HomeMy WebLinkAboutWPO201800088 Review Comments WPO VSMP 2019-06-26Phone (434) 296-5832
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COUNTY OF ALBEMARLE
Department of Community Development
401 McIntire Road, Room 227
Charlottesville, Virginia 22902-4596
VSMP Permit plan review
Project title: Pantops Corner — VSMP
Project file number: WP0201800088
Plan preparer:
Shimp Engineering
Owner or rep.:
Pantops Corner LC
Plan received date:
Nov 30, 2018
Jan 22, 2019
Apr 15, 2019
May 31, 2019
Date of comments:
Dec 28, 2018
Feb 20, 2019 (Rev. 1)
May 20, 2019 (Rev. 2)
June 26, 2019 (Rev. 3)
Reviewer:
John Anderson (Rev. 1,3)
David James (Rev. 2,3)
Fax (434) 972-4126
[keane@shimp-engineering. com]
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Janderson2(& albemarle. org
Di ames2(c�r�,albemarle. org
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. 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.
List named individual/s responsible for pollution prevention practices (Sec. 6E), and list named individual
as Qualified Personnel, Sec. 8.
Note: SWPPP cannot be approved unless responsible individuals are listed. (Rev. 1) Comment persists.
Applicant response: `This is still being determined pending the site bid process. This information will be
shared when determined, until then we understand this may be a repeat comment.' (Rev.2) Addressed.
B. Pollution Prevention Plan (PPP)
The PPP content requirements can be found in County Code section 17-404.
1. See A /Sec. 6 comments, above. List named individual, Sec. 6.E. (Rev. 1) Comment persists. (Rev.2)
Addressed.
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.
Calc. booklet
1. Revise post-dev POA drainage map, POA 1 Qloo-,, 67.28cfs, consistent with HyrdroCad routing for this
event (101.74cfs).
2. Revise and re -run postdev (detention system) routings using: primary device # 1 Invert Elev. =353', L
=47.25', slope=6.77%, and device #2 as 7.3" DIA orifice, not 7.3" vert. orifice/grate, unless this
designation is proper, and properly models hydraulics of a round orifice.
3. Revise detention system design as needed to ensure post-dev Q2, Qio peaks are < pre -development rates.
4. Copy LD-229 to plans.
5. Pantops Corner Worksheet 1 (water quality, VSMH, Vol. II, Appx. 5D) math is inaccurate. Post -
development impervious totals 6.85 Ac., not 5.11 Ac. Revise nutrient purchase estimate (lb.), if necessary.
6. (Rev.2) The calcs show Device #5 as a 8.0' long x 3.00' rise Sharp -Crested Rectangular while the plans,
detail 4/C16, show it as 8.0' x 2.28'. (Rev.3) Addressed.
7. (Rev.2) Provide analysis on how the Undetained Areas are meeting water quantity compliance.
a. Your pre -development D.A. map shows a total of 6.21 ac. Show/Account for the additional area(s)
of site (7.15 - 6.21 = 0.94 ac) and where runoff goes (POA 3?, etc.). Include this area(s) of
analysis in the pre-dev. HydroCAD model.
(Rev.3) Addressed. Applicant response: `All development area added to predev DA map.
Predev DA slightly revised per request to include drainage from areas outside the boundary line.'
b. Show/Account for area(s) of undetained runoff from site (7.15 - 5.93 = 1.22 ac) on the post -
development map and show POA. Include this area(s) of analysis in the post-dev. HydroCAD
model.
(Rev.3) Partially addressed. Applicant response: `All development area has now been accounted
for. The sheetflow runoff from the back of the property has been added to POA 1 in the maps and
HydroCAD model. The runoff at the front of the property has been added to the maps. Since this
front runoff discharges into the Rivanna River, where it meets the 1 % rule, this area's analysis is
covered in the Rte. 250 inlets section which demonstrates that the system contains the 10-year
storm. Please note that the 7.25 acre limits of disturbance is not the governing area for stormwater
analysis, as portions of existing land cover within the limits of disturbance will not be changed.
For example, the area within the current Rte 250 and Ret 20 road pavement, the area where the
rip -rap outfall will be improved, and the area near the retaining wall on parcel 5C. These areas are
included in the limits of disturbance, as the contractor will need to operate construction vehicles in
these areas but will not alter the land cover of these locations. Instead, we will provide quality and
quantity treatment for the development area which includes the onsite area plus the area of right-
of-way improvements. This area is 6.82 acres and complies with water quality and quantity
requirements.' As follow-up: Provide narrative details for Ex. Rte. 250 Str. 7-18P and 84P, since
LD-347, Hydraulic Grade Line, C11, indicates Inlet WSE < 2" below rim. If Str. are MH, energy
lines indicates 10-yr. event is contained. If these structures are drop inlets, WSE appears to be
higher than paved surface elevation at DI throat (and storm runoff would exit, not enter, DI).
