HomeMy WebLinkAboutWPO201900060 Review Comments WPO VSMP 2020-09-29� AI
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COUNTY OF ALBEMARLE
Department of Community Development
401 McIntire Road, Room 227
Charlottesville, Virginia 229024596
Phone (434) 296-5832 Fax (434) 972-4126
Project:
Plan preparer:
Owner or rep.
Plan received date:
(Rev. 1)
(Rev. 2)
(Rev. 3)
Date of comments:
(Rev. 1)
(Rev. 2)
(Rev. 3)
Reviewer:
WPO2019-00060
VSMP Permit Plan review
UVA Foundation — 1725 Discovery Drive
Anna Fontaine /Timmons Group [ anna.fontaine@timmons.com ]
608 Preston Ave., Suite 200 / Charlottesville, VA 22903
University of Virginia Foundation / P.O. Box 400218
Charlottesville, VA 229044218 [ cschoolev(d),uvafoundation.com ]
21 Oct 2019
13 Jan 2020 (digital-1/13/2020 3:55 PM)
30 Mar 2020 (digital)
20 Aug 2020 (digital)
20 Nov 2019
29 Jan 2020
1 Apr 2020
29 Sep 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 outlined, below.
The application may be resubmitted for approval if all comment items are satisfactorily addressed.
A. Stormwater Pollution Prevention Plan (SWPPP) (Rev. 1) Comments persist. Applicant response:
`Much of this information is not yet available. An updated SWPPP will be provided with the next
submittal.' Engineering accepts this response and anticipates update with next submittal.
(Ref. Applicant email: 1/13/2020 3:55 PM) (Rev. 2) Comments persist. Defer revised SWPPP till future
submittal (Applicant /county email: April 1, 2020 10:36 AM, 11:00 AM). (Rev. 3) Comments persist.
Applicant response (Aug 19, 2020 letter): `An updated SWPPP will be provided with the next submittal.'
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.
a. Sec. 1 (Registration Statement) Complete 2019 VPDES (VAR10) Registration
b. Sec. 4./5. —Update once ESC-SWM plan sheet revisions complete
c. Sec. 6.E. Name individual responsible for PPP practices
d. Sec. 8 List named individual responsible for inspections
e. Sec. 9 (Signed Certification) Please sign
f Sec. 11 (General Permit Copy) Please include 20I9 VAR10
g. Include 2019 Notice of VPDES Termination
h. List WPO2019-00060 on cover of SWPPP
The PPP content requirements can be found in County Code section 17-404. (Rev. 1) Comments persist,
see above. (Rev. 3) Comments persist. Applicant: `An update SWPPP — with updated PPP — will be
provided with the next submittal.'
1. If Sec. 6 PPP Exhibit is revised, please provide an updated Exhibit.
2. Sec. 6.A Revise PPP Exhibits, p. 28-29 SWPPP, to show rain gauge location/s.
Engineering Review Comments
Page 2 of 9
C. Stormwater Management Plan (SWMP)
VSMP Regulation 9VAC25-870-108 requires the VSMP authority to approve or disapprove a SWMP.
This plan is approved.
1. Revise plan title to include ref, to VSMP /WPO2019-00060.
2. Revise vicinity map to more clearly identify site location.
3. C2.0 — Provide existing contour labels, none are provided.
4. Include image, below (or similar), from Timmons Group UVA Foundation —1725 Discovery Drive Design
Calculations & Narrative, October 21, 2019, on C6.0 with caption /label that identifies 1725 Discovery
Drive (blue eifele image below, image removed w /Rev. 2 comments) to cross-reference and clearly
identify project site, relative to Pond 1.
5. Include image, below (image removed w /Rev. 2 comments) /similar: USGS 7.5' quadrangle, Earlysville
VA, 2016, to show approximate (county -estimate) watershed Pond 1 comprising —465 Ac., on sheet C6.0.
Revise drainage area reference on C6.0 which may underreport actual size of Pond 1 watershed (revise
83.90 Ac. reference to avoid confusion).
6. C6.0 — Provide note that identifies project location in sub -basin shown on Design Calculations & Narrative,
P. 9.
7. C6.0 — Provide additional qualifying descriptions to support how this 0.73 Ac. impervious gain fits within
p. 9 projections for sub -basin ultimate development impervious land cover without change to Exhibit CN
value. Identify p. 9 sub -basin (Exhibit) CN value that applies to project, a value that WPO plan and Design
Narrative maintain is unchanged with proposed development at 1725 Discovery Drive.
