20040286 Ver 1_Complete File_20020808

Weddington Road Comments (Speedway and 85)

Subject: Weddington Road Comments (Speedway and 85)
Date: Fri, 16 Aug 2002 09:53:55 -0400
From: "Todd St. John" <[e-mail]>
Organization: DWQ Wetlands Unit
To: [e-mail]
CC: "michael.parker" <[e-mail]>,
"STEVE CHAPIN (E-mail)..<[e-mail]>.
"john.dorney" <[e-mail]>

rJ2:-0l2-

Dr. McCrain,
We received your conceptual plans for the subject project and they
appear to be in line with what we had hoped for...

The only comments that I have are that most of the rip rap at the top of
the stream restoration area should be removed and that the SA/DA ration
for 70% imperviousnes should be 2.88 in regards to the wetlands.

Please forward my comments to Ms. Cardin of the City of Concord as we
discussed.

Thanks, Todd

r=

Todd St. John, P.E.
Environmental Engineer II
DWQ
Wetlands Unit

1 of 1

8/16/029:54 AM

State of North Carolina
Department of Environment
and Natural Resources
Division of Water Quality

James B. Hunt, Jr., Governor
Wayne McDevitt, Secretary
A. Preston Howard, Jr., P.E., Director

Division of Water Quality
November 9,1998

Mr. John L. Eddy, P.E.
Eddy Engineering, P.C.
Post Office Box 61367
Raleigh, NC 27661

Subject: Weddington Road
Stream Restoration
Cabarrus County

Dear Mr. Eddy:

The Wetlands Unit staff reviewed the stormwater management plans prepared by you on behalf of the City
of Concord Department of Engineering for the subject project and determined that additional information is
lleCeS2!llY to complete the technical review process. The required additional information is as follow~'

The stream channel design proposed in the current plans does not appear to be based on a natural channel.
The subject stream restoration must be based on relevant natural steam channel morphology to the
maximum extent practicable using a reference (undisturbed) reach. The plans and supporting
documentation do not contain the hydrological and other information used to evaluate stream bank stability,
morphology, and bed design. It also does not appear to include natural stream bed structures such as snags
or pools and riffles. This Office recommends that the channel design be based on the stream morphology
that existed prior to the stream impact (if known) or a reference reach of a similar, natural channel in the
vicinity. Please make any changes to the plans necessary to meet the above criteria or provide the necessary
information to support the fact the proposed design meets the above criteria.

If you have any questions or would like to discuss this project, please contact me at [phone].

Sincerely,

~{Jd1~

~hn R. Dorney
,btlandS Unit Su . or

cc: Todd St. John
John Dorney, Wetlands/401 Unit
Mooresville Regional Office
Central Files

4401 Reedy Creek Road, Raleigh, NC 27607
An Equal Opportunity Affirmative Action Employer

Telephone [phone] FAX [phone]
50% recycled/ 10% post-consumer paper

State of North Carolina
Department of Environment
and Natural Resources
Division of Water Quality

James 8. Hunt, Jr., Governor
Wayne McDevitt, Secretary
A. Preston Howard, Jr., P.E., Director

November 5,1998

Mr. Richard Harmon
Environmental Services, Inc.
1100 Wake Forest Road
Suite 200
Raleigh, NC 27604

Re: Proposed Weddington Road Impacts
Cabarrus County

Dear Mr. Harmon:

In response to your request on behalf of the City of Concord regarding the need for a NEP A document for
the subject property, Staff from this Office and the Mooresville Regional Office conducted a site visit with
you on October 30, 1998. As a result of the site visit and review of our files in regards to the subject
project, I have determined that a NEP A document will be required for this project. I have based this
determination on the following facts:

1) Public monies will be spent on this project.
2) State and Federal permits have been and will be required for this project.
3) Over 500 feet of significant stream channel would be impacted if the project is constructed as
proposed. The feet of impacted stream is based on impacts resulting from Weddington Road crossing a
stream certified as a part of an approval for the use of General Water Quality Certification No. 2671
(DWQ Project No. 960172, Interstate Combined Ventures) and the proposed impacts shown on
preliminary plans prepared by PBS&J for the City of Concord, dated April 1, 1998.

If you have any questions please call Mr. Todd St. John or me at 919-733-1786. We will be coordinating
this review for the Division of Water Quality.

Attachment

cc: Mooresville DWQ Regional Office
Todd St. John
Central Files

4401 Reedy Creek Road, Raleigh, NC 27607
An Equal Opportunity Affirmative Action Employer

Telephone [phone] FAX [phone]
50% recycled/ 10% post-consumer paper

1101 Haynes Street Suite 101 Raleigh, NC 27604 Telephone: [phone] Fax: [phone]

l
EcoScience

August 8, 2002

:''''! .is fa) ,-
),' t':r 1(., If:
~.,. ::."""'~~~.",-~2 ~
o .c', ,~._::-_:.,~_.,J;_:.'
,

Mr. Steve Chapin
U.S. Army Corps of Engineers
Asheville Field Office
151 Patton Avenue, Room 208
Asheville, North Carolina 28801-5006

AUG ~ 8 2002

Re: Weddington Road Mitigation, Concord, Cabarrus County, N.C.

