HomeMy WebLinkAboutWPO201200025 Review Comments Erosion Control Plan 2012-03-20ALg�,��
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COUNTY OF ALBEMARLE
Department of Community Development
401 McIntire Road
Charlottesville, Virginia 22902 -4596
Phone (434) 296 -5832 Fax (434) 972 -4126
Project: Monticello High School Parking Lot Improvements;
SDP - 2012 - 00011, WPO- 2012 -00025
Plan preparer: Mr. Darin Miller, PE; A. Morton Thomas and Associates
Owner or rep.: County of Albemarle School Board
Date received: 27 February 2012
Date of Comment: 20 March 2012
Engineer: Phil Custer
The minor site plan amendment and ESC plan for the parking lot improvements at Monticello High School
(SDP- 2012 -00011 and WPO- 2012 - 00025), received on 27 February 2012, have been reviewed. The plans
cannot be approved as submitted and will require the following changes /corrections prior to final approval.
A. Minor Site Plan Amendment Review Comments (SDP- 2012 - 00011)
1. The application is somewhat unclear as to what is being proposed in the existing gravel
parking lot. My sense is that the application proposes to remove the existing gravel, regrade
the lot, install new gravel, install curb and gutter, and install landscape islands. There is a note
referencing a bid alternative for pavement in this parking lot as well.
Regarding county review, any existing lot can remain as approved and constructed. However,
any parking lot being reconstructed must meet all county standards unless waivers are rag nted.
For the gated lot, this means that the maximum grade must be 5% and the area must be paved.
Since the parking lot upgrade is voluntary (not necessitated by an increase in building size or
other parking demand), the applicant is not obligated to construct any of the improvements
proposed in this plan. So, improvements necessary to bring the gated lot up to current
standards must be shown if the gated lot is to be upgraded, but all of these improvements can
be dropped by the contractor. Again, the plan approved by county staff must meet current
standards unless waivers are rg anted if a substandard area of the site is being modified.
The dropoff area improvements must meet the 5% standard as well. [18- 4.12.15.a, 18-
4.12.15.c, 18- 4.12.14]
2. Please show stop signs and stop bars on the eastbound, southbound, and westbound travelways
at the gated entrance so that the through movement from the public road is unimpeded. [18-
32.7.2]
3. Intersection sight distance, not stopping sight distance, must be used at entrances. I believe
the required sight distance at the new entrance is 445ft in both directions. [18- 32.7.2.1, 18-
32.7.2.7, 18- 4.12.17.b]
4. I suspect that the "Do Not Enter" signs flanking the new exit will not be enough to avoid
confusion at this location. Please provide at least one R3 -1 and at least one R3 -2 signs within
the VDOT ROW on the approaches to this exit at locations approved by VDOT. The left turn
lane in the middle of street may need to be hatch completely to deter southbound drivers from
considering the exit as an entrance.
5. Please more clearly show the proposed and existing topography in and around the new exit in
plan view, including existing contours along Mill Creek Drive. Please provide a centerline
profile of this entrance to confirm it is compatible with a VDOT CG -11. Also, the county
requires that the grade at entrances must not be steeper than 4% for a distance of 40ft from the
curbline. [18- 32.7.2.1, 18- 4.12.15.b, 18- 4.12.17.b, 18- 32.6.6.b]
6. The sidewalk from the sports fields terminates at the gated parking lot entrance. If the gated
lot is being modified, please provide a sidewalk to connect the front of the school to this point.
It seems the easiest way to do this is shift the parking lot 6ft to the northwest and propose 6ft
sidewalk adjacent to the 12, 10, and 6 sets of parking spaces. [18- 32.7.2.8]
7. Please specify the pavement section for the drop off area as well as ADT projections for that
travelway. [18- 4.12.15.a]
8. Please provide updated drainage maps and calculations for all drainage systems adjusted with
this plan, including the design of Mill Creek Drive to make sure that an insignificant amount
of runoff runs into the site from the street. All curb cuts should be treated as DI -3's in the
calculations. [18- 32.7.2.7, 18- 4.12.15.b]
The site plan cannot be approved until the applicant has Water Protection Ordinance (WPO)
plan approval. An Erosion and Sediment Control Plan has been provided and has been
reviewed in the section below. However, there seems to be no consideration for Stormwater
Management requirements. The WPO plan cannot be approved until the applicant has
demonstrated that all Stormwater Management requirements have been met. The existing
stormwater facilities for the area are in a file numbered 104.01 and 104.02 in the General
Services Department. Please contact Repp Glaettli (434- 296 -5823 x3424) to review these
files.
B. Erosion and Sediment Control Plan Review Comments (WPO- 2012 - 00025)
1. If the applicant decides to remove the modifications to the gravel lot from the plans, please
update the ESC narrative and esc plan accordingly.
2. To work properly, silt fence must be placed parallel to contours lines. As proposed, the silt
fence would divert all runoff to the low point where concentrated discharge would cause a
blow out and significant sediment loss. Silt fence would also be difficult to work with in and
around pavement and gravel base layers. Inlet protection is also not a viable alternative
because it is inefficient and subject to bypass. The BMP swale in the existing parking lot
would be damaged by this ESC plan as currently designed.
Instead of silt fence and inlet protection in the eastern parking lot, please provide diversions
and sediment traps to treat the concentrated runoff. Please provide calculations for all
proposed sediment traps as well. It appears that two small traps would be needed for the drop
off area construction and one larger trap would be needed for the gated lot construction.
Since esc treatment is provided with the traps, please remove all inlet protection measures
from structures outside of the limits of disturbance in the eastern parking lots. The inlet
protection will be acceptable for the exit construction, though the applicant must get VDOT
approval for the inlet protection shown in the ROW. Typically, this is not something that
VDOT will authorize.
3. Construction entrances must drain to a sediment trapping measure. Please relocate the
construction entrance to the dropoff area so that it drains to a sediment trap. Please remove
the inlet protection on the inlets at this divided entrance, since runoff would simply bypass
these ESC measures.
4. Please replace the construction entrance detail with the county's "Paved Wash Rack" detail
which can be found on page 28 of 35 in the County's Design Standards Manual. Since at
least one of the entrances is in existing pavement, it seems a note directing the contractor to
keep a 12ft by 70ft strip of asphalt in place would be helpful.
5. The ESC narrative is missing Adjacent Area, Off -site Area, Soils, and Erosion and Sediment
Control Measures sections.
6. Please provide outlet protection below the concrete spillways into the grassed Swale between
the parking lots.
7. Please provide Dust Control symbols (DC) throughout the limits of disturbance.
File: E1_mia esc_PBC_Monticello High Parking Lot Modifications.doc