HomeMy WebLinkAboutSDP202000031 Correspondence 2020-05-05 (2)608 Preston Avenue
P 434.295.5624
T I M M O N S GROUP suite 200 F 434.295.1800
Charlottesville, VA 22903 www.timmons.com
May 5, 2020
John Anderson
Albemarle County
Community Development
401 McIntire Rd, Rm 227
Charlottesville, VA 22902
RE: Boys & Girls Club, Northside — Final Site Plan Review — SDP2020-00031 (Also, see
SDP2020-00011)- Comment Response Letter
Dear Mr. Anderson:
We have reviewed your comments from April 20, 2020 and made the necessary revisions.
Please find our responses to the comments below in bold lettering.
1. VSMP/WPO plan approval is required prior to Final Site Plan approval. WP0202000005
is under review. Note: Applicant made critical slopes waiver request; based on
information submitted, including Applicant email, 02/27/2020 4:05PM, Engineering
supports critical slopes waiver request. (FSP) Persists. April 20, 2020 9:41 AM email
(Applicant):'...asked Megan to pull it from the 4/15 BOS agenda, as we knew it would
increase based on this latest set of plans. Once you've been able to review and give your
support, we will update and get it back to the County as quickly as possible.' Also, email
to Applicant, April 20, 2020 1:09 PM.
Critical Slopes wavier has been revised based on Engineering comments and resubmitted to
the County for review, BOS action.
2. Stream buffers exist on parcel. Requirements listed at Ch. 17, Article VI, Stream Buffers,
apply.
C1.1:
3. Flush curb detail indicates —10" base. Please confirm depth of base and identify base
material (asphalt, asphalt type; stone, stone type).
4. Similarly, VDOT Std. CG-3 / CG-2 details indicate — 10" base, each typ. section. Identify
base material and depth of each layer if base is mixed stone / asphalt composite.
5. C1.2: Include VDOT SL-1 detail (safety slab).
6. C2.0: Show and label stream buffers.
C4.0:
7. This plan sheet appears twice; please label 2nd occurrence C4.3.
ENGINEERING I DESIGN I TECHNOLOGY
8. Revise CG-2 to CG-6 along south side of heavy-duty asphalt access, S side of building.
Gutter is required to convey drive aisle / access / parking area storm runoff. Curb alone
is insufficient. (18-4.12.15.g.)
9. Label Jouett MS main building, to orient project.
10. Label Ivy Creek School main building.
Sheet C4.1:
11. Since proposed 8' (Max. ht.) retaining wall N of main parking area supports
infrastructure (parking), sealed geotechnical retaining wall plans are required prior to
FSP approval. Please ref. retaining wall checklist for plan reviewers (Attached). (FSP)
Persists. Applicant response (3/23/20): 'Acknowledged. Sealed retaining wall plans will
be submitted with future submission.'
Sealed retaining wall plans will be provided with a future submission.
12. Label typical narrowest width dimension of 19 proposed curvilinear parking spaces
13. Provide bollard at double -doors opening to 5' sidewalk and flush mount curb on south
side of building to protect occupants exiting blindly to sidewalk without visibility east, of
approaching vehicles. Place left of door, on exiting. Recommend bollards both right and
left. At a minimum, provide bollard to left on exiting.
14. Provide evidence of coordination and approval from ACSA concerning design approval
of sanitary sewer pump station connecting via 6" new force main to Ex. Pump station
alongside Jouett Middle School. (FS) Persists. Applicant: 'Sanitary sewer pump station
and force main plans have been submitted to ACSA with this submission. See Sheets
C8.0-C8.3.'
Sanitary sewer pump station and force main plans were once again submitted to ACSA with
this submission.
15. Consider sequence and pedestrian safety needed during force main construction.
Provide narrative and details to protect visitors to Jouett MS (parents, teachers,
students, etc.). (FSP) Addressed. Applicant: 'Sequencing and safety will be at the
forefront of construction. Force main construction adjacent to Jouett will most likely
take place during the summer, when parents, teachers, and students are not present.
Additional notes have been provided on Sheets C8.0-C8.3.'
16. (C4.1, C5.0, C5.2): Label proposed storm lines downstream of 70-1f and 700-1f x 96" DIA
CMP underground detention system public drainage easements. Provide easement plat,
showing SWM facility, facility access, and public drainage easements. Public drainage
easement must extend to a natural drainage feature, or to the property line. (FSP)
Persists. Applicant: '...An easement plat will be provided with a future submission.'
An easement plat will be provided with a future submission.
