HomeMy WebLinkAboutWPO202000005 Review Comments WPO VSMP 2020-06-05COUNTY OF ALBEMARLE
Department of Community Development
401 McIntire Road, Room 227
Charlottesville, Virginia 22902-4596
Phone (434) 296-5832 Fax (434) 972-4126
Project:
Project file#:
Plan preparer:
Owner or rep.
Plan received date:
(Rev. 1)
(Rev. 2)
(Rev. 3)
Date of comments:
(Rev. 1)
(Rev. 2)
(Rev. 3)
Reviewer:
VSMP Permit Plan Review
Boys and Girls Club, Northside — VSMP
WP0202000005
Kim Mellon, PE II, Timmons Group — kim.mellonAtimmons.com
Craig Kotarski, PE, Timmons Group — 608 Preston Ave, Suite 200,
Charlottesville, VA 22903 [craig.kotarski(a-)timmons.com ]
Boys and Girls Club, 1000 Cherry Ave., Charlottesville, VA 22903
[ jpierceLbeclubcva.org ]
22 Jan 2020
7 Apr 2020; ESCP only digital (email, A. Allison, April 7, 2020 12:57 PM)
20 Apr 2020 [ digital /Laserfiche ]
5 May 2020
6 Mar 2020
11 Apr 2020
23 Apr 2020
5 Jun 2020
John Anderson
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: two
new ESC comments; SWPPP updates /SWPPP reduced -size inserts; Calc. booklet update; need to record
SWM facility easement plat. 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.
1. Sec. 1, Registration Statement is incomplete. Complete Sec. I as condition of VSMP /WPO plan approval.
(Rev. 2, 3D Persists. Applicant: `TBD'
a. Sec. IV, E., (MS4); Please leave blank. (Rev. 2) Addressed.
b. Sec. VI, Certification: Please complete (print name, sign, date). (Rev. 2,1) Persists. Applicant: `A
signed certification will be provided once a contractor is chosen.'
2. Sec. 4, 5: Update these sections with revised ESC and SWM plan sheets, once comments are addressed.
(Rev. 2, �) Persists. Applicant: `Reduced ESC and SWM plan sheets have been provided.' Rev. 3
Engineering uncertain that reduced sheets are provided; please send .PDF, or link to reduced sheets.
3. Sec. 6.A. / Exhibit: Indicate location rain gauge. (Rev. 2) Addressed.
4. Sec. 6.E. — List named individual responsible for pollution prevention practices prior to VPDES permit
registration. (Rev. 2, D Persists. Applicant: `This will be provided once a contractor is chosen.'
5. Sec. 8. — List named individual qualified to perform compliance inspections. (Rev. 2,1) Persists.
Applicant: `This will be provided once a contractor is chosen.'
6. Sec. 9., Signed Certification: Individual who prepared SWPPP document must sign as condition of VSMP
/WPO plan approval. Also, Albemarle cannot register project with DEQ until SWPPP Sec. 9 is complete.
(Rev. 2, �) Persists. Applicant: `Acknowledged. A signed certification will be provided prior to
Engineering Review Comments
Page 2 of 7
VSMP/WPO plan approval.'
7. Include 2019 Notice of Termination form. Link:
http://www.albemarle.org/upload/images/forms_center/departments/Community Development/forms/Engineering and
_WPO_Forms/CGP Notice of Termination 2019_FINAL 201904.pdf (Rev. 2) Addressed.
8. Revise SWPPP title to include ref. to VSMP /WP02020-00005. (Rev. 2) Addressed.
B. Pollution Prevention Plan (PPP) — See above. (Rev. 2,1) Persists. See A.4. (SWPPP Sec. 6.E.),
above. 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 forfollow-up items 1, 2, below. The stormwater management plan content requirements
can be found in County Code section 17-403.
1. Easement Plat is required for SWM Facilities (SWM1, SWM2), SWM Facility Access, and Public drainage
easements downslope of SWM facilities. (Rev. 2,1) Persists. Applicant: `Easement plat will be provided
in a future submission.'
