HomeMy WebLinkAboutSUB201400063 Review Comments Preliminary Plat 2014-11-06� OF A.
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COUNTY OF ALBEMARLE
Department of Community Development
401 McIntire Road, Room 227
Charlottesville, Virginia 22902 -4596
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:
(Rev. 1, 2, 3)
Project Coordinator
Fontana — Phase 4C
Terra Engineering and Land Solutions, P.C.
Fontana Land Trust
6 June 2014
31 July 2014, not reviewed, revised
(31 -July plans revised, re- submitted 26 August)
1 October 2014
5 November 2014
20 June 2014
9 September 2014 (26 -Aug plan set); rev. 16- Sep -14
23 October 2014
6 November 2014, rev 7- Nov -2014
Michelle Roberge
John Anderson
Christopher Perez
Engineering has completed the review of application SU132014 -63.
A. Preliminary Subdivision Plat (SUB201400063)
A major comment immediately follows. It is new to the extent it addresses design, safety, and Open Space
in more detail than prior comments on grading, steep slopes overlay district, SWM requirements, and WPO
application. Please see prior comments #10, 13, 14, 17.c, and 18, p.2. Prior comments spotlight need for
design protections that meet county or state requirements.
Grading and design associated with proposed extended detention SWM basin design (at this location) is
problematic. (Rev. 2) Applicant suggests specific items are focus of revised design which will address
many comments (below) with next preliminary plat submittal: (Rev. 3) Comment addressed.
a. Extended Detention proposed top of embankment width is 8 -ft. The top of embankment is proposed to
serve as vehicle access in support of maintenance needs. A width sufficient as safe to support this use
and protect personnel is required. (Rev. 2) Assign evaluation of SWM facility to VSMP/WPO
Application.
b. 3:1 slopes shown in profile view of proposed basin understate grade. Existing slopes are 2' /i: 1. GIS
displays grade as 42% (vert. /horiz: 24/57: contours 496' -472'; 36/86: 508'- 472'). The most favorable
least steep contours are 512' -468', 44'/121', or 36.4 %. Slopes > 3:1 affect design and review. (Rev.
2) Comment (will be) addressed through revised design. Terra Engineering e-mail references slopes
below SWM basin: "All proposed slopes are 3:1, some existing slopes are slightly steeper, but are
planned to be left undisturbed outside grading limits." (October 23, 2014 5:13 PM). (Rev. 3) Comment
addressed.
c. Waiver to disturb preserved slopes (by right through legislative zoning action, § 18- 30.7.4.b. Lg)
remains subject to design standards listed at § 18- 30.7.5.c.1. ( #13, below). "Whenever vertical interval
(height) of any 3:1 (thirty -three (33) percent) slope exceeds 30', reverse slope benches or a surface
water diversion shall be provided." To construct either requires further disturbance of preserved
Engineering Review Comments
Page 2 of 8
slopes, pushes untenable grade further past limits. (Rev. 2) Comment will be addressed. Conceptual
stepped wall system above basin satisfies design standards found § 18- 30.7.5.c.1. (Rev. 3) Comment
addressed.
d. Extended Detention design will be reviewed carefully under WPO application. Without details of
basin, aquatic bench, forebay, primary/emergency spillways or pipe outfall, it is unclear if proposed
SWM facility will impact proposed grade. (Rev. 2) Assign evaluation of SWM facility to
VSMP/WPO Application. (Rev. 3) Comment addressed — preliminary review of extended detention
SWM facility indicates proposed (or similar) design could provide 2XWQV (210.9cy x 2) needed to
treat 113,256 SF impervious, 292,426 SF turf runoff (post- development - /section 3, portions sec. 1) if
basin depth = 4.6'( ±), x- sectional basin area 2.3' above floor = 2,475SF. Statement does not indicate
SWM plan or basin design approval. ACCD will furnish supportive detail. It is imperative that design
consider: direction of section 1 runoff, and whether runoff is routed to section 2 bio- filter, to section 3
extended detention basin, or is uncollected (front of Lots 16, 17, 18; essentially all of Lots 12, 13).
e. Open Space may include SWM facilities ( §18 -4.7, OPEN SPACE/b.) within limits ( §18- 4.7,c.3.).
