20000350 Ver 1_More Info Received_20090803

North Carolina State University is a land- Office of Finance and Business
grant university and a constituent institution Environmental Health and
of The University of North Carolina Public Safety Division
An Equal Opportunity/Aff irmative Action Employer
http://www2.ncsu.edu/ncsu/ehs
August 3, 2009
Eric Kulz
401 Oversight and Express Review Program
NCDENR Division of Water Quality
1650 Mail Service Center
Raleigh, NC 27699-1650
Natalie Landry
Surface Water Protection
NCDENR Division of Water Quality
1628 Mail Service Center
Raleigh, NC 27699-1628
Subject: Constructed Stormwater Wetland Repair
Centennial Biomedical Campus
NC State University
Dear Mr. Kulz and Ms. Landry:
Environmental Health and Safety Center
Campus Box 8007
Raleigh, North Carolina 27695-8007
Associate Vice Chancellor 919.515.4238
Environmental Affairs 919.515.6859
Industrial Hygiene 919.515.6860
Health and Safety 919.515.6858
Radiation Safety 919.515.2894
Business Continuity 919.515.5201
(Fax) 919.515.6307
Q?c?r?anr??
AUG 3 2009
OENR - WATER OUALITY
WETLANDS AND STORMWATER BRANCH
MO350
Enclosed for your review and approval is the proposed Centennial Biomedical Campus
Stormwater Wetland Repair plan.
I am available to answer your questions and respond to any comments. Phone [phone]
or e-mail duane [e-mail].
Sincerely,
Duane Knudson
Environmental Affairs Manager
Cc: Dr. Jean Spooner
Cameron Smith
Enclosure
Centennial Biomedical Campus (CBC) Stormwater Wetland Repair
Faculty: Kris Bass', Karen Hall', Rich McLaughlin, Jamie Blackwell, and Jean
Spooner'
(1) Biological and Agricultural Engineering, NCSU Box 7637
(2) Soil Science
Introduction
The stonnwater wetland system at NCSU's Centennial Biomedical Campus was designed
to control and treat stormwater from 38 acres of developed campus area. The system - -
consists of a forebay, which splits flow into two separate wetland.cells. The NCSU Water
Quality Group has been involved with monitoring these wetlands since 2006. In both
2006 and 2007, some adjustments were made to the wetland hydrology and additional
planting was completed. Monitoring reports submitted to the University detail the
progress of the wetland system.
In the 2007 report, the construction activities immediately upstream of the wetland
system were noticed. By the time of the 2008 report, a large amount of sediment had been
deposited in the upper wetland cell. This sediment had blocked much of the inlet boxes,
resulting in flow over the berms and through the emergency spillway of the upper
wetland. In 2008, the forebay was cleaned out and the inlets were partially restored. The
blocked flow spared the lower wetland from damage. However, by the spring of 2009, it
was clear that additional damage had been done to the upper wetland cell. Visits by DWQ
staff and consultation with the University resulted in pursuing the development of a
repair plan for the wetland.
NCSU Water quality Group was contracted to perform a survey of the wetland, and to
prepare a repair plan.
Repair Plan Tasks
Existing Condition Survey - Complete a topographic survey of the current conditions.
This survey will identify critical wetland features and detennine the current extent
and elevations of the wetland surface. The survey data will be used in combination
with soil sampling to estimate the amount of sediment deposited, and to determine the
earthwork required to restore design conditions. The survey will also serve as a base
map for construction schematics and developing the repair plan.
2. Wetland Performance Analysis - Calculations will be made to determine the amount
of sediment removal required to restore the intended storage volume of the wetland.
All calculations of runoff volumes and flowrates will be reviewed to ensure that the
repaired wetland will function as intended.
Wetland Repair/Redesign - A repair plan for the wetland will be developed that will
include schematics of the needed construction tasks to restore the site. Schematics
will include a grading plan, a planting plan, and any necessary details on soil
preparation. The plan will also include a review of current Erosion and Sediment
Control Plans and provide recommended erosion control and water management
activities that will help protect the wetland from future damage. The repair plan will
be supported with documentation that the wetland will perform to store stormwater
runoff as originally intended.
4. Repair Plan - Repair plan documents will be prepared for approval by DWQ and
circulation for possible construction estimates. This task will involve coordination
with NCSU groups, DWQ, and other agencies as necessary to provide an approved
plan and timeline. It will also involve meetings as necessary with the NCSU
Construction Management and the NCSU Environmental Health and Safety Center.
5. Construction. Assistance - Our group will provide assistance to NCSU Facilities and
contractors during any bidding processes and during construction. We will help
coordinate construction activities and facilitate all repair work as needed. Our staff
will help coordinate the selection and ordering of all plant material (temporary
vegetation, woody vegetation, and wetland aquatic vegetation), and its installation. In
addition, we propose to provide assistance with developing updating erosion control
protection for the on-going construction site.
6. Repair Completion - Final project completion tasks will include an as-built survey,
continued observation of plant survival, and any documentation or site visits needed
to gain approvals. It is anticipated that any detailed monitoring required will be
covered with our existing monitoring contract and activities.
Repair Plan
Based on our survey and analysis of the wetland, a repair plan has been developed. The
plan is separated into two main phases. The first phase involves major repairs and the
removal of sediment. This phase is planned to begin as soon as it has been approved and
a contract can be arranged. The second phase involves final grading, surface preparation,
and planting. The second phase shall be completed in the spring at an appropriate
planting time. The details of each phase can be seen in the Project Plans and are also
described in the Construction Manual.
In general, several feet of sediment have been deposited in the wetland interior. Repair of
the wetland will require the removal of this sediment. A total of 1200 cubic yards of
sediment will need to be removed from the area. The deposition has also covered topsoil
and wetland plants. The wetland will need to be finely graded and amended with topsoil
to promote plant growth. In addition, the hydrology of the wetland has been impacted by
the blocking of the wetland inlets. Each inlet will need to be repaired to the original
design conditions. The outlet of the upper wetland will need some minor repairs to ensure
its proper operation.
Several measures are proposed to protect the wetland from future sedimentation. The
measures are temporary erosion controls that may be removed once construction
activities of the adjacent areas have been completed. The installation of sedimentation
logs will promote deposition prior to flows reaching the wetland, in a way that can be
cleaned later. Although these measures will help protect the wetland area, continued
control of sediment from adjacent constriction activities will be crucial to the success of
this repair. Any disturbed areas will be seeded and covered with straw. Any trees lost
during the construction process with be replaced. In addition, the entirety of the upper
wetland will need to be planted once all activities are complete. The planting will occur
in the spring to facilitate plant growth. It is our recommendation that the wetland be
monitored closely during its first growing season to ensure plant survival and growth.
Conclusion
Based on our survey and analysis, significant repairs will be needed to return the wetland
to its intended functionality. The repairs would be best accomplished in two phases, and
must be maintained to ensure effectiveness. The proposed plan is described in this
document and in the inchided Project Plans and Construction Manual. Once this plan
gains approval, the University plans to implement the first phase as soon as possible, with
completion and planting planned for next spring (2010).
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