HomeMy WebLinkAboutWPO201500057 Review Comments WPO VSMP 2016-02-05COUNTY 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:
Avinity Estates
Project Number:
WP0201500057
Plat preparer:
Scott Collins; Collins Engineering [200 Garrett St., Suite K,
Charlottesville, VA 22902, scott&collins-en ing eerin'g com]
Owner or rep.:
Avon Properties LLC, P. O. Box 1467, Charlottesville, VA 22902
Plan received date:
19 Aug 2015
(Rev. 1)
8 Dec 2015
Date of comments:
28 Sept 2015
(Rev. 1)
5 Feb 2016
Reviewer:
John Anderson
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. Sec. 6 —Name an individual responsible for pollution prevention practices. (Rev. 1) Addressed.
2. Sec. 6 —Revise Exhibit LOD: 12.20 and 13.60 Ac. both listed. 12.20 Ac. listed on VPDES registration.
(Rev. 1) Addressed.
3. Sec. 6 —Given discussion at unrelated project meeting (24 -Sep; CCS/pre-con), please include/propose list of
chemical contaminants/products to include with Sec. 6. DEQ places emphasis on a comprehensive list of
on-site pollutants with potential to enter or impact waterways. (Rev. 1) Addressed.
4. Sec. 9 —Sign certification. (Rev. 1) Not Addressed.
5. Sec. 12 —Use increased inspection frequency. Delete (inspection log) standard inspection frequency,
consistent with Sec. 7 TMDL, Moore's Creek/impaired waterway. (Rev. 1) Addressed.
B. VSMP: SWPPP: Stormwater Management Plan (WP0201500057)
VSMP Regulation 9VAC25-870-108 requires the VSMP authority to approve or disapprove a SWMP. This plan is
disapproved for reasons provided in comments below. The stormwater management plan content requirements can be
found in County Code section 17-403.
1. Accept/respond to any VDOT plan review comments. (Rev. 1) Acknowledged.
2. Title p. —Delete SWM general note reference to upland rain gardens. Reference dry swales. (Rev. 1)
Addressed.
3. Calculations packet
a. In numerous tables, yellow text is unreadable. Reserve right to comment once text readable. (Rev.
1) Addressed.
b. "Dry Treatment Swale" `A' — Please consider totality of VA DEQ Stormwater Design No. 10.
Proposed facility `A' is neither a (linear) dry swale, nor a bioretention basin. It is most nearly an
Engineering Review Comments
Page 2 of 5
extended detention facility —item briefly discussed with S. Collins, 24- Sept. Revise
design/calculations. Also —see SWM items # 6/7, below. (Rev. 1) Addressed. Facility revised to
a bioretention basin.
c. Revise Energy balance calculation to reflect revised Facility `A' design. (Rev. 1) Addressed.
d. Please email VaRRM .xls to reviewer. (Rev. 1) Addressed/received 8 -Dec.
4. Sheet 3 —Delete Note 6, a design note. Provide design. Also —see SWM item # 8, below. (Rev. 1)
Partially Addressed. Asfollow-up: As discussed with Kaitlyn 3 -Feb., sealed geotechnical design is
required as critical prerequisite to WPO Approval. Special siting or design criteria apply to the lowest
retaining wall, bioretention basin `A, with TW/BW Elev. =496'/490' (compare with 10 -yr. WSE 495.3').
Nearly the full height of this wall will be submerged periodically, which requires special structural design.
If the lowest wall fails, walls at higher elevations may fail in series. Please also show protective permanent
barrier to prevent accidental trespass. SWM Facility and stepped walls pose multiple risks to subdivision
residents.
5. Sheet 5 —Revise proposed dry treatment swale W. It does not meet VDEQ BMP Clearinghouse design
specification. See related comments, items #3.b, above; 6, 7, below. (Rev. 1) Addressed/design revised.
Sheet 6
6. Swale `A' does not match BMP design specification: shape (linear; parabolic or trapezoidal cross-section);
ponding time/depth=6-hr/12"/Max. Revise design. 55' wide, non-linear design most nearly resembles an
extended detention basin. Attached VaRRM (.xls) illustrates hypothetical design that nearly matches
phosphorus load reduction of proposed swale W. It appears feasible using one possible combination
(bioretention with separate extended detention) to nearly replicate proposed design P -load reduction. (Rev.
1) Addressed. Facility revised to a bioretention basin (Level 1).
7. Review of Facility `A' suspended when reached p. 13 of Clearinghouse Spec. No. 10: Max. ponded depth.
Proposed Qio depth =4.697'. (Rev. 1) Acknowledged.
8. Show Facility `A' retaining walls in profile. Show geogrid length if geogrid provided. Provide design for
inundated conditions to the 100 -year storm elevation. If the lowest retaining wall is compromised, entire
south slope of facility is jeopardized. 2-, 10-, 100 -yr events inundate lower portion of lowest retaining wall,
Elev. =492'. Furnish design capable of withstanding inundation. Provide specifications, details, notes, etc.