02-002

Dear Steve,

The City of Concord is currently investigating options for remedial action and mitigation
planning for stream impacts associated with construction of the recently completed
Weddington Road extension. The two ~eas of concern include: 1) encroachment within
an intermittent unnamed tributary located west of, and parallel to, the Weddington Road
alignment; and 2) remedial action within 600 feet of tributary that was altered east of
Weddington Road.

EcoScience Corporation has been tasked with addressing both of these sites. Enclosed
please find a conceptual mitigation strategy report for the two areas. We would
appreciate your comments and input after which construction plans will be finalized and
implementation will be initiated. By copy of this letter, we are also requesting review
and concurrence from the N.C. Division of Water Quality.

If you have any questions, please do not hesitate to call me or Mr. Jens Geratz at our
office. Thank you for your help.

Sincerely,
ECOSCIENCE CORPORATION

{lhA ~~~

~Zrain, Ph.D., CEP
President

cc: Mr. Todd St. John, DWQ
Ms. Joni Cardin, City of Concord

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CONCEPTUAL STRATEGY REPORT

WEDDINGTON ROAD
STREAM MITIGATION

CABARRUS COUNTY
NORTH CAROLINA

PREPARED FOR:

CITY OF CONCORD
ENVIRONMENTAL SERVICES DEPARTMENT

PREPARED BY:

ECOSCIENCE CORPORATION
1101 HAYNES STREET, SUITE 101
RALEIGH, NORTH CAROLINA 27604

AUGUST 2002

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TABLE OF CONTENTS

Page

LIST OF FIGU RES .................................................................................................................. ii

LIST OF TABLES .................................................................................................................. ii

1.0 INTRODUCTION.............................................................................................................. 1

2.0 EXISTING SITE CONDITIONS.........................................................................................5

3.0 WETLAND MITIGATION.................................................................................................. 8
3.1 Wetland Site Hydrology......................................................................................... 8
3.2 Conceptual Constructed Wetland and Implementation Strategy............................ 8

4.0 STREAM RESTORATION ........................................... ..................................................... 12

4.1 Stream Site Hydrology .......................................................................................... 12

4.2 Stream Reconstruction... ....................................................................................... 14

5.0 SUMMARY .................................................................................................................. 23

6.0 REFERENCES................................................................................................................. 24

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Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Table 1

Table 2

Table 3

Table 4

LIST OF FIGURES

Paae
Vicinity Map: City of Concord Mitigation Plan ..................................................2

Weddington Road Mitigation Site ..................... .......... ............ ....... ......... ..........4

Weddington Road Wetland Mitigation Site: Existing Conditions .......................6

Weddington Road Stream Restoration Site: Existing Conditions ......................7

Conceptual Constructed Wetland System ........... .................... ..... ........ ............9

Weddington Road Wetland Mitigation Site: Conceptual Design........................11

Existing Stream Geometry: Plan View and Cross-Sections ..............................15

Existing Stream Geometry: Profile ........... ............ ......... .............. ................... ..16

Conceptual Design: Plan View and Cross-Sections .........................................19

LIST OF TABLES

Permanent Pool Size Required Under Existing
and Potential Build-out in the Watershed. ............................................................. 1 0

Stream Geometry and Classification: Existing and
Proposed Conditions for the Weddingtion Roa~
Stream Restoration Site .................................... ............. ....................................... 17

Species List for Proposed Plant Assemblages
in the Constructed Wetland Site. ........................................................................... 21

Species List for the Proposed Plant Assemblages
at the Stream Mitigation Site. ............................. .......... ............................ ............. 22

ii

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CONCEPTUAL STRATEGY REPORT

WEDDINGTON ROAD
STREAM MITIGATION

CABARRUS COUNTY,
NORTH CAROLINA

1.0 INTRODUCTION

The City of Concord recently completed construction of Weddington Road extending north from
Speedway Boulevard, across the Rocky River, and terminating slightly beyond Pitts School
Road. Construction of Weddington Road was completed in the fall of 2000. The new roadway
was built in conjunction with Interstate Combined Ventures, Inc. (ICV) to support the rapid
development occurring in the area and along the 1-85 corridor. Weddington Road was built to
service recent expansion of the planned mixed-use development associated with Kings Grant
and Gateway Court business communities located at the intersection of Speedway Boulevard
and 1-85. A vicinity map is shown in Figure 1.

A Section 404 permit application was submitted by ICV on February 15, 1996 for jurisdictional
impacts associated with development along the proposed Weddington Road project. Approval
of 401 Water Quality Certification was granted by Division of Water Quality (DWQ) on January
21, 1997 for 1.4 acres of wetland and water impacts associated with the commercial
development, Weddington Road crossing, and King's Grant Boulevard (DWQ Project #960172).
A detailed stream and wetland mitigation report and a stormwater management plan were
conditions of the permit. A conceptual wetland mitigation plan was completed and submitted in
March 1997 (ESI 1997). Detailed stream restoration and wetland mitigation plans were
developed in early 2000 in support of the permit conditions (Eddy .Engineering 1998, 2000).
Neither the wetland or stream restoration plans have been implemented to date.

