HomeMy WebLinkAboutWPO202100063 Review Comments WPO VSMP 2021-12-30�q off nig 401 McIntire Road, North Wing
Charlottesville, VA 22902-4579
County of Albemarle Telephone: 434-296-5832
COMMUNITY DEVELOPMENT DEPARTMENT WWW.ALBEMARLE.ORG
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VSMP Permit Plan Review
Project title:
Dunlora Farm VSMP & SWM Plan
Project:
WP02021-00063
Plan preparer:
Chris Mulligan, PE — Roudabush, Gale & Assoc., Inc.
999 Second Street, SE, Suite 201
Charlottesville, VA 22902 cmulligan(a),,roudabush.com
440 Premier Circle, Suite 200, Charlottesville, VA 22901
Owner /Applicant:
E. L. Phillips and Ann P. Phillips Liv. Trust, etal C/O Caroline Molina -Ray
6704 Menchaca Road, Unit 33, Austin TX, 78745
Applicant:
Southern Development Homes, 142 South Pantops Dr.
Charlottesville, VA 22911 charlesa(a),southem-development.com
Plan received date:
8 Nov 2021
Rev. 1
6 Dec 2021
Date of comments:
18 Nov 2021, QC -denied /email sent November 18, 2021 4:25 PM
Rev. 1
30 Dec 2021
Reviewer:
John Anderson, PE
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 for reasons listed below. 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 ESOP, (3) a SWMP, and (4) any TMDL measures necessary.
SWPPP
1. Please ensure SWPPP cover includes reference to WP02021-00063.
2. Submit SWPPP using county template located at:
httos: //www.albemarle. ore/home/showDublisheddocument/ 166/637202310327530000
a. Sec. 1: Registration Statement; please complete. Feel free to call if any questions.
b. Sec. 6.A.: PPP Exhibit: Please show initial location of
i. Rain gauge.
ii. Portable sanitary facilities (ports John), as required.
iii. Covered non -hazardous waste dumpster, if required.
iv. Vehicle wash waters, draining to trapping measure (Not a sediment trap design, per se,
but shallow depression — 1-2 backhoe buckets. Avoid direct drainage to Ex. storm
system, or pond/s.)
v. Concrete wash -out.
vi. On -site fuel, if required.
vii. Paint, stucco, chemical storage, if required.
c. Sec. 6E: List named individual responsible for PPP measures.
d. Sec. 8: Although county personnel will inspect, Applicant is required to retain qualified
(contractor/third-party) E&S inspection personnel to perform ESC inspections and evaluate
compliance relative to VESCH, Yd Edition, 1992.
e. Sec. 9: Ensure Signed Certification is signed and dated.
B. Pollution Prevention Plan (PPP) —see SWPPP item 2.b., above
Engineering Review Comments
Page 2 of 6
The PPP content requirements can be found in County Code section 17-404.
C. Stormwater Management Plan (SWMP)
VSMP Regulation 9VAC25-870-108 requires the VSMP authority to approve or disapprove a SWMP. This
plan is disapproved for reasons listed below. The stormwater management plan content requirements can be
found in County Code section 17-403.
1. General
a. Provide access easement to each permanent SWM facility.
b. Provide easement for each SWM facility.
c. Provide forest -open space easement.
d. Provide public drainage easement downstream of SWM facilities to the point discharge reaches a
natural receiving stream, or to the property line [see 14428].
e. Note: Easements a, b, c, d may be recorded with a final subdivision plat. Off -site easement (or
written agreement) needed to construct /maintain temporary ESC measures, sediment basins or
outfalls, for example, must be recorded (or copy of the written agreement provided to county)
prior to WPO plan approval.
f. Nutrient credit purchase is required prior to receiving a grading permit, but is not required for
WPO plan approval.
2. Provide Calculation packet:
a. Combine multiple routing documents submitted 12/6/21 into a single document. Additional
comments are possible.
b. Provide stormwater quantity and quality narrative that indicates compliance for overall
development, and at each discharge point.
c. Reference WPO202100063 on cover.
d. Include VaRRM.x1s.
e. Discuss runoff where plan indicates post -developed condition is sheet flow. Please note
requirements for sheet flow analysis at 9VAC25-870-66.D.
D. Increased volumes of sheet flow resulting from pervious or disconnected impervious areas, or from physical
spreading of concentrated flow through level spreaders, must be identified and evaluated for potential impacts
on down -gradient properties or resources. Increased volumes of sheet flow that will cause or contribute to
erosion, sedimentation, or flooding of down gradient properties or resources shall be diverted to a stormwater
management facility or a stormwater conveyance system that conveys the runoff without causing down -
gradient erosion, sedimentation, or flooding. If all runoff from the site is sheet flow and the conditions of this
subsection are met, no further water quantity controls are required.
f. Transfer Sheet 16 routing data to the Calculation packet.
g. It appears from Open Space Note that WPO plan intends to rely on all non -lot areas (35.77 Ac.