(Rev. 1) Applicant response (7 -Dec 2015): "The retaining walls will be shown in the profile upon receipt
of structural wall drawings. The geogrid lengths will be included per the structural engineering wall plans
upon receipt and prior to final approval. The wall design will accommodate inundated conditions." Also:
see item #4 (above) follow-up comment, above. (Rev. 1) Comment restated.
9. Swales 2, 3 —provide parabolic or trapezoidal cross-sections/label dimensions. Show media. Label depth
of media. Show underdrains. Provide infiltration rate testing (6.2, p. 12/Spec. 10). Label L x W/plan
view. (Rev. 1) Partially Addressed. Asfollow-up: Provide vertical, not 2:1 side slopes (below grade/dry
swale section; sheet 6). Ref. Typical Details for Level 1 and 2 Dry Swales, p. 5, VA DEQ Stormwater Design
Specification No. 10 [BMP Clearinghouse].
Sheet 7
10. Swale 1 —Provide items listed in item #9 above. (Rev. 1) Addressed.
11. Provide dimensions sufficient to construct the atypical geometry of SWM Facility #B. Provide more than
L, W. Dimension max length, insets, pinch points, etc. (Rev. 1) Addressed.
12. Revise bioretention basin `B'. Max. ponded depth —12 in. Ref. recent CE bioretention facility designs.
(CMA, Glenmore K2C, CCS). (Rev. 1) Addressed.
13. Level 2 bioretention basin `B' & Level 1 Filter Strip design detail: provide cross-section of ELS. (Rev. 1)
Addressed —the filter strip has been removed from the plans.
14. Level 1 Filter Strip detail: Spec. No. 2 Table 2.2 provides options. Select and apply one of the options.
Labeling is confusing: it appears as if all three slope/length options apply, appears that total L=150'. At
most, 6% to 8% slope requires L =65'. State that first 10' @ 2% slope (or <) is a minimum requirement,
not an option. (Rev. 1) Addressed —removed from plans.
Engineering Review Comments
Page 3 of 5
15. Level 1 Filter Strip detail: Provide cross-section of filter strip. (Rev. 1) Addressed -removed from plans.
16. Level I Filter Strip detail: Provide retaining wall (RW) length. Provide geotechnical RW details. (Rev. 1)
Addressed -removed from plans.
17. Dimension wall length. (Rev. 1) Addressed.
18. Floor elevation of SWM bioretention basin `B' must be at least 1' below floor elevation of SB -2. (Rev. 1)
Addressed.
19. Provide SWM Notes: Clearinghouse construction/inspection/maintenance specifications, all BMPs. (Rev.
1) Not Addressed -Provide Notes (similar to ESC Notes/Text, sheet 8).
New
20. Sheets 4, 5, 6 -Revise label reference to Phase I SWM facility Approved under WPO#2013000441 or
variation on this theme. County/CE discussed plan view schematic of 4 x WQV retention basin labeled
approved on 7 -Jan. Please remove reference to Approved; replace with approval pending. Applicant -
developer -contractor made change to Approved design in response to field conditions (shallow rock).
Decision to replace Approved WPO#201300044 basin design with revised geometry and basin elevations
independent of county review was without: notification; review; approval. Applicant must coordinate
Amendment Application for (a second) Avinity I WPO Amendment Plan to replace the Amendment plan
approved 20 Jun 2014. Any modification or revision to an approved SWM facility during construction
must be coordinated, reviewed, and approved -this or any project. If unapproved facility design is built,
there is risk beyond ordinary violation of local/state requirements: there is risk As -built construction may
require revision or replacement at severe expense to Applicant. County requests Amendment Application for
WPO201300044. Required submittal, review and approval will not delay approval of WPO201500057.
County requests plan, profile, hydrologic (TR -55), typical and specific details required to evaluate proposed
revised Avinity I retention basin against Part 11 C criteria. First Amendment may serve as template for level
of plan detail (see CE Plan d. 4/14/14). Amendment to Approved Plan Application fee ($200) is required.
21. Relocate grate shown in dry swale #2 detail (sheet 6) to west end of swale as discussed 3 -Feb to help ensure
adequate filtration.
22. Sheet 6/SWM Facility A, routing -Outlet str. 4/weir INV =495.33 is inconsistent with profile Elev. Please
reconcile. Confirm routing results.
23. Sheet 6/Bioretention basin `A' profile -Label floor elevation (487') to aid review and construction.
24. Sheet 6 -Review Bioretention basin `A' plan view design against need for off-site construction easements.
Retaining walls cannot be constructed without positioning men or equipment on adjacent parcel (2' away).