The construction of Weddington Road occurred in two phases. The first phase of construction
began in 1997, in conjunction with the adjacent development designed and implemented by
ICV. This phase of construction includes the section of Weddington Road that extends from
Speedway Boulevard to a point just south of the Rocky River. The work included culverting a
large section of a tributary of the Rocky River (also known as Stream A). The City of Concord
entered an agreement with ICV to pay for the box culvert. The second phase (also known as
Section B or Weddington Extension) of construction began in October of 1999 by the City of
Concord and includes the section of Weddington Road north of the Rocky River. Bridge
construction over the Rocky River was also initiated at this time.

The U.S Army Corps of Engineers (CaE) has requested remedial action for unauthorized work
in Stream A mentioned for restoration in the detailed plans. The unauthorized work includes the
channelization, widening, and placement of rip-rap within approximately 600 linear feet of
stream. The stream reach is bound by Weddington Road to the west, Gateway Court to the

1

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.....ii)........ EcoScience
Corporation
RaleWt. NGIlh CarllIinI

CITY OF CONCORD
MITIGATION PLAN
Cabarrus County, North Carolina

Own. by: MAF
FIGURE
CId by: JG
Dele: 1
APR 2002
Pmjec~ 02..(J()2

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south, and the Rocky River to the north and east. The COE and the Division of Water Quality
(DWQ) attributes remediation responsibility to the City of Concord because the City of Concord
owns the affected property. The COE has requested restoration/enhancement measures for the
purpose of returning the tributary to a more diverse biological system.

Additionally, DWQ has requested remedial action to replace lost functions due to additional
stream impacts caused during final construction activities related to the Weddington Road
extension. The alignment was shifted to the east in order to minimize impacts to an intermittent,
unnamed tributary located west of, and parallel to, the Weddington Road corridor. However,
during construction and utility placement, approximately 350 linear feet of this channel was
adversely impacted. The COE and DWQ have agreed to allow the creation of wetlands to
replace stream functions and water quality benefits within the adjacent road right-of-way.

The City of Concord has agreed to submit a mitigation strategy to include a conceptual
restoration, enhancement, or bioengineering plan for impacts to both stream systems described
above. This report examines a conceptual mitigation strategy to mitigate for impacts associated
with the impacts to the stream west of Weddingtion Road and to investigate options for
improving stream restoration alternatives along approximately 600 linear feet of the unnamed
tributary east of Weddington Road. A constructed wetland is proposed to replace functional
impacts to the stream west of Weddington Road (hereafter referred to as the Wetland Site).
The constructed wetland will be built within the old Weddington right-of-way. Stream restoration
work is proposed for the tributary east of Weddington Road (hereafter referred to as the Stream
Site). Stream restoration activities will include channel modifications and limited floodplain
excavation adjacent to the channel. A map with site locations is shown in Figure 2. A detailed
mitigation and stormwater plan for these two sites will be developed pending the COE and the
N.C. Division of Water Quality (DWQ) review of the conceptual mitigation strategy.

3

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LEGEND

~

_ Z!)I~___

STREAMS

MAJOR CONTOURS
MINOR CONTOURS
ROADS

WETLAND LINE

:";'-' -
<~~-?~-,

,.~o,,;-

I:~~~~~\: .

II
I.

WEDDINGTON
MITIGATION

ROAD
SITE

Own By; Ckd 9YI
MAF JG
Dote: FIGURE
APR 2002
ScQle:
1" -1200' 2
ESC Project No.:
02-002

.

-
EcoScience

Corporation

Raleigh, Nonb Carolina

Project:

Cabarrus County, North Carolina

:1

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2.0 EXISTING SITE CONDITIONS

The Weddington Road mitigation study area is located in the Charlotte Belt of the Piedmont
physiographic province of North Carolina. Physiography is characterized by moderately rolling
uplands and steep slopes with well defined, moderately sloping floodplains and drainageways.
Local elevations range from a high of approximately 735 feet above mean sea level (MSL) along
upland ridges to a low of 580 feet MSL along the Rocky River floodplain. This region is
characterized by moderate rainfall with annual precipitation averaging approximately 44 inches
per year (USDA 1988). Jurisdictional wetlands were delineated for the Weddington Road
corridor by Environmental Services Inc. in April 1995. The delineation was verified by the CaE
and DWQ in October 1995.

The surrounding development is part of Kings Grant and Gateway Court Business
Communities, a planned mix-use development located at the intersection of Speedway
Boulevard and 1-85. The remaining undeveloped areas are primarily located in the Rocky River
floodplain and on steep adjacent slopes. A quarry operation (Martin-Marietta Materials, Inc.) is
positioned north of the Rocky River immediately east of Weddington Road.

The Wetland Site is an open linear tract of right-of-way located directly west of the newly
constructed Weddington alignment (Figure 3). The Wetland Site supports approximately 350
linear feet of an impacted stream corridor. On-site elevation gradients extend from
approximately 640 feet MSL at the top of the Wetland Site to approximately 590 feet MSL within
the Rocky River floodplain. The adjacent property immediately west of the Wetland Site is
currently undeveloped woodland; however, this property is zoned for commercial development
and will likely be developed in the near future. A proposed access road to the adjacent property
will bisect the Wetland Site. The Wetland Site also contains electrical and sewer line
easements.