Open Space) to serve as forest -open space (FOS), for SWM purposes. Please provide discrete
areas that may be placed in forest -open space easement, since not all open space managed by the
HOA will qualify as forest -open space for SWM purposes. For example, areas will be maintained
/manicured as lawn or kept clear for aesthetic purposes, will not be allowed to revert to a natural
condition, and will not meet DEQ concept of post -developed SWM forest -open space
(unmaintained, max. bush -hogging 4 x per year, no plant removal, etc.). Far less than 35.77 Ac. is
likely available to list as forest -open space in VaRRM.x1s new development spreadsheet.
h. Revise VaRRM.xIs to reflect post -developed forest -open space land cover available to be placed
in permanent deeded easement, that meets DEQ concept of FOS.
3. VAC25-870-69.B.: Revise design to achieve at least 75% phosphorus reduction on -site. Sheet 17 indicates
TP load reduction required is 16.5 lb. if 35.77 Ac. is placed in (deed -protected) forest -open space. At least
12.375 lb. of the 16.5 lb. reduction must occur on -site.
4. Please confirm that preserved steep slopes shown with this WPO plan are consistent with revised preserved
steep slopes shown on approved Steep Slopes Exhibit by RGA, approved 3/23/21 (with preliminary plat),
Dunlom Farm, SUB202000223. This appears to be the case, that the WPO plan is consistent with the
Engineering Review Comments
Page 3 of 6
Exhibit since preserved slope limits reflect saw -like points /abrupt change in limits. If inconsistent, please
revise WPO plan to ensure consistency
5. Sheet 10
a. Shading of preserved steep slopes is ambiguous. It is unclear whether structures are proposed on
preserved steep slopes. Please clarify that no building sites are proposed to occur on preserved
steep slopes, that no structures are proposed to be built on preserved steep slopes.
b. Please label lots.
c. Show roof leader line runoff discharge to stormwater conveyance system. Sheet flow from lots is
untenable unless roof runoff is routed to storm collection and conveyance. Contractors and home
owners routinely direct downspout runoff to graded slopes, which is impermissible. Ref. 18-
4.3.3.C.4.: "Surface water diversions. Surface water shall be diverted from the face of all cut or
fill slopes or both, using diversions, ditches, and swales, or conveyed downslope by using a
designed structure. The face of the slope shall not be subject to any concentrated flows of
surface water such as from natural drainage ways, graded swales, downspouts, or similar
conveyances."
d. Label SWM facilities.
e. At each SWM facility outfall, indicate discharge is to an adequate receiving channel. SWM
facility discharge must be to an adequate receiving channel.
f. All SWM facilities appear to discharge to natural terrain. Provide energy balance equations for
each SWM facility discharge to natural terrain. Also, please see Calculation packet comment,
below.
g. Delineate Forest /Open Space Easement for SWM purposes.
h. Include Letter of Nutrient Credit availability, since nutrient credit purchase is proposed.
6. Sheets 12-15
a. Label primary spillway outfall elevation on profile.
b. Label primary spillway pipe type, length, slope, INV IN/OUT on profile
7. Include VA DEQ Stormwater Design Specification construction, maintenance, and periodic inspection
guidelines for extended detention facilities on the plan.
8. Include Construction Record Drawings (As -built) for VSMP on the plans, link
httos://www.albemarle.ore/home/showoublisheddocument/3381 /637327510536700000
9. Display permanent outfall protection, graphically. If OP is proposed off -site, obtain permanent public
drainage easement on adjacent parcel.
10. Label SWM facility outfall protection L x W x D.
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 for reasons listed, below. The erosion control plan content requirements can be found in
County Code section 17-402.
1. Provide Notes, sheets 6 and 7:
a. Preserved steep slopes (>25%) to be marked in the field and reviewed by Albemarle County ESC
inspector prior to land disturbance.
b. Field markers delineating preserved steep slopes are to be maintained throughout the course of the
project, are to be replaced if damaged.
c. No permanent or temporary disturbance of preserved steep slopes is permissible.
2. Sheets 6, 7
a. Label limits of disturbance, x.xx Ac.
b. Show and label ST weirs.
c. For sediment basins, show accurate contours at entrance to each emergency spillway.
d. If WPO plan is consistent with SUB202000223 Steep Slopes Exhibit, please revise to remove all
grading across preserved steep slopes. No temporary grading, ESC measures, permanent SWM
e.
Engineering Review Comments
Page 4 of 6
facilities, or proposed permanent grade across preserved steep slopes (limits revised per approved
SUB202000223 Steep Slopes Exhibit) is permissible.
Remove SB# 1 from preserved slopes. Eliminate grading of preserved steep slopes downslope of
SB#1. Additional comments possible with revised plan.
Remove SB#2 from preserved slopes. Eliminate grading of preserved steep slopes downslope of
SB#2. Additional comments possible.
Remove ST#1 from preserved slopes. Additional comments possible.
Remove ST#4 from preserved slopes. Additional comments possible.
Eliminate grading of preserved steep slopes downslope of ST#10. Additional comments possible.
