HomeMy WebLinkAboutSDP202100065 Correspondence 2022-01-31 (10)SHIMP ENGINEERING, P.C.
Design Focused Engineering
January 31, 2022
John Anderson
County of Albemarle
Department of Community Development
401 McIntire Road, North Wing
Charlottesville, Virginia 22902
RE: Response Letter #2 for SDP2021-00065 Albemarle Business Campus: Block 1
Dear John,
Thank you for your review of the final site plan for Albemarle Business Campus: Block 1. This letter
contains responses to County comments dated January 7, 2022. Our responses are as follows:
Site plan approval requires WPO plan approval. (Rev. 1) Persists. Amendment Application to WP02018-
00044 received 7 Dec 2021. Review pending.
RESPONSE: Continent received. WPO plan was resubmitted 01-28-2022. Both SDP & WPO plans
are concurrent.
2. WPO plan approval requires easement plat recordation for on -site SWM facilities. (Rev. 1) Addressed.
RESPONSE: Comment received. We expect 1 more review of the plat (SUB2021-00202) before it is
approved and recorded.
3. Provide public drainage easement for sections of storm pipe downstream of SWM facilities. (Rev. 1)
Persists. Applicant response (letter d. Nov-19 2021): `The SWM facilities proposed will be connecting to
existing facilities on Mountainwood Road in the public ROW.' As follow-up: Although the proposed SWM
facilities connect to existing facilities within public ROW, the portion of storm pipe/s downstream of each
underground detention facility requires public drainage easement, on -site. Please see blue circle sections of
storm pipe, image below (WP02018-00044, Amendment, C5): [image removed in comment response letter
01/24/20221
RESPONSE: Thank you for your comment. A revised easement plat (SUB2021-00202) is currently
under review.
4. Cl
a. Please list associated and active WPO plan for this parcel: WP0201800044, VSMP Plan
amendment, Royal Fern Phase 1, Now ABC Borrow Site. (Rev. 1) Partially Addressed. As
follow-up: Please revise title sheet note typo (WPO2020-00059) to read WP02020-00058.
RESPONSE: This typo has been corrected (typo was located on sheet C2)
b. Please submit WP0201800044 Amendment #2 Application at earliest convenience. (Rev. 1)
Addressed. Amendment Application to WP0201800084 received 7 Dec 2021.
RESPONSE: Comment received. WPO plan was resubmitted 01-28-2022.
5. C6
a. Provide and label CG-12 at site entrance. (Rev. 1) Addressed.
b. Clearly label ramp and curb type at HC-parking spaces. (Rev. 1) Addressed.
c. Label HC-parking space signs; provide typ. detail for HC-parking space signs. (Rev. 1)
Addressed.
d. Provide pavement markings or yield -stop sign to establish internal parking circulation right-of-
way. (Rev. 1) Addressed.
912 E. High Sr. Charlottesville, VA 22902 1434.227.5140 1 shimp-engineering.com
e. Label curb types (CG-2, CG-3, CG-6, roll-top, etc.). (Rev. 1) Addressed. As follow-up: Revise
CG-2 to CG-6 wherever storm runoff concentrates against curbing. [18-4.12.15.g.] [image
removed in comment response letter 01/24/2022]
RESPONSE: CG-6 provided wherever runoff concentrates against curbing.
f. Please label feature that appears to be an outdoor court between the clubhouse and building 102.
(Rev. 1) Addressed.
g. It is unclear whether site plan geometry at north end of parking lot allows adequate turn radius for
fire rescue apparatus. Engineering defers to ACF&R. (Rev. 1) Withdrawn. Applicant:`Fire/rescue
comments did not include turn radius at north end of parking lot.'
h. Provide and label ramps at either end of 4' stamped concrete pedestrian path. (Rev. 1) Addressed.
i. Revise design to avoid sight line conflict at south corner of building 102. (Rev. 1) Withdrawn.