The Stream Site includes approximately 600 linear feet of unnamed tributary to the Rocky River,
a narrow floodplain bench, and adjacent terrace (Figure 4). Approximately 1400 linear feet of
stream directly above the Stream Site has been culverted to allow for fill and construction of
commercial development. Impervious surfaces and intensively landscaped areas account for
an increasingly large percentage of land surfaces within the watershed. Currently, this site
supports an incised channel with significant bank erosion and down-cutting. A large, rip-rap
apron has been placed within 80 feet of the upper reach of the stream to dissipate energy and
reduce erosion at the stream culvert. An abandoned sediment basin is positioned north of the
stream and adjacent to the fill slope associated with Weddington road. A sewer easement runs
parallel to the stream along the southern bank. Early successional grasses and forbs dominate
current vegetation adjacent to the stream, including the road embankment to the west and the
sewer line easement to the south. A stand of mature bottomland hardwoods is located
immediately north of the stream.

5

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3.0 WETLAND MITIGATION

Stream impacts at the Wetland Site will be mitigated through the use of constructed wetlands.
The primary goal of the plan is to replace functions lost by fill and disturbance of the on-site,
intermittent stream (see Figure 3). Specific functions to be replaced include 1) a reduction in
stormwater runoff peak discharges, 2) reduction of pollutants in stormwater, and 3) replacement
of natural vegetated areas and associated wildlife functions. The proposed constructed wetland
will require re-contouring/grading the site to establish a catchment (i.e. forebay) and wetland
marsh to store, clean, and mitigate stormwater flows.

3.1 Wetland Site Hydrology
The drainage area for the Wetland Site encompasses approxima!illy-'87.4 i!('res (0.06 square
mile). The drainage area is primarily undeveloped hardwood forest, but development pressures
will likely alter this area to commercial use in the near future. Several stormwater culverts
associated with Weddington Road discharge into the site. The impacted stream corridor is
oriented on a north to south axis and is located directly west of the newly constructed
Weddington Road alignment. The stream above the site is best characterized as a narrow,
intermittent channel, which has experienced scouring and head cutting. The stream formerly
discharged, via sheet flow, into a wetland complex located in the Rocky River floodplain directly
below the Wetland Site. Approximately 200 linear feet of the stream within the site has been
completely obscured and blocked with fill. The remaining channel segments, which occur on
site, have been impacted by water diversion from woody debris and land clearing activities.
Hydrology appears to be supported py upstream, groundwater seepage or by upland and
stormwater run-off during precipitation events.

3.2 Conceptual Constructed Wetland and Implementation Strategy
A conceptual constructed wetland strategy was developed according to an integrated watershed
and natural drainage approach to stormwater management. Site planning will integrate a site-
specific management plan in combination with the preventive measures, preventive reduction
practices, and control measures as outlined in the North Carolina Stormwater Site Planning
Guidance Manual (NCDENR 1998).

Figure 5 provides a conceptual design for a constructed wetland. Similar to wet detention
basins, the constructed wetland will be designed with a forebay, or settling pool. The forebay
will be separated from the main pool to remove sediment from incoming stormwater, thereby
protecting the wetland from filling prematurely. The use of a forebay will also allow for easier
cleaning and extend the life of the constructed wetland. A certain percentage of the pond shall
be allocated to different pool depths. Approximately 70 percent of the surface area of the
permanent pool will need to be designated as "marsh" with a depth of 0 to 18 inches.
Approximately 35 percent of the pool will be between 0 and 9 inches in depth and another 35
percent will be between 9 and 18 inches in depth. A permanent pond (15 percent of surface
area) will also be required at the outlet location.

The runoff volume from long-term average storm volumes will determine the final design size.
One method for determining the permanent pool surface area uses the permanent pool surface
area/drainage area (SA/DA) ratios for given levels of imperviousness and basin depths.

8

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Preliminary estimates for permanent pool surface area, assuming a 4-foot deep pool, is shown
in Table 1. The size of pool needed would vary significantly between current and future build-
out conditions in the watershed. Coordination between the City of Concord and developers
within the watershed will be required to correctly size the constructed wetland. Using the basin
as a sediment trap during construction of the adjacent property may also be a consideration to
avoid likely sedimentation and clean out costs. All sediment deposited as a result of
construction would be removed before finished contouring and vegetation establishment would
begin.

Table 1. Permanent Pool size required under existing and potential build out in the watershed.
% impervious SA/DA Ratio Acres Required
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Current Conditions
Future
Build-out Conditions

Figure 6 provides the proposed location of the constructed wetland. Exact placement will
depend on precise measurements and detailed engineering studies. Three options for
deployment include:

. Option 1: Placement of the entire wetland above the proposed road, using the road as the
embankment. A likely drawback with this option is the limited space within the easement.

. Option 2: Placement of the permanent pond above the proposed road, using the road as the
overflow embankment into the micropools and marsh vegetation on the down slope side of
the road. The amount of space may be limited for wetland marsh construction below the
road may be limited.

. Option 3: Placement of the permanent pond above the proposed road; however, the
wetlands within the floodplain of the Rocky River would be incorporated into the design
either wholly or as part of the vegetative treatment area.