2. C6.2 (Channel protection) Energy Balance Equation should use pre -developed Analysis point 1 combined
drainage areas 1 + 2 values (4.66 cfs, 3 7,8 10 CF), which represent technical estimate of channel energy at
Point of Analysis 1 based on pre -developed DA characteristics. Engineering is unaware of rationale that
allows portion of pre-dev runoff to be excluded from the calculation, then added at the end. Doing this has
effect of increasing Qosst-dev 1-yr peak Allowable. Engineering believes the correct approach is to calculate using
combined values, which yields: Q post 1-yr peak Allowable = I.F. X Q pre (1-yrpeak) X Rv pre /Rv post. Or, Ql_yr
Allowable = 0.8(4.66cfs)(37,810cf) /37,810cf = 3.73 cfs. It appears design relies on calc. value (4.44cfs)
z 19% > if using combined drainage areas 1 + 2, while routings indicate Q1-, peak post-dev =4.21 cfs, a value
z13% higher than Q1-year peak post-dev• Please review /revise Energy balance calculation, as needed. (Rev. 2)
Withdrawn: review error but please see related follow-up, below. Applicant: `Pre -developed analysis point
1 combines pre -developed drainage area 1, which is onsite water, and pre -developed drainage area 2, which
is offsite water. As a result, drainage area 1 (onsite) is used within the energy balance equation, and the
reduction factor of 80% is applied to this portion of the water. Drainage area 2 (offsite) is then added to the
energy balance equation separately; this is so that the reduction factor is not applied to the offsite drainage.
The total of these two quantities then becomes the Qpre-developed for the project. This rationale has been
utilized and approved on various projects within Albemarle County, including WP0201800030 and
WP0201900010. We are happy to discuss further if there are remaining questions about the stormwater
scheme for this project.' As follow-up: Revised grade downslope of post -developed drainage Area 213 is
sheet flow, with revised grading. This flow does not concentrate until flat slopes undisturbed by project
grading give way to, and intersect, a defined drainage feature (see blue arrows, below). This sheet flow
does not reach Ditch C or SWM2 (C5.0). DA Area 213 is excluded from stormwater considerations by
virtue of proposed grade. It appears Qpre-post (DA Area 213) has no place in pre- or post -development
calculations. Timmons may find that proposed design of SWM2 is more conservative than anticipated.
Engineering requests: (Rev. 3) Addressed. Applicant response: `Area 213 has been removed from the
stormwater analysis in both the pre- and post -developed conditions. The calculations have been rerun and
updated on Sheet C6.2 and within the calculation book.' Asefollow-up: Please provide .PDF or link to
updated calculation booklet.
a. If SWM2 design proves adequate /more conservative, provide Notes only on C6.2 explaining that
DA Area 213:
i. Persists as relic of initial design; shown to minimize revision effort with county approval.
ii. Is not required to be shown, and including Area 213 has conservative effect on SWM2
design.
iii. Is included in SWM2 detention /capacity calculations, though not required to be included.
iv. Runoff is routed, though runoff from DA Area 213 will not actually reach SWM2.
b. If SWM2 design proves inadequate once DA Area 213 is excluded (from routing, energy balance,
quantity, or SWM2 detention capacity calculations), then
i. Revise calculations /routings.
ii. Revise design of SWM2 (ensure adequate).
Engineering Review Comments
Page 3 of 7
iii. Revise Analysis point 1 Q pre- /post calculations.
iv. Revise Energy balance equation, which includes DA Area 2B.
v. Revise calculation booklet.
Note: Engineering cannot predict effect of excluding DA Area 2B, but notes that: pre- _
post -developed condition (Area 2B); Qpre- /post values appear identical; Area 2B land cover
and topography are unaffected by project; and DA Area 2B runoff (once concentrated by
existing defined drainage beyond limits of project) discharges below Analysis Point 1.
C6.2 [image removed with Rev. 3 comments.]
C4.0 [image removed with Rev. 3 comments.]
C3.5: ADD separates Area 2B clean (off -site) water from Area 113 site (sediment -laden) runoff [image
removed with Rev. 3 comments.]
3. Alternatively, offsite runoff that transits site may rely on piped conveyance that bypasses the site entirely,
and does not compromise compliant calculation (Energy balance equation) at Analysis Point 1. (Rev. 2)
Withdrawn, but see SWMP item 2, above, since aspects of calculation -related comment at item 2 may be
relevant /persist.
4. Related: Post-dev (Analysis Point 1) Rv is given as 37,810 cf, which is identical with pre -developed Rv.
As forest is generally converted to post-dev site with 2.83 Ac. impervious cover, if Rv pre = Rv post =
37,810cf (i.e., values accurate) please explain. Else recalculate Q1-yrpeak Allowable, post-dev, using revised Rv-post.
Revise detention system /SWM facility design, if needed. (Rev. 2) Addressed. Also, SWMP item 2, above.
