HomeMy WebLinkAboutWPO202100063 Review Comments WPO VSMP 2022-06-29�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 Village (Farm) VSMP & SWM Plan
Project:
WPO2021-00063
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
(Rev. 2)
20 May 2022
Date of comments:
18 Nov 2021, QC -denied /email sent November 18, 2021 4:25 PM
(Rev. 1)
30 Dec 2021
(Rev. 2)
29 Jun 2022
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
VSNIP application content requirements can be found in County Code section 17-401.
Recommend virtual (or in -person) meeting to discuss SWM and ESC plan design. Further submittal based
on surface sand filter concept is likely unworkable.
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.
SWPPP
1. Please ensure SWPPP cover includes reference to WP02021-00063. (Rev. 2) Not Addressed, but county
approval stamp will identify project. No follow-up required. (SWPPP will be approved once all plan
revisions complete, and SWPPP I I" x 17" ESC/SWM plan sheet inserts are revised, as needed).
2. Submit SWPPP using county template located at: (Rev. 2) All other SWPPP review comments
addressed. [remaining 30-Dec comments removed.]
B. Pollution Prevention Plan (PPP) —see SWPPP item 2.b.. above (Rev. 2) Addressed.
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.
[ Items 1: 9.: 3/9/22 email, Albemarle to RGA — see Additional review detail. ]
Engineering Review Comments
Page 2 of 7
1. Please provide a separate VaRRM.xIs for phased development indicating (by phase lines, and calculations)
that minimums (forest -open space easement) shown on plans are sufficient. Sheet 2 lists Ph I,11,111, IV
(4.0, 4.0, 4.0, 2.5 Ac.).
2. Engineering evaluates filtering practices in comparison with VA DEQ Stormwater Design Specification
No. 12 (strict evaluation against):
a. Maximum contr i ng CDA of 5 Ac. for surface sand filters, and a maximum CDA of 2 Ac.
(recommended for perimeter or underground filters). Revise design per Spec. 12.
Applicant response (5/12/22 letter): `Plunge pools and demising walls have been introduced to
reduce the maximum drainage area to under 5 acres to each filtration bed.' As follow-up: 5 Ac.
CDA is a design maximum for a surface sand filter. Please revise design. — Also, see Additional
review detail.
b. Please note that "filters have been used on larger drainage areas in the past, but greater clogging
problems have typically resulted." VA DEQ Tech Spec No. 12,.44. (Rev. 2) Reminder.
c. Soil testing requirements: Ref. 6.2, Soil testing requirements, P. 7, BMP specification No. 12.
(Rev. 2) Persists. Applicant: `Soil testing will be provided as available.'
d. Overall sizing requirements, Ref. 6.1. — see Additional review detail.
e. Depth to water table and bedrock, Ref. p. 4. — see Additional review detail.
f. 7.3, Steep Terrain, several key design criteria, including (p. 11): — see Additional review detail.
g. 7.4, Cold climate and winter performance (p. 11). — see Additional review detail.
h. 6.5, Filter media and surface cover, Impervious drainage area: — see Additional review detail.
i. 6.4, Conveyance and overflow (p. 8): — see Additional review detail.
3. It is unclear if filtering practices with associated upslope forebays and distilling ponds are capable of
meeting energy balance at release points to natural conveyances:
a. Each discharge to a natural channel or terrain feature is required to meet 9VAC25-870-66.B.3,
Energy balance. (Rev. 2) Partially addressed. Applicant: `Shown for each concentrated outfall
proposed. In addition, all capturable sheet -flow is to be directed to the SWM devices. Perimeter
terrain offers some limitations to achieving this goal, and is depicted on the Outfall Summary
Sheet.' As follow-up:
i. A combined calculation packet with water quality /quantity tabulated QI_n data for each
of the 8 outfalls depicted, with narrative (numeric /summary) information is required.