Applicant: `The sight line conflict is with the retaining wall set off of building 102, however, the
top of wall is at grade to create a below -grade patio area for the basement unit.'
j. Stripe pedestrian crosswalk at site entrance. (Rev. 1) Addressed.
6. C4
a. Please provide prominent plan label to identify portions of ABC development east of Old
Lynchburg Road as Not Included in Final Site Plan for ABC, Block 1. (Rev. 1) Addressed.
b. Recommend label/s (for portion excluded from ABC Block 1) identify plans that correspond with
(and approve designs for) ABC, Block 5; i.e.: SDP202100022, WPO202000058. (Rev. 1)
Addressed.
7. C7: Provide bypass for Stormtech systems, should system outlets (low flow weir orifices) obstruct.
Consider system failure. Provide bypass piping details (sheet C9) with next submittal. (Rev. 1) Persists.
Applicant: `Please see the revised utility plan as well as the detail provided on C9.' As follow-up: If bypass
design overlooked, please notify. Engineering notes Utility Plan, C7, does not appear to provide bypass at
any location that may experience critical obstruction (but may have overlooked bypass design), including:
a. Str. C3. C4-C3 is 33.05 LF 18" HDPE, 0.0% slope. Revise slope to provide positive drainage.
This is an atypical detention system (small diameter pipe, no slope, flexible pipe material (HDPE))
with potential for deflection, ponding, or pipe joint issues not as prevalent as RCP material.
Increase slope to positive value for HDPE, to lesser positive value for RCP, and please consider
effect on at -grade facilities (parking, basement unit—bldg. 104), should storm pipes obstruct, or
back up. Blue arrows, below, though not predictive, indicate possible flow paths should
underground 0% pipe, C4-C3, obstruct. Please provide bypass at Str. C3. [image removed in
comment response letter 01/24/2022]
RESPONSE: small positive slope provided for C4-C3. Main revisions for SWM system, with
this resubmittal, has been to improve better design for easier maintenance. For example,
with BMP 1: additional orifice has been added, so that if the bottom weir orifice is clogged,
the top orifice allows water to drain such that the BMP will not remain full, and so that there
is a manageable lie, fixable with a simple submersible pump) amount of water in that
structure. For BMP 1, a clogged bottom orifice would result in only 0.9' (-11") of standing
water in the BMP chambers, and 3' of standing water in structure C3 (due to the new
provision of the 4" orifice). This provides better ease of maintenance, and better design by
provision of redundancy.
b. Sir. C1: [image removed in comment response letter 01/24/20221
c. Please show inlets to each BMP in profile view (linework /perspective of each BMP).
RESPONSE: inlets shown in profiles via labelstnotes. The ADS BMP design on Sheets C8/C9
of the VSMP plan lists the additional detail. Contractor will be supplied with all plans to
assist in correct construction.
d. Provide storm profile, BMP2. Provide bypass, should entry point/s to BMP2 obstruct.
RESPONSE: Storm profile for BMP 2 is in detail 2, sheet C9. Bypass is internal to the BMP
structure (by way of internal HDPE manifolds, thru the system, furthermore it is highly
unlikely that 24" HDPE manifolds, which are supplied by 15" and 18" pipes, will ever be
obstructed, since debris which would clog a 24" pipe would be unable to enter through the
smaller pipes. Thus, the ADS -designed internal bypass should be sufficient.
912 E. High St. Charlottesville, VA 22902 1434.227.51401 shlmp-engineeong.com
e. Recommend high -flow bypass at Str. CI.
RESPONSE: The high -flow bypass are already internally included, it is the non -isolator row
(2' row west of building 103).
f. Recommend high -flow bypass at Str. A4.
RESPONSE: A4 has been revised for better maintenance access in event of failue.