Proposed SWM facility and preserved slopes occupy 90 -95% of 0.85 Ac. open space, which exceeds
limits. Ref. Limitation on Certain Elements. (Rev. 2) Comment withdrawn; defer to Planning.
Note- with stepped wall system above basin, preserved slope areas diminish.
f. Please furnish L x W dimensions for basin access turnaround shown in schematic view, C3.0.0.
Turnaround must allow service trucks larger than cars space to reverse and exit in a forward direction.
(Rev. 2) Assign evaluation of SWM facility to VSMP/WPO Application.
g. Existing conditions: show contours below proposed detention basin at least as far as stream, elev.
460' ±. Show Fontana Drive, C2.0.0, C3.0.0, at least this far. Existing conditions include slope, road,
and stream, each relevant to review. (Rev. 2) Comment not addressed. As follow -up, ACCD
acknowledges obstacle to working on adjacent property. Retrieve contour data (< 2 -yr old) from data
repository - County GIS, for example if possible. Request restated as recommendation. (Rev. 3)
Comment addressed.
h. Hyland Ridge: Easement agreement with property to north is required to maintain drainage: basin to
stream ( §14 -431). (Rev. 2) Comment withdrawn. Off -site drainage easement not required if Qto
post - development < Qio pre - development.
i. Basin outfall with WPO application, furnish details of ESC measures for primary spillway: basin to
stream. 2 -yr. storm and bypass events may not concentrate flow (surface water) on the face of T /2:1
preserved slopes ( §30.7.5.d). (Rev. 2) Assign evaluation of SWM facility to VSMP/WPO
Application.
j. Sequence —with WPO application, outline steps for constructing sediment basin assumed to be
coincident with extended detention basin location. Show ESC measures required to construct a basin
while protecting streams and off -site areas. (Rev. 2) Assign evaluation of SWM facility to
VSMP/WPO Application.
k. Show temporary construction easements. (Rev. 2) Comment withdrawn; show limits of disturbance
on VSMP/WPO Application.
1. DEQ Stormwater Design Specification, Appendix A, Earthen Embankment, Ver. 1.0, March 1, 2011,
defines height (p. 1):
The height of an earthen embankment is the vertical distance from the natural bed of the stream
or watercourse, measured at the downstream toe of the embankment, to the top of the
embankment. If the embankment does not span a stream or watercourse, the height is the
vertical distance between the lowest elevation, measured at the outside limit of the embankment,
and the top of the embankment.
For total height of embankment 25 or more feet, table (p. 9) states minimum top width is 15 -ft. —Link:
http: / /www.vwrrc .vt.edu /swc/NonPBMPSpecsMarchll /Introduction Ann% 20A_Earthen %20Embankments_SCrafto
nRev_03012011.pdf
Yet widening top of embankment creates steeper slopes. Request to widen embankment does not suggest
downslope grade may exceed 3:1. Rather, requirements highlight need for alternative design or new
SWM facility location, away from preserved slopes above Hyland Ridge. (Rev. 2) Assign evaluation of
SWM facility to VSMP/WPO Application. Also, website lists BMP technical specifications for projects
subject to 9VAC25- 870 -65. Project appears to be subject to 9VAC25- 870 -96 criteria (old criteria).
Engineering Review Comments
Page 3 of 8
M. VDEQ Construction Specifications for Earthen Embankments (item k.) is referenced. Design
considerations for site: Maintenance & Safety (p. 10/1. 4., Link, above) — "a 6 to 10 foot wide bench
should be provided at intervals of 10 to 15 feet of height, particularly if slopes are steeper than
3H:1V' ; piping (p. 8); soils investigation (p. 3/1. -3.); embankment stability (p. 511. -3.). All
considerations apply to proposed location. (Rev. 2) Comment withdrawn. —see item 1., above.
n. A geotechnical investigation is required for this location prior to final grading plan approval, and
prior to preliminary plat approval ( #17.c., below). (Rev. 2) Assign evaluation of SWM facility to
VSMP/WPO Application. Also, item 1., above.