8. C6.1: Pre/post CN value =67 (reported with cross section 1 — 4 profiles) appears unrelated to Exhibit p. 9
CN values. Please clarify. Ref, image, below. Image removed w /Rev. 2 comments
9. Note: This and other development projects that rely on Pond 1 for quality and quantity compliance are not
strictly grandfathered unless requirement at 9VAC25-870-48. L(iv.) is satisfied between individual project
sites and Pond 1, yet, if (iv.) is true at Pond 1 outfall, and if Pond 1 was built per design, and if Applicant
confirms that, to -date, watershed development impervious area does not increase the CN value in any sub -
basin of Pond 1 (Ref. p. 9 /Design Report), then review position is that Pond 1 provides SWM for projects
within Pond 1 watershed, per 9VAC5-870-48. Please confirm that this is the case: that CN value in project
sub -basin is unchanged with new building /additional parking. Albemarle still considers channel and flood
protection between proposed development and Pond 1. While Pond 1 may provide SWM quality -quantity
control at limits of analysis, channel and flood protection between development sites and pond is a review
and regulatory concern, unless proven otherwise.
9VI AC25-870-48. L(iv.): ` and iv has not been subsequently modified or amended in a manner resulting
in an increase in the amount of phosphorus leaving each point of discharge, and such that there is no
increase in the volume or rate of runoff.'] While there may be increase in the amount of phosphorus
leaving a specific site compared with the pre -development condition, provided proposed design of 1725
Discovery Drive is consistent with Dewberry & Davis, October 1997 document CN value for its sub -basin,
then review position is that there is no increase in permitted volume or rate of runoff from Pond 1 outfall.
10. C6.1: Channel Adequacy /capacity -velocity between 1725 Discovery Drive development, and Pond 1:
a. Ref. 9VAC25-870-97: Stream channel erosion, para. B., references 9VAC25-840-40, Minimum
Standards.
b. Min Std. 19 (9VAC25-840-40.19.b.(2.)(a.) requires `Natural channels shall be analyzed by the use
of a two-year storm to verify that stonnwater will not overtop channel banks nor cause erosion of
channel bed or banks.'
c. Ref. VESCH, 3rd Edit., 1992, Table 5-22. Provide additional data on receiving stream substrate.
Compare with table values to ensure velocities at x-sections 1- 4 are non -erosive. Table 5-22
indicates velocities above 2.5 fps may be erosive in certain unlined earthen (natural) channels.
Report /list observed substrate between development and Pond 1 at each x-section, on sheet C6.1.
d. Ref. DEQ guidance /DCR Technical bulletin # 1 (link:
https:Hwww.deq.virginia.gov/Portals/0/DEO/Water/Publications/TechBulletinl.pdf ) Stream Channel
Erosion Policy Guidance. Review especially guidance, DCR TB 1, p. 11, Ultimate Development
Engineering Review Comments
Page 3 of 9
Conditions, and confirm analysis performed for (WP02019-00060) submittal includes Engineer's
best estimate of ultimate development along the receiving stream between 1725 Discovery Drive
and Pond 1, which may in future contribute additional runoff, and increase volume or velocity in
this receiving stream (blue circle, image, below). Image removed w /Rev. 2 comments.
e. Once ultimate development conditions are analyzed, `If existing natural receiving channels or
previously constructed man-made channels or pipes are not adequate, the applicant shall `consider
measures listed at DCR TB 1, p. 7. Also, please review DCR TB 1, pp. 8-11. Revise design, as
needed.
f. Revise Water Quantity Analysis — Channel Adequacy text block, C6.1, as needed. Velocity < 5fps
is not always nonerosive. Also, base design on ultimate development conditions. Please note
multiple road stub -outs for future development along Discovery Drive (GIS image, above).
g. Channel cross sections panel:
I. Label Lewis and Clark Drive.
ii. Label Ex. structure beneath L&C Drive.
iii. Evaluate Ex. structure beneath L&C Drive based on ultimate development conditions. If
inadequate to convey runoff from ultimate development, propose remedy.
iv. If design remedy requires modification to Ex. structure beneath L&C Drive, provide
comprehensive profile and plan design information, including LD-229.