Plan
8. Revise 0.0% detention system slope to ensure positive grade to weir. 0.0% invites debris accumulation,
obstruction, pooling, even negative slope, without care. Ensure 0.25 -0.50% slope, high end to low end. If
a manufactured system and Mfr. recommends 0% slope, provide written recommendation to that effect.
9. If underground detention system is a Mfr. system, provide Mfr. installation notes on plans.
10. If Mfr. system, include periodic maintenance and inspection guidelines on plans.
11. LD-229 indicates Q from A6 to A5 exceeds pipe capacity; revise design.
12. (Rev.2) Provide stormwater inlet design [LD-204]. (Rev.3) Partially addressed. Asefollow-up: Ref. item
7.b., above, concerning Ex. Rte. 250 structures 7-18P and 84P.
13. (Rev.2) Provide Stormwater Narrative on plans.
a. State how you meet Water Quality Compliance & Show Letter of Availability from nutrient credit
bank.
b. State how you're meeting Water Quantity Compliance for the site.
(Rev.3) Addressed.
C3
14. Label proposed /existing easements.
15. SWM facility access easement appears discontinuous. Revise for clarity. (Rev. 1) Partially addressed. As
follow-up: Please show SWM Facility and Access easement on C3, not C11. Also, provide SWM facility
easement width based on smallest of: CI I Underground Detention Construction Notes/CMP Detention
Notes #1, 2, and Albemarle County Design Standards Manual easement width diagram, pg. 15. (Rev.2)
Addressed.
16. Show /label Rt. 20 right-of-way.
17. (Rev.3) Show disturbance outside of property line in an easement. Note: Retaining Wall Construction
/Maintenance Easement and Access Easement Agreement at bk.-pg. 4553-473 substantially addresses
(never issued) review comment. Also, off -site easement requirements will be addressed via easement plat
(under review); ref. CDD file SUB201900059, Pantops Corner. No WPO plan revision required.
C4
18. Label inlets (assign IDs) located in Wawa Pantops parking lot. (Rev. 1) Addressed. Sheet C4, Plan Note:
`Storm sewer on TM 78-5A to be designed under Wawa Site Plan. This VSMP Plan covers the conveyance
and treatment of runoff from Parcel TM 8-5A but not the storm sewer design for this parcel.' Engineering
accepts plan note.
19. Provide storm line profile for these inlets. (Rev. 1) Addressed. `Wawa will provide.' Engineering accepts
this.
20. Provide storm line profile for A10 to AIOC.
21. Label proposed easements. (Rev. 1) Partially addressed. As follow-up: Show SWM Facility and Access
easement on C3, not C11. Also, see item #11, above. (Rev.2) Addressed.
22. Provide /label dimensions of underground detention system in plan view. For example, 5 lines at x.xx'.
23. (Rev.2) Show proposed roof drains from buildings and where they connect to. (Rev.3) Addressed.
Applicant response: `Downspouts are anticipated where roof drains are not shown. The planned roof drain
locations are shown for the self -storage building on parcel 5E.'
C5
24. Provide spot elevations to ensure runoff does not pool on parking surfaces, near contour 393', Wawa
Pantops parking lot (5-space parking at N end Wawa site). Also, A8A rim elev=380.50, while spot
elevations on C5 show identical elevation in near vicinity (3-space HC parking). Provide flow lines or
additional spot elevations to ensure runoff reaches inlet ABA.
25. Need flow lines south of 3-space HC parking (preceding item) to ensure runoff reaches Str. ABA.
26. Provide inlet in corner of parking spaces immediately to right on entering Wawa site, to avoid ponding.
27. 0.0% flow line on parking surface north of building A is confusing. Provide positive grade at this location.
(Rev. 1) Comment withdrawn.
28. Provide several spot elevations at corners and inset corners of island positioned immediately above the
underground detention system.
29. C6: Applicant proposes to purchase 8.30 lb./phosphorus nutrient credits. Coordinate nutrient credit
purchase with Ana Kilmer, Albemarle County, prior to purchase (434.296-5832-0246).
(Rev.2) Nutrient credit agreement required prior to VSMP plan approval.
(Rev.3) Comment persists in revised form: 8.49 lb cr. required prior to issuing grading permit.
