20090940 Ver 1_Staff Comments_20091103

Lucas, Annette
From: Lucas, Annette
Sent: Tuesday, November 03, 2009 1:45 PM
To: Euliss, Amy; Homewood, Sue
Cc: Lucas, Annette
Subject: 09-0940 Duke Energy Dan River Combined Cycle Project
Attachments: 09-0940 Duke Energy Dan River Combined Cycle Project.doc
Amy & Sue,
My comments are attached and I have spoken with the consultant Jason Ispanioly about them and emailed them to him
as well. Please let me know if you have questions.
Thanks,
A
Annette Lucas, PE
NC Division of Water Quality - 401 Oversight/Express Unit
2321 Crabtree Boulevard, Suite 250
Raleigh, North Carolina 27604
Phone: [phone]
Fax: [phone]
Email correspondence to and from this address may be subject to the North Carolina Public Records Law and may be
disclosed to third parties.
09-0940 Duke Energy Dan River Combined Cycle Project
AML comments
November 3, 2009
Please address the following design issues with the Bioretention Cell:
a. A specification for the soil media must be provided.
b. A minimum depth of three feet of planting media must be provided (Sheet
C-7.1 specifies "2' to 4' of conditioned soil."
c. Bioretention cell plants must be backfilled with soil media, not with
organic material per the note on Sheet C-7.2.
d. A greater variety of shrubs and trees should be provided in the planting
plan.
e. The planting detail for shrubs and trees shows the rootball placed too low
- one-half to one-third of the rootball should be above the level of the soil
media.
f. The outlet weir should be constructed of poured concrete or an equivalent
stable material that will support a precise elevation for the temporary pool.
Please provide a hard copy of the soils report that supports the levels for the
SHWT that are stated on the Bioretention and Wet Detention Pond Supplement
Forms.
3. Please provide a liner for the Wet Detention Pond that is designed or compacted
such that the infiltration rate is no more than 0.01 inch per hour. This will insure
that the pond will be able to sustain a permanent pool of water.
4. Please provide signed and notarized Operation and Maintenance Agreements for
the Bioretention Cell and the Wet Detention Pond.