25. Sheet 6 -Defer to Collins' design decision to construct swale 21.5' wide. Recommend ref. VA DEQ
Stormwater Design Specification No. 10 (4'-8' wide).
26. Sheet 7/Level 2 dry swale #1 detail: Swale as drawn is not 4'-8' wide at east end. Increase width.
27. Sheet 7/Bioretention basin `B' profile -Label floor elevation (486') to aid review and construction.
28. Sheet 7/Bioretention basin `B' profile -Show/label low -flow orifice: "with BMP debris cage."
29. Sheet 7/Level 2 Bioretention basin `B' -Provide defined SWM facility access. Provide smooth grade at a
distinct point to allow maintenance vehicles to exit Pebble Drive. Also, revise detail title (No filter strip).
30. Sheet 7/Level 2 Bioretention basin `B' plan view 55' notch inconsistent with profile view 25' notch;
reconcile.
31. Sheets 6, 7/13ioretention basin profiles -Provide Contech or Hanson trash racks, each riser.
C. VSMP: SWPPP: Erosion Control Plan (WPO201500057)
Virginia Code §62.1-44.15:55 requires the VESCP authority to approve or disapprove an ESCP. This plan is disapproved
for reasons provided in (limited) New comments below. The erosion control plan content requirements can be found in
County Code section 17-402.
1. Sheet 8 -Provide paved CE detail. (Rev. 1) Addressed.
2. Sheet 9 -Reconcile LOD =12.2 and 13.6 Ac. (Rev. 1) Addressed.
3. Sheet 9 -Remove Filter strip/ELS: do not show with ESC Plans. (Rev. 1) Addressed.
Engineering Review Comments
Page 4of5
4. Sheet 10 —Provide additional existing off-site contour elevation labels west and south of development.
(Rev. 1) Addressed.
5. Sheet 10 —Provide additional proposed contour labels. (Rev. 1) Addressed.
6. Sheet 9/10 —Filter strip: Add note "Prevent soil compaction by heavy equipment." [Spec. No. 2, Table 2.2.]
(Rev. 1) Addressed —filter strip removed from plans.
Sheet 11
7. SB-1/plan: Label floor dimensions (58' X 120'). (Rev. 1) Addressed.
8. SB-1/plan: Adequate space does not exist for 52 L exit channel. Revise design. (Rev. 1) Addressed.
9. SB-2/plan: Adequate space does not exist for 70 L exit channel. Revise design. (Rev. 1) Addressed.
10. SB-2/plan: Label floor dimensions (43' X 115') —provide full complement of dimensions required to
construct. Also, SWM item # 11. (Rev. 1) Addressed.
11. SB-2/plan: Remove Filter strip/ELS: do not show with ESC Plans. Add note: "Prevent soil compaction by
heavy equipment." [Spec. No. 2, Table 2.2.] (Rev. 1) Addressed —filter strip removed from plans.
12. SB -1/2 Design Tables, or profiles: Address riser anchoring per VESCH spec. 3.14, p. III -107. (Rev. 1)
Addressed.
13. SB -1/2 Design Tables, or profiles: Specify riser embedment in concrete base. (Rev. 1) Addressed.
14. SB -1 Design table: Revise depth of water at spillway crest. (=3.70') (Rev. 1) Addressed.
15. SB -1 Design table v. plan view emergency spillway bottom widths are inconsistent (41'v. 35'). Revise.
(Rev. 1) Addressed.
16. SB -2 Design table: Revise emergency spillway slope of existing channel. 3% should likely read 33%.
(Rev. 1) Addressed.
17. SB-2/profile: Bottom of basin must be at least V higher than floor of proposed SWM bioretention facility.
(Rev. 1) Addressed.
18. SB-2/profile: Delete extraneous rock weir label. (Rev. 1) Addressed.
New
19. Sheet 9 —Provide safety fence (SAF) between areas to be graded and TMP# 91-16A1+ to east and TMP#
90-35F/Pebble Drive to south.
20. Sheet 9 —Identify feature (appears to be riprap slope protection) at ends of 24" diversion berms.
21. Sheet 9 —Label 24" diversion berms with typical VESCH symbol, for comparison with ESC specification.
22. Sheet 10 —Recommend avoid dry swale locations during grading (avoid compaction); recommend SAF to
protect future SWM facility locations, and limit equipment trespass.
23. Sheet 10 —Install/show SAF at VDOT RW, Rt. 20.
24. Sheet 11/SB1, S132 profiles —Confirm Hanson Concrete Anti -vortex Trash rack (v. Contech StormRax).
Engineering is available from 2-4 PM on Thursdays for review meetings. Please call if any questions: 434-296-5832
—x3069.
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
Engineering Review Comments
Page 5 of 5
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 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 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;
htW://www.albemarle.orp-/deptforms.asp?dei2artinent--cdengno
Thank you -434.296-5832 —0069
File: WPO201500057 Avinity Estates VSMP-020516revl