construction conference, should
everything proceed satisfactorily, a joint VSMP and grading permit will be issued by the County so that
work may begin.
County forms can be found on the county website forms center under engineering;
http://www.albemarle.org/deptforms.asp?department=cdengwpo
File: E1_vsmp_review_projectname.doc
Engineering Review Comments
Page 3 of 3
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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
VSMP Permit plan review /Approval
Project: Old Trail Village,Block 15 AMENDMENT(VSMP for blocks 11, 14, 12, 15)
Plan preparer: Chris Mulligan,Bill Ledbetter—Roudabush,Gale&Assoc, Inc
914 Monticello Road,Charlottesville,VA 22902,cmulligan@a roudabush.com,
bledbetter@roudabush.com
Owner or rep.: March Mountain Properties LLC [1005 Heathercroft Circle, Suite 100]
Dave Brockman,dave@oldtrailvillage.com
Plan received date: 8 Sep 2015,review deferred
(Rev. 1) 29 Sep 2015
(Rev.2) 29 Sep 2015
(Rev.3) 10 Nov 2015
Date of comments: 19 Sep 2015(e-mail/ref. CV)
(Rev. 1) 5 Oct 2015
(Rev.2) 21 Oct 2015 (DRAFT—released 30 Oct 2015,w/CD Director's permission;email,JEA)
(Rev.3) 17 Nov 2015 Approved/(Also:G.Brooks,email:Nov 17,2015 8:18:00 AM)
Reviewer: John Anderson/staff(8 Sep 2015;Rev. 1)
Glenn Brooks,County Engineer(Rev.2/3)
SEE ALSO WPO2O1400047,PLAN REVIEW COMMENTS DATED 12 MAR 2015,(REv.2,BLOCK 15)
Note:Applicant requested defer review of plans d.9/8/15—Engineering withheld review until received
revised,9-29 plans.
With 10 Nov 2015 plans,prior Engineering comments addressed.
WPO201500066 is approved as an alternative to the prior approved plan,WPO201400071.
A. Stormwater Pollution Prevention Plan(SWPPP)
The SWPPP content requirements can be found in County Code section 17-405. A SWPPP must contain(1)
a PPP,(2)an ESCP,(3)a SWMP,and(4)any TMDL measures necessary.
1. Revise General VPDES Permit Registration to reflect Estimated Area of Disturbance/Area of
Development. [block 9]
B. VSMP: SWPPP: Stormwater Management and Mitigation Plan(WPO201500066)-VSMP
Regulation 9VAC25-870-108 requires the VSMP authority to approve or disapprove a SWMP. This plan is
approved. —Prior comments removed for clarity;available with review comment documents/CV system.
C. VSMP: SWPPP: Erosion Control Plan(WPO201500066)—Virginia Code§62.1-44.15:55 requires the
VESCP authority to approve or disapprove an ESCP.This plan is approved. —Prior comments removed for clarity;
available with review comment documents/CV system.
*ear Now
Engineering Review Comments
Page 2 of 2
Process:
WPO201500066 is approved and bonded. A pre-construction Meeting was held 19 November 2015 with County
ESCNSMP inspector Mark Hopkins. There are no outstanding permit or application fees, approvals,or issues.
Project has obtained a grading permit,and is authorized to proceed in accordance with approved WPO201500066.
Please let us know if this correspondence meets your needs.
Thanks for your patience.
434.296-5832—x3069
Cl _. •
COUNTY OF ALBEMARLE
Department of Community Development
401 McIntire Road, Room 227
Charlottesville, Virginia 22902 -4596
Phone (434) 296 -5832 Fax (434) 972 -4126
i
Project: Old Trail Village, Block 15 amendment
Plan preparer. Roudabush, Gale & Assoc. [bledbetter roudabush.com]
Owner or rep.: March Mtn Prop [dave @oldtrailvillage.com]
Plan received date: n/a (rework of prior review)
Date of comments: 21 Oct 2015
Reviewer: Glenn Brooks, P.E.
A. Stormwater Management and MitigationPlan (WP0201500066)
1. Please remove all the computations fran the plan set, including the numbers in site data and tables I
would like to be able to approve the plans witlout being in complete agreement with the computations,
since I am doing my own checks. The more you place onthe plan, the less likely we will have
agreement. These are also a confusion tothe inspectors and contractors.
