HomeMy WebLinkAboutWPO200800054 Review Comments Erosion Control Plan 2008-10-10ALg�,��
�'IRGINZ�
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 - 00054, Faulkner Falls Subdivision
Plan preparer: Mr. Brian Smith, PE; Brian Smith Engineering fax 434.296.2041
Owner or rep.: Faulkner Falls LLC fax (unknown)
Date received: 19 May 2008
Revl: 29 Aug. 2008
Date of Comment: 2 July 2008
Rev1: 1 Oct. 2008
Engineer: Phil Custer
Revl: John P. Diez
The SWM, ESC, and road plans for Faulkner Falls Subdivision, received on 29 August 2008, have been
reviewed. The plans cannot be approved as submitted and will require the following corrections before
approval can be granted:
A. General Review Comments
1. Please provide a benchmark on the plan.
(Rev. 1) Comment has been addressed
2. Please state what datum the topography has been generated with.
(Rev. 1) Comment has been addressed
3. The scale of sheet E -1 appears to be 1 " =50' and not 1 " =40'.
(Rev. 1) Comment has been addressed
B. ESC Plan Review Comments
1. Please provide adequate channel analyses for all concentrated discharge points. It appears
adequate channels are needed from the detention facility to the stream and from the roadside swale
on lot 7.
(Rev. 1) Comment has been addressed. Although Point "A" is satisfied, Point `B" needs to be
addressed. Please design a level spreader at the outlet of the facility and extend the stormwater
management easement to include the level spreader. As an alternative, you can construct an
adequate stormwater channel to the perennial stream.
2. Please provide a brief construction sequence for the plan. It appears that after the ROW is cleared,
cut needs to be taken in the second half of the road to fill the first half.
(Rev. 1) Comment has been addressed
3. Please call out the roadside ditch on the east side of the roadway as a diversion (DV).
(Rev. 1) Comment has been addressed
4. The wet storage calculations appear to indicate vertical soil walls between elevation 439.5 and
441.99. The maximum slope in wet storage is 1:1. Please modify grading on sheet ESC -2 to
match the calculations sheet.
(Rev. 1) Comment has been addressed
5. The wet storage calculations appear to be incorrect. For instance, between the first two elevations
439.5 and 441.99, I calculated the incremental volume to be close to 69cy. Similarly, the volume
between the 2nd and 3rd elevations (441.99 and 442) was found to be close to Icy. Unless the
sediment basin grading below the 442 elevation is hollowed, the dewater orifice needs to be placed
at a higher elevations.
(Rev. 1) Comment has been addressed
6. The cleanout elevation of the basin must be located at the elevation when half of the wet storage is
filled with sediment. At elevation 442, according to the calculations sheet, 522cy of 635cy will
have settled.
(Rev. 1) Comment has been addressed
7. When determining the diameter of the dewatering orifice, the value should be rounded down (5 ")
to ensure that the drawdown is not less than 6 hours.
(Rev. 1) Comment has been addressed
8. Please specify outlet protection (OP) at the outfall of the sediment basin.
(Rev. 1) Comment has been addressed
9. Please move the sediment trap inline with the roadside swale.
(Rev. 1) Comment has been addressed
10. Please show the grading for the sediment trap.
(Rev. 1) Comment has been addressed
11. Why isn't the permanent structure specified in the SWM plan used for ESC purposes?
Engineering review maintains a policy that "structures and embankments match permanent design
for facilities to be converted to permanent stormwater management facilities. [DM]
(Rev. 1) Comment has not been addressed. The top of the permanent structure is not 445.8 in
the stormwater calculations. Also, please label all pertinent information on the detail on Sheet
8 (top matching calcs and ESC plan, and orifice dimensions).
12. Please show th, safety fences around both the sediment trap and basin.
(Rev. 1) Comment has been addressed
13. Please note that a grading permit will be withheld until a copy of the state VSMP permit is given
to the county. Please contact Mr. Matthew Grant, DCR, at 804.225.3068 for more information.
14. The ESC portion of the WPO bond will be computed once all comments have been addressed.
C. SWM Plan Review Comments
1. Please provide a SWM facility south of the roadway at Sta. 3 +00. [17- 314.C]
(Rev. 1) Please show the permanent biofilter on the plan.
2. Please provide modified simple spreadsheets for both SWM facilities.
(Rev. 1) Comment has been addressed
3. Please provide on the plan the standard county notes for SWM management.
(Rev. 1) Comment has been addressed
4. All quality SWM facility must have sediment forebays' for each discharge point. Forebays must
be sized to VSMH standards.
(Rev. 1) Comment has been addressed
5. The SWM computations do not appear to compare routed peak flow rates to the pre - development
condition.
(Rev. 1) Comment has been addressed as per the previous discussion.
6. The detail states that the bed elevation is 443.60 but the grading indicates a bed area of 443.
Please clarify.
(Rev. 1) Comment has been addressed
7. Please dimension the outlet protection from the biofilter detention basin.
(Rev. 1) Comment has been addressed
8. Gravel layer in the biofilter must be 18 ". [DM]
(Rev. 1) Comment has been addressed
9. Underdrain pipe must be 6 ". [DM]
(Rev. 1) Comment has been addressed
10. Please change all callouts for Luckstone biofilter mix to "state approved mix." [DM]
(Rev. 1) Comment has been addressed
11. The SWM portion of the WPO bond will be computed once all comments have been addressed.
D. Road Plan Review Comments
1. An application for a road plan review was not received with this submittal. A county review of
the road plan was performed, but copies were not sent to VDOT until July 1st, 2008.
(Rev. 1) To request a road bond, please submit a Road Bond Request Form and a schedule of
completion. The final plat cannot be approved until this bond is posted.
2. VDOT approval is required. At this time, VDOT comments have not yet be received.
(Rev. 1) Comment has not been addressed. VDOT approval is still pending.
3. Please provide traffic control signage on the road plan.
(Rev. 1) Comment has been addressed
4. Please provide street name signs on the road plan.
(Rev. 1) Comment has been addressed
Please show a culvert at the driveway to the existing house and callout VDOT Standard PE -1.
(Rev. 1) Comment has been addressed
It appears a crossdrain is needed at Sta. 1 +50.
Comment being withdrawal due to previous conversation.
\\ Cob- dts01 \cityviewlnk\Docs \2008 \WPO \WPO200800054- Faulkner Falls Subdivision\E2_esc swm rp_JPD_08 -054
Faulkner Falls Subdivision.doc