HomeMy WebLinkAboutWPO201300002 Review Comments 2013-03-25Review Comments
Project Name: NORTHTOWN, PHASE 11 -A Erosion and Sediment Control Plan
Date Completed: Monday, March 25, 2013
Reviewer: Ana Kilmer
Department/Division/Agency: CommDev-Central Ops
Reviews
3/21/2013 - swa was received
3/21/2013 - swa was forward to CAO for approval as to form
3/21/2013 - swa was approved by CAO
3/22/2013 - swa was signed by County Executive
3/25/2013 - swa will be recorded at the clerk's office
3/25/2013 - swa recorded in deed book 4322, page 165
Review Status: Approved
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: Northtown Phase IIA -Final
Plan preparer: Collins Engineering [293-3719]
Owner or rep.: United Land Corporation [975-3334]
Plan received date: 11 Mar 2013
Date of comments: 18 Mar 2013
Reviewer: Michelle Roberge
A. Stormwater Management (WP0201300002)
1. The 10 year peak discharge rates for post -development are higher than the pre development. Please
raise the riser by V to elevation 450.
2. Please raise the 6" orifice to elevation 447 to allow the first 1" to be treated in the biofilter.
3. Please show the forebay as separate from the basin by raising the embankment below the weir.
4. Please show the plants for the biofilter. Refer to section 3.11-20 of VSMH.
5. Please show the cleanouts on biofilter.
6. Please show the SWM notes/detail from the approved plan WP0200600050- Northown Phase 1. This
detail I/S 11 describes the offsite improvements for adequate downstream channel.
Sincerely,
I)Q_It�
Michelle Roberge
File: E1_rp,esc,swm,fsp_GEB_template.doc
A ' .
arnational I
ick
- .....
....:..................................................................................
S 11 scale: 1" = 2'
The applicant shall restore the channel from the property line of TMP 45-110 to the permanent
pool of the first Carrsbrook Pond on TMP 4581 -01 -OA -3 as a compromise solution for meeting
MS19 "Adequate Channels" as per the agreement reached between the applicant and the County
on May 29, 2008. The applicant will excavate the channel to the cross-section designed by
Albemarle County Engineering and provided to the applicant on January 4th, 2008. A copy of this
cross-section is shown as detail H/S11 on Sheet S11 of the Final Site Plan. The routing of the
channel will follow the natural course of the stream to the best extent possible. A detailed route
will be provided for the County's review and approval prior to commencement of channel
restoration. In the event the County would like to modify the route, the applicant agrees to route-
it
outeit as directed.
The above agreement requires the applicable permits from DEQ/ACOE, as well as permission or
easements from the property owners affected by the restoration. The applicant shall request
permission from the affected land owners upon issuance of a grading permit for Phase 1 of
Northtown. Once permission is granted by all affected property owners the applicant shall have the
route designed and submitted for approval by the County. Upon approval of the stream routing,
the applicant shall apply for and obtain all necessary DEQ and ACOE permits. The applicant shall
also submit a plan for stream diversion while the work is being performed for approval by the
County. -As per the agreement reached, the applicant-- will seek permission from .the affected land
owners. for a time period that starts at issuance of a grading permit and extends for two years,
after the first Certificate of Occupancy is granted for the site. If permission from all affected land
owners is not obtained within that time frame the applicant shall not be required to restore the
channel. If permission is granted by all affected land owners, but DEQ/ACOE will not permit the
work, the applicant cannot, through no fault of their -own, perform the restoration.
Typical Cross -Section for
for Adequate Downstream
NOT TO SCALE
9t1
itective Lining
�5
L
n=;015
DEP Qn DEP
110
Q10
Additional
Flows
Total
10yr Flow
DEP
Remarks
1,4
0.63
7.07
0.42
2.02
2.44
0.70
E C-2
!4
0.90
6.76
0.83
5.52
6.35
1.00
EC -2
15
0.90
6.54
1.03
5.52
6.55
1.00
EC -2
i9
0.88
6.34
1.23
5.52
6.75
0.99
EC -2
19
0.70
6.16
1.31
5.52
6.83
0.78
EC -3, Type A
0.07 0.21
4.71
1.12
6.95
8.07
0.49
Paved Flume
12
0.88
5.33
5.54
0.98
EC -2
32
0,55
5.18
5.43
0.62 EC -3, Type A
38
0.48
5.12
5.39.