2. Lower the dam to better protect the road and achieve a 3:1 downstream face for maintenance. There
appears to be room in the current desig► if 3:1 slopes are used throughout(above normal pool) By my
computations, a dam aroundEL 651' with 8' top width, a 60" riser, no notch, and a 40' concrete
spillway control section at EL 649.5' works. A sketch is provided below.
3. There is no downstream channel to the receiving stream. Adequate channel provisions must be nteby
providing a reasonable discharge channel or level spreader to the receiving stream.
4. Provide a 10'x10'typical planting scheme for the wetland shelf, and tabulate total plantingsby type.
5. Revise the profile on sheet 8 to show the correct slopes and structure details. They are incorrect. In
addition, a 10 to 1 shortening of the horizontal measurement is too skewed to be useful. A 2 to 1
should be used, if the drawing must be skewed to fit the sheet.
6. Provide a guardrail atthe end of the road or travelway abovethe slope leading to the pond. A similes
safety measure may be needed depending on the final spillway design next to the sidewalk on Old
Trail Drive.
7. Revise the spillway and channel sctions to show proper details; he excavated dimensions, liners, rip
rap thickness, and final constructed hydraulic dimensions required.
8. Rather than providing rip -rap aprons as shown, the forebay itself should be designed to prevent scour
of the earthen fill and facing slopes. The inflow points are Blown submerged, and the standard outlet
protection computations do not apply.
9. Rather than providing standard Tecification language on the construction of the dam, please provide
specific detailednotes; For example, existing materials b be tested for adequate compaction andsoils
prior to placement of fill. Fill is to be benched intothe existing dam after the existing surface is
stripped of vegetative materialsand prepared. A toe drain is to be installed perthe provided detail.
All construction and testing is to be documented and sealed by a professional engineer and provideth
the VSMP authority with as -built surveys, etc.
This plan is to change the approved stormwater design from a biofilter to a pond. Other items on this plan set were
not reviewed.
See Mitigation Flan
Engineering Review Comments
Page 2 of 2
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COMMONWEALTH of VIRGINIA
DEPARTMENT OF TRANSPORTATION
1601 Orange Road
Culpeper, Virginia 22701
Charles A. Kilpatrick, P.E.
Commissioner
October 14, 2015
Mr. John Anderson
County of Albemarle
Department of Community Development
401 McIntire Road
Charlottesville, VA 22902
Re: WPO- 2015 -00066 Old Trail Village Block I5 & Ph. II, Block 12
Dear Mr. Anderson:
The Old Trail Village Block 15 WPO Plan, with revisions dates of July 30, 2014 and September 29, 2015
and a seal date of September 29, 2015 has been reviewed.
VDOT has no objection to the plans as submitted.
If you need further information concerning this project, please do not hesitate to contact me at
(434) 422 -9373.
Sincerely,
Shelly A. Plaster
Land Development Engineer
Culpeper District
701 VDOT Way
Charlottesville, Virginia 22911
WE KEEP VIRGINIA MOVING
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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:
Old Trail Village, Block 15 AMENDMENT (VSMP for blocks 11, 14, 12, 15)
Plan preparer:
Chris Mulligan, Bill Ledbetter — Roudabush, Gale & Assoc, Inc
914 Monticello Road, Charlottesville, VA 22902, cmulligankroudabush.com,
bledbetter(a)roudabush. com
Owner or rep.:
March Mountain Properties LLC [1005 Heathercroft Circle, Suite 100]
Dave Brockman, dave(koldtrailvilla ee com
Plan received date:
8 Sep 2015, review deferred
(Rev. 1)
29 Sep 2015
Date of comments:
19 Sep 2015 (e -mail /ref. CV)
(Rev. 1)
5 Oct 2015
Reviewer:
John Anderson
SEE ALSO WP0201400047, PLAN REVIEW COMMENTS DATED 12 MAR 2015, (REV. 2, BLOCK 15) Note:
Applicant requested defer review of plans d. 9/8/15 — Engineering withheld review until received revised, 9-
29 plans.