10

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4.0 STREAM RESTORATION

Approximately 700 linear feet of Priority 2 and 3 restoration is proposed for the unnamed
tributary within the Stream Site. The primary goals of the stream restoration plan include 1)
construction of a stable stream channel, 2) establishment of a natural vegetation buffer along
the stream channel, and 3) restoring water quality and wildlife functions associated with the
riparian corridor. Components of this plan may be modified based on detailed studies or
engineering, construction, and access constraints.

4.1 . Stream Site Hydrology
The drainage area of the Stream Site encompasses approximately 1344 acres (2.1 square
miles). Impervious surfaces and intensively landscaped areas account for an increasingly large
percentage of land surfaces within the watershed. The large percentage of non-point source
discharge suggests the rate of storm run-off entering the current stream channel is more rapid
and intense than historic levels when the watershed was primarily forested.

The unnamed tributary originates west of 1-85 and southwest of Concord Mills Mall. Based on
USGS mapping, the watershed includes approximately 30,000 linear feet of stream prior to the
confluence with the Rocky River. From its headwater tributaries, the stream crosses under 1-85
and extends in a northeasterly direction along 1-85 in a modified, rip-rapped channel. The
stream then enters two ten foot, double barrel, box culverts, which extend approximately 1400
feet under commercial development, before it enters the Stream Site.

The valleys of the upper watershed historically supported a relatively narrow floodplain area with
moderate floor slopes of approximately 0.015 (rise/run). Lower reaches of the stream supported
relatively broad floodplains with low to moderate floor slopes of less than 0.005 (rise/run).
Based on valley characteristic and a cursory review of the watershed it would appear that
meandering, riffle-pool streams might have historically persisted in the lower watershed. Slopes
in portions of the upper reach suggest transitions to relatively high wadient, rapid dominated,
step-pool sequences.

Discharge .
Bankfull discharge represents the most difficult variable to predict within a developing
watershed. Therefore, several methods have been used to estimate bankfull discharge under
various development scenarios, including regional hydraulic geometry curves and available
research (Nunnally and Keller 1979).

Discharge estimates for stream restoration utilize the definition of "bankfull" and the return
interval associated with the bankfull discharge. For this study, the bankfull channel is defined as
the channel dimensions designed to support the "channel forming" or "dominanf' discharge
(Rosgen 1996, Gordon et al. 1992). Flow resistance reaches a minimum at bankfull stage as
excess discharge is distributed within the floodplain area. Research indicates that a stable
stream channel may support a return interval for bankfull discharge, or channel-forming
discharge, between 1 to 2 years (Gordon et al. 1992, Dunne and Leopold 1978). The methods
of Ftosgen (1996) indicate calibration of bankfull dimensions based on a potential bankfull return
interval of between 1.3 and 1.7 years for rural conditions. Due to urbanization, the

12

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reconstruction of a stable bankfull channel at the Stream Site assumes a 1.2-year bankfull
discharge return interval, as deemed appropriate by this method. Recurrence intervals of
bankfull events are traditionally based on the Log-Pearson Type III distribution of peak-annual
data.

Based on available data, bankfull discharge for a rural, Piedmont stream with a 2.1 square mile
watershed averages approximately 152 cubic feet per second (cfs) (Harman et al. 1999). Using
the North Carolina flood frequency equation, a 2-year return interval would have a discharge of
227 cfs (Pope et al. 2001). Assuming linearity, the 1.2-year return would be approximately 136
cfs.

Bankfull indicators in the field have also been utilized to predict bankfull discharge. The cross-
section area associated with field indicators has been compared to regression equations that
relate discharge to cross-sectional area in urban streams. The average bankfull cross-sectional
area was estimated between 35-40 square feet, suggesting a bankfull discharge of
approximately 225-275 CFS.

The available data suggest that bankfull discharge at the Stream Site will increase dependent
upon the build out conditions within the watershed. For this project, the stable "design' channel
is assumed to support a bankfull discharge at a 1.2 year return interval of between 200-275
CFS under existing watershed conditions. Further study is needed to refine discharge values.

Stream Geometry and Substrate
Stream geometry and substrate data have been evaluated to orient stream restoration based on
a classification utilizing fluvial geomorphic principles (Rosgen 1996). This classification stratifies
streams into comparable groups based on pattern, dimension, profile, and substrate
characteristics. Primary components of the classification include degree of entrenchment,
width/depth ratio, sinuosity, channel slope, and channel substrate composition. Stream types
associated with the on-site stream include C, B, F, and G. Each Stream type is further
subdivided appending a number 1 through 6 (example E5) to denote a stream type which
supports a substrate dominated by 1) bedrock, 2) boulder, 3) cobble, 4) gravel, 5) sand, or 6)
silt/clay. At the Stream Site, the channel bed is dominated by sand in the lower reach and small
boulders (rip-rap) in the upper reach.

Due to past dredging and stabilization efforts within the channel, the stream currently contains a
transitional reach that supports characteristics of G (gully), F (widened gully), and B (rapid
dominated) stream types. The G stream types are characterized as highly entrenched (down
cut) streams with low width/depth ratio (<12). Due to entrenchment, G stream types tend to
widen by eroding channel banks during peak flows. Over time, the wider gully develops into an
F stream type that supports a relatively high width/depth ratio (> 12) and the presence of
developing point and mid-channel bars. Given time, the stream would erode the banks and
begin to form a new floodplain at a lower elevation. The increase in width/depth ratio in the
bottom of the channel would subsequently give rise to a meandering, riffle-pool, C channel.
During this stream evolution process, excessive sedimentation from bank collapse and erosion
may pose water quality problems within the on-site reach and ultimately all downstream rivers.
Where the F stream is geologically controlled by rip-rap the stream supports a B stream type

13

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which is characterized by moderate entrenchment, broadly sloping valley walls, and
predominantly rapid dominated plan form with step-pools and irregularly spaced pools.

