20070389 Ver 2_Emails_20070420 (2)

Re: DWQ Project #07-0389 Granville County

Subject: Re: DWQ Project #07-0389 Granville County
From: Annette Lucas <[e-mail]>
Date: Fri, 20 Apr 2007 13:19:25 -0400
To: [e-mail]
Tim,
A dry detention basin is not an allowable alternative to a level spreader because it
removes very few nutrients. Here is a quote from the document on the allowable
options:
If the topography of the filter strip is too steep for a level spreader, a different
type of BMP will be needed. The Riparian Buffer Rules allow for new stormwater
outfalls through the buffer if a BMP is provided to control nutrients and attenuate
flow. Routing stormwater to a BMP that outfalls into directly into or through the
buffer is "allowable" (require written approval from DWQ) for protected buffers in
the Neuse, Tar-Pamlico and Catawba river basins. The BMPs that control nutrients and
attenuate flow are:
- */Extended detention wetland: /*This BMP provides the highest level of nutrient
control and also can meet state and local peak flow requirements.
- */Bioretention:/* This BMP also provides a high level of nutrient control. In order
to attain an appropriate level of peak flow control, an extended dry detention basin
may be needed up slope.
- */Wet detention pond:/* This BMP may also be used only on a case-by-case basis when
the drainage area is less than 25 percent impervious.
Annette
SITE TECHNOLOGIES INC wrote:
Annette:
I've reviewed the design manual for level spreaders that you refer to. If
you could please take a look at the pdf file attached to the last email, you
will see that there is nowhere to move the level spreader that is less
steep. I'm not sure what is involved in obtaining a major variance from
Environmental Management Commission to place a level spreader in series. As
an alternative, we might be able to fit a dry detention basin in this area
without encroaching into Zone 1 riparian buffer. I would value your opinion
on this. I've also refigured the runoff from the 1" storm for level
spreader #1 and #3 on the PDF plan and would appreciate your comments as to
the appropriate size.
Thanks, Tim
-----Original Message-----
From: Annette Lucas [ma.i..lto:arrrrette.lur.,as:~ncmail.net] Sent: Friday, April 20, 2007
12:51 PM
To: tastall~~'earth_i.i_nk.net
Cc: Dan Bliley; Julie Wright; Cyndi Karoly; Cynthia F Van Der Wiele; Ian
McMillan
Subject: Re: DWQ Project #07-0389 Granville County
Tim,
We recently completed a Level Spreader BMP Manual Chapter that explains the
options that area available when the slopes are too steep for a level spreader. It
is available on our web site at:
http://h2o.enr.state.nc.us/ncwetlandsldocuments/LevelspreaderBMPManualchapte
r.doc
Hopefully this document will address your questions about steep slopes. If you
continue to have questions, please contact me via email or phone.
1 of 2 5/7/2007 11:50 AM

Re: DWQ Project #07-0389 Granville County
This email will trigger your request to keep the project open beyond the 4/23 date
if necessary.
Annette
SITE TECHNOLOGIES INC wrote:
~ Annette:
I am redesigning this project following the initial review by DWQ. The
redesigned subdivision will eliminate one stream crossing (leaving only one
stream crossing). You had comments regarding the three level spreaders included
for the stream crossing to remain. Level spreader #1 and #3 were determined to
be undersized. I calculate the C value to be less than 0.4 but will agree to
use a C value of 0.50 (appropriate for developed large lot subdivisions).
Please take a look at the attached pdf file with "sticky note" comments. Level
spreader #2 is in an area that exceeds 6% slope. Due to the proximity of the
streams there is no other place for this level spreader. We will either need to
use a level spreader in series or use a dry detention basin for this location.
Do you have a recommendation here?
I need to respond in writing this week to keep this review open with DWQ. I
believe we can modify the drawings with your help. Thank you.
Tim Stall
Site Technologies, Inc.
Land Planning & Landscape Architecture
P.O. Box 1612
Oxford, NC 27565
[phone]
2 of 2 5/7/2007 11:50 AM