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 ESOP, (3) a SWAP, and (4) any TMDL measures necessary.
1. Revise General VPDES Permit Registration to reflect Estimated Area of Disturbance / Area of
Development. [block 9]
B. VSMP: SWPPP: Stormwater Management and Mitigation Plan (WP0201500066) -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.
General comments
1. Use cloud revisions in future to note all revisions from last submittal. For example, compare sheet 9, 9 -8-
15 and 9 -29 -15 plan sets: 10.60 Ac. impervious area revised to 9.07 Ac.
2. Describe impervious areas in detail. 9.07 Ac. impervious area is unacceptable since blocks 11, 14, 12, 15
impervious area listed (by applicant) =10.21 Ac. in .xls attachment to 10- Mar -15 email. Restore and design
to higher post - developed impervious areas for blocks 11, 14, 12, 15. It is untenable to use lower values for
blocks for which there is historical correspondence and prior- approved WPO SWM plans.
3. Revise impervious areas used in performance calculations, since design revisions may alter size or capacity
of retention basin III to the point it may not provide 65% total phosphorus removal efficiency, triggering
reliance on Lickinghole Basin for a percentage of phosphorus reduction/water quality compliance.
4. Please revise SWM Master Plan (14 -April 2015) for review so that if or when on -site constraints require
reliance on Lickinghole Basin, there is programmatic agreement, a structure in place to guide review
decisions. Although Albemarle County has issued guidance, please note that 21 -Nov 2014 Albemarle
County Community Development Director email is a "set of guidelines to follow in development of a
stormwater master plan that avoids the need to amend the zoning." If on -site Part IIC BMPs cannot meet
Part IIC compliance requirements, and design relies on Lickinghole Basin, there is no framework
agreement that allows VMSP plan approval. This circumstance has been discussed and shared in writing.
5. Pre - development DA Map Acreage should match 15.3 Ac. post - development DA Map Acreage.
Engineering Review Comments
Page 2 of 7
6. Plan does not include sheet 4, 5, 6, from WPO201300021, though sheets listed in index. Please restore
these sheets. The reason is that for the moment the approved SWM plan for blocks 11, 14, 12 (phase 1)
relates to SWM facility design presented in these sheets. Drainage Areas, WPO201300021, also relevant.
7. Stormwater Data listed with SITE DATA, sheet 1, is unacceptable. Revise. Also, see items 1, 2, 3, above.
8. Revise plan title to include reference to blocks 11, 14, 12, and 15, as this plan is proposed to replace prior
(or serve as approved) plan for these blocks (WPO201400071, most recent), which will then be void.
Please include reference to project file number in title: WPO201500066.
9. Min. Std. 3.02, Principal Spillway —p. 3.02 -23: Provide anti - floatation calculation for principal spillway
riser structure (buoyancy calculation). Ensure that calculation considers embedded depth of riser in
embankment; that is, ensure calculation reflects scaled design.
10. Min. Std. 3.03, Vegetated Emergency Spillway —p. 3.03 -2: "An armored emergency spillway over the top
of an embankment should be designed by a qualified professional." Provide design as well as dimensions.
Include control section: "the point of the spillway where the flow passes through critical depth. It is
recommended that the control section be installed close to the intersection of the earthen embankment and
the emergency spillway centerlines."
11. Min. Std. 3.03 — Ensure that design complies with hydraulic design criteria listed at pp. 3.03 -5 and 3.03 -6
(eight bullet points listed). For example: items 5, 6 —the exit channel should have a "straight alignment and
grade and, at a minimum, the same cross - section as the control section." "The inlet channel should have a
straight alignment and grade." Revise design. Note proximity to Old Trail Drive, relative elevations of
street/spillway, curved design, possible siting of spillway on roadway embankment fill (prohibited), and
substantial revision to spillway width since 9 -8 submittal. Level of care with design may ensure few safety
or long -term performance issues for spillway, BMP, pedestrians, and primary means of access to Old Trail
(Old Trail Drive).
