HomeMy WebLinkAboutWPO201400038 Review Comments 2014-12-30 tGAY AN D N E E L, INC. ENGINEERING V LANDSCAPE ARCHITECTURE V SURVEYING
December 30, 2014
Mr. John Anderson
County of Albemarle
Department of Community Development
401 McIntire Road, Room 227
Charlottesville, VA 22902-4596
RE: Emerson Commons Site Development Plan
Job No. 1770.3
Dear Mr. Anderson:
Please find enclosed a resubmittal on the above referenced project for your review and
comment. Below is an itemized list of the enclosures in this package.
• Four (4) copies of the Site Development Plan dated December 29, 2014.
• Four (4) copies of the WPO/VSMP Plan dated November 26, 2014.
• Two (2) copies of the Narrative dated November 12, 2014.
We received your letter dated October 9, 2014 and have addressed your comments as
follows:
A. Stormwater Management Plan (WP0201400038)
4. Comment: Please model 24-hr storm; evaluate 2-, 10-, 100-yr storm events against bio-
filter designs. The Modified Rational Method does not use a 24-hr storm distribution.
ACCD has adopted SCS method for storm water management reviews. In reviewing report
titled Final Storm water Calculations, Project Number:1770.3, dated April25, 2008, revised
March 7, 2014, all computations appear to rely on the Modified Rational Method, and
appear to be dated April 2008. (Rev. 1) Comment partially addressed. As follow-up to
discussion Oct-1 with K. Conner, drainage area or ground cover revisions to VaRRM (.xls)
may affect design, may affect models requiring revised DA/cover conditions—ref New#1,
below(as well as#5, 16).
Response: Drainage maps, quality and quantity models have been updated.
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Emerson Commons Site Development Plan Page 2 of 6
Job No. 1770.3
5. Comment:MS-19 analysis is incomplete(p. 108, report). Rather than the 1%analysis point
being a single point of analysis, it is a limit, with points upstream subject to analysis of
project contribution to erosion or flooding of downstream natural or manmade channels.
Each release point should be analyzed until it reaches an adequate channel. (Rev. 1). As
follow-up(as with#4)revised contributing drainage areas (ground cover)may affect 1-yr,
24 hr storm QDeveloped, QPre-developed rates of runoff. Please revise as necessary MS-
19 compliance demonstration, p.-58 of SHEFLEE COHOUSING SITE DEVELOPMENT
PLAN/EROSION AND SEDIMENT CONTROL AND STORMWATER MANAGEMENT
NARRATIVE, AUG. 11, 2014 (hereafter, Narrative report). Narrative report uses energy
balance equation (9VAC25-870-66.8.3.a. Values, calculations may change):
QDeveloped` I.F.*( Pre-developedp RVPre-Developedf!RVDeveloped
-Also#16, below. Please revise units, p. 58: RVd, RVf, RVp=cf, rather than cfs.
Response: Drainage maps,quality and quantity models have been updated. Also, units
have been corrected so that Runoff Volume is in cubic feet.
7. Comment:Include pre-post-development drainage area maps as sheets in revised plan set.
Please be sure post-development drainage area reflects proposed current design (parking,
structures,final grade). Show size of each drainage area (square feet, or acreage). (Rev.
1) Comment partially addressed. As follow-up to Oct-1 discussion, please consider runoff
from entire development, including cross-country private sanitary sewer line (C4-02) and
improvements to Parkview Drive (C2-01/C3-01).
Response: All limits of disturbance have been included (see Pre and Post Land Cover
Maps).
13. Comment: 3/7/14 Report (Final Storm water calculations): we would expect to see post-
development tc of 5-6 min and channel as well as overland length for each drainage area,
especially since no runoff collection is proposed. Please review post-development channel
length and tc for each DA. Please revise calculations to include reasonable channel length
when calculating post-development flow for SWM #5. Please review post-development
channel length and tc for each DA. Please revise calculations to include reasonable
channel length when calculating post-development flow for SWM #5. As follow-up to
discussion 1-Oct,please review drainage area values used in VaRRM spreadsheet.—ref New
#1, below.
Response: Drainage maps, quality and quantity models have been updated.
16. Comment: Report, pp. 108-109. Delineate project area. Furnish project area acreage on
topographic map titled 1% Analysis Point Map, d. 3/6/14. (Rev. 1) Comment addressed.
As follow-up, revise MS-19 compliance demonstration, p.-58, Narrative report. Revise
units: RVd, RVf, RVp=ct rather than cfs. —ref#5, above.
Response: This has been fixed.
