HomeMy WebLinkAboutWPO200800103 Review Comments Erosion Control Plan 2008-12-19ALg�,��
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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: WPO- 2008 - 00103, Pounding Branch Phases II and III
ESC, SWM, and Road Plans
Plan preparer: Mr. Tim Miller, PE; Dominion Development Resources, L.L.C.
Owner or rep.: H &S Properties LLC
Date received: 05 November 2008
Date of Comment: 19 December 2008
Engineer: Phil Custer
The ESC, SWM, and Road Plans for Pounding Branch Phases II and III, received on 05 November 2008,
have been reviewed. The plans cannot be approved as submitted and will require the following
changes /corrections prior to final approval:
A. General review comments:
1. Please shade all critical slopes. [DM]
2. Please be sure that the VEPCO easement is shown on all possible sheets.
3. Disturbance to critical slopes to install ESC measures is not considered exempt. However, if these
ESC measures were to be converted to SWM facilities, then additional critical slope disturbance
will not require a waiver.
4. The current lot layout does not appear to match the approved preliminary plat. Please contact the
Current Development planner prior to submittal of the final plat.
B. WPO- 2008 - 00103; Road plan review comments:
1. VDOT approval is required.
2. Please show the floodplain and stream buffer limits on sheet R -3.
3. Please provide the FEMA floodplain map reference details in the road set.
4. A horizontal curve appears to be missing on Mechums Edge Road.
5. Please call out the end treatment for all proposed guardrail.
6. At Pounding Branch Lane, please call out the stop sign.
7. Please provide pavement design computations.
8. In this set, please provide Albemarle County General Construction Notes for Streets, verbatim.
The seventeen note list appears to be from a previous design manual.
9. Please station all vertical curve vertex points. [DM]
10. All slopes steeper than 3:1 must have low maintenance, non - grassed groundcover specified.
Please make sure this is clear in the roadway section and in plan view.
11. When guardrail is used, the shoulder must be increased 3ft in width rather than lft. This is a
requirement of the county. [DM]
12. In the culvert profiles, please show the existing and proposed grades past the end sections.
13. Please specify the grate type for all DI-7's.
14. Concrete inlet shaping is required on all DI -7's because of the drop from surface to bottom.
15. In the road profiles, please show the scour protection at the outlet to all culverts.
Albemarle County Community Development
Engineering Review Comments
Sheet 2 of 3
C. WPO- 2008 - 00103; Stormwater Management plan review comments:
1. SWM facility maintenance agreements will need to be recorded for both properties before the
plans are approved. Please submit these documents with fees directly to Pam Shifflett after
consulting the guidelines available on the county website.
2. There does not appear to be any detention provided on site. Please provide calculations showing
that the development is in compliance with section 17 -314. A detention waiver may be granted by
the program authority as long as it is clear that downstream channels are adequate. If a waiver of
detention is desired by the applicant, please submit a letter to the County Engineer with the
justifications for the waiver as outlined in 17- 314.F.6.
3. A large portion of the proposed impervious area is not captured by a Stormwater management
facility. Please capture as much roadway runoff as possible. [17 -315] It appears that an attempt
has been made to eliminate roadside ditches to provide sheet flow in the proposed condition so that
SWM facilities will not be required. This tactic is at odds with Section 17 -315.A and should be
avoided when practical alternatives are available.
For this development, many erosion and sediment control traps on the downhill side of road
culverts can reasonably be converted into SWM facilities. Additional permanent roadside ditches
are necessary at the toe of fill slopes to direct more road runoff into these facilities rather than
temporary diversion dikes. New ditches should be provided at the following locations to capture
and treat road runoff: Sta. 17 +00 to Sta. 20 +00 Mechums Edge Road (north side), Sta. 40 +00 to
Sta. 49 +00 Sprouse Mountain Road (both sides), Sta. 25 +00 to Sta. 33 +00 Sprouse Mountain
Road (east side); and Sta. 13 +75 to Sta. 21 +50 Sprouse Mountain Road (east side).
