HomeMy WebLinkAboutWPO201400087 Plan - Revision 2022-03-08Frank Pohl
From: Frank Pohl
Sent: Tuesday, March 8, 2022 1:37 PM
To: Richard Park
Cc: Geoff Elsie; Dan Ratzlaff
Subject: RE: LM - Lofts at Meadowcreek Biofilter
Richard,
This is allowed per the DEQ biofilter guidance, therefore, there are no objections. I've added dimensions to your sketch to reflect your text below. Please let us
know when you begin the work, as Geoff will probably want to visit the site. Please document all steps in the process to make the closeout easier for all of us by
taking photos, including showing gravel conditions, dimensions/thickness of each layer, etc.
MIXTURE IN
ACCORDANCE TO
VIRCINN BMP
CLEAPoNGHOUSE
SPECIFICATIONS.
LATEST EDITION
Emm (e,wen LrG,R�frAen
�Mo �..m ree mvra �ora.a.
TOP OF
—:vlenn.. ��H
MULCH
ELEV, s28.50
Js,m. 7fl" 1
PEA
GRAVEL
12
FILTER STONE
VDOT NO. 57
AGGREGATE
PROVIDE MINIMUM BOTTOM OF8'
DN.
6' SUMP BELOW BIORETENTION
PERFORATED
UNDERDRAIN FACILRY-425.00
UNDERDRAIN
Don't hesitate to let me know if anything else is needed from us at this time. I will include this in the file.
Thanks,
Frank
Frank V. Pohl, PE, CFM
County Engineer
Albemarle County
fpohl@albemarle.org
434-296-5832 x7914
401 McIntire Road, North Wing, Charlottesville, VA 22902
From: Richard Park<rpark@pinnacleconstructionva.com>
Sent: Tuesday, March 8, 2022 12:51 PM
To: Frank Pohl <fpohl@albemarle.org>
Cc: Geoff Elsie <gelsie@albemarle.org>
Subject: LM - Lofts at Meadowcreek Biofilter
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Frank,
Per our previous discussions, the biofilter at Lofts at Meadowcreek is not draining as specified. We had F&R collect and analyze samples of the filter media and it
has insufficient sand and excess soil fines which are causing this lack of permeability. We have reviewed the VA DEQ Stormwater Design Specification No. 9 for
Bforetention and propose the following to remedy this issue:
1. Remove the existing shrubs and trees (which have mostly drowned) and mulch
2. Remove the existing biofilter media down to the top of the small stone layer ("pea gravel' on the detail below)
3. Assess the small stone choker layer to make certain it is sufficiently permeable
4. In lieu of the 24" depth of V1.9 biofilter media, Install =20" deep layer of sand with =4" of V1.9 biofilter media on top
5. In lieu of the Tree, Shrub, and Herbaceous Plants planting template, use the Turf and Tree planting template. To this end we will eliminate the shrubs
shown on the original plan, plant (4) suitable trees in the biofilter area (smaller trees than the sycamore shown on the original plan as it will quickly
outgrow the available space and its leaf litter is a continuous problem), sow the Ernst Rain Garden Mix onto the surface of the V1.9 topping layer, then
cover with turf which will provide a great nurse cover and prevent the Rain Garden Mix from being displaced before becoming established.
Relevant info from Specification No. 9:
Section 6.6 (page 25):
• Alternative to Mulch Cover. In some situations, designers may consider alternative surface
covers such as turf, native groundcover, erosion control matting (coir or jute matting), river
stone, or pea gravel. The decision regarding the type of surface cover to use should be based
on function, cost and maintenance. Stone or gravel are not recommended in parking lot
applications, since they increase soil temperature and have low water holding capacity.
Media for Turf Cover. One adaptation is to design the filter media primarily as a sand filter
with organic content only at the top. Leaf compost tilled into the top layers will provide
organic content for the vegetative cover. If grass is the only vegetation, the ratio of compost
may be reduced.
Section 6.8 (oaae 26):
and free. This option is a lower maintenance version of the tree -shrub -herbaceous
cover. Trees are
to prevent
Since we will not be mowing this area, mulched islands are neither needed nor desired.
See proposed revisions below (in color) to the original cross section detail from Sheet C.20 (attached).
3
PEA
GRAVEL
BIORETENTION SOIL
MIXTURE IN
ACCORDANCE TO
VIRGINIA BMP
CLEARINGHOUSE
SPECIFICATIONS,
LATEST EDITION
TOP OF
MULCH
GI nit -d9A Sn
(Ernst Conservation Seeds Rain Garden)
Mix with sod nurse crop cover
v1.9 filter media
r_-71
�a!�iiia!!.-aa&jilliii
r�
i
LYI
Ste. ♦LYL�� yLY�•rI Y�.��.Y�.,^mow, „dpy�
FILTER STONE
VDOT NO. 57
AGGREGATE PROVIDE
MINIMUM)
6" SUMP BELOW
UNDERDRAIN
BOTTOM OF J
BIORETENTION
FACILITY=425.00
FILTER
NOT TO SCALE
dULCH
`6• DIAI
PERFORATED
UNDERDRAIN
I have highlighted the proposed trees from the original plan Sheet C.22. Yellow — sycamore; purple — redbud; green — maple. This is a fairly small space for four
trees, particularly with a sycamore.
Please let me know at your earliest convenience if these proposed measures will be a suitable approach to this issue as we want to get this completed.
Best regards,
Richard Park I Vice President
Pinnacle Construction and Development Corporation
1821 Avon St. Ext., Ste 200 Charlottesville, VA 22902
Office: 434.979.2900
rpark@pcdcva.com I www.pinnacleconstructionva.com
/I PINNACLE CONSTRUCTION
& DEVELOPMENT CORPORATION
OVER 30 YEARS OF PROFESSIONAL SERVICE
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