Emerson Commons Site Development Plan Page 3 of 6
Job No. 1770.3
New:
1. Comment: Narrative report, p. 6, states: "The site is one parcel with a 6.16 acre area.
...total area of land disturbance for this project is 6.71 acres." Report, p. 26(VaRRM.xls),
and pre-/post-development drainage maps (plan sheets) use areas =7.45 Ac, with 3.20Ac
(post-developed)as forest/open space. Several comments: Areas used in VaRRM.xls must
be owned, or easements must allow permanent conservation of on-site/off-site
forest/open space, if these values are used with VaRRM.xls. I plan to send sec. VDEQ SWM
Plan Review Manual that considers post-developed land use/ground cover, as it relates to
VaRRM .xls. Revise areas. Also, consider off-site area land disturbance required to install
cross-country sewer line (C4-02) and widen Parkview Drive (C3-01). Ensure that pre-/post-
re-development land cover areas are equal.
Response: Drainage maps have been revised to include only the parcel and limits of
disturbance off-site. Pre and post land development values are equal.
2. Comment: WPO/VSMP plans require additional sheets (now part of site plans); WPO
plans should include: C0-01/02; C2-01; C3-01/2/3/4; C4-02; C5-01/02; C6-01; C7-
01/02/03. Include pre/post-(re)development drainage maps. Include drainage maps in
index. Revise title, C0-01 (WPO plans) to read: Sheeflee Cohousing WPO/VSMP Plan,
WPO201400038. (Not all details on sheets C7 pertain to WPO, but it may be easier to
include all details, rather than try to rearrange or eliminate 1 or 2 sheets.)
Response:WPO now includes all sheets. The title has been renamed,as the project title
has changed from Sheeflee Cohousing to Emerson Commons. The C7 series has been
eliminated, and details have been moved to sheets according to their respective C-
series (i.e. all ESC Details have been moved to the C5 series).
3. Comment: Revise drainage areas shown on pre- and post-development drainage area
maps. Include all project-related areas of disturbance. —see#1, above.
Response: Drainage maps, quality and quantity models have been updated.
4. Comment: Furnish General VPDES Permit coverage letter. It is critical that Estimated Area
to be Disturbed (VAR10F561)match Area of Disturbance in Narrative report, which it does
(6.71Ac). If disturbed area changes,since project is registered having 2014 VPDES permit,
then with your permission, ACCD will work with VDEQ to revise database value/s. We
request copy of VPDES permit coverage letter.
Response:This has been included within the SWPPP.
5. Comment: (SWPPP/PPP) While Narrative Report considers potential pollution sources,
§17-404 and§17-405 establish plan form and content. A new Albemarle SWPPP template
should be available (on-line) Oct-15, or soon thereafter. Longer templates are
available now (US EPA, for example). A plan sheet that identifies location of potential
pollution sources listed on p. 8-9 of the Narrative report, as well as plan/profile details
of spill containment for refueling, or basins to capture concrete wash-out or
entrance wash waters are minimal SWPPP plan/drawing requirements. Examples from
other projects are available.
Emerson Commons Site Development Plan Page 4 of 6
Job No. 1770.3
Response: The SWPPP has been provided as instructed. Some items will be filled out
later as no decision on the site contractor has yet been made.
6. Comment: Furnish SWPPP/PPP, per§17-404, 17-405. SWPPP certification statement is
found at VAR10, Part Ill K 4 (p. 18/21; link:
h ttp://www.deq.virginia.gov/Portals/0/DEQ/Water/Publications/CGP2014.pdf).
Response: The SWPPP has been provided.
7. Comment: Narrative report, p. 56, bioretention design appears to discount upstream
BMPs. Current design tied to current DAs appears conservative. After revising DAs, design
may benefit if consider runoff removal of upstream BMPs. Tv (p. 56) =2775.14cf, but Tv
(bioretention) appears=1517cf—ref. p. 31 (VaRRM.xls).
Response: Bioretention calculations have been revised to account for runoff reduced by
the upstream BMP.
8. Comment: BMPs include:Spec#1, simple rooftop disconnection: Ensure that plans include
details and notes listed at
http://www.vwrrc.vt.edu/swc/documents/2013/DEQ%20BMP%2DSpec%20No%201 DISC
ONNECTION Final%20Draft v1-9 03012011.pdf needed to aid review and effect proper
installation, inspection, and maintenance. Note:SW maintenance agreements will attach
to deeds for dwellings utilizing this BMP (dwellings owned separately within undivided
parcel).
Response: Rooftop disconnection has been removed from the plan as a BMP.
9. Comment: Furnish schedule showing which buildings (Drainage Areas A, B) are
disconnected; list impervious area/ea rooftop. Ensure space is available and individual
BMPs are shown on C3-02 (each disconnected rooftop) Furnish private drainage
easements for each BMP.