o. A. -N. may be read in context of adjacent properties, downstream resources, transfer of SWM
maintenance responsibility to HOA, those who will maintain SWM facilities, and families of Fontana,
and in light of trust ordinance places in imperative need to evaluate design against risk. (Rev. 2)
Comment is opinion, withdrawn.
p. Water quality design criteria at 9VAC25- 870 -63 (Part II -B) or energy balance equation may offer
relief from design or space constraints (item h.). [Links:
http:// albemarleengineer .blogspot.com/2014 /02 /how -to- avoid -fixin -ig nadequate.html VAC:
http: / /lis.virginia. ov /c ii�gp604.exe ?000 +reg +9VAC25- 870 -63 ] (Rev. 2) Assign evaluation
of SWM facility to VSMP/WPO Application.
[ Code references: §18-8.5.5.2.e. Applicability of chapter 17; §18-8.5.5.4.b/c, grading; §17-
102.a./b./c. purpose (ch.17); §17-107 —State laws; §18-30.7.1 steep slopes overlay district; §14-
104.A — (other) applicable requirements. ]
A. Preliminary Subdivision Plat (SUB201400063), cont.-
1) Please submit a separate road plan with an application. Please address on road plans
the abrupt grade changes near the entrance of Belluno Lane and Brunello Ct. Show a sag
curves. The road plans included on this preliminary subdivision plat will be thoroughly
reviewed with the road plan application.
Comment not addressed. This is a subdivision application. Please submit a road plan
application for this project. (Rev. 1) Comment response: Applicant indicates road plans
are being prepared. (Rev. 2/3) ACCD requests road plans once Final Grading Plan is
approved. Road plans may be submitted prior to preliminary plat approved, once Proffer
Condition #2 Final Grading Plan is approved.
2) Please state on plan if roads are public or private. Also, label existing roads as public or private.
Comment addressed.
3) The pedestrian paths for Phase 4C are not shown. Please clarify the trail location.
The trails should show interconnection with other Fontana phases.
Comment not addressed. Please show interconnectivity of trailways to existing Fontana
Subdivision. (Rev. 1) Comment addressed; Applicant response: "The trails have been
resolved and approved by Amelia McCauley."
4) Proffer 5 states that pedestrian paths shall be Class A, Type 1 from the Albemarle
County Design Standards Manual. Please show section detail. Comment not addressed.
Please show interconnectivity of trailways to existing Fontana Subdivision. (Rev. 1) Comment
partially addressed; see item 3. As follow -up, two pedestrian section details are confusing.
Class A type 1 trails occur not only on Via Florence. Select and revise a single trail typical
section: retain Class A type 1 label and 10' corridor width — ACDSM, I.7.H. [Also, end doc]
(Rev. 2) Comment not addressed. Two pedestrian section details are confusing. Retain Class
A type 1 label and 10' corridor width — eliminate Pedestrian Path section, C5.2.0. — please call to
discuss. (Rev. 3) Comment addressed.
5) Trails should be in common areas, and maintained through neighborhood covenants or private
agreements. When not in common areas, all trails are required to have easements which must be a
Engineering Review Comments
Page 4 of 8
minimum of 10' wide.
Comment addressed. Please show interconnectivity of trailways to existing Fontana Subdivision.
(Rev. 1) Comment partially addressed; see #4 above. Label trails and common areas, C3.1.0., C4.1.1.
(Rev. 2) Comment not addressed; please address. (Rev. 3) Comment addressed.
6) Brunello Court is proposed as 24' wide f/c to f /c. Are you proposing parking on one side or no
parking at all? Please clarify.
Comment partially addressed. Engineering still needs to meet with Planning to discuss road width.
(Rev. 1) Comment addressed.
7) It is not clear why Belluno Lane is designed as a rural road with a ditch. The curb and gutter
waiver request for Belluno Lane does not appear to have been approved by the Planning Commission
or the BOS. Also, the road section on sheet C6.0.0 does not appear to meet VDOT road standards.
Please revise to meet VDOT road standards from Appendix B(1) -14. Comment not addressed. This
will need to be approved by the Board of Supervisors. (Rev. 1) Comment addressed.