12. Min. Std. 3.04, Sediment Forebay —p. 3.04 -3: "The sediment forebay should be sized to hold 0.25 inches of
runoff per impervious acre of contributing drainage area, with an absolute minimum of 0.1 inches per
impervious acre." Regardless of final size or dimensions of retention basin III, size the sediment forebav to
hold an absolute minimum of 0.1 inches per impervious acre, or 0.1 X 10.21 Ac., or 3,706 cf, but a higher
value is preferred. Provide sediment forebay design calculations. Provide forebay design volumes,
independent of retention basin III. Please note: "The volume of the sediment forebay is not in addition to
the required volume of the retention basin permanent pool, but rather as part of the required pool volume."
13. Min. Std. 3.05, Landscapes —pp. 3.05 -2 and 3.05 -3: Provide plant selection (planting plan) for plant zones
1, 2, 3, 4, 5, 6 (deep water, shallow water, shoreline fringe, riparian fringe, floodplain terrace, upland
areas). Specify species; provide schedule, with quantities. Provide plan view planting plan, with
legend/plant abbreviations. There are difficult -to- resolve Mitigation plan issues at Old Trail Village
unrelated to March Mountain, and unrelated to RGA, but that affect residents. We would like to avoid
planting issues wherever possible. Ref. p. 3.05 -5, SWM BMP landscape plan minimum requirements.
Design should address minimum requirements.
14. VSMH, Vol. 1, p. 2 -11, BMP Selection Criteria should be reviewed, principles applied to design proposal for
these and future development blocks.
15. VSMH, Vol. 1, p. 2 -23 —Also, item 2, above.
When improvements on a site are concentrated such that the impervious area is collected and
drained to a single receiving channel (connected impervious cover), it is reasonable to expect
that the developed condition runoff will have an impact on the receiving system in terms of
water quality impairments, regardless of the overall "site" percent imperviousness, and
therefore should be considered in the water quality strategy. In such cases, DCR recommends
that the percent impervious cover calculation be based on the drainage area being collected
by the improved drainage system.
16. Min. Std. 3.0 1, Earthen Embankment —text on sheet 9 (Added to 9 -29 -15 plan) is copied verbatim from p.
J.01 -15 with limited consideration of intent behind copied text. Sheet 9 does not address questions raised
in 9 -19 -15 email. Please accept:
Engineering Review Comments
Page 3 of 7
a. Specify embankment design. Ref. Fig. 3.01 -1a/ -lb (homogenous /zoned). Design and show cutoff
trench, drains, impervious core, etc., in profile view. (Ref. Fig.)
b. Geotechnical Guidelines — "The validity of the design depends on the thoroughness of the site
investigation, the adequacy of the testing program, and the soundness of the designer's judgment.
Design components based on quantitative soil tests, such as analyses of slope stability, seepage,
and settlement, are not discussed herein, but they are necessary to design large dams. Such
analyses will logically follow the selection of a preliminary design. Even for small earth dams
that have a low hazard potential, the following criteria should be considered in a geotechnical
report — A geotechnical engineering study should consist of 1) a site investigation, 2) laboratory
testing, and 3) an engineering analysis." [p. 3.01 -5] —Also, see 19 -Sep email: "The retention basin
earthen embankment will be reviewed in detail. All applicable requirements in DEQ BMP
Clearinghouse Appendix A, Earthen Embankment, should be considered, including: subsoil
analysis /permeability tests; max. slopes; pool depth; materials; density/compaction (tests during
construction required); cut -off trench; other. Please reference DEQ Appendix A Earthen
Embankment, as review will reference it often." Ref. Min. Std. 3.01. Provide Geotechnical
Report.
c. Stream diversions — "The design of some earthen embankments will require provisions for stream
diversions around or through the embankment site during construction. A stream diversion can be
accomplished by a variety of acceptable means, including open channels, conduits, coffer dams,
and pumping." [p. 3.01 -6] Provide details and plan /profile of stream diversion required to install
new riseribarrel. Runoff from post - developed highly impervious area must be conveyed across the
site without site, stream buffer, or off -site impacts. Review will focus on stream diversion design.
d. Embankment Stability — Review Min. Std. 3.01 and provide design relative to differential
settlement, seepage, and shearing stresses (within the embankment and foundation) ... The
embankment cross - section should be designed to provide an adequate factor of safety to protect
against sliding, sloughing, or rotation in the embankment or foundation." [p. 3.01 -7] Provide
details of desi,gn/eeotechnical study consistent with Embankment stability design requirements.
e. Foundation cutoff — "A foundation cutoff trench of moderately impervious material should be
provided under the embankment. The cutoff trench should be installed at or upstream of the
dam's centerline, and should extend up the abutments to the 10 -year water surface elevation." [p.