Response: Rooftop disconnection has been removed from the plan as a BMP.
10. Comment: BMPs include:Spec#4, grass channel(A/B soils): Ensure plans include details
and notes found at
http://www.vwrrc.vt.edu/swc/documents/2013/DEQ%20BMP%20Spec%20No%203 GRASS%20C
HAN NELS Final%20Draft v1-9 03012011.pdf needed to aid review and effect proper
installation, inspection, and maintenance. Furnish private drainage easements for each
BMP.
Response: See installation notes and inspection and maintenance schedule provided on
sheet C3-06.
Emerson Commons Site Development Plan Page 5 of 6
Job No. 1770.3
11. Comment: BMPs include:Spec#9, bioretention (Level 2): Ensure plans include details and
notes from specification at
http://www.vwrrc.vt.edu/swc/documents/2013/DEQ%20BMP%20Spec%20No%209 BIO
RETENTION FinalDraft v1-9 03012011.pdf needed to aid review and effect proper
installation, inspection, and maintenance. Note especially excavation depth
requirements listed at p. 33, if bioretention basin location is to be used as a sediment
trap (as is the case in this instance).
8.1. Construction Sequence
Construction Stage E&S Controls.Micro-bioretention and small-scale bioretention areas should
be fully protected by silt fence or construction fencing, particularly if they will rely on
infiltration(i.e., have no underdrains). Ideally, bioretention should remain outside the limit of
disturbance during construction to prevent soil compaction by heavy equipment. Bioretention
basin locations may be used as small sediment traps or basins during construction. However,
these must be accompanied by notes and graphic details on the E&S plan specifying that(I)the
maximum excavation depth at the construction stage must be at least I foot above the post-
construction installation, and (2) the facility must contain an underdrain. The plan must also
show the proper procedures for convening the temporary sediment control practice to a
permanent bioretention facility,including dewatering,cleanout and stabilization_
Response: Installation notes and inspection and maintenance schedule have been added
to sheet C3-06.Trap to bioretention notes have been provided in the detail on sheet C5-
03.
12. Comment: Include Bioretention Installation Notes, sec. 8.2, Notes (Spec#9), steps 1-12.
Include text/details, preferably verbatim. —p. 34-35, Spec. #9.
Response: Installation notes have been added to sheet C3-06. Details shown on this
page do not accurately reflect this particular bioretention installation and thus were
not used. See details provided on sheet C3-04.
13. Comment: Furnish private drainage easements for this BMP.
Response: Per our discussion, Public BMP Access/Maintenance Easements have
been shown on the plan and will be recorded in the plat.
B. Erosion Control Plan (WPO201400038)
New:
1. Comment: Furnish sediment trap L x W floor dimensions, ST 1-4, in table, C5-02.
Response: This has been added to the table.
2. Comment: Include ST5 data (C5-01) in table (C5-02) identical with that provided for ST
1-4.
Response: This has been provided.
Emerson Commons Site Development Plan Page 6 of 6
Job No. 1770.3
3. Comment: Furnish ST5 plan/profile schematic, to scale (not VESCH detail). This ST is
coincident with bioretention BMP.
Response: Detail has been provided on sheet C5-03.
4. Comment: Furnish paved construction entrance with wash rack —ACDSM/p.-27
[detail/.pdf-Attached].
Response:The detail has been added to the plan.
C. Road Plans (SDP200800074)
3. Comment: With 23 parking spaces accessed via a travelway to NW, 22 spaces accessed
via travelway to NE, and with 6 spaces at intersection of these two travelways,
recommend signed intersection (2-way stop, or stop/yield). (Rev. 1) Comment
addressed. As follow-up, show small stop sign proposed at intersection on C3-02. —
Also, see New(SWM)#2, above (response letter/Aug 13, 2014).
Response: Sign is visible on C3-02 but is labeled on sheet C2-01.
D. Mitigation Plans (WPO201400038)
2. Comment: Delineate areas of stream buffer impact on sheet C6-01 (shade or hatch);
show area of impact for each area (square feet, acreage). (Rev. 1) Comment not
addressed. Response: "We discussed this and it was not needed." Partially true. For
accuracy, reference tracking, (possible) reporting, and as matter of public record:
delineate areas of stream buffer impacts, C6-01 (shade or hatch). Report square ft/Ac.
—Also, road plan, #4, above.
Response:The stream buffer impact area has been delineated and hatched on sheet
C6-01. This area has been called out and square footage and acreage reported.
Thank your for your time in reviewing this project. If you have any questions, please
feel free to contact me.
Sincerely,eGay a , -el, Inc.
�j
even D. onn- , .A.
Senior Project Manager
Enclosures
cc: Peter Lazar
KDC/scw