0.54
EC -3, Type A
Offsite Improvements
Channel
*Structural HDPE Trash
Rack Manufactured by
Plastic Solutions, Inc.
(540)-722-4694
(or approved equal)
3.0'
5 {
s
B'1,0 -Filter
..............................................
S11 NOT TO SCALE
#4 Rebar #4 Rebar ® 12" O.C.
Both Directions
.G,
/ \
Trash Rack*
STR-34
Manhole W/DI-7 Top
EIev=449.00
6" 0 Orifice
EIev=447.0_ 00
0Surface of Biofilter
EIev=446.00
Michelle Roberae
From: Michelle Roberge
Sent: Tuesday, March 05, 20135:13 PM
To: 'Graham Murray'
Subject: WPO20130002 - Northtown Phase IIA -Final
Graham,
I have reviewed the first revision to WPO20130002 - Northtown Phase IIA -Final. The biofilter is still undersized. We will
need to resolve the SWM facility before we can move any further. I look forward to hearing from you this Thursday to
discuss this project.
-Michelle Roberge
Michelle Roberge I County Engineer
Department of Community Development
County of Albemarle, Virginia
401 McIntire Road I Charlottesville, VA 22902
434.296.5832 est. 3455
1
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: Northtown Phase IIA -Final
Plan preparer: Collins Engineering [293-3719]
Owner or rep.: United Land Corporation [975-3334]
Plan received date: 7 Jan 2013
Date of comments: 7 Feb 2013
Reviewer: Michelle Roberge
A. Stormwater Management (WP0201300002)
1. It appears that the biofilter on site is now undersized due to the increase in drainage area from 7.5 acres
(from phase 1) to 10.95 acres (shown in this plan). Adding the forebay is great for pre-treatment, but it
also reduces the basin's volume capacity. For quality, the floor area of the biofilter should be 5% of the
impervious area. Based on these comments, the biofilter does not meet both the quality and quantity
criteria and a redesign is required.
2. Please include the drainage calcs for stormsewer in this WPO package when you resubmit.
3. For drainage inlet 28, the worst case scenario is to reduce the drainage area up to the wall. This will
reduce your time of concentration from 10 min to about 5 minutes. Please revise storm sewer
computations.
4. The curb cuts on the median should be treated like a curb opening inlets without depression and
analyzed for spread. Please provide analysis.
5. The stormdrain calcs show a CG -6 curb and gutter, but sheet 3 calls out CG -2 on travelways. Please
revise.
6. Please show all drainage easements, including the proposed stormsewer easements.
7. Please provide a scaled detail of the biofilter (preferably at a scale of 1"=30' or 1"=20'). Please show
just one bioretention basin detail which includes the cross section of the travelway, the spillway, the
54" culvert bypassing the system, the 10 yr and 100 yr elevations, the outlet, forebay, cleanouts, etc.
See details located on sheet 6.
8. Please provide the geotech fabric in basin.
9. The shape of the biofilter NW of site has slightly changed. Please differentiate between the existing
and the revised easements. The revise easement should encompass the 100 year high water mark.
10. Please show the approved site layout and drainage layout for the approved phase 1 on all sheets. If
there are changes to the phase 1, an amendment to phase 1 will be required. Phase 1 and 2 must be
looked at as a whole to ensure a well coordinated site layout, E&S plan, and SWM design.
B. Erosion Control Plan (WP0201300002)
1. Please provide a narrative for your project.
2. Please show the limits of clearing and grading. This must match the landscaping plans.
3. Sediment trap 2 is not necessary and I recommend providing another type of erosion control measure.
Provide soil stabilization blanket & matting with silt fence at the bottom of LOD.
4. The rip rap should not be placed at an angle from the pipe. Please revise.
Engineering Review Comments
Page 2 of 2
5. Please update the topo for the site. Also provide the as-builts for SB 1 or clarify if the basin will not be
reconstructed.
6. SB 2 is undersized. Please revise.
7. The wet storage volume is undersized for STI.
If you would like to come in to discuss other BMP measures that could be explored, please feel free to
schedule a meeting on Thursdays from 2pm-4pm.
Sincerely,
Michelle Roberge
File: E1_rp,esc,swm,fsp_GEB_template.doc