Initial submittal included a series of individual routings. Please combine individual
routings to create a single calculation packet with compliance narrative for each outfall.
ii. Provide /show (in calc. packet) energy balance equation for each outfall to a natural
receiving stream using equation listed at state administrative code 9VAC25-870-66.B.3.
iii. Provide calculations for flood protection for each outfall; ref. 9VAC25-870-66.C.
iv. Perform analysis to limits of analysis (9VAC25-870-66.B.4 /9VAC25-870-66.C.3.).
v. Sheet 12 depicts a series of Level Spreaders (ELS); for each ELS:
1. Provide discrete design: plan /profile (at a scale small enough to discern detail).
2. Reference ELS design criteria at VA DEQ Stormwater Design Specification No.
2, Sheet Flow to Filter or Open Space, Table 2.2.
b. Can RGA provide detail or at a conceptual outline of how proposed SWM concept meets energy
balance at each discharge point? (Rev. 2) Persists. Applicant: `Runoff Reduction Calculations
including pre/post mapping provided with this submittal.' Unless overlooked, calculations (single
document) not attached to May submittal. Please see item 3.a. for information requested.
c. — see Additional review detail.
d. — see Additional review detail.
4. Given BMP design criteria, Engineering evaluates concept plan (as presented): — see Additional review
detail.
a. Likely requires adjustment /concept revision to ensure compliance with: — see Additional review
detail.
i. Max. CDA
ii. Impervious CDA
iii. Steep terrain design criteria
iv. SWM quality /quantity requirements (likely not met with limited number of filtering
devices proposed)
Engineering Review Comments
Page 3 of 7
v. Note: Numerous, smaller, strategically placed filtering practices may be required.
vi. Engineering cannot approve, per ordinance (17408.C.2.), BMP design that does not
attain BMP Clearinghouse Website design criteria.
Design that deviates from BMP Clearinghouse design criteria is an unapproved BMP
(design).
vii. — see Additional review detail.
5. — see Additional review detail.
As follow-up: Engineering anticipates FOS easement will be proposed with phased final subdivision plats.
Also, related comments, elsewhere.
6. Rooftop runoff not captured /conveyed to SWM facilities: SWM /WPO plan design (and later, independent
homebuilders) may not propose release of concentrated downspout runoff to fill or cut slopes (Ref. 18-
4.3.3.C.4). (Rev. 2) Persists. Applicant: `Noted in plans. Physically capturable rear yard drainage is being
directed via rear yard swales toward stormwater inlets of facilities.' As ollow-up:
... Proposed grading (unless overlooked) does not clearly define swale conveyance to stormwater inlets of
facilities. Sheet 17 includes detail titled sheet flow measure-uncaptured, non-SWMareas with caption that
reads `Note: Utilize measure as necessary or required to prevent re -concentration of runoff from adjacent
impervious surfaces. Rear yards shall be directed to an approved SWM facility when possible.
Concentrated runoff leaving the rear yard toward steep slopes without sheet -flow management or storm -
water management controls is prohibited.' Sheet 17 note that reflects ordinance requirement/s, prohibition,
measures as needed, while helpful, lacks detail required to prevent rooftop runoff (concentrated storm
runoff) release without capture /treatment.
7. Please exercise caution when representing uncollected runoff as sheet flow, in post -developed condition,
for example: rooftop runoff requires transition to sheet flow, if not conveyed to a dedicated SWM facility.
(Rev. 2) Persists. Applicant: `Since the uncollected runoff areas were not included /treated as a portion of
the necessary stormwater compliance strategy, areas of concentration are being directed to Level Spreaders,
so as to achieve sheet -flow. Smaller, more remote and uncapturable areas —due to terrain constraints —shall
have graded yards to initiate the sheet -flow conditions.' As follow-up: Please see comments related to ELS,
elsewhere.
8. Items above relate to compliant filtering practice design (Engineering evaluates against BMP
specifications), compliance with 9VAC25-870-66.B.3, and 9VAC205-870-69.
9. Additional comment may be possible with additional detail.
best, J. Anderson
[ Items I 10., below, based upon 30-Dec 2021 review comments —Also, see Additional review detail.]
1. General (Rev. 2) Items below persist.
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 La, 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: (Rev. 2) May persist. — see Additional review detail.
a. Combine multiple routing documents submitted 12/6/21 into a single document.
b. Provide stormwater quantity and quality narrative that indicates compliance for overall
development, and at each discharge point. (Rev. 2) Persists.