On Pounding Branch Lane, the collection of the road runoff will not be necessary if buffers are
offered over the natural channels running parallel to the roadway and mitigation planting provided
where the proposed buffer is a meadow.
4. In the post - development drainage area map, please provide the runoff coefficient and time of
concentration for each drainage area.
5. Easements over the SWM facility and access path must be called out as " Stormwater management
easement" and should not be included in the drainage easement.
6. Biofilter 7 is unnecessary.
7. A SWM facility on the east side of Sprouse Mountain Road at its intersection with Dick Woods
Road appears to be necessary.
8. All water quality facilities require sediment forebays at each inlet point. Volume in the sediment
forebays count towards the total water quality volume of the facility. Each forebay should be sized
to capture between 0.1 -0.25 in of runoff over the impervious area of the watershed for each inlet
point.
9. Please show a graded 1Oft wide access path meeting the requirements of the design manual for
each facility. The path should provide access to all forebays, spillways, and risers.
10. The ponding elevation in a biofilter should be Ift if the 5% impervious area footprint is to be used
for sizing. Otherwise, a volume calculation must be provided.
11. Biofilter underdrains must be 6 ".
12. The planting configuration within the biofilter must be shown. No trees or shrubs should be
placed within the sediment forebay.
13. The planting schedule should specify the caliber of trees and height of the shrubs. (See the VSMH
for requirements.)
14. Please show cleanout locations in plan view.
15. The SWM portion of the WPO bond will be computed when the plan has been approved.
16. Based on the required changes, additional comments may be required.
Albemarle County Community Development
Engineering Review Comments
Sheet 3 of 3
D. WPO- 2008 - 00103; Erosion and sediment control plan review comments:
1. If the applicant intends to use "super silt fence ", a variance is needed from the program authority
because the method is not listed in the VESCH. Please submit a letter requesting this variance
including reasons why the measure is proposed and a fee of $760.
2. Please submit an erosion and sediment control narrative meeting all of the county checklist
requirements.
3. The limits of clearing and grading do not appear to encompass all proposed work.
4. Silt fence has been placed across contours in several instances. Silt fence should be installed so
that it is perpendicular to sheet flow.
5. Changes to the ESC plan will be necessary based on SWM comment #3. Roadside ditches should
be labeled as DV in the ESC plan.
6. A sediment trap is needed at Sta. 22 +50 on Sprouse Mountain Road. A diversion dike should
direct runoff from the stockpile area to this trap.
7. Both construction entrances must drain to a sediment trap or basin. This requirement may
necessitate the reconfiguring of the traps near the construction entrances.
8. Please show tree protection to the proper VESCH standard or remove completely from the plan.
The 28" oak tree on Sheet E -3 is called out as having tree protection fencing but grading is shown
within the dripline of the tree. The state standard requires fencing at the dripline for each tree. It
appears a tree wall is necessary to protect this tree. Another option would be to place the SWM
facility at the other end of the pipe to significantly reduce the grading in the vicinity of the tree.
(Please see SWM comment #3.)
9. Please show a stockpile area on Pounding Branch Lane.
10. Please show a staging and parking area for both Pounding Branch Lane and Sprouse Mountain
Road.
11. Engineering review maintains a policy that "cleanwater" diversions are not to be used to reduce
the required size of a sediment trap or basin. Please size the settling facility for the watershed
draining to it without the use of cleanwater diversions. This will require revisions to several
sediment settling facilities.
12. Adequate channel analyses will be needed for all concentrated discharge points. Please consult the
latest version of the design manual for adequate channel analysis requirements.
13. The weir length on trap 2 is incorrect.
14. The ESC portion of the WPO bond will be computed when the plan has been approved.
File: El_esc swm rp_ PBC_wpo200800103 Pounding Branch_II and III.doc