3.01 -8] Sheet 9 inadequate. Provide foundation cutoff trench design: dimensions, plan/profile. —
Also, Fig. 3.01 -3.
f. Embankment zoning and seepage — "For most stormwater management facilities, determining the
location of the phreatic surface will often suggest the need to install seepage collars on the barrel.
(Refer to Minimum Standard 3.02, Principal Spillway, for a discussion on seepage control along
conduits.) For larger stormwater facilities, especially those with a permanent pool, the location of
the phreatic surface may require additional design considerations such as an internal drain." [p.
3.01 -9] Consider /design for seepage: collars, foundation, abutment and /or embankment drains.
g. Maintenance and Safety — "The following design considerations are provided to help reduce the
long -term maintenance burden on the owner(s): 1. Internal drainage systems in embankments
(e.g., drainage blankets, toe drains) should be designed such that the collection conduits discharge
downstream of the embankment at a location where access for observation is possible by
maintenance personnel. 2. Adequate erosion protection is recommended along the contact point
between the face of the embankment and the abutments. Runoff from rainfall concentrates in
these areas and may reach erosive velocities depending on the gutter slope and embankment
height. Although a sod gutter will be satisfactory for most small embankments, an evaluation
should be made to decide if another type of gutter protection is required. For most embankments,
a riprap gutter is preferred to a paved concrete gutter. 3. Trees shrubs, or other woody plants
should not be planted on the embankment or adjacent areas extending at least 25 feet beyond the
embankment toe or abutment contacts." [p. 3.01 -13] Provide: 1. Accessible /visible internal
drainage outfalls; 2. Adequate erosion protection along edge of facility, at adjacent property line.
Off -site permanent SWM easement is required from off -site property owner. Provide off -site
Engineering Review Comments
Page 4 of 7
easement; 3. Revise retention basin design to avoid impacts to streamward 50 -ft of buffer. Since
3.01 requires a clear no -plant zone to extend at least 25 feet beyond the embankment toe, proposed
grade will impact buffer within 25 -ft of Slabtown Branch. This is not permissible [Ch. 17, Article
VI]. Embankment toe may not extend within 75 -ft of Slabtown Branch.
h. Maintenance and Safety — "Embankment slopes should be no steeper than 3H:1 V if possible, with
a maximum combined upstream and downstream slope of 5:1 (3:1 downstream face and 2:1
upstream face)." [p. 3.01 -13] Revise downstream embankment face to 3:1, or flatter.
17. Min. Std. 3.06, Retention Basin -text on sheet 9 (Added to 9 -29 -15 plan) is copied verbatim from p. 3.06 -20
with limited consideration of intent behind copied texj. Sheet 9 does not address questions raised in 9 -19-
15 email. Please accent:
a. "All retention basins should be a minimum of 20 feet from any structure or property line (as
required by local ordinance)..." [p. 3.06 -5] Recommend revise design to locate edge of emergency
spillway 20 -ft. from public RW, Old Trail Drive.
b. "Final acceptance and design should be based on an actual subsurface analysis and a permeability
Lest, accompanied by appropriate engineering recommendations. The references listed at the end
of this standard and at the end of Minimum Standard 3.10, Infiltration Practices provide more
detailed information regarding the feasibility analysis of subsurface conditions for various soil
types. Due to its complexity, this topic is not covered here. Note that the geotechnical study
required for embankment design (reference Minimum Standard 3.01, Earthen Embankment) will
often provide adequate data to verify the soil's suitability for a retention basin." Provide
geotechnical study. [p. 3.06 -5] —Sheet 9, Note 4 shifts design to the future, which is unacceptable.