Engineering Review Comments
Page 4 of 7
c. — see Additional review detail. (Rev. 2) Addressed.
d. Include VaRRM.xIs. (Rev. 2) Partially addressed. As follow-up: Comments elsewhere request
VaRRM.xls to show post -developed forested condition for phased development, with minimum
post -development land cover (forest) values that correspond with intent to develop Dunlora
Village in phases. These min. values are likely to be 4,4,4,2.5 Ac. for Phases I, lI, I11, and IV.
e. Discuss runoff where plan indicates post -developed condition is sheet flow. Please note
requirements for sheet flow analysis at 9VAC25-870-66.D. (Rev. 2) Persists. Also, seefollow-u
at (email) review items 3.a.v., and 6., above. — see Additional review detail.
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.
€. Tfans€erSheet-16fatiting-data to t;eGaleula'don Faeke`. 'r (Rev. 2) Persists.
g. — see Additional review detail. (Rev. 2) Withdrawn. Ref. email to RGA, June 24, 2022 8:25 AM.
It. 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. (Rev. 2) Persists. Please see
comment request for individual VaRRM.YJs tied to each phased plat, since plan indicates a
minimum area to be platted as FOS easement, with each of (the 4) final subdivision plats.
3. —see Additional review detail. -(Rev. 2) Addressed, also, see 3/9/22 email section, above.
4. — see Additional review detail. (Rev. 2) Withdrawn —Engineering accepts design is consistent with Steep
Slopes Exhibit.
5. Sheet 10
a. — see Additional review detail. (Rev. 2) Withdrawn. See item 2.g., this page.
b. Please label lots. (Rev. 2) Persists.
c. Show roof leader line runoff discharge to stormwater conveyance system. — see Additional review
detail. Please ref. email review item 7. above, for follow-up comments.
d. Label SWM facilities. (Rev. 2) Partially addressed. As follow- Please review plan sheets that
display SWM facility design, and ensure facilities are labeled in plan view: SWM `A', `B', etc.
e. At each SWM facility outfall, indicate discharge is to an adequate receiving channel. SWM
facility discharge must be to an adequate receiving channel. (Rev. 2) Persists. Please ref. email
review item 3.a.iii-iv. above, for follow-up comments.
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. (Rev. 2) Persists. Please ref. email review item 3.a./3.a.ii., above, for follow-up
comments.
g. Delineate Forest /Open Space Easement for SWM purposes. (Rev. 2) Partially addressed. Please
ref. item 2.d. this page, for follow-up comments.
It. — see Additional review detail. (Rev. 2) Addressed.
6. Sheets 12-15 (Rev. 2) Partially addressed. Please see email item 2_i., above, for follow-up comments.
a. Label primary spillway outfall elevation on profile.
b. Label primary spillway pipe type, length, slope, INV IN/OUT on profile
7. — see Additional review detail. (Rev. 2) Addressed.
8. — see Additional review detail. (Rev. 2) Addressed.
9. — see Additional review detail. (Rev. 2) Addressed. Ref. sheet 17.
10. — see Additional review detail. (Rev. 2) Addressed.
D. Erosion and Sediment Control Plan (ESCP)
Engineering Review Comments
Page 5 of 7
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. (Rev. 2) Partially addressed. As follow-up: Please revise
Note 3, sheet 6, 7, to read: "Preserved steep slopes (>25%) to be marked in field by contractor and
reviewed by Albemarle County ESC inspector prior to land disturbance." That is: Albemarle does
not mark slopes, but reviews contractor /engineer flagging.
b. — see Additional review detail. (Rev. 2) Addressed.
c. No permanent or temporary disturbance of preserved steep slopes is permissible. (Rev. 2)
Partially addressed. As ollow-up7 Please revise Note 5, sheet 6, 7, to read: "No permanent or
temporary disturbance of preserved steep slopes is permissible unless related to storm or utility
line installation, and only if. No alternative exists, impacts are minimized, slopes are immediately
stabilized, and pipe location across steep slopes is shown on an approved WPO or site plan." That
is: extremely limited temporary disturbance is permissible for utility line or storm pipe installation
only, where no other utility corridor exists, or is impracticable.
2. Sheets 6, 7
a. Label limits of disturbance, x.xx Ac. (Rev. 2) May persist. Please direct reviewer to label (x.xx
Ac.) on plan sheet 6 or 7, if overlooked.
b. — see Additional review detail. (Rev. 2) Addressed.
c. — see Additional review detail. (Rev. 2) Addressed. Note: SB#3 emergency spillway removed.
d. — see Additional review detail. (Rev. 2) Addressed.
e. — see Additional review detail. (Rev. 2) Addressed.
f — see Additional review detail. (Rev. 2) Addressed.
g. — see Additional review detail. (Rev. 2) Addressed.
h. — see Additional review detail. (Rev. 2) Addressed.
i. — see Additional review detail. (Rev. 2) Addressed.
j. Sediment basin and sediment trap outfalls are problematic:
i. Provide off -site permanent public drainage easement for SB#4 outfall (OP4 is off -site).