8) Previous comments mentioned that a waterline connection from the existing Ashcroft
Subdivision may be necessary to achieve adequate fire flows. Please clarify if this is still the case.
Comment addressed and applicant clarified waterline connections.
9) Driveways cannot be sloped greater than 10 %. Please label all the driveway grades to clarify if
proffer 2(G) is satisfied.
Comment addressed.
10) Please note that the SWM and Drainage calcs will be thoroughly reviewed with a WPO
application. An approval of this preliminary plat does not allow you to grade the site. An approved
WPO application (E &S and SWM plans), along with posting of bonds will be required prior to
obtaining a grading permit.
Comment acknowledged by applicant. (Rev. 1/2/3) ACCD restates comment, which has been
acknowledged.
11) Please show the approved pedestrian/emergency connector from the Cascadia Subdivision to
Fontana 4C. This should match the approved ZMA2004 -18.
Comment not addressed. The R/W is shown to property line, but the design needs to be shown to
the property line. Please discuss with the Planning Dept. (Rev. 1) Comment partially addressed;
Applicant's response expresses legal position (ref response letter, 20- Aug -14): "The grantor, Fontana
Land Trust, will convey upon demand..." Contours and design for the emergency connector from
Cascadia Subdivision to Fontana (Phase 4C) must be shown on preliminary plat, and built prior to final
plat approval. (Rev. 2/3) Comment not addressed; issue is in dispute. Engineering cannot resolve but
resolution does not affect Final Grading Plan approval since grading for a Cascadia Connector is shown
on C4.0.0.
12) Label the standard VDOT driveway aprons and show the detail.
Comment addressed.
13) The critical slopes section in the ordinance has changed. A critical slopes waiver was already
approved, but plans should meet Section 30.7.5 Design Standards. This is in conjunction with
comment # 17.
Comment not fully addressed. Not all slopes are "managed slopes." Please refer to Albemarle GIS
to clearly show all "preserved" and "managed slopes on plan. Please note a critical slope waiver
has already been approved for this project. (Rev. 1) Comment not addressed. Ref. pg. 1 /c. Revise
grading on preserved slopes in accordance with §18- 30.7.5.x1. Also, display managed/preserved steed
slopes (drawing layers) on sheets C4.0.0, C4.1.0. (Rev. 2) Comment not addressed; please address. —
see underlined text, above. (Rev. 3) Comment addressed.
Engineering Review Comments
Page 5 of 8
14) Please show SWM easements and access easements on plan.
Comment not addressed. Please show the easement around the SWM facilities. A SWM agreement
will need to be completed prior to the approval of the SUB application. (Rev. 1) Comment
addressed.
15) Some trees on the landscaping plan are in conflict with the storm sewer pipes. Please address.
Comment addressed.
16) It appears that the existing rip rap should be removed on final grading plan. Please clarify.
Comment addressed.
17) Please address Final Grading Plan comments to satisfy Proffer 2. (Rev. 2) Also, please incorporate
proposed design features [22 -Oct, 23- Oct -14 email] to extent necessary, as required to meet Proffer #2:
a. There appears to be a significant amount of 2:1 slopes behind lots as backyards. Proffer 2(D) calls
for 3:1 slopes. Any slopes steeper than 3:1 up to 2:1 should be the last resort since ground cover will
be harder to establish.
Comment not addressed. The ZMA condition regarding the slopes was to develop the site with
less steep slopes. The plan shows a significant amount of 2:1 slopes. (Rev. 1) Comment not
adequately addressed; response: "The amount of 2:1 slopes has been reduced (about 17 %) by adding
retaining walls and rc- grading as requested by County Engineering." Retaining wall on Lots 23 -27
eliminates some 2:1 slopes, but 2:1 slopes remain in this area and in back of Lots 29 -33. Please
consider ways to further limit or eliminate 2:1 slopes, consistent with proffer condition/Grading Plan.
