HomeMy WebLinkAboutSUB202000098 Correspondence 2020-08-03 (5)SHIMP ENGINEERING, P.C.
Design Focused Engineering
July 31, 2020
John Anderson, PE
County of Albemarle
Department of Community Development
401 McIntire Road, North Wing
Charlottesville, Virginia 22902
RE: Response Letter #1 for SLTB202000098 Galaxie Farm Road Plan — Engineering
Dear John,
Thank you for your review of the Road Plans for Galaxie Farm Subdivision. This letter contains
responses to County comments dated July 16, 2020. Our responses are as follows:
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1. Ensure land use schedule impervious area is consistent with WPO plan for this development.
Area reviewed for consistency.
2. Note: Picase submit WPO plan for development at earliest convenience. WPO received
(WP0202000037).
Acknowledged.
C2/C3
3. C2 does not clearly indicate two parcels. There are two parcels. Please show current parcel
boundaries.
Labels and lineweights revised to make this fact more clear.
4. Label Cow Branch.
Cow Branch labeled.
5. Label steep slopes (preserved /managed).
Slopes labeled.
6. Note: If roof runoff is proposed to be collected and conveyed via leader lines to drop inlets or will
intersect proposed 15" DIA storm lines, show leader lines.
Only lots 46-48 require roof drain routing, leaders have been shown. Drains (intentionally)
outlet to front yards.
7. Please consider recent Building Inspections Div. guidance which may influence design of
retaining walls or affect plan approval. Albemarle County Building Official advises that:
"Retaining walls shall either be independent and terminate at the property [read, lot] line or an
easement and maintenance agreement shall be executed between property owners involved." We
mention this now so that it does not cause issues, or delay or impede subsequent plan (or building
application) reviews /approvals.
Thanks for the reminder, we have notified the developer of this condition. Developer is
preparing retaining wall deed and maintenance agreements to be submitted with the
912 E. High Sr. Charlottesville, VA 22902 1434.227.5140 1 shimp-engineering.com
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subdivision plat. For now, wall Maintenance easement, with access from ROW, added to
plans. We will finalize deed/agreements by the time the subdivision plat is filed.
8. Label lots. Also applies to C7, C8.
Lot labels added to these sheets.
9. Please examine remnant existing and proposed contours on Lots 7-11. Provide storm runoff
capture /conveyance such that surface runoff does not cross more than 3 lots, without capture
/conveyance. Ref. Drainage Plan Checklist for plan reviewers. p. 1. Drainaac section. list item.
[yard inlets appear to be required].
The grading on these lots was slightly revised to ensure sheetflow does not cross more than
3 lots.
10. Lots 53-56 runoff is shown sheeting across Road E. Provide drainage to intercept sheet runoff and
convey via street -side pipes or yard inlet pipe system. Design must prevent offsite runoff from
traversing Road E street surface.
This design is intentional as part of a low impact design strategy. As part of the rezoning
application, we were granted a curb & gutter waiver for Road E. So we were allowed to
have the small amount of water from Lots 53-56 sheetflow across Road E. And although the
CG-7 on the downhill side is not required, we judged that this design would provide better
public benefit for runoff control than if no curb & gutter were provided. So as it has been
designed, this street section goes above what is required by the zoning requirements for this
road.
It. Provide temporary (off -site) construction /permanent grading easement/s as needed to construct
proposed retaining wall across parcel lines, Lots 1-7.
Permanent wall maintenance easement added. While we anticipate minor construction
disturbance in the Galaxie Farm ROW, this activity is permitted as long as full access is
provided for the residents who use the road. Grading will not disturb past the existing
fence, thus full access is ensured, thus no other easements are necessary for construction.
12. (C7, C 12): Calculate depth in roll-top gutter, Road E. Ensure runoff does not enter driveways
(esp. Lots 57, 58).
Acknowledged, this calculation was added to the LD-204 page. The curb is adequate per
VDOT standards — with a flow depth of 0.21' (2.5") for a storm with I=6.0.
13. C3, C4: 8' wide ditch crossing lots 23 thru 38 is an infeasible design. Revise surface ditch to
subsurface drainage (inlet /pipes). Owner of multiple lots may flatten obscure ditch and disrupt
drainage since each lot has such limited lawn area. A surface ditch design crossing 15 lots will
not in this instance be approved. (Recall homeowner resistance to Swale construction across lawn
areas at Hillbrook Subdivision.).
Ditch removed from Lots 23-38 and replaced with yard drains & storm pipe. Yard drains
placed to ensure flow does not cross more than 3 lots. Drains daylight in Open Space B past
the (revised) emergency connection.