17. For both detention systems, provide overland relief to protect improvements against
flooding, and critical slopes against erosion in event of weir plate obstruction. Design
overland relief to convey 10-yr event. Assume complete bypass of systems, should one
or both become non -operational. (FSP) Addressed. Applicant: 'SWM1 would overflow to
structure 202 if the weir plate was obstructed. In this case, the overflow drainage would
make its way south and end up in Ditch C, which would then convey it to SWM2. If the
weir plate in SWM2 became obstructed as well, the drainage would overflow to
structure 402. This structure is more than 1' below the adjacent building FFE, so no
impact to the building is anticipated. Ultimately, this drainage would overtop the curb
and sheet flow south down the slope. Due to the proposed grading, this overflow
drainage would not be channelize. While it is important to consider all possible
outcomes, it is very unlikely that this situation would occur; Boys and Girls Club will
enter into a Stormwater Maintenance Agreement with the County to ensure that the
underground detention systems are maintained and monitored so that the weir plates
never become fully obstructed. For this reason, and those listed above, we believe
adequate protection is provided for both site improvements and critical slopes.'
18. C4.1, C5.0, C5.1: Revise CG-2 to CG-6 at all locations where storm runoff collects against
a curb. CG-2 alone is insufficient. (18-4.12.15.g.).
19. Recommend revise parking drive aisle grade slightly, provide DI at pipe 209 intersection
with CG-6 (rev. CG-2) in front of N side of building. Proposed grade requires exact
construction to bend drive aisle runoff between contours 543 and Str. 206. A more
reliable design (a recommendation) is to direct runoff to a new DI at pipe 209 (rev. CG-2
to CG-6 between Str. 234 and new DI, then CG-2 after new DI); then, after new DI,
provide grade directing runoff to Str. 206. Water flowing across a paved surface tends to
travel straight. A likely better long-term drainage design that more nearly meets
expectations for pavement/drainage performance is to collect runoff traveling west at a
new DI, then collect runoff traveling north in parking aisle/areas N of the building.
Collection of concentrated flow at main entrance to facility avoids ice which is likely
consequence of sheet flow over this distance, west then north, if proposed pavement
grade is constructed. At entrance to the building, pipe 209 is immediately below, and for
slight expense, a DI may greatly reduce risk to patrons, including children unaware of
risk or hazard of black ice in winter. (FSP) Addressed. Applicant: 'Ditch F has been added
to ensure that additional drainage does not make its way to the drive aisle directly in
front of the building. Additionally, CG-6 has been added to the entirety of the eastern
internal parking island to more effectively convey the water coming down the sloped
drive aisle to structure 206. As a result of these improvements, we do not believe an
additional structure is needed in front of the building.'
C4.1, C4.2:
20. Label underground detention systems. If Mfr. System, include name of Mfr. In plan or
profile view. (If Mfr. System, for VSMP/WPO plan, include recommended installation
guidelines, maintenance, and periodic inspection guidelines). (FSP) Persists only at
WPO202000005. (SWMP review item 6, follow-up: Technical installation notes
provided. Please furnish periodic inspection and Lane mfr. — recommended
maintenance procedures on the [WPO] plans).
Periodic inspection notes for underground detention systems have been provided on Sheet
C1.0. Lane mfr.-recommended maintenance procedures have also been provided on Sheets
C6.3 -C6.4.
21. For VSMP and final site plan, ensure manway entries to underground facilities permit
visual check of weirs without entry. Manways should provide check of SWM facility
operation, especially weirs. Do not place SWM facility manways in a designated parking
or loading space.
22. Add FM (force main) size descriptor (6" DIA).
23. Ensure Nyloplast pipes and risers are identified and labeled. Provide Nyloplast typical
construction installation and periodic maintenance and inspection guidelines.
24. Provide drainage calculations (LD-229, LD-204) for all storm pipes and inlets. (FSP)
Addressed — See 4/20/2020 WPO2020-00005 submittal Design Calculations & Narrative
booklet, rev. April 17, 2020, p. 4-7.
25. Provide, show, label basketball court fencing.
26. C4.3: Label loading area/s, if any.
C5.0:
27. Revise proposed contours, consistent with grading required to install Ditch B.
28. C5.0, C5.2, proposed 2:1 slopes on critical slopes do not, for the moment, appear to
include reverse slope benches. Ensure contours and labels guide construction of reverse
slope benches. (FSP) Persists. Transfer fill slope benching detail from WPO202000005,
C5.2, to final site plan, C5.2.