11. Label drainage structures across plan sheets to correspond with Design Calculations & Narrative, Pipe and
Inlet Computations tables.
12. Design Calculations & Narrative: Revise Project Narrative — Stormwater Management Summary consistent
with review comments above, and any plan or channel or pipe revisions required by ultimate development
conditions.
13. Note: Since Pond 1 Drainage Area > 460 Ac., analysis downstream of Pond 1 is unnecessary. Project LOD
< 1% Pond 1 DA. Project total LOD z1.29 Ac. Ref. DCR TB 1 one -percent rule, p. TB 1-7. (Rev. 1) As
follow-up: Please see Sec. D., ESCP, below, minor item 1. (Rev. 2) Addressed,
14. Furnish relevant Pond 1 As -built data that corresponds with approved Pond 1 dam /spillway elevation data.
Although this data was requested in connection with SUB201800171, unless mistaken, it was not
furnished. As -built data for pond 1 dam /spillway is requisite to approval of WP0201900060. Please see
request sent December 03, 2018 4:57 PM (J. Anderson to J. Showalter) in connection with SUB20180017 —
Lewis and Clark Drive Extension, including text, reading (in part): (Rev. 1) Comment persists. (Rev. 2)
Addressed, As follow- Revise title of Pond 1 Analysis report (a new submittal with Rev. 2) to reference
WP0201900060). This is only request relative to As -built condition of Pond 1. Additional details request
no revision. Pond 1 Analysis will be useful for current /future land development projects at UVA Research
Park, for areas draining to Pond 1. Albemarle appreciates the effort and care taken to prepare this
important reference resource.
(Additional details:
UVA RESEARCH PARK -POND t ANALYSIS, VSMP DESIGN CALCULATIONS & NARRATIVE, MARCH 27, 2020
a. Pe. 13 is a HydroCAD (routing) diagram that correlates:
I. C6.0 Stormwater Narrative
ii. Dewberry & Davis Oct 1997 document
iii. C6.0 Image 2, Timmons Group Exhibit, Dec 2018
iv. 3127120 Discovery Drive Development Design Calculations and Narrative, p. 12 Exhibit
(* Drainage Divides and Area Names taken from Dewberry & Davis, Oct 1997 report. )
v. Pond I As -built condition (schematic, below*, divides /area names, blue circle, below).
Engineering Review Comments
Page 4 of 9
b. Pe. 5-10 are Dewberry & Davis Pond 1 design documents.
c. Pg. 11-12 satisfy County request for `As -built' information for Pond 1 embankment.
( As -built drawings d. March 20, 2020 by Timmons Group, checked by Joe Medley )
( As -built drawings incl. w/ 94-p. Pond 1 Analysis under PE -seal, 3/27/20 /Craig Kotarski)
d. Remainder of 94-p, report are routings (2, 10, 100-yr routings, with pond WSE)
e. Pe. 3-4, Pond outfall analysis:
( D. 3)
Pond Outfall Analysis
The existing pond was originally designed to provide water quality and quantity storage
with the use of an earthen embankment, and a concrete spillway. The asbuilt pond
includes 2 9'x10' culverts, a concrete control structure, and an earthen emergency
spillway. The asbuilt pond with the ultimate offsite drainage area and fully developed
onsite drainage areas was analyzed using HydroCAD software to determine that the
asbuilt pond meets or exceeds the freeboard of the original design. Below is a table
comparing the design and asbuilt Water Surface Elevation (WSE), the freeboard
provided, and the flow in and out of the facility.
( D. 4) outfall analysis, cont.
Relevant pages from the approved design are provided in the appendix. The WSE can be
found on page 9 of 60 and 32 of 60. The HEC-1 routing of the designed pond can be
found in section 8 of the report. Also provided, is the survey dated March 20,2020 that
was used to model the pond as it was constructed. Pond I was modeled utilizing the
ultimate development offsite and post -developed conditions onsite drainage areas from
the approved design report. Sub basins CI, C2, DI, D2, El, E2, FI, F2, GI, and G2 drain
to pond 1. The drainage area, CN Values, and time of concentration values are listed in
the table below.