Bankfull cross-sectional area has been sized to regional curve data (Figure 7). Cross-sections
depict the existing grade and bankfull channel size. The stream profile data includes both water
and bed elevations (Figure 8). A grade change and the migrating head-cut (station 140) is
clearly depicted using the profile data. Existing stream geometry and classification is
summarized in Table 2. Currently, the upper reach of the stream has been classified as a B2
channel, which is transitioning to a G2 stream type at the point of a migrating head-cut. The
lowerreach has been classified as an F5, which is transitioning to a C5 channel.

The stream reach currently supports a flood-prone area ranging from 40 feet to 60 feet in width
with an entrenchment ratio ranging from 1.3 to 2.1 in the upper B channel, and approximately
1.7 in the lower F channel section. The upper portion of the stream is laterally confined by the
road embankment to the north and west and the rip-rap protection placed along the eastern
bank. Hardened structures, within and adjacent to the channel, appear to have stabilized the
channel within the upper portion of the channel. However, dredging in the lower part of the
channel has induced a head-cut at the base of the in-stream, rip-rap apron, which seriously
jeopardizes the future stability of the stream.

Due to past dredging of the lower reach, water surface elevations are closely tied with the
Rocky River. Rapid establishment of streambank vegetation has stabilized the banks, reducing
erosion rates and limited lateral migrat.ion. However, bank collapse and erosion is expected to
continue until the stream has developed a new floodplain. Subsequently, a meandering C
channel would be expected to develop within the reestablished floodplain. Because streams
entering larger floodplains are generally unstable and susceptible to frequent migration, work
proposed in the lower reach would involve limited excavation of a bankfull bench and
establishment of riparian and buffer vegetation.

4.2 Stream Reconstruction
A conceptual stream reconstruction strategy was developed according to constructs outlined in
Rosgen (1996), Dunne and Leopold (1978), Harrelson et al. (1994), the North Carolina Wildlife
Resource Commission NCWRC (1996), and North Carolina Division of Environment and Natural
Resources (NCDENR 1999). Stream pattern, dimension, and profile under stable
environmental conditions were extrapolated to the dredged and straightened system at the
Stream Site, using regional hydraulic geometry curves and a regional database for streams
located within the Piedmont physiographic region of North Carolina.

Reference and Proposed Stream Geometry
Regional reference curves can be utilized to predict bankfull stream geometry including cross-
section area, average width, and average depth for any given drainage size. Development of
regional curves for the Piedmont physiographic region of North Carolina were based on rural
watersheds and may not fully predict stable stream geometry in urban areas. Establishment of

14

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specific design channel attributes will require measurements of a reference stream (relatively
undisturbed and stable) within the hydrophysiographic region. Preliminary estimates are based
primarily upon data observations along the existing reach, regional curves, and the regional
database. Table 2 provides a summary of measured stream geometry attributes under existing
conditions and preliminary estimates of stable stream attributes.

A reconfigured B channel is proposed within the upper reaches of the stream. The stability of a
proposed 8 stream type within upper reaches will limit bank erosion and sediment in the lower
watershed. The rapid, step-pool morphology will also avoid or lessen impacts to established
bottomland forest and the sewer easement. The channel bed would consist of a series of rapids
and pools. A floodplain or bankfull bench will be created using existing on-site materials.
Stream banks will be gently graded to minimize bank collapse and sedimentation. To further
minimize flow velocities and minimize erosion, riparian and stream buffer vegetation will be
established along stream banks, flood prone areas, and terrace areas, as allowed. Figure 9
depicts conceptual cross-sections and proposed bank excavation.

In summary, a stable 8-channel design exhibits an entrenchment ratio of 2.1, a bankfull width of
24 feet, an average depth of 1.5 feet, and a width/depth ratio of 16. The cross sectional area is
approximately 35 square feet. Water surface slopes for existing conditions range from
approximately 0.021 rise/run in the upper 8 stream reach to approximately 0.0004 in the lower F
reach. The proposed water surface slope for the restored upper reach is 0.012. Other
important variables in the channel design include pool-to-pool spacing (Lp-p = 100 feet),
meander length (Lm = 150 feet), sinuosity (1.3 stream length/valley length), and radius of
curvature (Rc = 65 feet). Following the Rosgen (1996) classification system, a 82/3c stream
type is proposed for approximately 350 linear feet of the upper reach of stream.

Restoration concepts associated with the F-type channel in lower reach will include increasing
the belt width through the excavation of bank walls and the establishment of riparian vegetation.
The increase in floodplain width will allow the channel in this region to develop into a C-type
channel. Approximately 250 linear feet of channel are expected to -receive this treatment. A
typical cross-section and excavation areas associated with bank excavation are depicted in
Figure 9.

