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COUNTY OF ALBEMARLE
Department of Community Development
401 McIntire Road, Room 227
Charlottesville, Virginia 22902 -4596
Phone (434) 296 -5832 Fax (434) 972 -4126
Project: Cascadia - WPO
Plan preparer: Dominion Engineering [434- 979 -8121 ]
Owner or rep.: Cascadia Development, LLC
Plan received date: 11 Mar 2014
Date of comments: 21 Apr 2014
Reviewer: Michelle Roberge
Engineering has completed the review of application WP0201300032.
A. Erosion & Sediment Control Plan and SWM Plan (WP0201300032)
1) The application states Early Grading Permit. For this type of application, there should be
no structures shown on this plan. Please clarify how you would like to pursue application.
Even though this may be an early grading plan application, I have reviewed plans for E &S and
SWM just in case it was a typo on the application.
2) On sheet SW3, please label preserved and managed slopes.
3) Temporary slope drains are not designed per VESCH standards. Typical designs show a
compacted earthen dike to divert runoff to slope drains. Please show.
4) Per meeting on Feb 6, 2014, we discussed revising the existing topography. Please
address. A sewerline was installed along northern and eastern portion of the site. We discussed
possibly using this road as a means to divert runoff to a sediment trap.
5) For phase 1 (northern and eastern portion), it will make more sense to have diversion dikes
at bottom of slopes to sediment traps. Then grade up the steep slopes. These diversion dike are
partially shown for the eastern portion of site.
6) The diversion dikes which splits the site on sheet SW8 and SW 13 does not appear to work
for clearing, grubbing and grading. This coincides with comment 4. I suggest removing these
diversion dikes and enlarging sediment trap 1. The diversion dikes at the bottom of the slope
should be extended for more capture to sediment trap 1.
7) The challenge is how to address erosion control in Phase 2 once the walls on eastern side
are installed. The dd's behind homes will not work.
8) The temporary slope drains on phase II erosion control on eastern portion will not work.
They should outlet into perimeter controls, such as as sediment trap.
9) S13-1 on calcs appear to be S13-2. Please revise name and note "post condition ".
10) On SW -5, SB -1 is an existing pond. Please correct label. This should not be used as a
sediment pond. What is the benefit of reducing the amount of drainage area to existing pond 1
when both ponds are owned by Dr Hurt.
11) Also, it appears that the ponds proposed does not match the approved ZMA2002 -04 plans.
Please clarify. This may have been discussed already while Michael Koslow was the reviewer.
12) On SW24, the pond labels do not match report. Please revise.
Engineering Review Comments
Page 2 of 2
13) It appears that the target phosphorous removal is 43 %, not including the future
development. Please take the future development into account. The current proposed
development shows the retention pond to be sized to treat 4* WQV (Retention Pond II),
275,880 cu -ft. When you add the future development, the BMP choice may change. Page 6 on
your report reflects the correct impervious areas, but this is not reflected in removal rate calcs.
Please revise removal rate calcs.
14) Once 13 is addressed, please meet all three below if site has inadequate channels:
a) Detain the WQV (1" runoff) and release over 48 hours.
b) Detain the 1 year 24 -hour storm and release over 24 hours.
c) Detain and reduce the peak flow for a 1.5, 2 and 10 year 24 -hour storm, to the following
level; peak flow <= Qf (VfNpost), where Qf is flow from the site in a well forested
condition (C = 0.25, or CN = 51), and Vf is volume from the site in a well forested
condition.
15) Show detail of emergency spillway.
16) It appears that a majority of the eastern portion is untreated. I recommend increasing the
size of the biofilter on the north and addressing more treatment on eastern portion of site.
17) Please provide SCC calculations.
18) All plans and calculations shall be signed, sealed and dated when it is ready to approve.
Sincerely,
r&T-
Michelle Roberge