c. Permeable soils are not suited for retention basins. [p. 3.06 -51
d. "As the depth of the permanent pool increases, the increased head or pressure on the soil may
increase the infiltration rate. If necessary, a liner of clay, geosynthetic fabric, or other suitable
material may be used in the basin (as specified by a geotechnical engineer). Refer to the design
criteria for basin liners." [p. 3.06 -6] —Also, item 17.0., below.
e. "Downstream Impacts- ...The release depth of the control structure, overall pond depth, hydraulic
residence time, and other design features can be manipulated to help meet the site specific needs
of the downstream channel." [p. 3.06 -7] —As information
f. Safety — "Basins that are readily accessible to populated areas should include all possible safety
precautions. Steep side slopes (steeper than 3H:1 V) at the perimeter should be avoided and
dangerous outlet structures should be protected by enclosures. Warning signs for deep water and
potential health risks should be used wherever appropriate. Signs should be places so that at least
one is clearly visible and legible from all adjacent streets, sidewalks, or paths. A notice should be
posted warning residents of potential waterborne disease that may be contracted by swimming or
diving in these facilities." [p. 3.06 -9] Provide all possible safety precautions, including:
i. Signs/Notices
ii. Hansen Anti -Vortex device, with frame and grate. StormRax not acceptable.
iii. Provide desi label permanent fence for retention basin, Normal WSE =8.75' depth.
ESC SF appears to be shown, but is not labeled. Permanent fence is required given
immediate vicinity to streets, future walk, residents, and school -age children.
iv. Modify downslope face of retention basin, 3H: IV, Max. [ref. Min. Std. 3.01]
g. "Vehicular access to the permanent pool area and release structure must be provided to allow for
long -term maintenance operations (such as sediment removal) and repairs, as needed. ...An onsite
area designated for sediment dewatering and disposal should also be included in the design." [p.
3.06 -9] Provide Access. Provide on -site sediment dewatering.
h. "A sign should be posted near the basin that clearly identifies the person or organization
responsible for basin maintenance." [p. 3.06 -9] Provide sign.
i. Emergency spillway — "An emergency spillway that complies with Minimum Standard 3.03,
Vegetated Emergency Spillway should be provided when possible, or appropriate." [p. 3.06 -10]
Provide Emergency Spillway design consistent with 3.03.
Engineering Review Comments
Page 5 of 7
j. Sediment basin conversion — "If modifications to the riser structure are required as part of the
conversion to a permanent stormwater facility, they should be designed so that a) the structural
integrity of the riser is not threatened, and b) large construction equipment is not needed within the
basin. Any heavy construction work required on the riser should be completed during its initial
installation. It is NOT recommended to install a temporary riser structure in the sediment basin
and then replace it with a permanent riser after final stabilization. This may affect the structural
integrity of the existing embankment and barrel." [p. 3.06 -11] Please see 9 -19 -15 email. Provide:
detailed sequence of construction required to remove existing barrel and riser, install new barrel,
riser, and cutoff trench. There is no evidence a cutoff trench exists in existing sediment basin
embankment. A cutoff trench is required for earthen embankments per Min. Std. 3.01, not simply
at barrel location, but the entire embankment length. This embankment must be modified from
floor elevation up, one end to the other. Sheet 9 Notes 7 -9 provide insufficient detail. Subsequent
review will focus on embankment and sediment basin conversion issues. Plans must provide
detail adequate to guide construction/inspection, and comply with VSMH, 1999 Min. Standards to
help ensure long -term performance. After- the -fact design introduces issues since prior facility
designs are insufficient to meet ultimate development requirements, blocks 11, 14, 12, 15.
k. Permanent Pool — "The depth of a stormwater management basin should vary to include as much
diversity as possible, with an average depth of 3 to 6 feet. Approximately 15% of the basin area
should be less than 18 inches deep." [p. 3.06 -12] Calculate and report average depth of permanent
pool. Calculate and report area of basin less than 18 inches deep. Show calculations.