14. Similarly, provide subsurface storm runoff collection /conveyance for Lots 15-22.
Fot these lots, runoff does not cross more than 3 lots, but sheetflows into a natural channel
just behind the rear property line. the runoff is captured at structure EX where this
channel re-enters the property.
912 E. High St.. Charlottesville, VA 22902 1434.227.51401 shimp-engineering.rom
15. Ensure storm runoff from impervious areas, Lots 15-38 is conveyed and treated or detained, as
needed, to comply with state or local code, including MS-19. It appears a necessity that given
close proximity to property line to SW that impervious rooftop storm runoff must be collected,
since splash block -only discharge cannot transition to sheet flow in limited space available (Lots
15-22, especially).
Acknowledged, this runoff is captured in E7C (serves lots 15-22) and in yard drains (serves
lots 23-58). since 15-22 sheetllows into a natural channel, with no downstream impact (since
this channel is re -captured at Lot 22), MS-19 requirements are met.
16. C4:
17. Provide guardrail, Road F, at stream crossing. Alternatively, provide 12:1, 4'-wide graded
shoulders before transitioning to steeper embankment grades. Infrequent use reduces but does not
eliminate risk posed by unrecoverable slope with z7.25' vertical drop to streambed.
Noted, however Road F has been removed and replaced with a superior connection that
utilizes the existing fire access road for Avinity subdivision.
18. C4 (C6, C8): Ensure lots are located entirely outside the (100') stream buffer. Ref. ZMA Sheet 7,
Note F. Portions of Lots 57, 58, 59 appear to be within stream buffer.
Lots 57-59 revised to be outside the stream buffer.
19. C5: Provide additional preliminary design detail for transition from Road A2 to Ex. Galaxie Farm
Lane which provides access to multiple parcels beyond proposed development. Note reading
Connect Galaxie Farm Lane to new road is insufficient for an existing road that must remain in
continuous use. Compare spot grade at transition to Galaxie Farm Lane at end of Road A2 to
existing Elev. of Galaxie Farm Lane. Provide preliminary travel way design and drainage to
ensure smooth transition.
Acknowledged, additional detail added to plan & profiles. While exact extent of grading will
be based on Held conditions (survey w. 2' contours allows only an estimate of how far mill &
overlay extends), more direction has now been provided.
20. C5, C6 (Subdivision Layout), and C7, C8 (Grading and Utility Plans) mix incomplete views of
easements, and utilities. For example, C5, C6 show ACSA easements, but not all. For example,
C5 does not provide ACSA waterline easement south of Road Al in the direction of Rt. 20, to
include new FH near Int. Rt. 20. New ACSA water easement is shown along Road E, with utility
schematic (C7), allowing easy check of easement. Provide and label all utility easements on C7,
C8.
Easements now properly shown.
C5/6
21. Show /label CG-12 ramps wherever sidewalks intersect roads [@ intersections of Roads: B1-A2,
132-A2, 131-Al, Al-D, 132-C, C-E, at entrance to parking area SE of Open Space C].
CG-12 Type B ramps (w. notation) added at all these locations.
22. Provide and label traffic connul signs: atop, no parking, �pxd limit.
Signs added where needed.
23. Provide and label street name signs.
Street signs added.
912 E. High St.. Charlottesville, VA 22902 1434.227.51401 shlmp-engineenrig.rom
24. Show intersection sight distance lines for internal street intersections.
LSD lines for internal streets added.
25. C5
a. Lot 60: Provide Auto -turn figure to show vehicle reversing from driveway clears N-bound lane
completely before advancing in a forward direction. If Road E is insufficient length, a typical
passenger vehicle will strike curb or run off Road E before it clears N-bound (in -bound) lane.
House & driveway orientation has been reversed to provide adequate reversal space.
b. Provide fixed barriers both as pedestrian protection and to prevent vehicles from running off
the end of Road E. A curb -less design at N end of Road E cannot be approved. Providc v11:)njrail
pedestrian protection between end Road E, and Road Al sidewalk. Provide curb at cl
GR-2 guardrail provided. Curb was not provided as this is an uphill section, and guardrail
serves as a more sturdy and effective barrier.
c. Lots 57, 58: Drive entrances propose acute angles (>90-deg). Provide Auto -turn figures to
show a typical passenger vehicle may enter driveways without running off paved drives and onto
lawns.
Lot 58 driveway is no longer acute; lot 57 driveway revised for better maneuverability.
These revisions should provide a solution to Engineering's concerns, however auto -turn
diagrams are not required for private driveways on private streets, and are not provided.