30. (Also, items 7, 8, above) (Rev. 1) Partially addressed. As follow-up:
a. Provide level of design detail required to prepare an As -built Construction Record Drawing. (Rev.
1), see c, d, i, k, m.-q., below. (Rev.2) Addressed.
b. Place Construction Record Drawing (As -built) for VSMP* on SWM Plan sheet.
c. Provide bedding detail /specifications for detention system. (Rev. 1) Confirm corrugation height>
1". If > 1", VDOT 57 stone is acceptable, since 25-60% #57 stone passes'/2" screen. (source:
http:Hcapitolflexipave.com/)Mp-content/uploads/2012/08/AASHT0-57-Stone-Specs.pdf); ref. C11
Underground Detention Construction Notes/CMP Detention Notes #4. (Rev.2) Addressed.
d. Provide backfill detail /specifications for detention system. (Rev. 1) Detail 3-C11: Show /specify
AASHTO M 43 Size 33 as backfill. #57 stone is ineligible backfill material, per Mfr. Note.
(Ref. C 11 Underground Detention Construction Notes/CMP Detention Notes #7. Source, image,
below: htt2://Iaurelaaareaates.com/aashto-3 )
C
MEN
(Rev.2) Addressed.
e. Provide recommended installation guidelines, if a manufactured system.
f. Provide construction installation, and construction inspection notes on the plans.
g. Provide manufacturer recommended periodic inspection guidelines and frequency, on the plans.
h. Provide and label all access ways to the underground system.
i. Ensure access is possible to all portions of the underground system. (Rev. 1) Revise design such
that 2' wide side of weir is accessible to maintenance personnel, not simply a camera. At present,
access to the 2'-w side of weir is via 17' deep /high MH, and 30" HDPE pipe. It is imperative that
maintenance checks that may reveal deficiency (requiring access) allow access other than by a 30"
DIA pipe, to the outlet side of the weir. Engineering recommends provide at least 3' space, which
is still narrow and quite confined (see generic web -image, below).
Data: If upturned portion of elbow were to extend as a circular shape to INV elev. 353.00', then
lost volume by shifting weir plate to allow 3' as opposed to 2' space behind the weir = 39.014 ft3.
Actual lost volume is less, given curved floor of typical CMP detention elbow (ref. image).
Engineering advises work with detention manufacturer to compensate for actual lost volume such
that 10-yr event does not overtop (top of weir) elevation. A 0.776' length (-9 in.) of 8' DIA CMP
z 39 ft3. Also: revise weir plate detail, 4-CI 1, since'/z weir plate width =3.46' (not 4') at
proposed position, or 3.87' at recommended position, with curve radius = 4' only at the bottom.
Albemarle cannot disregard effect of accurate dimensions, of shifting weir plate (to allow 3'
is an inaccurate
(Rev.2) Addressed.
j. Provide installation notes for weir plate; if MH-weir plate is fabricated prior to delivery,
state this.
k. Provide orifice debris cage/s. (Rev. 1) Provide detail for debris cage. (Rev.2) The side and top
views do not appear to correlate with the isometric view. (Rev.3) Comment persists. Revise
front, bottom, top 2-dimensional orifice sections, as needed; appear inconsistent with isometric.
1. Ensure orifice debris cage is accessible for periodic maintenance.
in. General Note for SWM Plans #2 requires pipe and riser joints to be watertight. Provide detailed
notes and specifications for joints, as needed. (Rev. 1) Comment restated. CI I Underground
Detention Construction Notes/CMP Riser Note 9 alone is insufficient. Provide Notes and
specifications. Also:
i. CMP Riser Note 4 appears to mandate slip joints.
ii. Provide Mfr. installation guidance for slip joints.
iii. Provide slip joint detail on plans.
Depth from finished grade to base of stone bedding is 25'.
Quality of installation is a high priority.
(Rev.2) Addressed.
n. Provide step detail. Review design to ensure no conflict between steps and weir plate. (Rev. 1)
Provide additional profile detail of access riser w/ladder, with ladder steps continuing as needed,
per Mfr. guidance, to allow safe county inspection, or maintenance access to floor of the system.
If steps end at ceiling, personnel cannot access proposed 8' DIA system. Provide schematic detail.
(Rev.2) Addressed.
o. Show and provide SWM Facility and permanent drainage easements. (Rev. 1) Ref comments
elsewhere. (Rev.2) Rename easement labels from `NEW SHARED PRIVATE SWM ESMT' to
`NEW SWMESMT' or similar and include all outfall pipe/structures (A4 to Al) in the easement.
