20130686 Ver 1_Stormwater Info_20141202

Fox, Tim
From: Fred Grogan <fred @equinoxenvironmental.com>
Sent: Tuesday, December 02, 2014 11:49 AM
To: Fox, Tim
Cc: 'Mike Lewis'; 'Ben Cathey';'David Tuch'
Subject: Lake Craig Bmp
Attachments: xs_Ce112.pdf, planspotadjustments_Ce112.pdf, underdrain_detail.jpg
Tim -
Per Mike's guidance, I am sending this a -maiIto request approval to adjust bioretention cell 2 at the Lake Craig project.
Asa precautionary measure prior to installation, a test pit was excavated +/-2' below the original bioretention cell
bottom elevation in which water was later observed. Although it was not verified that this was indeed the SHWT,
approval of reduction in the cross section of the bioretention cell is being requested as a conservative measure. After
exhaustive exploration of options considering both the as -built infrastructure and existing conditions, it was determined
that this cross section reduction would be the most feasible solution. However, this will result in a few deviations from
the BMP design manual.
1. The bottom of the cell will clear the observed water by approximately 1.5', while if IWS of 0.75' is included, the
clearance would be over 2'.
2: Minimum media depth is suggested at 3' to support trees /shrubs and 2' forgrass. We will have 2.25' total
media depth, but have woody material specified. Fortunately, the originally approved under drain detail
(attached) will not prohibit root systems from growing through all zones and into the in -situ soils.
3. Reduction of temporary ponding to 6" due to as -built infrastructure constraints.
4. The bottom of the cell is to be roll compacted (as opposed to scarified as suggested) to reduce infiltration rates.
Please see the attached hand sketch & plan of the proposed adjustments for reference.
We have also verified that we still meet volume requirements with the proposed reductions.
Please let us know if these adjustments are acceptable.
Best,
Fred Grogan, RLA
Land Planner
,WEQUINOX
w,knm +�r0egn mope+�bnNng
37 Haywood Street, Suite 100
Asheville, NC 28801
(828) 253 -6856 extension 203
Check out our new website and b/og! Visit us at www.equinoxenvironmental.com

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