Stream Reconstruction Methods
Channel construction will occur in phases. The first phase will include the installation of erosion
control measures and the installation of access routes and staging areas. An erosion control
plan and construction/transportation plan will be developed for the Stream Site. Erosion control
will be performed 'Iocally throughout the site and will be incorporated into construction
sequencing. Planting of exotic perennial grasses will not represent a component of the erosion
control plan. Exposed surficial soils in the region typically re-vegetate rapidly after disturbance.
Use of on-site material including rip-rap and root mats will be incorporated into the plan to
minimize waste. The transportation plan, including access routes and staging areas, will be
placed to minimize disturbance to existing vegetation and soils to the maximum extent feasible.
The plan will specify spoil stockpile locations and set specific clearing limits, if necessary.

18

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The second phase will include channel bank excavation and sloping in the lower reach portion
of the site. Figure 9 depicts the conceptual design plan view and cross-sections. The objective
of excavation and bank sloping is to remove eroding material and increase the flood-prone area
from an average of 30 feet to greater than 55 feet. After excavation, the slopes will exhibit a
gentle gradient prior to tie-in with the existing land surface. The existing land surface will be
immediately stabilized using biodegradable erosion control matting, mulching, or brush
mattresses.

The third phase will include the removal and placement of material within the stream channel
and the excavation of channel banks. The base flow will be captured and pumped around the
work zone. The new channel corridor will be staked according to the geometry, cross-sections,
and profile as outlined in Table 2 and conceptually depicted in Figure 9. The stream banks,
bankfull bench, and belt width area will be excavated according to detailed grading plans.
Existing rip-rap embankment will be removed and stockpiled for later use. In-stream rip-rap will
be removed to allow for corrected elevation of channel bed. Stockpiled rip-rap will be placed as
channel material in rapids, along inside bends to bankfull elevation, and along the outside bend
of the first pool.

Grade control structures including J-hook vanes and cross-vanes may be used in the channel to
elevate local water surfaces, divert shear stress from stream banks, and enhance habitat. The
structures will be constructed from large flat, faceted boulders. Rocks measuring 2 feet by 3
feet are expected to be used in this effort.

For the constructed B channel, in-field staking and laser surveys will be used to insure correct
elevations. The cross-sectional area upon construction will measure approximately 35 square
feet. The pool-to-pool spacing will average approximately 100 feet and be characterized by a
radius of curvature averaging approximately 65 feet. Channel slope and resulting sinuosity will
mimic the parameters outlined in Table 1 and shown in Figure 9. Stream banks and local belt
width area of the constructed channel will be immediately planted with shrub and herbaceous
vegetation. Particular attention will be directed towards providing vegetative cover and root
growth along outer bends of each meander.

Planting Plan
A planting Plan will be developed for both the wetland and stream restoration sites during
detailed planning. However, a list of potential species to be utilized at each site can be found in
Table 3 and 4.

Monitoring Plan
A monitoring plan will also be developed during detailed planning for both mitigation sites. This
plan will follow constructs outlined in COE and DWQ guidelines and will require a minimum of 5
years. .

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Table 3. Species List for Proposed Plant Assemblages in the Constructed Wetland Site.

Side Slope Shrub Assemblage
1) Tag Alder (Alnus serrulata)
2) Elderberry (Sambucus canadensis)
3) Silky Dogwood (Comus amomum)
4) Pepperbush (Clethra alnifolia)
5) Black Willow (Salix nigra)
6) Spicebush (Lindera benzoin)

Shallow Emergent (up to 0.5 feet inundation)
1) Common Three Square (Scirpus pungens)
2) Marsh Hibiscus (Hibiscus moscheutos)
3) Sedges (Carexspp.)
4) Switchgrass (Panicum vergatum)
5) Sweetflag (Acorus calamus)
6) Rushes (Juncus spp.)

Deep Emergent (up to 1.5-foot inundation)
1) Arrow Arum (Peltandra virginia)
2) Duck Potato (Saggitaria latifolia)
3) Smartweed (Polygonum spp.)
4) Lizard tail (Saururus cernuus)
5) Soft-stem Bulrush (Scirpus validus)
6) Soft Rush (Juncus effusus)
7) Spike Rush (Eleosharsis baldwiniJ)
8) Rush (Juncus validus)

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Table 4. Species List for the Proposed Plant Assemblages at the Stream Mitigation Site.

Stream-Side Shrub Assemblage
1) Tag Alder (Alnus serrulata)
2) Elderberry (Sambucus canadensis)
3) Silky Dogwood (Comus amomum)
4) Pepperbush (Clethra alnifolia)
5) Black Willow (Salix nigra)

Piedmont Bottomland Forest
1) Cherrybark Oak (Quercus pagoda)
2) Swamp Chestnut Oak (Quercus michauxit)
3) American Elm (Ulmus americana)
4) Tulip Poplar (Liriodendron tulipifera)
5) Green Ash (Fraxinus pennsylvanicum)
6) Shagbark Hickory (Carya ovata)
7) Bitternut Hickory (Carya cordiformis)
8) Ironwood (Carpinus caroliniana)
9) Flowering Dogwood (Comus f1orida)
10) Sycamore (Platanus occidentalis)

Mesic Mixed Hardwoods
1) American Beech (Fagus grandifolia)
2) Red Oak (Quercus rubra)
3) Sugar Maple (Acer saccharum)
4) Flowering Dogwood (Comus f1orida)
5) Red Maple (Acer rubrum)
4) Tulip Poplar (Liriodendron tulipifera)

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5.0 SUMMARY

The City of Concord recently completed construction of Weddington Road extending north from
Speedway Boulevard, across the Rocky River, and terminating slightly beyond Pitts School
road. Weddington Road will help service recent expansion of a planned, mix-use development
associated with Kings Grant and Gateway Court business communities located at the
intersection of Speedway Boulevard and 1-85. The COE and DWQ have requested remedial
action for stream impacts at two sites adjacent to the new roadway. Restoration or
enhancement measures should be implemented to replace or increase lost functions.

