20040385 Ver 1_Emails_20040331

imap://john.dorney%40dwq.denr.ncmail.net @cros.ncmai1.net:143/fe...
Subject: Regarding Swansboro Isolated Wetland Issues
From: Ken Pohlig <[e-mail]>
Date: Wed, 31 Mar 2004 11:42:44 -0500
To: [e-mail], Kim Colson <[e-mail]>
CC: Cecil Madden <[e-mail]>
John and Kim,
Cecil Madden (my boss) asked me to send an e-mail to you both regarding the Swansboro
Isolated wetlands issues, and to let you know that I'd be happy to go along with you
all to visit the Swansboro proposed spray + storage pond site, if you all decide to
visit the site. I've already visited the site, along with Wilmington Regional Office
staff (Bruce Parris, Groundwater Section - now in the Mooresville Reg. Office, and
Jim Bushardt, WQ Section). My schedule is generally open any day, with the exception
of April 7th (when I would not be able to go).
I thought I'd take this opportunity to provide some background on the proposed
project. As you well may know, currently the Swansboro 6VWTP discharges into Fosters
Creek in the White Oak River Basin. They were told by the WQ Section years ago that
the entire discharge into the White Oak Basin had to be eliminated; hence the driving
force behind this totally non-discharging project. The WWTP currently is rated at
0.3 MGD, but will be increased to 0.6 MGD. The WWTP will use oxidation ditch
technology with denitrification capability, with tertiary filters (rotating cloth
filters, already installed) with W disinfection to generate Reclaimed Water.
The proposed site is several miles west of the Swnasboro WWTP, off Rt. 24. It is
roughly a 200+ acre tract of land purchased by the Town just for this spray
irrigation project, of which about 109 acres is useable irrigation land, after you
carve out the required buffers. [Note: The 109 spray acres supplies about 0.485 MGD
of spray disposal, not the full 0.6 MGD. Therefore this is how we intend to write
the permit.] Two small streams dissect the site: one is class' 'ed as SA, the other
is not. it
C" ?eN'e.
The proposed reclaimed water holding pond originally was not to be line but now
will be lined with a 60-mil HDPE synthetic liner. This was based mainly on our
comment to the Engineer (Leo Green of Green Engineering) about preventing seepage on
the outside berm walls. The holding pond will hold roughly 18 MG of water, and is
roughly 6 acres at a maximum water depth of 10 feet in the holding pond. There are
two isolated wetlands in question that will be completely covered by the pond
footprint: one about 1 acre in size, and the other about 0.06 acres. The exising
ground elevation across the proposed footprint varries from about 30.x to 40' MSL,
with the proposed pond bottom being at 30' MSL. This implies obviously that the
footprint will need to be excavated and the surface prepared for the installation of
the 60 mil HDPE liner. The larger isolated wetland ground elevation is about at 31'
MSL, and the smaller one at about 32' MSL. Several subsurface drainpipes are
proposed to be placed under the liner to ensure that groundwater hydrostatic pressure
will not cause liner installation problems, in addition to operational problems with
the liner in the future.
With this current pond design, the berm walls are at a maximum of about 10 feet
tall. If the pond bottom were not placed at 30' MSL but rather the bottom were
placed at a higher elevation, then this obviously shoves up the berm walls higher.
At some point, Dam Safety will get involved (at the 15' mark) which obviously they
would like to avoid. The other problem, however, is that this land is not flat, and
in order to practically install a liner, a flat bottom is required. Therefore,
either cutting and leveling is required, or filling and leveling is required. They
obviously prefer to cut and level, and we here at CG&L would agree with them.
There are several other isolated wetlands dotted throughout the site, which are
buffered out from the spray irrigation wetted area.
Hopes this gives you some useful background information.
1 of 2 4/4/04 11:56 AM
Ken Pohlig
Construction Grants & Loans Section
715-6221
2 of 2 4/4/04