HomeMy WebLinkAboutWPO200900070 Review Comments Erosion Control Plan 2010-02-23ALg�,��
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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: SDP - 200900100 & WP0200900070, Pleasant Grove — Final Site Plan
Plan preparer: AC Shelton (ac00 @comcast.net)
Owner or rep.: Pleasant Grove Baptist Church C/O James E Thomas
Date received: 16 December 2009
Rev. 1: 16 February 2010
Date of Comment: 13 January 201
Rev. 1: 23 February 2010
Engineer: John P. Diez — Engineering Technician
The Final Site Plan for Pleasant Grove, received on 16 February 2009 has been reviewed. The plan cannot
be approved as submitted and will require the following corrections before approval can be granted:
A. General Review Comments
1. All slopes 25% and over (critical slopes by County Zoning Ordinance) must be shaded [18- 32.6.6]
(Rev. 1) Comment has not been addressed. Please shade all existing critical slopes that are
shown on the plan.
2. Please specify on the plans that "All proposed slopes steeper than 3:1 must be provided with low
maintenance (not grass) ground cover.
(Rev. 1) Comment has been addressed.
3. All entrances must have VDOT designations (PE -1, CG -9a, etc.)
(Rev. 1) Comment has not been addressed. Please provide the VDOT designation that connects
the proposed entrance with State Route 743.
4. Please provide unobstructed sight distance triangles at the entrance.
(Rev. 1) Comment has not been addressed. The sight distance triangles must be shown in plan
view to verify whether the sight distance profile is accurate.
5. !2.5' minimum radii at the entrance (or per VDOT requirements, typically 25' -35') must be
provided.
(Rev. 1) Comment has been addressed.
6. VDOT approval must be obtained for any plan affecting public right -of -way.
(Rev. 1) Comment has been acknowledged.
7. Some parking areas exceed the 5% grade minimum. Please revise.
(Rev. 1) Comment has been addressed.
8. Parking width x depth x aisle width is 9'x18'x24' or 10'x18'x20' (where a 2' grass overhang is
possible, parking spaces can be 16' deep per detail 2 of the Design Standards Manual).
[18- 4.12.16]
(Rev. 1) Comment has not been addressed. The northeast curb on the southeast parking lot can
be moved 12" inches towards the northeast to achieve the required parking space dimensions.
9. Sidewalks abutting parking must be a minimum of 6' wide (exclusive of curb), or bumper blocks
must be provided. Please refer to the Design Standards Manual.
(Rev. 1) Comment has been addressed.
10. Sidewalks must be a minimum of 5' wide, exclusive of curb. Please refer to the Design Standards
Manual.
(Rev. 1) Comment has been addressed.
11. Please show all existing utilities on the plans.
(Rev. 1) Comment has been addressed.
12. Please provide a tree survey showing existing trees within the No Disturbance Zones.
(Rev. 1) Due to further review, please disregard comment.
B. SWM Plan Review Comments
13. Manufactured pre - fabricated water quality facilities must have a written approval from the
manufacturer.
(Rev. 1) Comment has been addressed.
14. A completed copy of the standard stormwater maintenance agreement and fee for recordation for
any stormwater management facilities must be submitted. [I 7-304E]
(Rev. 1) Comment has been acknowledged.
15. Please provide a drainage profile for the proposed stormwater pipes.
(Rev. 1) Comment has been addressed. Though, the profile may need to be updated based on
other comments within this letter.
16. Please provide details and computations for the control riser for storm water detention.
(Rev. 1) The detention plan as provided by the applicant is not satisfactory. First of all, in the
plan and calculations, I could not find the pre- development rates which the detention facility
must be designed to meet. Using a pre- development drainage area of 1.03acres, C -value of 0.3,
and a time of concentration of 15 minutes, I computed the 2 and 10 year discharge rates to be
1.05cfs and 1.40cfs, respectively. Second, the calculations did not match the plan in many
instances (outlet structure of Reservoir 2, starting elevation of the pipes, the volume pipe system
appears to be over - estimated, etc.). The time of concentration for hydrograph I and 3 is too
high. The critical storm does not appear to be routed. Based on this comments, additional
comments will likely be necessary.
By having two detention pipes in series, proving detention compliance becomes much more
difficult and time consuming. I recommend simplifying the system by reducing the pipe
between 2 and 3 to 15 ". make structure 3 a VDOT Standard End Section, and providing the
detention volume upstream of structure 2. I found that by adding a 5" orifice plate on the inlet
end of the 15 "pipe from structure 2 and converting the 42 "pipe to 48" as well as adding 2
additional 70ft sections of 48 "pipe, detention will be met. This is assuming a 0.5% grade on
the detention system.
17. Please provide coefficient and time of concentration for each drainage area.
(Rev. 1) Comment has been addressed.
18. Please provide an adequate channel analysis (MS -19).
(Rev. 1) As a courtesy to the applicant, County personnel made a visit to the site and concluded
that MS -19 will be addressed once the following is shown in the plan:
- Detention of the 2 and 10 year storms to pre - development flows,
- Construction of a properly -sized channel from the drainage system outlet on
site to the existing VDOT culvert (Permission from the adjacent owner will be
required), and
- Repair of the existing VDOT inlet structure.
C. Erosion and Sediment Control Review Comments
19. Please provide an Erosion and Sediment Control Narrative.
(Rev. 1) Comment has not been addressed. Please refer to VI -24 of the Virginia Erosion and
Sediment Control Handbook (VESCH) for a detailed sample of the E &S Narrative.
20. It appears that the sediment trap will not capture most of the runoff during construction.
Engineering recommends that the sediment trap be moved to the south side of the site (by the
proposed SWM outlet). In addition, please provide a diversion dike along the southeast side of the
site to capture and direct the runoff to the sediment trap.
(Rev. 1) Comment has been addressed.
21. Please provide details and computations for the sediment trap.
(Rev. 1) A trap has been provided in the correct location but it is not large enough for the
drainage area. It appears that the proper trap size can be achieved with the addition of a
retaining wall and /or the use of 2:1 on the southeastern slopes. If 2:1 slopes are used, please
specify a low maintenance, non -grass groundcover. The southern travelway can also be
reduced to 24ft.
22. The diversion dike on the northeast side of the site is not necessary; Please remove.
(Rev. I) Comment has been addressed.
23. Silt fence must not be installed across contours. Please remove the silt fence on the northeast side
of the site.
(Rev. 1) Comment has not been addressed. Please remove the silt fence along the northeast side
of the site and replace it with diversion dike.
24. Please provide dust control (DC) on the plans.
(Rev. 1) Comment has not been addressed.
25. Please provide temporary and permanent seeding (TS, PS) on the plans.
(Rev. 1) Comment has not been addressed.
26. Please provide a stockpile and staging area.
(Rev. 1) Comment has not been addressed.
27. Please provide a construction sequence.
(Rev. 1) Comment has not been addressed.
28. Please install outlet protection to all proposed outlets.
(Rev. 1) Comment has been addressed.
29. Please provide inlet protection (IP) to the culvert of the proposed entrance.
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