A constructed wetland is proposed to replace functions lost from impacts to a stream west of
Weddington Road. The constructed wetland will provide a reduction in stormwater runoff peak
discharges, a reduction of pollutants in stormwater, and replacement of natural vegetated areas
and associated wildlife functions. Stream restoration work is proposed for the tributary east of
Weddington Road. Stream restoration efforts will provide approximately 350 linear feet of stable
B-type channel restoration and approximately 250 linear feet of stable C-type channel
restoration. Additional benefits of stream restoration include the return of natural vegetation
buffer along the stream channel, water quality improvements, and wildlife functions associated
with the riparian corridor.

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5.0 SUMMARY

The City of Concord recently completed construction of Weddington Road extending north from
Speedway Boulevard, across the Rocky River, and terminating slightly beyond Pitts School
road. Weddington Road will help service recent expansion of a planned, mix-use development
associated with Kings Grant and Gateway Court business communities located at the
intersection of Speedway Boulevard and 1-85. The COE and DWQ have requested remedial
action for stream impacts at two sites adjacent to the new roadway. Restoration or
enhancement measures should be implemented to replace or increase lost functions.

A constructed wetland is proposed to replace functions lost from impacts to a stream west of
Weddington Road. The constructed wetland will provide a reduction in stormwater runoff peak
discharges, a reduction of pollutants in stormwater, and replacement of natural vegetated areas
and associated wildlife functions. Stream restoration work is proposed for the tributary east of
Weddington Road. Stream restoration efforts will provide approximately 350 linear feet of stable
B-type channel restoration and approximately 250 linear feet of stable C-type channel
restoration. Additional benefits of stream restoration include the return of natural vegetation
buffer along the stream channel, water quality improvements, and wildlife functions associated
with the riparian corridor.

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6.0 REFERENCES

Dunne D. and L.B. Leopold. 1978. Water in Environmental Planning. W.H. Freeman and
Company, NY.

Eddy Engineering, P.C. 1998. Unpublished.
Weddington Road Stream Restoration Site.
Inc.

Hydrologic and Hydraulic Analysis,
Prepared for Environmental Services

Environmental Services Inc. (ESI). 1997. Unpublished. Conceptual Wetland Mitigation
and Stormwater Plan. Technical Report prepared for the City of Concord and
Interstate combined Ventures.

Gordon, N.D. T.A. McMahon, and B.L. Finalyson. 1992. Stream Hydrology: An
Introduction for Ecologists. John Wiley& Sons, Ltd. West Sussex, England.

Harman, W.A., G.D. Jennings, J.M. Patterson, D.R. Clinton, L.A. O'Hara, A. Jessup, and
R. Everhart. 1999. Bankfull Hydraulic Geometry Relationships for North Carolina
Streams. AWRA Wildland Hydrology Symposium Proceedings. AWRA Summer
Symposium. Bozeman, MT.

Harrelson, C.C., C.L. Rawlins, and J.P. Potyondy. 1994. Stream Channel Reference Sites:
An Illustrated Guide to Field Techniques. Gen. Tech. Rep. RM-245. USDA Forest
Service. Rocky Mountain Forest and Range Experiment Station. Fort Collins,
Colorado.

N.C. Division of Environment and Natural Resources (NCDENR). 1999. The Draft
Technical Guide for Stream Work in North Carolina, Version 1.0. Raleigh, North
Carolina.

N.C. Division of Environment and Natural Resources. 1998. North Carolina Stormwater
Site Planning Guidance Manual. Division of Water Quality. Raleigh, North Carolina.

North Carolina Wildlife Resource Commission (NCWRC). 1996. Draft Guidelines for
Stream Relocation and Restoration in North Carolina. Raleigh, North Carolina.

Nunnally, N.R. and R.E. Keller. 1979. Use of Fluvial Processes to Minimize Adverse
Effects of Stream Channelization. Water Resources Research Institute of the
University of North Carolina. Report No. 144.

Pope, P.F., G.D. Tasker, and J.C Robbins. 2001. Estimating the Magnitude and
Frequency of Floods in Rural Basins of North Carolina. U.S. Geological Survey.
Water-Resources Investigations Report. 01-4207. Raleigh, North Carolina.

Rosgen, D. 1996. Applied River Morphology. Wildland Hydrology (Publisher). Pagosa
Springs, Colorado.

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U.S. Department of Agriculture (USDA). 1988. Soil survey of Cabarrus County, North
Carolina, USDA Soil Conservation Service.

25