5. Provide profile views of each 96" DIA detention system; include elevations for: (Rev. 2) Partially
addressed. As follow-up: Snippets of SWM1, SWM2 visible in storm profiles are partial, and insufficient.
(Rev. 3) Addressed.
a. Base elevation of bedding stone,
b. Base of 96" pipe [ incl. 0.15% slope, consistent with Hydrocad routings],
c. Top of 96" pipe,
d. Depth of select fill above pipe,
e. Proposed grade above each system (in profile view/s, several spot elevations along L of pipe)
6. If underground detention is a Mfr. system (ADS, Contech, etc.), please include Mfr. recommended
installation and construction inspection guidelines on the plan. Please also include periodic maintenance
inspection guidelines on the plan (Mfr., or otherwise). (Rev. 2) Partially addressed. As follow-up: Partial
system are shown on C6.3, C6.4 (Lane, SWM 1, 2) and C6.2. Technical installation notes provided. Please
furnish periodic inspection and Lane mfr.-recommended maintenance procedures on the plans. (Rev. 3)
Addressed.
Also:
a. Provide trash rack details and mounting details for 10", 8", and 4" DIA weir plate orifices. (Rev.
3) Addressed.
b. Revise SWM1 10" orifice inv. Elevation, which appears to be 3'-7" above 8' DIA pipe invert, or
at 527.58'. (Rev. 3) Addressed.
7. Include Albemarle county guidance document found at:
http://www.albemarle.org/upload/images/forms center/departments/Community_ Development/forms/En ing eerin
g_and _WPO_Forms/WPO VSMP Construction Record Drawings Policy 23May2014.12df titled Construction
Record Drawings (As -built) for VSMP on the VSMP /WPO plan. (Rev. 2) Addressed.
8. Revise plan set title to include ref. to VSMP /WP02020-00005. (Rev. 2) Addressed.
9. Easement plat must be recorded prior to VSMP /WP02020-00005 approval. (Rev. 2, 2) Persists. Applicant
acknowledges. (Rev. 3) Applicant response: `An easement plat will be provided in a future submission and
recorded prior to VSMP /WPO approval.'
New
(Rev. 2)
10. WP0202000005 proposes 4.87 lb. nutrient credit purchase to meet stormwater quality compliance
requirements. Please coordinate nutrient credit purchase documents with Ana Kilmer prior to purchase to
avoid duplicative effort, or delay (Ana Kilmer, Analyst, 434.296-5832-x3246, akilmergalbemarle.org ).
(Rev. 3) Persists. Applicant response: `A letter of credit availability has been provided on Sheet C6.2.
Engineering Review Comments
Page 4 of 7
Purchase of nutrient credits will be coordinated with Ana Kilmer.'
11. Please provide identical notes on at least one ESC, at least one grading, and at least one spot -grade plan
sheet. (Notes need not appear on the FSP.) Notes should state: (Rev. 3) Addressed.
a. Contractor will flag limits of critical slopes to be disturbed with survey ribbon or stakes prior to
disturbance of critical slopes.
b. Contractor will flag limits of critical slopes to be preserved with survey ribbon or stakes prior to
disturbance of critical slopes.
c. Contractor is to notify Albemarle County inspector /provide opportunity to review limits of critical
slopes prior to disturbance.
d. Contractor must maintain ribbons or stakes that delineate critical slopes not to be disturbed, for the
duration of the project.
e. Pre -construction staked/flagged limits of critical slopes to be disturbed need not be maintained,
once slopes are disturbed.
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 approved once revised in response to single follow-up, item 12, below. (Rev. 3) This plan can be
approved once revised to address new items 21, 22, below.
C3.0 — (Rev. 1) C3.0 comments Addressed.
1. As condition of Engineering support of 0.45 Ac. critical slope impact (waiver request; e-mail to Timmons
/Developer, 2/28/2020 8:59 AM), and Engineering support of a revised estimate of z0.60 Ac. impact to
critical slopes (incl. storm line crossing critical slopes; 3/5/2020 11:09 AM), please note that comments,
below, or request to revise the ESC plan may not be limited to initial review or follow-up review comments
but may also include ESC inspector directive (a circumstance already assured by VPDES permit) to deploy
additional control measures that may be needed or evaluated necessary to limit impacts to critical slopes.
