HomeMy WebLinkAboutWPO201400028 Review Comments Erosion Control Plan 2014-05-30COUNTY OF ALBEMARLE
Department of Community Development
401 McIntire Road, Room 227
Charlottesville, Virginia 22902 -4596
Phone (434) 296 -5832 Fax (434) 972 -4126
Project: Pantops Corner
Plan preparer: Shimp Engineering PC [Justin Shimp, 201 E Main St., Suite M,
Charlottesville, VA 22902 -5273]
Owner or rep.: Pantops Corner LC [100 Harris Street, Charlottesville, VA 22903 -5317]
Plan received date: 28 Mar 2014
Rev. 1 15 May 2014
Date of comments: 10 Apr 2014
Rev. 1 30 May 2014
Reviewer: John Anderson
Erosion Control Plan (WP0201400028)
1. Move and redesign the sediment basin to the low point on the site's perimeter without
encroaching on preserved steep slopes. (We also noticed discrepancies between computations
and plan details, which should be cleaned up with the redesign.)
(Rev. 1) Comment addressed, yet computational or detail discrepancies remain:
a. DIA dewatering orifice/ flexible tubing, S13-1: compare plan sheet 5/Data sheet.
Reconcile
b. S13-1 has an emergency spillway. Qp = Q2 = 13.1cfs. Item 21, Data sheet: Qe = Q25 — Qp
= 20.1 — 13.1 = 7.0 cfs. Please revise.
c. With Qe = 7, from Table 3.14 -C, bottom width (b) = 10' Revise Sediment Basin 1 Cross -
Section (SB -1) and Outfall Profile to show 20' (or greater) emergency spillway length
(L); 10' W.
d. With Qe = 7, using VESCH Table 3.14 -C, length of exit channel, x, = 33' —please revise.
Also, revise Emergency Spillway Detail (33, sheet 5)
e. Data sheet: Item 23. Revise depth of water at principal spillway crest (Y) = 8.0 ft.
f. Item 23, revise L,r. L = 54.17 ft.
g. Item 24, with LS = 54 ft, collar dimensions = 4.25'. Please revise collar dimensions.
h. Sheet 4, Sediment Trap Design Data, Z (ft) —please revise to 1.5.
2. Update the topography to reflect actual site conditions, demolished structure, actual trees and
paved areas, etc. (Rev. 1) Comment addressed.
3. Ensure the storm conveyance channel or diversions do not impede construction access or grading.
(Rev. 1) Comment addressed.
4. Provide a sediment trap and diversions at the SW corner on Rt. 250. Rev. 1 Please furnish a
plunge pool to receive diverted runoff flowing west. Design should redirect this westward flow,
and release it to the north to be conveyed along diversion dike to S13-1. The idea is to redirect
runoff flowing W to the N, to prevent and avoid runoff release at the SW corner of the site.
5. Provide silt fence (SF) between LOD and off -site stream below the new basin location, E side of
site. (Rev. 1) Comment partially addressed. SF label indicates general location, but please
include line- dash -x (legend symbol, SF) to aid installation and bond estimate (sheet 3).
6. Provide SF along N side of site (approx same locations as safety fence) and W side. (Rev. 1)
Comment not addressed. Please show SF in these locations.
Engineering Review Comments
Page 2 of 2
7. SAF (safety fence) is needed on the south side of site to protect the pedestrian walkway adjacent
to US 250. SAF or better perimeter fencing should be provided at all sidewalks and areas where
the public may be at risk. (Rev. 1) Comment addressed.
8. Limits of disturbance (LOD) must include the construction entrance and all land disturbances.
(Rev. 1) Comment addressed.
9. It appears an off -site waste area is required. Please amend sheet 2 Notes, and include on the plan
the destination of waste dirt, which must be an approved off -site waste area. (Rev. 1) Comment
addressed
10. Provide stockpile locations. (Rev. 1) Comment addressed.
NEW
11. Sheet 3 — Show OP for 90.9' -18" CMP outfall below outfall of sediment basin (SB -1).
12. Sheet 3 — Show sediment trap floor dimensions (ST -1).
13. Sheet 3 — Provide 1' depth of cover (MIN) for 18" CMP culvert for construction access; furnish
CIP /OP for temporary CMP.
File: PantopsComer_wpo20l400028- 053014 -REVI