(Rev. 2) Persists. Space for future maintenance problematic: limited or non-existent
where detail shows SB#4 emergency spillway touching property line.
ii. — see Additional review detail. (Rev. 2) Addressed.
cF@m o o f P9Q ,,,.,.ume . [image removed with Rev. 2 comments]:
iii. Revise SB#3 Emergency Spillway: (Rev. 2) Persists. Emergency spillway eliminated
with revision. Plan now shows sediment trap spillway at property line, which does not
address concern expressed with initial review comment (reprinted as L,2.,3., below).
1. Eliminate curved exit. Design using straight exit channel, per DEQ ref. doc.
From p. 3, DEQ Emergency Spillway document:
The topography most 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)
Engineering Review Comments
Page 6 of 7
required to implement VESCP measures must be in place prior to WO plan
approval.
iv. SB#4 Emergency spillway: (Rev. 2) Not addressed.
1. Revise to avoid undercutting fill slope SB embankment. Provide straight exit.
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. (Rev. 2) May persist. Please see
item 2.i.iii, above.
vi. SB#1 Emergency spillway: (Rev. 1) Not addressed.
1. Revise, since armored spillway terminates at top of fill slope, extend armor to
base of fill slope. Adhere to DEQ Vegetated Emergency Spillway design
criteria, and guidance
3. Sheet 8
a. — see Additional review detail. (Rev. 2) Addressed.
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. (Rev. 2) Not
addressed. Geotechnical considerations are critical for earthen embankments.
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. (Rev. 2) Partially addressed. As
follow-up:
i. SB#I, sheet 13 (comments (may) also apply to SB#2, SB#3, SB#4):
1. SB #1 profile indicates 1,380.2 CY storage required, 749.0 CY storage provided.
SB#1 appears undersized. If so, revise SB#1 to provide sufficient stored volume.
2. Provide profile consistent with VESCH Plate 3.14-2, to include these elevations
(in addition to top of dam and riser crest top elevations provided):
a. design high water
b. top of dam
c. dewatering device
d. sediment clean -out point
e. bottom of base of riser structure
3. Show continuous proposed grade across floor of sediment basin #L
4. Show clay core, cutoff trench, collars, as needed. Sheet 17 typical provides
inadequate detail.
5. If collars required, show in profile, and label collar dimensions.
6. Show /label 24" pipe end section (VDOT ES-1, for example).
7. Permanent riser ht. >12' requires safety slab (VDOT SL-1).
8. Label SB#1 floor dimensions (L x W).
9. Provide baffles, as needed.
10. Label 24" pipe INV OUT.
ii. SB#2, sheet 14
1. Label ST#14 in plan view.
2. Apply SB#1 comments to SB#2, as needed.
3. WQV (storage) required /provided not listed on profile.
iii. SB#3 & Outfall to SB#4 (sheet 15)
1. Recommend compaction note for MH /pipe nearly entirely in fill section.
2. Comments for SB#1 may above also apply.
Engineering Review Comments
Page 7 of 7
3. Label is confusing: `Sediment basin 3 shall be a sediment trap until the storm
sewer outfall into sediment basin 4 is constructed (limit contributing drainage
area to less than 3 Acres). Note: Divert all runoff to SB#4 until basin & SWM
`D' outfall is operational'. Clarify proposed sequence /interdependence of SB#3
(basin/trap), SB#4, SWM `D'.
iv. SB#4, sheetl6: Apply SB#1 comments, as needed.
c. Provide Sediment basin design (tables), per VESCH, 3.14 (size, baffles, collars, spillways, etc.).
(Rev. 2) Not addressed.
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.
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. ore/government/community-develonment/aooly-for/engineering-anolications
Thank you.
Please call if any questions — tel. 434.296-5832-x3069, or email 4anderson2(a)albemarle.ore .
WPO202100063—Dunlora Farm-Village-062922rev2—condense-save-send.doc