f. Table 1:
g. Table 2:
1997 Design'
Top of Dam: 464.2 It
2020Asbuilt
Top of Dam: 467.0 ft
2 yrWSE
454.4
It
156.6
ft
10 rWSE
457.5
It
458.3
ft
100 r WSE
460.4
ft
460.6
ft
2 yr Freeboard
9.9
It
10.4
ft
10 yr Freeboard
6.8
ft
8.7
ft
100 yrFreeboard
3.8
It
6.4
ft
2 yr Peak Inflow
1483
Ns
IS31
CIS
10 yr Peak Inflow
2472
cfs
2623
cfs
100 yr Peak Inflow
3708
cfs
4687
cfs
2 yr Peak Discharge
636
cfs
862
crs
10 yr Peak Discharge
1483
cfs
1%6
cfs
100 yr Peak Disd,m
2437
cfs
U91
cfs
Table 1 - Pond 1 Comparison
•I997 Da4M values were wnvmed from mnva w fee[ and m3h w cfs
Approved Drainage Areas and CN Values
7/2371997
Area (Ac.)
CN
Tc (min)
C3
27.38
80
5
C2
85.94
82
5
D3
12.33
78
5
D2
84.03
86
7
El
27.9
81
6
E2
17.28
83
8
F1
66.44
91
11
F2
31.64
91
8
91
48.9
92
14
G2
49.05
92
14
Table 2 — Drainage Areas to Pond 1
Engineering Review Comments
Page 5 of 9
Alb. County Dec. 03, 2018 4:57 PM email / text: `Engineering needs to correlate Lewis & Clark Road Ext.
to a prior -approved plan for TMP #32-6R, under whatever guise (Approved Master Plan, Approved Cox
Engineering plans, Approved Dewberry Davis Study, etc.). Important documents are contemporaneous
with suspended site plans, but we cannot locate a clearly -approved SWM plan for UVA Foundation
Research Park, especially for ponds 1 and 2. Important documents and applications are twenty years old.
This is the task: identify a prior -approved SWM plan (with SWM facilities) meeting Part IIC design criteria
for improvements proposed under WPO201800073. We need Timmons to make the connection —please
consider:
1. Identification of prior -approved storrnwater management plans for ponds 1 and 2.
1 have researched this without luck. I cannot make clear connection between a prior -approval and this
Application.
It is not enough that recently approved WPO plans may have referenced Dewberry Davis Study, or
Cox Engineering plans.
2. Design of ponds 1 and 2 relative to VSMH, 1999, Vol. II, Appendix 5D worksheets (ponds 1 and
2).
3. As -built condition of ponds 1 and 2 relative to approved plans. We cannot locate As -built
drawings.
4. Location of ponds 1 and 2 relative to drainage divides, relative to improvements
(WPO201800073).
5. USACE approval of wetland impacts associated with WPO201800073 /SUB201800171.
6. Cumulative development ( % impervious) relative toprior-approved SWM plan/s.
That is, with WPO201800073, % impervious cover from a cumulative standpoint.'
[Also, county email, James Howard -Smith to Jonathan Showalter, Timmons, 12/19/2018 7:07 AM, Re.
SDP199800043 Approved Final Site Plan and Comps, Pond 1. sheet 32: Spillway / Dam Profiles. Note:
plan is metric.]
Link to SDP199800043: hMs:HIfweb.albemarle.org/weblink/search.aspx?dbid-3&searchcommand=%7b%SbCDD-
Planning%5d: %SbAppl icationNtunber%5d=%22SDP 199800043%22%7d.]
New (Rev. 2)
C6.0
15. Narrative references Analysis Points 1 & 2. Cannot locate Point 2 in pre- /post -development DA images.
(Rev. 3) Addressed. Applicant : `Analysis Point 1 is the only AP now and has been clarified in the
drainage area images.'
16. "Air building" is shown in post -development drainage area. Please confirm that 2.32 Ac. impervious area
includes Air building. If not, recommend revise impervious area to include the Air building, and consider
text edits, as needed, to Stonnwater Narrative. (Rev. 3) NA. The air building has been removed from the
proposed plan.
17. 3/27/20 UVA Research Park —Pond 1 Analysis Design Calculations & Narrative: Provide qualitative
information on existing double 9 x 10 box culvert pond 1 outfall, relative to stream bed /channel stability.
Although this is beyond limits of analysis, request is made in context of `As -built' condition. Albemarle
must ensure As -built condition of pond 1 dam embankment /outfall is stable, on this date. Narrative,
observational statement that stream bed and channel banks are stable at pond 1 outfall is sufficient. (Rev.
