HomeMy WebLinkAboutSUB201400063 Review Comments Preliminary Plat 2014-09-09t ?RGS131A
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Department of Community Development
401 McIntire Road, Room 227
Charlottesville, Virginia 229024596
Phone (434) 296 -5832 Fax (434) 972 -4126
Project:
Fontana — Phase 4C
Plan preparer:
Terra Engineering and Land Solutions, P.C.
Owner or rep.:
Fontana Land Trust
Plan received date:
6 June 2014
(Rev. 1)
31 July 2014, not reviewed, revised
(31 -July plans revised, re- submitted 26 August)
Date of comments:
20 June 2014
(Rev. 1)
9 September 2014 (26 -Aug plan set); rev. 16- Sep -14
Reviewer:
Michelle Roberge
(Rev. 1)
John Anderson
Project Coordinator: Christopher Perez
Engineering has completed the review of application SUB2014 -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:
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.
b. 3:1 slopes shown in profile view of proposed basin understate grade. Existing slopes are 2'/2:1. 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.
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 slopes, pushes untenable grade further past limits.
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.
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.
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.
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.
h. Hyland Ridge: Easement agreement with property to north is required to maintain drainage: basin to stream ( §14 -431).
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 2'h:l preserved slopes ( §30.7.5.d).
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.
Engineering Review Comments
Page 2 of 6
k. Show temporary construction easements.
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/NonPBMPS12ecsMarchll /Introduction App %20A Earthen %20Embankments SCraftonRev 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.
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:IV"; piping (p. 8); soils investigation (p. 3/1. -3.); embankment
stability (p. 5/1. -3.). All considerations apply to proposed location.
n. A geotechnical investigation is required for this location prior to final grading plan approval, and prior to preliminary plat
approval ( 417.c., below).
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.
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- fixine- inadequate.html
VAC: htlp:Hlis.vir ig nia.gov/c i- bin/legp6O4.exe ?000 +reg +9VAC25- 870 -63 ]
[ 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.
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.7.11. [Also, end doc]
Engineering Review Comments
Page 3 of 6
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 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.
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 Commision 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. 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.
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.c.1. Also, display managed /preserved steep
slopes (drawing layers) on sheets C4.0.0, C4.1.0.
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 stormsewer pipes. Please address.
Engineering Review Comments
Page 4 of 6
Comment addressed.
16) It appears that the existing rip rap should be removed on final grading plan. Please clarify.
Comment addressed.
17) Please address the Final Grading Plan comments to satisfy 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 re- 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.
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.
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) 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.
e. Clarify stormsewer behind lots 30 -34. There is only one inlet between lots 29 -30. Capture as much
of the impervious area into the stormsewer. It appears that a substantial berm may be needed to
divert drainage from steep slopes to the SWM facility.
Comment not addressed. Applicant has designed the roofs of lot 29 -34 to drain to the
stormsewer pipes. Roof drains to stormsewer 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.
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?
Engineering Review Comments
Page 5 of 6
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) 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:
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.
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]
Notes:
See VDOT Road and &edge Standards, Sid. PE -1 for cuUfill details.
All antmnce grades shall stars hack of rho shoulder line.
If drainage is necessary, the ditch line may he moved track to provide 9 inches (min.) cover aver pipe.
Enlrances shall b 12 ft wide and tr ansition smoothly into the roadway surface. Drivaway entrance
pavement shall extend to the righl of line. When an existing street is re- develaped and modification at
an existing driveway entrance is required. the entrance pavement shall La extended to the right of way
line or the extent of di:sturbance to the existing driveway.
❑Fof nttrancee to madraya having AOT of 2006 or more.
Lb a I U r of 20 feel. For AUT under 26W fadius may
m 12 feet
Pipe wlvert
it necessary
12 FT
Ic �e
SURFACE
o
RAVE 16 F
Ditch How line
See v
Radius Note F o
.F
. -
Z.
Shoulder
` Edge of roadway pavemenl
ROADWAY PAVEMENT a0,
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.
24) Furnish detail for proposed yard inlet (typical).
Engineering Review Comments
Page 6 of 6
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.
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)
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.
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.
Sincerely,
John Anderson
434.296 - 5832 —ext. 3069
ACDSM, I.7.H. /Trail Standards:
H. Trail Standards:
C]assiFicatian
Min. surface
requirements
Min.
I width
Design
alt nment
Other design
considerations
Class A — type
2" asphalt
5' surface
10% maximum
Drainage design as
1 low-
over 4"
longitudinal
given below
maintenance
aggregate
grade, 2%
pedestrian
base
maximum cross-
path
grade
SUB201400063- fontana4C -PPT- 090914