Cl. All subdivision Lots: Related to 25.c., revise all driveway widths to 12' (Absolute Minimum;
see VDOT CG-9D). Also, item 40 below. Please apply CG-9D Min. drive width to this/future
design.
All driveways now have min. 12' width.
e. Lots 48-50: Driveway entrances problematic relative to angle with cul-de-sac, or location in
radius curve sections of curb. Provide perpendicular driveway /street intersections. Relocate
driveways out of curved sections of cul-de-sac curb.
These driveways are perpendicular to the road/cul-de-sac.
f. Show sight distance lines (left/right; NE/SW) at Int. Road Al and Route 20.
Sight distance shown on C19 & C20.
g. Label highlight line -type, image below. If an easement or setback, this line intersects structures
(likely impermissible).
That unlabeled line is the 18' garage setback, label has now been added. House can
encroach garage setback, but the garage must provide min.18' of driveway from back of
sidewalk.
26. C5(-C13, 8 sheets): Show driveway entrance radii graphically. Additional comments possible.
Radii now shown graphically.
27. Carry-over review comment, SUB201900198: `(220120, Revised) Revise cul-de-sacs, Roads D1 and
D2 to 45' Min. Ref. VDOT Road Design Manual, Appendix B(1)-3, Roadway Geometric Design Criteria, B.
Local Roadways, 1.: "A single -unit (SU) truck design vehicle, as defined by AASHOT, should be used for
the design of all local subdivision streets. Dimensions far this vehicle are depicted in Figure 2-2 of
AASHTO Geometric Design of Highways and Streets 2011, shown in Figure 1. Nate: Fig. I shows path of
front overhang of a single -unit (SU) truck design vehicle Min. radius=43.5'.
912 E. High St.. Charlottesville, VA 22902 1434.227.51401 shlmp-engineenrig.rom
(New, Feb 12, 2020 1:54 PM email) Using a SU design vehicle then, there is option of: 45' R,
which meets VDOT RDM B(1)-24 with proposed Road DA / D.2 FC/FC street width =24% or
30' R cul-de-sac with FC/FC street width =30'. Either is acceptable. To provide neither would not
meet AASHTO /VDOT RDM, or ACDSM requirements. To provide one or the other also
alleviates concern relating to parcel deliveries (ever more common) and waste management
access needs outlined in email sent 2/7/2020 8:48 AM (below). Albemarle defers to VDOT
/ACF&R should either impose requirement for radius > 30'. Road plan design should
accommodate whatever these review, transportation, and emergency response agencies require.'
RDM, Appendix B(1) Fig. 1.
Noted, we have coordinated with, and received blessing from, VDOT & Fire Rescue on cul-
de-sac radii.
28. Provide details, plan labels (or both) for: a. Knox box (Road F), b. Bollards (Road F).
Label for Knox Box Added, label and detail for Bollards added.
29. Label distance along Route 20 to nearest street intersection (both directions).
Acknowledged, see plan sheets.
30. Provide curb extensions for parallel parking, Road B2; see design standard at VDOT RDM, B(1),
pE. 59 (nR. 61 of. PDF).
Curb extensions provided.
31. C7/C8, Grading and Utility Plan: [SUB201900198 review. If addressed w/ ROAD plan, please
disregard]:
a. (2/20/20, Revised) Engineering cannot recommend preliminary final plat approval of 2 x 60"
HDPE w / headwall at Cow Branch. Please provide additional design information for this
crossing; design for the 25-yr event. For perspective, please see photo d. 7/27/18 (by Albemarle),
below, which shows drainage structure beneath Rt. 20 upstream of proposed Road A.1 crossing.
Hydraulic design provided, which shows this design accommodates the 25-yr event.
b. ACSA Sanitary Easement may impede ability to develop Lots 29, 41, 31, 33, 35, 37, and 39, as
intcndcd with current design.
San sewer location was revised (unchanged in this second submittal) to allow necessary
development for these lots. Easement lies within front setback, sewer placed to allow street
trees.
c. ACSA Waterline Easement may impede ability to develop Lots 58-61, as shown.
N/A — WL is in public ROW.
d. Label roads. New: Label lots.
Acknowledged, lots now labeled on all sheets
e. Note existing natural drainage that clips end of Road A2. Provide conveyance of storm runoff
that transits this natural drainage feature in the post -developed condition.
This is provided by a combination of F2 & F3 inlets.
f. Avoid nuisance ponding on any private or public road; for example in circular /bulb portion of
Road B (south end Road E). Provide inlet capture and adequate conveyance at this location.