1. Geometry — "Short circuiting ...can also be avoided by designing a meandering flow path through
the basin, rather than a straight line flow path. In either case, a length -to -width ratio of 2:1 should
be maintained. If site conditions prevent using the proper ratio, then baffles made from gabion
baskets, earthen berms or other suitable materials may be used to lengthen the flow path (see
Figure 3.06 -3). [p. 3.06- 12/13] Provide baffles, see Fig. 3.06 -3.
m. Release depth — "A release depth of approximately 18 inches from the water surface is
recommended (Galli, 1992) to avoid extremes in temperature, nutrient levels, and dissolved
oxygen (see Figure 3.06 -4)." [p. 3.06 -16] Provide design for recommended release depth.
n. Aquatic bench — "An aquatic bench is a 10 to 15 foot wide area that slopes from zero inches at the
shoreline to between 12 and 18 inches deep in the basin (see Figure 3.06 -5). This bench provides
suitable conditions for a variety of aquatic plants and emergent vegetation. Specific landscaping
requirements for an aquatic bench should be provided on the landscaping plan per Minimum
Standard 3.05, Landscaping." [p. 3.06 -17] Provide adequate aquatic bench profile. Sheet 8 profile
provides no relevant design guidance. Also, provide landscaping plan.
o. Liner to prevent infiltration — "Where infiltration is anticipated, ... then a retention or detention
facility should not be used unless an impervious liner is installed. When using a liner, the
specifications provided in Table 3.06 -3 for clay liners and the following recommendations apply: 1.
A clay liner should have a minimum thickness of 12 inches; 2. A layer of compacted topsoil
(minimum thickness 6 to 12 inches) should be placed over the liner before seeding with an
appropriate seed mixture (refer to the VESCH, 1992 Edition.); 3. Other liners may be used
provided the engineer can supply supporting documentation that the material will achieve the
required performance." [p. 3.06 -18] Provide geotechnical report, and liner design, per geotechnical
engineer recommendation, if needed. Also, item 17.b.
p. Access — "A 10 to 12 -foot wide access road with a maximum grade of 12% should be provided to
allow vehicular access to both the outlet structure area and at least one side of the basin. The
road's surface material should be selected to support the anticipated frequency of use and the
anticipated vehicular load without excessive erosion or damage." [p. 3.06 -18] Provide access.
q. Landscaping — "A qualified individual should prepare the landscape plan for a retention basin.
Appropriate shoreline fringe, riparian fringe and floodplain terrace vegetation must be selected to
correspond with the expected frequency and duration of inundation. Selection and installation
guidelines should be per Minimum Standard 3.05, Landscaping." [p. 3.06 -19] Provide landscaping.
Engineering Review Comments
Page 6 of 7
r. Buffer Zones — "A vegetated buffer strip should be maintained beside the basin. The strip should
be a minimum of 20 feet wide, as measured from the MAximum water surface elevation. Refer to
Minimum Standard 3.05, Landscaping." [p. 3.06 -19] Provide buffer zones.
s. Provide pond drain [p. 3.06 -23]
Specific comments (May be stated elsewhere)
Sheet 8
18. Revise stormwater management summary table. Impervious areas inconsistent with prior- approved plans
(blocks 11, 14, 2, 15).
19. Revise Pollutant loading equations —use standard equation: [VSMH, 1999, Vol. 11, p. 5 -102]
Ll-(Bmp) = [O.05 + (0.009 x _1,(Bhrr)j x Ate; amp x 228
Equation 5 -18
Pollutant Load to Existing BMP (LP(BMP ))
where: Lp_(Besr) = relative pre - development total phosphorous load entering existing
BMP (pounds per year)
1,_(BMp) = existing impervious cover to existing BMP (percent expressed in
whole numbers)
A_j, ,,,p = drainage area to existing BMP (acres)
20. Revise road plans as necessary to reflect VSMP design, when approved.
21. Stage- storage- discharge inconsistent with routings report, p. 62.
22. Revise retention basin III profile:
a. 4:1, 2:1 basin embankment side slopes are identical, cannot be accurate.
b. Revise embankment downslope face slope to 3:1, or flatter.
c. OP -1 riprap appears suspended above basin side slope. Revise.
d. Show NWSE intake /release depth, per Min. Std. 3.06.
e. Show /dimension concrete base —show to scale.
f. Provide rev. horizontal scale for basin: 1" =20' Max.
g. Show /label Anti -vortex device.
h. Show /label Q2 /Qlo WSE.