Slope benching details from WPO202000005 have been transferred to FSP. See Sheet C5.2.
29. Provide EC-3, pipe or concrete channel section at proposed 90-degree change in
direction of runoff proposed for Ditch D.
30. (C5.0, C5.1, C5.2): Provide guardra" (VDOT GR-1) with typ. Details along south side of
heavy-duty asphalt access located on south side of building. Although CG-2 is proposed,
proposed grading is an unrecoverable slope. Guardrail is required. (FSP) Partially
addressed. As follow-up: Provide VDOT GR-1 detail on the plans.
Per email dated 4/29/2020, County requests VDOT GR-2 guardrail. This has been provided on
the plans (Sheets C4.1— C4.3). Details have been provided on Sheet C1.2.
31. C5.2: Revise aisle grade on south side of building between contour elevations 534 and
516 to concentrate flow against CG-6 curb (revise CG-2 to CG-6) for reasons of
practicality and safety stated elsewhere Proposed grade assumes sheet flow over 18-ft.
vertical interval when effort should be made to eliminate runoff from the drive aisle
(place against curb) rather than design to spread runoff across entire width of the drive
aisle.
32. C5.0, C5.2: Label proposed slopes (3:1, 2:1) south and west of building. Slopes steeper
than 2:1 are impermissible.
33. Engineering recommendations to approve waiver to impact critical slopes (south and
west of building) requires design incorporate construction standards at 18-30.7.5,
including reverse slope benches. (FSP) Persists. Also, item 28, above. Transfer
WPO202000005, C5.2, fill slope benching detail to FSP, C5.2.
Slope benching details from WPO202000005 have been transferred to FSP. See Sheet C5.2.
34. Increase separation between pipe 303 and back face of retaining wall, especially at NW
end of wall, �ee� image.
35. Provide and define ditches /channels formed by proposed/existing contours N of
playfield, and elsewhere (blue aFFe s images belew. Note presence of critical slopes
immediately downslope of many locations.
C5.1, C5.2:
36. Provide channel design for ditches formed by existing/proposed grade. Ref. Images,
below (FSP) Addressed. Applicant: 'Grading has been revised to limit channelization of
water where proposed grade meets existing grade. In the case shown below (Sheet
C5.2), an existing channel exists in this area. Proposed grading mimics existing grade to
the largest extent practical, while reducing channelization in the proposed condition.'
37. Show full extent of proposed grade, south of SE corner of basketball court. Grade=?
C5.4:
38. 18-4.12.19.b (Drainage Plan checklist, drainage item 7): Revise contours to prevent
storm runoff running through dumpster enclosure. Recommend direct pad to drain to a
surface stone (French) drain to right of pad, then exit surface drain via curb cut to drive
aisle surface. Minimize contamination of stormwater runoff due to contact with solid
waste.
39. Consider highlight section downslope runoff without, in most cases, defined grade to
intercept runoff prior to curb, or sidewalk. Provide capture/conveyance in locations with
7', 10' or 15' vertical interval leading to sidewalk, curb, basketball court, or heavy-duty
concrete.
40. Provide curb or hardscape edging between earth slopes and heavy-duty concrete east of
main building (image, above).
C7.0, C7.1:
41. Recommend plan note emphasize compaction requirements beneath pipes or MHs
entirely in fill section; prior VDOT specification would be appropriate. (Str. 402, 404,
501, RD3, nearly all Str. 412 — SWM2A)
42. Include safety slab label in storm profiles for MH ht.>12-ft. Str. 102, 108, for example.
43. Recommend VDOT anchoring of storm pipe that approaches 16% grade. Conservative
design, care, and precautionary measures for storm pipe installed at steep grade on
critical slopes are appropriate. VDOT drainage manual, p. 9-37. (FSP) Addressed.
Applicant: 'The proposed outfall pipe layout has been revised so that the slope does not
exceed � [15%] at any point. As a result, VDOT anchoring is not required.
44. SWM1— Str. 100: Label reverse slope bench. (FSP) Comment revised to request ditches
be labeled in storm profiles. Reverse (fill slope) benching does not intersect storm lines,
so will not appear in storm profiles.
Ditches have been labeled in storm profiles. See Sheets C7.0 — C7.1.
45. Label SWM1 and SWM2 in plan view (C5.0).
46. Show/label riprap in profile at outfall Str. 100.
We have included PDF copies of the plans and calculations for your review. If you have any
questions or comments, please feel free to email me at kim.melIon@timmons.com.
Sincerely,
Kim Mellon
Project Engineer