This is provided by current inlet design (ref. LD-204, inlet drainage map)
912 E. High St.. Charlottesville, VA 22902 1434.227.51401 shlmp-engineenrig.rom
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g. (2/20/20, Revised) Provide inlets and piped drainage of runoff, Road E. Withdrawn (email,
2/6/20, 6:12pm).
N/A, but note that Road E runoff routed to storm system via. CG-7 curb & gutter.
h. (2/20/20, Revised) Engineering recommends care with design of private drive entrances to
dwellings along Road E. Storm runoff collection and conveyance applies to Road E. Also,
comments elsewhere. Withdrawn (email, 2/6/20, 6:12pm).
Acknowledged — curb and gutter, although waived by planning commission, will provide
conveyance and runoff.
i. Provide /show Qabel public drainage easement at NE corner Int. Road D and Road Al (Open
Space). Note: A portion of public drainage, Str. D3 —D1, lies outside public ROW.
Public drainage easements added to plans (covers all channels, including Cow Branch,
outside of ROW).
j. Provide /show public drainage easements crossing Lots 29 and 61.
Public drainage easements added where necessary within these lots.
k. Provide storm drain inlets at low point /sag, Road At.
Inlets C2 & C3 already serve the sag in Road Al.
1. Remove entirety of proposed SWM facilities from stream -ward 50' of Cow Branch stream
buffer.
No SWM facilities lie within 50' of Cow Branch.
in. Show proposed grading, Road F; utilize F design contours, if necessary.
Road F removed.
n. (2/20/20, Revised) Provide design for Cow Branch crossing, Road F. Size pipe /culvert to pass
the 25-yr event without overtopping Road F (Emergency Access). New: County email to Shawn
Maddox, ACF&R, 2/20/2020 11:07 AM requests guidance on ACF&R access needs relative to
existing pipe at stream crossing along dedicated fire -rescue access (2nd point of subdivision
access).
Road F removed. Second crossing of Cow Branch no longer proposed.
o. New: Relocate private waterline laterals outside public ROW, all lots.
This is not a requirement, and is the purview of ACSA.
p. New: Coordinate with USACE. Provide copy of Nationwide or Virginia General Permit to
perform construction in live stream (Cow Branch).
Acknowledged, nationwide 18 permit exhibit submitted. Will send confirmation when
received.
32. Provide Class B — Type I primitive trail section (Ref. ZMA, sheet 9; image below).
Section added to C15.
33. Road Al profile: Label drainage structure dimensions /material type, INV elev., top of structure
elevation (at sag curve). Ensure adequate cover, given 10-'/2" pavement section, subgrade CBR
912 E. High St.. Charlottesville, VA 22902 1434.227.51401 shlmp-engineenrig.rom
requirement, and apparent -F distance between top of culvert and road finished grade. Cover
appears inadequate.
Acknowledged, drainage structures (Culverts) added. Inverts not shown as they vary, but
cover requirements (which are met - the previous iteration was drawn wrong)
34. Road Al profile: Show double -line culverts as two lines, not one line.
Profile revised per request.
35. Road Al profile: Label drainage structures.
Culverts labeled.
36. Show Road A2-Ex. Galaxie Farm Road transition. Provide grading /design that ensure smooth
transition.
Acknowledged, this is now shown.
C10
37. Road B 1 /Road B2 include sag curves that do not meet Min. K value =15; provide Min. K-value.
Also, ref. VDOT Road Design Manual, Appendix B(1), Table 1 reference to 2011 AASHTO
Green Book. See also, 2011 AASHTO Green Book, Table 5-3. Albemarle may at times rely on
2001 AASHTO Guidelines for Geometric Design of Very Low Volume Local Roads (ADT<400
ADT), which lists Min. rate of vertical curvature for Crest Vertical Curves (Exhibit 12), and
refences Ch. 5 of Green Book for sag curve Min. rate of vertical curvature. Albemarle requires
Min. K-values of 5 and 15 for crest and sag curves, respectively.
Road B vertical curves revised to fully comply with VDOT standards for a 25 mph road.
Since this street is expected to handle future traffic which would likely put the daily trip
count over 400, crest K of 12 and sag K of 26 have been provided.
For Road D, since trip count < 100, AASHTO Guidelines for Very Low Volume Local
Roads were used to determine sight distance. Sheet 35 of this book states that a sight
distance of 125' is appropriate for this scenario.
38. C 12: Road D, Revise to provide Min. K-value /sag curve > 15.
Acknowledged, this is provided.