2. Revise sequence to accommodate additional requested (Phase II-b) ESC Plan measures; see below.
ST3 with bottom trap dimensions = 4' X 178' are so narrow that, although wet /dry storage volumes are
provided, they are not available. The trap is equivalent to a 178' flat channel, 4' wide. Sediment -laden
runoff will reach ST3, lose velocity and particles will settle in portions of the trap nearest the diversion trap
inlets at either end. ST3 will short-circuit; this design cannot be approved. Revise design to activate a
broader -width sediment trap; consider, for example, a series of smaller traps moving downslope, each more
conventionally shaped and receiving reduced LOD runoff, removed once no longer needed. ST3 is a linear
ST proposed in Phase I, yet is at the very outer limit of eventual site disturbance, but it appears that a trap at
this location could be delayed if smaller, successive areas are cleared via phased grading. (Note: It is rare
for Engineering to recommend phasing or specific locations of ESC measures, but given Critical Slopes
Waiver, a conservative least -impact design approach to minimize critical slope impacts is crucial.)
Please confirm ST1 dry vol. vs. elevation values. It appears that wet volume (depth =3') and dry volume
(depth =1.5') with 2:1 side -slopes are not equal, though reported equal. Dry volume (Vol. above base of
weir), if calculated, appears ='/z wet volume (1.5' v. 3') + (6' X 6' x 1.5' + 1/3 (1.5' X 6' X 6')) (2°d term
—Vol. pyramid /corners; 1st term —additional distance dry volume shifts outward /2:1 side -slopes), or''/z wet
+ 2.66 cy; or ('/2 wet Vol.) —72.35 cy + 2.66 cy z 75 cy. There is some discrepancy between listed dry vol.
—144.7 cy and value derived using elevations and 2:1 wet /dry volume side slopes. Please ensure reported
design ST1 wet -dry Vol. is sufficient and consistent with proposed grading and ST typical detail elevations.
5. C3.1: Provide paved construction entrance detail.
C3.2:
6. Let SAF be discontinuous across CE, unless gated. If gated, please include SAF gate label. (Rev. 1)
Addressed.
7. Label floor dimensions, L X W, each sediment trap (ST). (Rev. 1) Addressed.
8. Include L X W X D dimensions for all weirs, and riprap outfalls. Applies to other sheets, as well. (Rev. 1)
Addressed. Asfollow-up, please see email sent 4/11/2020 7:55 PM, email item 1. (Rev. 2) Addressed.
Note: Timmons' (Rev. 2) 4/20/20 comment response letter addresses all four (4) 4/11/20 e-mail items.
Engineering Review Comments
Page 5 of 7
9. C5.0, C5.1, C5.2, C5.3: Label proposed 2:1 fill slopes. Specify Landscape Plan that includes partial
reforestation of slopes, and stabilization of slopes steeper than 3:1 with vegetation hardier than grass.
Species and plant qty. require bond. (Rev. 1) Comment persists. Also, 4/11/2020 7:55 PM email, item 4.
(Rev. 2) Addressed.
10. Show and label critical slopes across all plan sheets that show LOD, ESC measures, or improvements.
(Rev. 1) Addressed.
11. C3.3, C3.4, C5.2 (ST1): (Rev. 1) Addressed.
Silt fence alone is insufficient given proposed extent of 2:1 fill slopes, and vertical interval. At a minimum,
provide reverse slope benches (permanent feature) with corresponding contour lines labeled to clearly
convey design intent. At base of proposed 2:1 slopes, provide intermediate sediment trap, ESC Plan Phase
IIIIb (once ST1 is removed) to intercept sediment -laden runoff from proposed 2:1 slopes at base of slope.
Blue -circles indicate vulnerable 2:1 slopes that may degrade quickly without reverse slope benches. Even
with reverse benches, there is potential for sediment -laden runoff that merits trap as an intermediate
perimeter measure to help limit impact to critical slopes SW of basketball court. Trap should be sized for
DA and removed with county ESC inspector approval once all upslope areas (2:1 fill slopes) are stabilized.
(C3.3, C3.4, C5.2, below) [ Images removed with Rev. 2 comments.]
C3.3, C3.4, C5.0 (ST2): Provide intermediate sediment trap, ESC Plan, Phase II-b, once ST2 removed and
Ditch C installed to intercept sediment -laden runoff prior to Str. 704 (grate); IP alone is insufficient inlet
protection given disturbance required to construct the play field 2:1 embankments, and to remove ST2 —
images, below; blue -circle area (3rd image) is a possible small trap location. Once Ditch C and play field
embankments are stabilized, this small trap should be removed, with county approval:
(C3.3, C3.4, C5.0, below) [ Images removed with Rev. 2 comments.]
