HomeMy WebLinkAboutSDP201200032 Review Comments Site Plan Waiver 2012-06-22*-&A
County of Albemarle
Department of Community Development
Memorandum
To: Joanne Tu Purtsezova, Planning Review
From: Phil Custer, Engineering Review
Date: 22 June 2012
Subject: Miller School Entrance Drive; Site Plan Waiver (SDP -2012- 00032)
Engineering has reviewed the site plan waiver for the Miller School Entrance Drive (SDP- 2012 - 00032),
received 25 May 2012, and offers the following comments.
The applicant has included in his site plan waiver submittal a list of all items from sections 18-
32.5.6 and 18- 32.6.5. Engineering review offers no objection to the waiving all items requested
by the applicant except the following sections:
a. 18- 32.5.6.f The applicant should identify that the site is located within a reservoir
watershed.
b. 18- 32.5.6.q The applicant should formally include on the cover sheet the traffic counts for
the site. The ADT for the site is double the count from the Headmaster's letter because a
trip in and out of the site counts as two trips. The review of the rest of the plan is
contingent on these values.
c. 18- 32.6.1 The plan must be stamped and signed by a licensed professional.
d. 18- 32.6.5.e The applicant should identify the edge of pavement radii at all intersections
for the new travelway. The internal intersections must have a minimum radius of 15ft.
The minimum radius for the intersection on the public street is 25ft.
2. Travelways must be a minimum of 20ft wide, possess curbing, and be no steeper than 10 %. The
applicant has requested a waiver of the first two standards and proposed a rural shoulder and ditch
section with 18ft of pavement. This comment will serve as engineering's perspective on the
requested waivers per 18- 4.12.2.c.2.
An 18ft wide travelway would not equally or better serve the public health, safety, or welfare when
compared to a 20ft wide travelway. It should be noted that the VDOT width requirement for
streets with less than 400 trips a day is 18ft.
A roadside ditch is less efficient and is more likely to erode than curbing which would not equally
or better serve the public health, safety, or welfare. Though, it is understood that waivers of
curbing requirements are often granted in cases like this for "rural area" aesthetics. In which case,
engineering will review ditch linings to make sure they are sized appropriately.
Although it wasn't requested, I will comment on a possible waiver of the 10% maximum grade for
travelways. The applicant shows a maximum grade for Connector Road A at 15% which would
not equally or better serve the public health, safety, or welfare when compared to the county's 10%
standard. It should be noted that the maximum grade accepted by VDOT is now 15 %, consistent
with AASHTO standards. However, the grade transitions at the top and bottom of Connector
Road A are unsafe. Raising the grade of the loop road so this connector road is not as steep is
recommended.
3. Please provide stop signs or equivalent pavement markings at all new perpendicular intersections.
Albemarle County Community Development
Engineering Review comments
Page 2 of 2
4. Please provide a typical detail within the set for the retaining walls used to protect the large trees
on site. County policy is to limit retaining wall heights to 4ft for those without a handrail. Given
the nature of the site, handrails on these retaining walls would look unusual, so please examine
ways of reducing the height of retaining walls to less than 4ft. For instance, the wall at Sta. 21 +50
could be reduced by extending the 10% grade farther up the hill (which would also help with the
extreme grade on Connector Road A) and providing another culvert at Sta. 21 +95 and a 3:1 slope
from 2ft off the edge of pavement to the bottom of the retaining wall.
5. Please include in the set the County's General Construction Notes found in the latest edition of the
design manual.
6. Please provide a low maintenance groundcover for all slopes steeper than 3:1 on the plan. Special
consideration should be provided to the area of the 1.5:1 slopes.
7. Please show grading for a sump condition for the culvert at Sta. 17 +14 and specify its depth.
Please also specify the sump depth for the culvert at Sta. 18 +55.
8. Circular culverts are not allowed on perennial streams. The culvert upstream of the junction box
has a watershed of 58acres and is likely perennial.
9. The culvert at Sta. 37 +08 has a headwater of greater than 1.5 times the diameter of the pipe which
is usually the maximum allowed by VDOT and is the standard the county reviews plans to as well.
But, recognizing the undocumented reduction of flows due to the lily pond and the benefit of
metering peak discharges to help reduce erosion in the stream channel, the culvert is approved as
designed. No change to the plan is required by this comment.
10. VDOT approval is required.
11. This site plan cannot be approved until the ESC plan is approved
Idle: F.1_sim—PBC_Miller School Site Plan SDP201200032.doc