3) Addressed. Applicant: `Please see image of the outfall area. The bed and banks appear stable.'
Image
Engineering Review Comments
Page 6 of 9
18. Note: 3/27/20 UVA Foundation — Discovery Drive Development Design Calcs & Narrative,.33, para. 3
states: "Drainage Area C2 consists of 83.90 ac. with a CN value of 67 (see Table 1)". Table 1,.55, reports
CN =69. Revise for consistency. (Rev. 3) Addressed. Applicant: `The 67 references the "Lewis and Clark
Drive — Stormwater Management Exhibit for Pond 1" dated 12/2018 while the 69 is the updated CN value
based on incorporating the numbers within this WPO plan. To make this more clear, the "Lewis and Clark
Drive — Stormwater Management Exhibit for Pond 1" has been updated throughout the plans and Narrative.
With the new plan, the CN value updated to include the proposed development is 68.'
19. C6.1: Confirm pipe capacity (LD-229) between Sir. 300 and inlet, S side of Discovery Drive, is adequate to
convey runoff from (conservative estimate of) impervious areas associated with potential air building. A
goal discussed 3/6 with Applicant is an approved plan that addresses SWM quality /quantity requirements
(if not ESC) associated with a potential air building; this plan comes quite close. Also, ESC Plan, item 13.
(Rev. 3) Addressed. Applicant: `This pipe is now proposed to be removed the capacity of the new pipe
crossing Discovery Drive has been verified to be adequate.'
20. C63: If WPO201900060 is to include potential air building, include inset for air building on site drainage
area Map 2 that shows DA parameters and location of air building, relative to Phase 2 improvements. (Rev.
3) NA. The Air Building is no longer proposed.
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 disapproved for reasons listed, below, beginning middle of p. 8. The erosion control plan content
requirements can be found in County Code section 17-402.
..ote: I+j+EiaLrevrew, comments addressed; graysc e
1. C3.0 total LOD Area (appears) =1.31 Ac. Please revise. (Check my math.) (Rev. 2) Partially addressed.
As follow-up: see New item 8, below. (Rev. 3) Addressed. LOD is now 3.41 Ac.
2. C3.1 Check for CE-SF conflict, it appears SF may partially obstruct CE. Limit SF to avoid conflict (Rev.
2) Addressed,
L C3.0 — Since LOD areas of this two-phase project (building' parking) do not overlap, revise project
description to clarify that total limits of disturbance z1.29 Ac.
2. C3.1 — Provide RWD at end paved construction entrance.
3. C3.3 — Label existing contours.
4. C3.4 (Also, site plan -related)
a. Eliminate nuisance pending in right-angle comers of lower elevations of proposed upper parking
lot.
b. Label CG-2 / CG-6.
c. Label drive aisle width.
d. Provide typ. dimensions, parking spaces.
e. Label concrete ribbon curb at each entrance to upper parking lot. Provide detail.
f. Recommend profile for north and south side entrances to proposed upper parking lot that show
smooth transitions, and spot elevations.
g. Recommend receiving walks on east side of existing lower parking lot that align with proposed
sidewalks (2 locations) on west side of lower parking lot.
h. Label retaining wall.
i. Please ref. 18-30.7.5.a.1./2. construction standards, re. wall ht.' stepped walls required if wall ht.
>6' (proposed design wall ht. =10.3' on managed steep slopes cannot be approved.) Image
removed with Rev. 2 comments.
j. Apply for building permit for retaining wall.
k. WPO plan approval does not approve retaining walls.
1. Provide CG-12 wherever walks encounter curbing (label ramps).
5. Provide safety fence to protect building occupants and visitors during all phases of project.
Engineering Review Comments
Page 7 of 9
New (Rev. 2: Scope of work revised /discussed with Timmons, Albemarle Planning /Engineering, and UVAF at
meeting at county office building, 3/6/20.)
6. C3.5: Recommend label sediment traps as STI, ST2 (excavated drop inlet ST) in plan view. (Rev. 3)
Addressed.
7. It appears excavated drop inlet sediment trap does not provide 100.5 cy wet storage volume. If top of inlet
elev.=540.5' and volume provided at elevation 541'=94.2cy, it appears wet storage volume is insufficient.
(Rev. 3) Addressed. As follow-up: Also see item 26 below.