23. Sheet 10: Revise riser pipe base conditions for wet pond conversion detail. Schematic is inaccurate relative
to true proposed position of riser within embankment. Ref 3.0 1, Fig. 3.01 -3.
24. Sheet 10: Qlo, OP1 /OP2, = 0.73/33.3 cfs, respectively (34.03 cfs /total). Routings indicate Qio peak inflow
to Wet Pond is 74.40 cfs. Inflow to sediment forebay would be identical. Review routings, revise design
of OP 1 /OP2 consistent with routing peak inflow. (Report, p. 27)
25. Revise device #5 (routing) dimensions. Plan indicates breadth of device (Emergency spillway) is 12', not
18'. Revise routings.
26. Provide VSMH, 1999, Vol. II Appendix 5D Worksheets (separate report; Attach to routings is fine).
C. VSMP: SWPPP: Erosion Control Plan (WPO201500066) — 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. Label Limits of Land Disturbance with this plan (exclude blocks 11, 14, etc.), sheets 2/3.
2. Sheet 4 — Proposed contours extend off sheet. Show entire extent of proposed contours.
3. Sheet 4, 7 —Show existing contours at least 50 -ft beyond property line to the east, Albemarle County
Schools.
4. Sheet 4, 9 —648' contour label, E side of embankment face, is ambiguous. Clearly identify 648'
contour.
Engineering Review Comments
Page 7 of 7
Engineering plan review staff is available from 2 -4 PM on Thursdays, should you require a meeting to discuss this
review. Plan review staff also available at 434 - 296 -5832 ( -ext 3069) should you have questions.
Process:
After approval, plans will need to be bonded. The bonding process is begun by submitting a bond estimate request
form and fee to the Department of Community Development. One of the plan reviewers will prepare estimates and
check parcel and easement information based on the approved plans. The County's Management Analyst will
prepare bond agreement forms, which will need to be completed by the owner and submitted along with cash,
certificates or sureties for the amounts specified. The agreements will need to be approved and signed by the
County Attorney and County Engineer. This may take 2 -4 weeks to obtain all the correct signatures and forms.
Stormwater Management Facilities Maintenance agreements will also need to be completed and recorded. The
County's Management Analyst or other staff will prepare the forms and check for ownership and signature
information. The completed forms will need to be submitted along with court recording fees.
After bonding and agreements are complete, county staff will need to enter /update project information in a DEQ
database for state application processing. DEQ will review the application information based on local VSMP
authority approval. Note: VPDES Permit VAR 100043 disturbed area acreage requires revision.
Applicant will need to request a pre - construction conference by completing a form, and pay the remainder of the
application fee. The form identifies the contractor and responsible land disturber, and the fee remaining to be paid.
This will be checked by county staff, and upon approval, a pre - construction conference will be scheduled with the
County inspector. At the pre - construction conference, should everything proceed satisfactorily, a grading permit
will be issued by the County so that work may begin.
County forms can be found on the county website forms center under engineering;
htt-D://www.albemarle.orLy/der)tforms.aSD?deDartment--cdenizwDo
WP0201400047- WPO201400071- WPO201500066 -OTV- block 11,14,12,15 100515 rev
COMMONWEALTH of VIRGINIA
DEPARTMENT OF TRANSPORTATION
1601 Orange Road
Culpeper, Virginia 22701
Charles A. Kilpatrick, P.E.
Commissioner
October 1, 2015
Mr. John Anderson
County of Albemarle
Department of Community Development
401 McIntire Road
Charlottesville, VA 22902
Re: WPO -2015 -00066 Old Trail Village Block 15
Dear Mr. Anderson:
The Old Trail Village Block 15 WPO Plan, with revisions dates of July 30, 2014 and September 8, 2015
and a seal date of September 9, 2015 has been reviewed.
VDOT has no objection to the plans as submitted.
If you need further information concerning this project, please do not hesitate to contact me at
(434) 422 -9373.
Sincerely,
'Shelly A. Plaster
Land Development Engineer
Culpeper District
701 VDOT Way
Charlottesville, Virginia 22911
WE KEEP VIRGINIA MOVING