HomeMy WebLinkAboutWPO201800088 Review Comments WPO VSMP 2019-02-20COUNTY 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:
Pantops Corner — VSMP
Plan preparer:
Justin Shimp, Shimp Engineering, 912 E. High Street
Charlottesville, VA 22902[iustin(a)shimp-engineering.com]
Owner or Rep:
Pantops Corner LC, 12704 Crimson Court, Suite 101; Henrico,VA 23233-7657
Plan received date:
30 Nov 2018
(Rev. 1)
22 Jan 2019
Date of comments:
28 Dec 2018
(Rev. 1)
20 Feb 2019
Reviewer:
John Anderson
WP0201800088
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
application may be resubmitted for approval if all comment items 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. Link to County template:
httn://www.albemarle.oriz/unload/imaees/forms center/demrtments/Community Develonment/forms/Eneineerine and
_WPO_Forms/Stormwater_Pollution _ Prevention_Plan _SWPPP template.pd
1. 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.'
SWM Plan
Note: if grayscale, comment addressed with (Rev. 1); no need for follow-up.
Calc. booklet
1. Revise post-dev POA drainage map, POA 1 Qloo-yr, 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.
Engineering Review Comments
Page 2 of 6
Plan
6. 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.
7. If underground detention system is a Mfr. system, provide Mfr. installation notes on plans.
8. If Mfr. system, include periodic maintenance and inspection guidelines on plans.
9. LD-229 indicates Q from A6 to A5 exceeds pipe capacity; revise design.
C3
10. Label proposed /existing easements.
11. 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.
12. Show /label Rt. 20 right-of-way.
C4
13. 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.
14. Provide storm line profile for these inlets. (Rev. 1) Addressed. `Wawa will provide.' Engineering accepts
this.
15. Provide storm line profile for A10 to Al OC.
16. Label proposed easements. (Rev. 1) Partially addressed. Asfollow-up: Show SWM Facility and Access
easement on C3, not C11. Also, see item #11, above.
17. Provide /label dimensions of underground detention system in plan view. For example, 5 lines at x.xx'.
C5
18. 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 A8A.
19. Need flow lines south of 3-space HC parking (preceding item) to ensure runoff reaches Str. A8A.
20. Provide inlet in corner of parking spaces immediately to right on entering Wawa site, to avoid ponding.
21. 0.0% flow line on parking surface north of building A is confusing. Provide positive grade at this location.
(Rev. 1) Comment withdrawn.
22. Provide several spot elevations at corners and inset corners of island positioned immediately above the
underground detention system.
23. C6: Applicant proposes to purchase K30 lb./phosphorus nutrient credits. Coordinate nutrient credit
purchase with Ana Kilmer, Albemarle County, prior to purchase (434.296-5832 x3246).
24. (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.
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'h" screen. (source:
hgp:HcWitolflexipave.com/wp-content/uploads/2012/08/AASHTO-57-Stone-Specs.pdf); ref. C11
Underground Detention Construction Notes/CMP Detention Notes #4.
d. Provide backfill detail /specifications for detention system. (Rev. 1) Detail 3-Cl 1: Show /specify
AASHTO M 43 Size 33 as backfill. #57 stone is ineligible backfill material, per Mfr. Note.
Engineering Review Comments
Page 3 of 6
(Ref C 11 Underground Detention Construction Notes/CMP Detention Notes #7. Source, image, below:
http:Hlaurelaggregates.com/aashto-3 )
MM
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-C 11, since 'h 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' space), or of model routing results using weir
plate R
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.
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. C11 Underground
Engineering Review Comments
Page 4 of 6
Detention Construction Notes/CMP Riser Note 9 alone is insufficient. Provide Notes and
�pecifications. 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.
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.
o. Show and provide SWM Facility and permanent drainage easements. (Rev. 1) Ref. comments
elsewhere.
p. Record all necessary easements prior to VSMP approval. (Rev. 1) Comment persists.
q. New: C 11 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.
* Link, Construction Record Drawing (As -built) requirements:
httn://www.albemarle.ore/unload/images/fonns center/deDartments/Community Develonment/forms/Eneineerin
_and _WPO_Forms/WPO_VSMP_Construction _ Record_ Drawings Policy 23May2014.pdf
C10
25. 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.]
26. Label MH structures requiring safety slab (ht. >12', Inv Out to RIM).
27. Provide safety slab detail.
28. Provide note /specification for'/z inch steel plate in bottoms of "step down" MHs with drops >4ft.
29. MHs in fill are susceptible to settling; request bedding/compaction Note for Str. B1A and B2. VDOT
language available.
30. 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.
31. Provide storm line profile: A1OC to A10.
C11
32. Provide bypass design for underground detention such that if orifices and weir are obstructed, storm lines
will not flood parking areas or streets.
33. 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
34. Weir plate detail: provide material type and weir plate thickness.
35. Also, please see item 24., above.
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.
Engineering Review Comments
Page 5 of 6
C. Erosion and Sediment Control Plan (ESCP)
Note: if grayscale, comment addressed with Rev. 1, with no need for follow-u .
Virginia Code §62.1-44.15:55 requires the VESCP authority to approve or disapprove an ESCP. This plan
is disapproved for reasons outlined, below. The erosion control plan content requirements can be found in
County Code section 17-402.
C6
36. Revise stage 4 (sequence) note 3 to require county inspector approval prior to removal of ESC measures.
37. Stormwater Management Note 3: revise 8.30 lb. qty. if Appx. 5D worksheet calculations alter nutrient
credit purchase estimate.
C7
38. Provide soil stabilization blanket at SW corner of Trap 1 at point of diversion dike discharge, to limit trap
embankment erosion.
39. Show break in SAF at PCE, Rt. 20.
40. Dimension and label riprap outfalls (L x W x D), Trap 1, Trap 2, plan view. (Rev. 1) Label depth of riprap.
C8:
41. Provide IP, Str. A9
C9:
42. Check value B, sediment trap design data, Trap 1.
43. C2: Provide bk.-pg. ref. and parcel owner name, parcels under development and adjacent parcels.
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.
Prncp%%
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. 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 may issue a modified or
revised permit coverage letter. This should be copied to the county.
Easements must be recorded prior to VSMP approval. Proof of purchase of nutrient credits is required to receive a
Engineering Review Comments
Page 6 of 6
Grading Permit.
After DEQ coverage is issued, 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;
hqp://www.albemarle.orgJdeptforms.asp?department=cdeng3Wo
Ifyou have questions or concerns, please contact me at janderson2((&albemarle.org or at 434.296-5832 ext.
3069.
Thank you.
J. Anderson, Engineering Division
WPO201800088 Pantops Corner 022019rev1