(Rev.3) Addressed.
p. Record all necessary easements prior to VSMP approval. (Rev. 1) Comment persists. (Rev.2)
Comment still valid. (Rev.3) Comment persists (SUB201900059 under review).
q. New: C11 Underground Detention Construction Notes/CMP Detention Notes 8 and 10 point
to information not shown on plans. Provide table (Note 8 and final backfill material
specifications (Note 10 . Also: CMP Riser Note 7 states `Manhole risers in applications
where traffic loads are imposed require special design considerations.' Provide evidence
that design addresses special MH design considerations, since six of seven detention system
MHs are located in traffic areas.
(Rev.2) Addressed.
r. (Rev.2) Provide an underdrain across facility bottom. -Must insure system will drain properly.
(Rev.3) Withdrawn. Applicant response: `Per engineering meeting on 5/23/19, we agreed that an
underdrain is not necessary. We have not designed the stone bed under the pipes to provide
storage and have excluded the stone bed under the pipe invert from the storage area in the
HydroCAD model. Any water within the stone bed under the pipe invert will eventually soak into
the underlying soil. All water above the invert will drain thru the 7.5" orifice.' Engineering
accepts this position /meeting note.
31. . Note: Ref. item 17., above.
* Link, Construction Record Drawing (As -built) requirements:
http://www.albemarle.orgLupload/ima2es/forms center/departments/Community Development/forms/Engi
neering_and _WPO_Forms/WPO_V SMP_Construction_Record_ Drawings_ Policy_23May2014.pdf
CIO
32. Provide note for steel plates in MH with fall >4ft., per VDOT Drainage Manual (please call if questions).
[Initial comments VDOT Drainage Manual image removed.]
33. Label MH structures requiring safety slab (ht. >12', Inv Out to RIM).
34. Provide safety slab detail.
35. Provide note /specification for''V2 inch steel plate in bottoms of "step down" MHs with drops >4ft.
36. MHs in fill are susceptible to settling; request bedding/compaction Note for Str. B IA and B2. VDOT
language available.
37. Provide profile for inlets /pipes on Wawa site. Revise LD-229 to include these inlets, once labels assigned.
(Rev. 1) `Wawa designer swill provide these in their final site plan.' Engineering accepts this statement.
38. Provide storm line profile: A1OC to A10.
C11
39. Provide bypass design for underground detention such that if orifices and weir are obstructed, storm lines
will not flood parking areas or streets.
40. A cross-section of the UG system is provided, but not a profile. Provide underground detention system
longitudinal profile showing: (Rev. 1) Request restated: show detention barrel lines 2, 3, 4, 5, 6, and 7 in
profile. Ref. items b, c, d, below.
a. Slope
b. High end invert elevation, if slope
c. Low end invert elevation, if slope
d. Manway access with safety slab (Rev. 1: overall ht. finished grade to floor system > 12-ft.)
e. Bedding material and depth
(Rev.2) Addressed.
41. Weir plate detail: provide material type and weir plate thickness.
42. Also, please see item 24., above.
C12
43. (Rev.2) Show design storm elevations at the weir plate. Show invert elevation of 15" orifice end of UD
system. - Detail 5/16. (Rev.3) Addressed.
44. (Rev.2) Add MH access to UD system at A4 end just before weir plate. (Rev.3) Addressed.
A 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.
C6
1. Revise stage 4 (sequence) note 3 to require county inspector approval prior to removal of ESC measures.
2. Stormwater Management Note 3: revise 8.30 lb. qty. if Appx. 5D worksheet calculations alter nutrient
credit purchase estimate.
C7
3. Provide soil stabilization blanket at SW corner of Trap 1 at point of diversion dike discharge, to limit
trap embankment erosion.
4. Show break in SAF at PCE, Rt. 20.
5. (Rev.2) See comment 11 below. (Rev.3) Addressed.
6. Dimension and label riprap outfalls (L X W X D), Trap 1, Trap 2, plan view. (Rev. 1) Label depth of
riprap. (Rev.2) Addressed.
C8
7. Provide IP, Str. A9
8. (Rev.2) Provide low maintenance ground cover (not grass) for any grades proposed steeper than 3:1.
(Rev.3) Addressed.
C9
9. Check value B, sediment trap design data, Trap 1.
C2
10. Provide bk.-pg. ref. and parcel owner name, parcels under development and adjacent parcels.
11. (Rev.2) Existing riprap channel is in disrepair due to lack of adequate riprap. Replace riprap in channel
leading to stream. Show riprap replaced on sheet C7.
(Rev.3) Addressed.
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 (or revise) 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--cdengMo
WPO201800088 Pantops Corner 062619rev3-dj ja