Unfortunately with the stormwater management regulations, alternate or additional high -
flow bypass options are not feasible without an entire site redesign, as the level of detention
required dictates the detention system water surface elevations. Bypass/overflow for this
system is provided by the open DI-7 structure top at A4. Water can flow out of this in an
emergency. However, current TR-55 storm modelling via HydroCAD (see WPO Plan) shows
that not even the 100-year storm would outflow from the DI-7 top if the system is properly
maintained. Maintenance for this BMP was improved in this submittal by the addition of a
PVC orifice 2' above the weir bottom with a removable threaded cap. This can be removed
to help drain the system to allow for an easy (residual 2' of standing water in the Structure
A4, none in the BMP 2 chambers with an open 4" access orifice) to allow for better
maintenance and cleaning in the event of a bottom orifice clog. With this revised design,
improved due diligence design has been provided.
g. Recommend high -flow bypass at Str. B 1.
RESPONSE: BI bypass is the 24" manifolds which connect to A5. This is detailed in the
BMP design in the WPO plan.
8. C8
a. Obtain public drainage easement for new storm pipe downstream of SWM facilities proposed to
be off -site, from property line to the point new storm pipe connects with existing storm network
on Mountainwood Road. (Rev. 1) Persists. Comment revised: Provide public drainage easement
downstream of on -site SWM facilities to property line; also, item 3., above.
RESPONSE: noted, see updated labelling.
b. Provide safety railing labels and railing details for retaining walls >4'. (Rev. 1) Addressed.
c. Note: A separate building permit is required for wall ht. >3-ft, unless integrated inU, buildir-
design. (Rev. 1) Reminder comment; item persists.
RESPONSE: railings, and retaining wall designs provided with this submittal. General
Contractor understands that permits are required.
d. Note: Sealed geotechnical design is required for retaining wall In. >4' unless wall is integrated
into building structural design, in which case it is reviewed with that building permit application.
(Rev. 1) Persists. Applicant: `Geotechnical plans are forthcoming.'
RESPONSE: wall designs provided with this submittal.
9. C9
a. Str. A3, A4: Provide note for t/2" steel plate in floor, since INV IN - INV OUT >4'. (Rev. 1)
Addressed.
b. Design appears to route impervious area runoff from 3-1/2 residential buildings plus clubhouse
and perhaps 2/3 of all paved parking to a 158 LF 60" StormTechTM system, while runoff from just
1-1/2 residential buildings and 1/3 of site parking route to a 125LF 60" StormTech chamber
detention /treatment system. WPO plan should clarify disparity in runoff vs. detention /treatment
system capacity. Note: the 125 LF system also appears to route to or through the 158 LF system.
(Rev. 1) May persist. Applicant: `That is a correct analysis. Full detail and explanation
forthcoming in WPO submittal. This system is sufficient to detain and manage stormwater runoff
from this site.' Engineering to evaluate with WP0201800044, Amendment #2 submittal.
RESPONSE: noted, we believe with the current revisions that we have addressed
outstanding issues and provided a design which promotes public health and welfare.
c. Provide LD-204, LD-229 storm inlet and storm drain design computations. Additional comments
on drainage design possible. (Rev. 1) Addressed. Applicant: `We will be sure to include this in
WPO plan sheets.' WP02018-00044 Amendment #2 received 12/7/21.
10. C16: Please include primitive path detail. (Rev. 1) NA. Applicant: `The primitive path has been removed
and replaced with typical sidewalk material.'
11. C 17: Engineering defers to VDOT on MOT plan for public rights -of -way. (Rev. 1) Persists, but under
VDOT purview.
RESPONSE: MOT plan has now been improved, however yes this is ultimately subject to VDOT.
912 E. High St. Charlottesville, VA 22902 1434.227.51401 shlmp-engineenrig.rom
If you have any questions or concerns about these revisions, please feel free to contact me at
Keane@shimp-en 'ngi eerin,g com or by phone at 434-227-5140.
Regards,
Keane Rucker, EIT
912 E. High St.. Charlottesville, VA 22902 1434.227.51401 shimp-engineenrig.rom