8. Please confirm total LOD z4.10 Ac C( 3.0, Project Description). Phase 2 (2.54 Ac.), Phase 1 (0.47 Ac.). If
"Air building" comprises -1.09 Ac. disturbance, then on C3.0, please reference possible location of "Air
building" shown on C6.0, C6.1. (Rev. 3) Addressed. Applicant: `The removal of the proposed Air
Building eliminates this confusion. LOD is now 3.41 acres.'
9. Include Ex. pipe /structure demolition in sequence of construction notes. Ensure storm runoff conveyance
via existing or new stone lines (structures) is continuous during all phases of construction (C2.4 /C3.0).
(Rev. 3) Addressed. Also, as follow-up: See item 26.e., below
10. C3.5: Provide proposed grading and/or label to ensure STI discharge is to the new inlet structure located
just SW of STI weir. (Rev. 3) Addressed. Applicant: `E&SC Plans have been updated.'
The following comments also relate to site improvements. Please ensure final site plan (SDP2020-00009) and
WPO plan are consistent
11. C2.1 C5.0: Provide CG-12 at each end of the short sheltering short walk between new access to metal
building and existing parking, 1725 Discovery Drive (blue eireles, be!@ ). Also, provide CG-12 ramp
within 1725 site to receive middle ramp pedestrian traffic (image ) [Images removed with Rev. 3
comments.]. (Rev. 3) Addressed. Applicant: `There are two existing curb ramps in these locations that had
not been picked up by the surveyor.'
12. C5.0: Check LD-229, Narrative & Design Cale, p. 7 (pipe 315), against plan sheet labels, pipe 315, to
/from. (Rev. 3) Addressed. Applicant: `LD229 design computations have been updated.'
13. C5.0, C5.1: Label all existing structures (listed on the LD-229) in plan view drawings, .
[Image removed with Rev. 3 comments.] (Rev. 3) Addressed.
14. LD-229 lists Ex 7 - Ex 1 at 99.46% pipe capacity. Recommend more conservative design. (Rev. 3)
Addressed. Applicant: `Pipe cities and areas have been checked and updated. Pipe is now at 75%
capacity.'
15. C5.2: Provide swale /similar and label/s at top of retaining wall to ensure storm runoff is not channelized at
the top of the wall, but is separated by swale or grading from the top of the wall. (Rev. 3) Withdrawn.
Applicant: `Grading has been designed to ensure stormwater ems away from proposed walls.'
16. C5.1: Assign storm line label to 10" HDPE line N of Sir. 310. Provide a structure at bend in this line.
Assign Str. ID. (Rev. 3) NA. This line has been removed.
17. C5.1, C7.0: Revise storm 309 grade to < 16%. (Rev. 3) Addressed. Applicant: `All storm pipes are
proposed to be no more than 5%.' Note: It appears two lines are < 0.50%. Engineering does not request
revision but will request As -built calculations should either line be installed at < proposed 0.489 and
0.497% slope. ACDSM and Drainage Plan Checklist for plan reviewers require Min. slope >_ 0.5%.
18. Increase pipe 309 diameter? 10" (upstream pipe: 10" DIA HDPE; Str. 309: 11.11' of 8" HDPE @19.80%).
(Rev. 3) NA. Applicant: `Storm pipe network has changed and this comment no longer applies.'
19. C5.1: "10" HDPE (1% slope min.)" label is ambiguous. Provide profile. Defines pipe /slope. Also, item
17, above. (Rev. 3) NA. Applicant: `Storm pipe network has changed and this comment no longer applies.'
20. C5.1: Provide grading at Str. 316 to accommodate 13.464" ponding depth at inlet to ensure capture (ref.
LD-204). (Rev. 3) NA. Applicant: `Storm pipe network has changed and this comment no longer applies.'
21. C5.1: Revise throat length, inlet 400. 6.114" depth appears to exceed DI-3C 5.5" high inlet opening. (Rev.
3) Addressed. Applicant: `Inlet 400 throat length has been increased to 10 feet to ensure depth does not
exceed top of inlet. This change has been verified with the updated inlet Drainage Area.' [ Image removed
with Rev. 3 comments. ]
Engineering Review Comments
Page 8 of 9
22. Provide details /notes, etc. for T-connections in storm lines (similar to inlet shaping) to ensure flow at
Inserta tees V is not susceptible to debris accumulation, or obstruction. Inlet shaping is required within
structures to re -direct flow to minimize chance of accumulation, or obstruction. (Rev. 3) Withdrawn.