Sediment basin and sediment trap outfalls are problematic:
i. Provide off -site permanent public drainage easement for SB#4 outfall (OP4 is off -site).
ii. Revise SB #2 emergency spillway, which is shown parallel with contours rather than
perpendicular to contours. Avoid emergency spillway in fill section. Ref. DEQ
Clearinghouse document, Vegetated Emergency Spillway,
httos: Hswbmpvwrrc.n.prod. es. cloud.vt.edu/W -
content/unloads/2017/11/lntroduction Apo-C Vegetated-Emergencv-
Soillways 03012011.p_df
From p. 2 of DEQ document:
5EVi1UN U4: ENVIKON MEN IA-L AND LUmmllrlffY l:ON51DERA' IONS
The adjacent topography (steepness of the abutments), the existing or proposed land use, and
other factors (such as a roadway over the embankment) influence the design and construction of
a vegetated emergency spillway.
Vegetated emergency spillways must be built in existing ground or "cut. Even though an
emergency spillway helps to extend the life expectancy of an impoundment and lowers the
associated downstream hazard conditions, it should not be located on any portion of the
embankment till. Therefore, additional land disturbance beside the embankment must be
accounted for during the planning stages of a project. Sometimes, an emergency spillway may
not be practical due to this or other considerations.
If site topography or other constraints preclude the use of a vegetated emergency spillway in
"cut," the principal spillway can be oversized to pass the additional flows or an armored
emergency spillway may be provided. A cost analysis may be helpful to aid in the selection of
the spillway type. If armoring is chosen, then riprap, concrete or any other permanent,
nonerodible surface may be used. Note, however, that an armored emergency spillway over
the top of an embankment should be designed by a qualified professional.
iii. Revise SB#3 Emergency Spillway:
1. Eliminate curved exit. Design using straight exit channel, per DEQ ref. doc.
From p. 3, DEQ Emergency Spillway document:
The topography must be carefully considered when constructing an emergency spillway. The
alignment of the exit channel must be straight to a point far enough below the embankment to
insure that any flow escaping the exit channel cannot damage the embankment. This may result
in additional clearing and/or grading requirements beside the abutments, property line, etc.
2. Current design overlaps emergency spillway and fill slope at base of fill slope.
There is a relatively high likelihood that flow may escape the exist channel and
erode the embankment. Revise design.
3. Insufficient space: Emergency spillway is coincident with development property
line. There must be adequate space to construct /maintain the spillway on the
development parcel. Alternatively, off -site easement is required prior to WPO
plan approval. Easements in connection with ESC measures may not be
deferred until final subdivision plat, but any easement (or written agreements)
required to implement VESCP measures must be in place prior to WPO plan
approval.
iv. SB#4 Emergency spillway:
1. Revise to avoid undercutting fill slope SB embankment. Provide straight exit.
Engineering Review Comments
Page 5 of 6
v. Provide armored emergency spillway design for any SB emergency spillway proposed to
be in fill rather than cut. Consider velocity, channel dimensions, riprap classification, etc.
Provide calculations for armored emergency spillways.
vi. SB#1 Emergency spillway:
1. Revise, since armored spillway terminates at top of fill slope, extend armor to
base of fill slope. Adhere to DEQ Vegetated Emergency Spilhvay design
criteria, and guidance
3. Sheet 8
a. Revise sediment trap design tables:
i. Revise bottom trap dimensions to L x W, for each ST.
ii. Provide weir length, each ST.
4. Sheets 12-15
a. Since each SB is destined for permanent service as a SWM facility, include relevant geotechnical
design, construction, inspection, and maintenance notes on the plan. Ref. VA DEQ Stormwater
Design Specification, Appendix A, Earthen Embankment. Without these notes, there is risk or
likelihood of inadequate geotechnical material testing, inspection, etc. during construction of
embankments that transition from VESCP measure to permanent SWM facility.
b. Provide sediment basin profiles. Do not combine SB and SWM detention as a single profile. SBs
are temporary ESC measures, bonded, built, inspected, and maintained independent of future use
as a SWM facility. Segregate ESC profiles from SWM profiles.
c. Provide Sediment basin design (tables), per VESCH, 3.14 (size, baffles, collars, spillways, etc.).
Process:
After approval, plans will have 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 have to be completed by the owner and submitted along with cash,
certificates or sureties for the amounts specified. The agreements will have to be approved and signed by the County
Attorney and County Engineer. This may take 24 weeks to obtain all the correct signatures and forms.
Stormwater Management Facilities Maintenance agreements will also have to be completed and are recorded. The
County's Management Analyst or other staff will prepare the forms and check for ownership and signature
information. The completed forms will have to be submitted along with court recording fees.
This project appears to propose nutrient credit purchase, may require off -site written agreements or easement to
support ESC measures, and requires forest -open space easement (for SWM purposes), SWM facility and SWM
facility access easement, and public drainage easement. (Off -site easement or written agreement with adjacent
landowners required to construct or maintain temporary ESC measures is required for WPO plan approval.)
After bonding and agreements are complete, county staff will 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 have 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 must 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.
Engineering Review Comments
Page 6 of 6
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 Applications:
httos://www.albemarle.org_/govemment/community-development/apl2ly-for/en ing eerin2-a l2lications
Thank you.
Please call if any questions — tel. 434.296-5832-x3069, or email 4anderson2&aibemarle.org .
WPO202100063—Dunlora Farm-123021revl