(Rev. 2) Comment (will be) addressed through revised design. Terra Engineering e-mail: "All lawn
areas are now 3:1 or flatter in all of Section 3." (October 22,2014 1:59 PM). (Rev. 3) Comment
addressed.
b. It will be difficult to grade and maintain the swales behind lots 19 -27 and lots 14 -18. These swales
are too close to decks. This also assumes that homeowners will not regrade their own backyards. There
are also areas that do not meet the "inlet for every 3 lot" policy. I recommend showing retaining walls
to provide backyards for lots and showing easements for swales along the retaining wall.
Comment not addressed. Provide an inlet between lot 22 and lot 109. Also, there was no
attempt to address reducing the steep slopes. This is in conjunction with comment 17 a. (Rev. 1)
Comment partially addressed. As follow -up, please select line weight, symbol, or other convention
to demarcate swales/berms on Lots 20 -26, 15 -18, wherever they occur. Dot -dash lines /arrows appear
to show flow lines, but may indicate swales. HP (highpoint)/berm labels provide clues but not enough
clarity for review or construction. If ditch section, C4.1.0, applies to ditches on C4.1.0, please label
ditches in plan view. If ditch section applies to berm or swales, it is unclear. Three terms lend
confusion as to what, exactly, ditch section applies to. Please clarify plan view features
(berm/swales /ditches); tie each to berm, swale, or ditch detail. Provide cross sections of drainage
feature at points along berm/swale on Lots 21, 23, 25, C4.0.0. (Rev. 2) Comment not addressed —
please call to discuss. (Rev. 3) Comment addressed.
c. Please note the final grading plan shall be approved by the County Engineer prior to the approval
of the first preliminary subdivision plat.
Comment acknowledged. (Rev. 1/2/3) ACCD restates comment, which has been acknowledged.
d. On Brunello Court, there is a low point near station 14 +50. Please label the elevation on Sheet
C4.0.1. It appears this area will need to address relief for lots 23,24, and 31 if inlets are clogged.
Comment not fully addressed. Please provide inlets on both sides of road at low spot. (Rev. 1)
Comment substantively addressed. As follow -up, relocate curb inlet, Lot 31, which conflicts with
driveway entrance. (Rev. 2) Comment not addressed; please address. —see underlined text, above.
(Rev. 3) Comment addressed.
e. Clarify storm sewer behind lots 30 -34. There is only one inlet between lots 29 -30. Capture as much
of the impervious area into the storm sewer. It appears that a substantial berm may be needed to divert
Engineering Review Comments
Page 6 of 8
drainage from steep slopes to the SWM facility.
Comment not addressed. Applicant has designed the roofs of lot 29 -34 to drain to the storm
sewer pipes. Roof drains to storm sewer pipes cannot handle the 10 year storm. Provide a swale
to capture more runoff to grate inlets behind lots. (Rev. 1) Comment addressed. As follow -up,
see 17.b., above; there is need for clarity with respect to swales, berms, and ditches. (Rev. 3)
Comment addressed.
f. There is a proposed swale and berm behind lots 1 -5. It appears grading will be beyond the
property line. Please address and obtain permission from adjacent property owners.
Comment addressed
g. Clarify where runoff for single family dwellings will be diverted for lot 5 -11. Will it be towards
front of homes or released in backyards? Comment clarified.
New Comment:
18) Please note that the extended detention basin and biofilter is not approved under this application.
This will be reviewed with a WPO application. (Rev. 1/2/3) Comment noted. ACCD restates
comment, which has been noted.
19) Applicant has the option to use the new runoff reduction method that will be in effect on July 1,
2014. (Rev. 1) Comment noted.
New, Rev.1
20) Please include note with trail section detail; from ACDSM: (Rev 2.) Comment not addressed;
please include Note. (Rev. 3) Comment addressed.
Drainage provisions where referenced above are to Follow VDOT standards for a 2year
design storm. Concentrated runoff must not run across the trail, and culverts or footbridges
are to be provided, especially where the trail crosses ditches. Where the trial crosses Swampy
areas, provisions such as boardwalks are to be provided for a dry surface. Where a non -
paved surface is used, trail breaks and erosion prevention measures must be used on grades
above 7% to prevent repeated washout of the surface.