Applicant: `An InsertaTee detail has been added to sheet C 1.1 [C 1.4]. The incoming pipe at the InsertaTee
location is proposed to connect above the bottom of the pipe. This will aid in preventing obstruction at the
invert of the connection.'
C7.0:
23. Note that concrete inlet shaping (IS-1) is to be provided on all structures may not be possible with
Nyloplast line of dome grate /risers. Clarify IS-1 is possible for Str. 310. Also, item 22, above. (Rev. 3)
Addressed. Applicant: `The note on sheet C7.0 has been updated to reflect inlet shaping for all concrete
structures.'
24. Provide Ex. 24" (CPP) stone profile from Str. 300 (beneath Discovery Drive) to inlet structure on S side of
Discover Drive. (Rev. 3) NA. Applicant: `This comment no longer applies.'
25. Plan note stating that MH Str. over 8-ft in height shall require a stepdown structure with %: steel plate to
serve as a safety slab appears more stringent than VDOT standard. Please confirm design intent to equip
all MH Str. over 8-ft. in height with SL-1. Ref. VPOT cr 1 94, bela . [ Image removed with Rev. 3
comments.] (Rev. 3) Addressed. Applicant: `After further review of height of the structures, the referenced
note has been removed from Sheet C7.0.'
New
26. Engineering recommends (0.5):
a. Consider infrequent event (less frequent than design event), since any failure of ST2 will likely
have immediate impact on Discovery Drive that may disrupt facility access, construction, or both.
This caution applies since proposed trap is located immediately adjacent to Discovery Drive.
b. Label weep holes for dewatering in plan view (See ST2 Detail, Excavated Drop Inlet Sediment
Trap, C3.1).
c. Confirm Ex. 15" plastic line beneath Discovery Drive utilized as outfall for ST2 is in good
condition without visible defects between DI-7 and flared end section S of Discovery Drive.
Applicant may address via Note to contractor, but lack of information now risks less than ideal
required response during construction if contractor discovers defect or deficiency with Ex. line
beneath Discovery Dr. Engineering recommends Timmons examine integrity of this pipe now,
rather than shift burden to site contractor, later. Ref. C2.4, C3.5.
d. Recommend a label reference to Note on C2.4 (to contractor to replace DI-7 top with DI-3C set
per final grading plan) on both sheets C3.4, C3.5.
e. Consider interim phase between ESC Phase 2B and 2C when ST2 is removed. Anticipation may
define success as site transition from unbuilt to final condition (parking /building), once ST2 is
removed. ST2 must remain until all upslope areas are stabilized and while proposed conveyance is
constructed. Phase 2B shows pipes and protected inlets; what is less clear is how site runoff
transitions from sediment trap to storm inlet catchment, all while limiting potential for sediment -
laden runoff to leave the site.
27. C 1.2: Inlcude VDOT ST-1, IS-1, PB-1 details (MH steps, inlet shaping, pipe bedding), unless overlooked.
28. C2.0: Label Discovery Drive.
29. C3.1: Include VESCH Plate 3.01-1, also, please include label/s for safety fence post embedment in asphalt,
since SAF is proposed to be installed in asphalt.
30. C3.2, C3.3: It is unclear how building occupants that my park south of the building will enter the building
along a safe path that does not conflict with construction activities, CE, or SAF. Please clarify.
Engineering Review Comments
Page 9 of 9
The VSMP permit application and all plans may be resubmitted for approval when all comments have been
addressed.
Given Covid-19 restrictive policy on meeting Applicants, for the time being Engineering review staff is unable
to meet to discuss this review, but recent productive on-line review meeting with Timmons staff (Andrew
Allision) was a collaboration that might work in this instance, if preview prior to submittal is requested.
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 may 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 agFeements aw is 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 entails provided on the application (SWPPP Registration Statement).
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, the County can hold a pre -construction conference. Applicants will need to complete
the request using 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 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,
htti)://www.albemarle.org/del)tforms.asp?department--cdengwI)o
Ifyou have questions or concerns, please contact me at 4anderson2Aalbemarle.orQ or at 434.296-5832 -
x3069.
Thank you
I Anderson, Engineering Div.
WP0201900060 UVA Foundation— 1725 Discovery Drive 092920rev3