12. C3.3, C3.4, C5.2 (ST3):
Similar to previous items, provide intermediate ESC measure/s between C3.3 and C3.4 until proposed 2:1
slopes on critical slopes are stabilized. Consider 2-layer protection (dash lines). Consider wire -backed SF.
Permanent reverse slope benches are required. Consider small traps at strategic points, and trap removal.
It is imperative to limit impacts to or across critical slopes. It is insufficient to remove ST3 without
intermediate ESC measure/s in place. Further, Engineering encourages a plan view of development,
intermediate to partial site grading shown in Phase II and final build out depicted in ESC Plan Phase III.
For example, it may be possible to retain ST2 and ST3 with diversion dikes while parking areas are graded.
Engineering encourages design to retain ST2 and ST3 as long as possible, prior to removal. (0.0 Phase II
Sequence appears to suggest building pad elevation can be constructed prior to ST2, ST3 removal.) Also,
please note need to disperse concentrated ditch runoff via level spreader (or similar) for channels formed by
proposed and existing slopes (`V' feature, blue arrow, below, at approximate location TSD, circled). (Rev.
1) Partially addressed. As follow-up, please see email sent 4/11/2020 7:55 PM, email item 2. (Rev. 3)
Addressed. (Rev. 2) Partially addressed. As follow-up: C3.5 reference to reverse bench slope detail
obscured by Note to contractor. Please shift this Note to contractor. (Rev. 3) Addressed.
[ Images removed with Rev. 2 comments; last images removed with Rev. 3 comments.]
13. C3.4: Remove construction entrance (CE), this view. (Rev. 1) Addressed.
14. C3.4: Check dams are not a permanent feature. Replace any check dams proposed or discussed in narrative
as permanent with: rock -lined channel, concrete flume, EC -II or EC -III, or other appropriate permanent
stabilization structure. Check dams do not persist, but weather and scatter, offering unreliable permanent
protection against erosion. CDs pose risk to equipment and personnel required to maintain landscape areas.
(Rev. 1) Addressed.
15. Ref. Engineering site plan review comments, d. 3/3/20. Address VSMP /WPO plan -related ISP comments.
(Rev. 1) Site plan ESCP-related comments Addressed; site plan SWMP-related comments may persist.
(Rev. 2) Note: Ensure Site Plan, WPO Plan, and Critical Slopes Waiver request are consistent. (Rev. 3)
Addressed.
16. Additional comments possible, once ESC Plan revised. (Rev. 1) Addressed.
Engineering Review Comments
Page 6 of 7
17. Recommend replace STI, ST2, ST3 typical details with scaled (accurate) specific profile depictions. (Rev.
1) Withdrawn.
18. Revise alignment of CE across plan sheets to align with movement of construction traffic approaching from
the NE. A skew is preferable to 90-deg angle, given limited width of Lambs Lane. (Rev. 1) Addressed.
19. Include Note on plans requiring each underground detention system be free of sediment, trash, and
construction debris at two points during construction: once all upslope grading is complete and denuded
areas are seeded per VESCH standards; and once construction is complete, prior to issuance of a CO. This
note does not replace Construction Record Drawing (As -built) for VSMP requirements, but highlights both
difficulty of preventing sediment entering these underground systems during construction, and imperative
to leave both systems free and clear of debris, sediment, etc. before contractor is released, or demobilizes.
(Rev. 1) Addressed.
20. New: C3.1: Recommend FD and TSD details. (Rev. 2) Addressed.
21. New (Rev. 3) Engineering requests canopy tree (whip) landscape plan for critical slope areas behind the
building. E-mail, 6/5/2020 10:49 AM. [ Note: Relates to board consent agenda approval of critical slopes
waiver on 6/3/20.]
22. New (Rev. 3) Please ensure final WPO includes revised C5.2 shared via email, 6/2/2020 5:52 PM.
PALUSTRINE /
FORESTED
10
WETLANDS
010= 18.68 CF
0.5' AVG DIA. RIPRAP f
CLASS All - x
WIDTH 1 = 6' x
WIDTH 2 = 14' x 4
LENGTH = x x 1
DE P '-1
.PDF preview welcome.
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 review staff is unable to meet with the public due to the covid-19 pandemic, until further notice. Please
call if any questions. J. Anderson, 434.296-5832 -0069.
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 2-4 weeks to obtain all the correct signatures and forms.
Stormwater Management Facilities Maintenance agreements will also have 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 7 of 7
information. The completed forms will have to be submitted along with court recording fees.
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;
hLtp://www.albemarle.org/deptforms.asp?department=cdenp"o
WPO202000005_Boys and Girls Club 060520rev3