39. C13: Road F profile: Label drainage structure dimensions/material type, INV elevation, top of
structure elevation (at sag curve). Ensure adequate cover.
Road F profile removed along with the road.
40. C15: luclude VDOT CG-9D, Standard Entrance Gutter -Ref. 2016 VDOT R&B Standards, Rev.
,1 ()7/ i
Detail added to C12.
41. C18
a. Add SL-1 or 11/2" steel plate labels to MHs, as needed (for example, Str. E7, which requires
both).
Profiles updated with these required items.
b. Profile Al-A2: Provide , it design.
Wingwall design provided based on VDOT specs. See added details, C17.
c. Ensure proposed culvert INV elevation comports with USACE countersinking requirements.
912 E. High St.. Charlottesville, VA 22902 1434.227.51401 shlmp-engineenrig.rom
Inverts are countersunk 6".
d. If culvert is a double line (B l — 132, for, I e), label profile for clarity ( dbl. line).
Used notation (double) instead of (2) on profile.
e. Revisc Piuiuc F i-F_ cayuuii w icau F i-F- .
Caption revised.
ZMA201800012 Sheet 7-related comments relating to SUB201900198
42. Note B: both 30' Access Easement and ACSA waterline (public utility) easements appear to
extend 5' within lots on west side of Road E, Lots 58-61, while 30' Access Easement intrudes 5'
into Lots 62-65 on east side of Road E. Note: No structures or improvements may occupy 20'
ACSA easement, or 30' Access easement. Please consider possible conflict at time of future
building permit application. Recommend propose no structural improvements within easements
on preliminary or final plat, or Road or WPO plans.
Acknowledged, there are no ACSA conflicts with this plan.
43. Note F: Remove lots from stream buffer. Also, item 18 15, above.
Lots removed from stream buffer.
44. Note G: Also, item 7 10, above.
Acknowledged.
45. Note K: Also, item 24.b.
Acknowledged.
46. Also, please consider Albemarle County Engineer's comments on ZMA201800012, 9/23/19,
which appear relevant to preliminary plat, and subsequent plan applications, reprinted as text,
below:
`Waiver Requests:
(1) Double Fronted Lots: No objection.
Acknowledged, thank you.
(2) Private Streets:
- Road D: The Design Standards Manual requires private streets to meet VDOT minimum
standards, however, the County has allowed by policy the use of ASHTO Geometric Design of
Very Low Local Roads for private streets with an ADT under 400 trips per day. If Block 1 is
modified to serve only multi -family (i.e. a site plan), standards may be reduced further as shown
in the Design Standards Manual.
Acknowledged, Road D revised to meet standard.
- Road E: Must also meet low volume road standards. Identify if any additional waivers are
required.
Acknowledged, no additional waivers required.
(3) Private Street Design Requirements:
- Road D: Street must meet design standards noted above, unless serving multi -family only.
- Road E: Identify the purpose of the "bulb" on this road. Parking must meet County design
requirements. Has VDOT approved spacing requirements for public road intersections?
912 E. High St.. Charlottesville, VA 22902 1434.227.51401 shlmp-engineenrig.rom
Acknowledged, Road D revised to meet standard. Road E bulb/cul-de-sac is to provide ease
of turnaround for residents. Parking meets county requirements (no parking on the Road E
bulb/cul-de-sac). VDOT had no objection for spacing requirements.
(4) Modification of Setbacks: No objection.
The road exhibits show a corner lot in Block 1, a few lots in Block 2, and the sidewalk in Block 2
within the stream buffer. These improvements are not exempt and cannot be located in a stream
buffer. This comment was previously made during the ZMA review, which did not (does not)
show these impacts.'
Acknowledged, these have been revised — all are moved out of stream buffer.
47. Calculation packet:
a. Confirm that 10-yr event is design basis of LD-229, p. 13 of packet.
Yes,10-yr storm is the basis of LD-229, heading note revised to state this.
b. If so, please revise design of culverts to ensure pipe capacity> calculated peak discharge
during design event; for example, please examine and revise as needed design of:
i. G2 to GI
ii. F2 to Ft (unless designed as detention pipe)
iii. E5 to E4
iv. E4 to E3
v. E3 to E2
vi. B2 to B 1
vii. A2 to Al.
Culvert designs revised to provide full capacity for these pipes.
If you have any questions or concerns about these revisions, please feel free to contact me at
keane@shimp-en ing eering com or by phone at 434-227-5140.
Regards,
Keane Rucker, Err
Shimp Engineering, P.C.
912 E. High St.. Charlottesville, VA 22902 1434.227.51401 shlmp-engineenrig.rom