21) Label BW elevations for corresponding TW elevations for walls behind Lots 23 -27, and Lots 29-
30. (Rev 2.) Comment not addressed; please label BW Elev. (Rev. 3) Comment addressed.
22) Drive entrances, lots 12 -18, Via Florence Road, intersect street without curved dimension; please
revise per detail below, R =12'. [VDOT Road Design Manual, Appendix B, Subdivision Street Design Guide,
Sec. B -4, H. 3. Private Entrance Detail]. (Rev 2.) Comment not addressed. (Rev. 3) Comment
addressed.
Engineering Review Comments
Page 7 of 8
Notes:
Sea VDOT Road and 9ridge Standards, Sid. PE -1 for caaM details.
All enhance grades shall slarl hack of 1he shoulder line.
If drainage is necessary, the ditch line may he moved back to provide 9 inches {min -} cover aver pipe -
Entrances shall be 12 A wide and transition smoothly into the roadway surface- Driveway enharroe
pavement shall extend to ffw right of line. When an existing street is re- developed and modMGation of
an existing driveway entrance is required, 1he entrance pavement shall he extended to the rghl of way
line or the extent ddislu rbance to 1he existing driveway.
Pipe wlvwt
I
Desirable Radu6 Note:
M `
For enlrer5 to madrrays havvg ADT ct 2000 or more,
use radu6 of 20 feel. ForADT under 2000 radius may
be 12 feet
o
Ditch Row line
1
see a .ffi
Pipe wlvwt
if necessary
12 Fr
#'
SURFACE'
o
Ditch Row line
RODE 1B FF
see a .ffi
Radius Note p °
Shoulder
Edge of roadway pavemenl
ROADWAY PAVEM ENT �
FIGURE 9 — PRIVATE ENTRANCE DETAIL
Link: http: / /www.virginiadot.org /business /resources /appendb.pdf
23) Retaining wall, Lot 29, is 8' high in one location (TW 556.0; C4.0.0). §18- 30.7.5.a./1,2
proscribes retaining walls > 6' on preserved slopes. Propose alternative design. (Rev 2.) Comment
withdrawn — cannot apply § 18- 30.7.5.a./1,2, to this location in this instance while insisting no lawns
slopes exceed 3:1. (Proffer Condition #2, Final Grading Plan)
24) Furnish detail for proposed yard inlet (typical). (Rev. 2) Comment not addressed — please call,
if overlooked. (Rev. 3) Comment addressed.
25) Show and label flow lines as swale/berm (C.4.1.0) across back yards of Lots 4, 3, 2. Define
drainage on Lot 3, especially, to indicate storm runoff reaches yard inlet on Lot 2, rather than releasing
onto the Ashcroft Development. (Rev 2.) Comment not addressed; please address. (Rev. 3)
Comment addressed.
26) C4.1.1, Belluno Lane: Ascending steep grade (400') may require additional inlets. (The road
plans included on this preliminary subdivision plat will be thoroughly reviewed with the road plan
application. —see #1, above). (Rev. 2/3) Comment re- stated.
27) 4H: IV slope beyond Belluno Lane (C4.1.1, sta. 15 +20) may present driveway (max grade)
design challenge. Recommend ensure driveway grade, Lot 5, meets Proffer Grade Plan. (Rev 2.)
Comment withdrawn.
28) Furnish guardrail on Brunello Court and Fontana Drive Ext. as vehicular barrier above proposed
2:1 slopes above proposed extended detention SWM facility, C4.0.0. (Rev 2.) Comment (apparently)
not addressed. Furnish guardrail. (Rev. 3) Comment addressed.
Sincerely,
Engineering Review Comments
Page 8 of 8
John Anderson
434.296 - 5832 —ext. 3069
ACDSM, I.7.H. /Trail Standards:
H. Trail Standards.
ClassWication
Min. surface
requirements
Min.
width
Design
alignment
Other design
considerations
Class A — type
2" asphalt
5' surface
10% maximum
Drainage design as
1 law-
over 4"
longitudinal
given below
maintenance
aggregate
grade, 2%,
pedestrian
base
maximum cross -
path
grade
SUB201400063- fontana4C- PPT- 110714- rev3rev