HomeMy WebLinkAboutSUB200700396 Review Comments Road Plan and Comps. 2008-07-31From: Hamidi, Ajmal [ Ajmal.Hamidi @VDOT.virginia.gov]
Sent: Tuesday, July 29, 2008 1:35 PM
To: Amy Pflaum
Cc: Denunzio, Joel D., P.E.
Subject: SUB - 2007 -00396 Clifton Lake Subdivision
SUB - 2007 -00396 Clifton Lake Subdivision
Amy Pflaum,
We have reviewed the above plan and have the following comments:
General
a.. Since the full implementation of Chapter 527 regulations went into effect
in June of 2008, this plan requires a Traffic Impact Analysis.
b.. A preliminary flexible pavement design worksheet must be completed for
each public subdivision road. This worksheet can be found on Appendix IV of the
VDOT Pavement Design Guide.
c.. On sheets R12 and R14, S. R. 729 has the following description: "50'
Private R /W ". This road should be labeled as public not as private.
Geometrics
a.. Road "A ", Road "B ", and Road "C" which are all private roads must meet the
requirements for standard private subdivision road entrances given in the VDOT
Minimum Standards of Entrances to State Highways. Currently, the entrances to
these roads from the Shadwell Road Ext. have proposed radii of 15 feet and
roadway widths of 20 feet. The radii should be increased to 25 feet, and the
entrances should be paved to a minimum width of 24 feet.
b.. Road "C" does not provide a 50 -foot landing at its intersection with S.R.
729 (North Milton Road) nor does it have a 24 -foot wide paved entrance.
c.. The radius of horizontal curve #1 on the Shadwell Road Ext. is only 120
feet, and the radius of horizontal curves #1 and #2 on Shadwell Court are 150
feet and 180 feet respectively. The minimum centerline radius for a design speed
of 25 mph is 200 feet. Either the horizontal alignment of these roads must be
adjusted so that no curve has a radius less than 200 feet, or the design speed
of the road must be reduced to 20 mph.
d.. The K- values of vertical curve #1 and #2 on Shadwell Court are below the
minimum allowable values. Vertical curve #1 has a K -value of 22.22 whereas the
minimum K -value of a sag curve for a 25 mph design speed is 26. Vertical curve
#2 has a K -value of 9.23 while the minimum K -value of a crest curve for a 25 mph
design speed is 12. Either the K- values of these vertical curves must be raised
to the required values, or the design speed of the road must be reduced to 20
mph.
e.. Based on the existing contours on sheet R3, the grade of Shadwell Road
appears to be 8% where it meets the Shadwell Road Ext. at station 10 +00. The
proposed grade of the Shadwell Road Ext. is 5% at this station. Either the
proposed grade needs to be increased to 8% to match the existing grade, or a
vertical curve is needed to connect this grade change.
f.. The sight distance to the east at the intersection of Road "C" and S.R.
729 is actually much less than the 500 feet shown because the line of sight is
vertically obstructed by the high terrain to the south of S.R. 729. A sight
distance easement will be needed in order to perform the grading necessary to
eliminate this obstruction.
g.. The typical sections on R13 show 2:1 fill slopes. The fill slopes should
be 3:1.
h.. The typical sections on sheet R13 show that a 4 -foot graded shoulder is
proposed for Shadwell Road Ext. and Shadwell Ct. where there is no guardrail and
a 6 -foot graded shoulder where there is. According to Appendix B, the minimum
graded shoulder width for a road with a 25 mph design speed is 5 feet without
guardrail and 9 feet with guardrail. If the design speed is reduced to 20 mph,
the minimum shoulder width would be 4' where there is no guardrail and 7' where
there is.
i.. The typical sections do not show the proper placement of guardrail.
According to the VDOT Guardrail Installation Training (GRIT) Manual, the
guardrail should be placed within 2' of the hinge point of the road. In this
case, the hinge point is where the slope changes from 1 ":1' to 3:1.
j.. For a cul -de -sac with a completely paved surface, a 45 -foot radius should
be used unless the County in consultation with emergency services specifically
approves a smaller radius. If the approval is granted, the minimum radius of
the cul -de -sac would be 30 feet.
Drainage
a.. The culvert calculations need to be revised to reflect any geometric
changes prompted by the above comments.
b.. Culverts within the State's right -of -way must meet cover requirements.
Culverts A and C do not have the required 2' of cover.
c.. All culverts within the State's right -of -way must be designed to provide
18" of freeboard (defined as the difference between the elevation of the edge of
shoulder and water table) in accordance with section 8.3.2.2 of the VDOT
Drainage Manual. Culverts A and C do not have 18" of freeboard.
If you have any questions, please contact Joel DeNunzio or me.
Thanks,
A.J. Hamidi, EIT
Charlottesville Residency
(434) 293 -0011
ajmal.hamidi @vdot.virginia.gov