Stamley Farm Mitigation Site

A
AGENCY PACKET
STAMEY FARM MITIGATION SITE
IREDELL COUNTY, NORTH CAROLINA
Prepared for:
%??Of NORTH C4 pG9
9
OF TRAj
Wk*%D,14010800
q PR 2,8 2003
?AI?RQUW17?sEpON
North Carolina Department of Transportation
Raleigh, North Carolina
April 2003
1.0 SUMMARY
The Stamey Farm Mitigation Site encompasses a reach of Back Creek, two unnamed tributaries to Back
Creek, and an associated floodplain wetland. The majority of the on-site stream reaches appear to have
been impacted by land clearing, livestock grazing, hoof shear from livestock, and erosive velocities
resulting from culverts extending below Interstate 40. The majority of the on-site channels are classified
as E-type streams with the northernmost tributaries classified as F-type channels and a small reach in the
southern portion of the Site classified as a C-type channel. Mitigation options propose to restore
approximately 6395 linear feet of stream in place through bench excavation, incorporation of in-stream
structures, and planting; and restore/enhance approximately 0.5 acre of jurisdictional wetland by filling
drainage ditches and planting. A 18-acre conservation easement is proposed to surround all mitigation
options within the Site.
2.0 INTRODUCTION
Stamey Farm encompasses approximately 338.5 acres of land located 5.5 miles west of Statesville, NC in
Iredell County. The Stamey Farm Mitigation Site is located immediately south of Interstate 40 and
immediately west of Stamey Farm Road (State Road 1512) (Figure 1). EcoScience Corporation is
currently evaluating the potential mitigation opportunities within an approximate 18-acre conservation
easement located within the Stamey Farm property hereafter referred to as the "Site."
Potential mitigation opportunities have been presented based primarily upon professional judgment. If
mitigation activities are implemented on the Site, a detailed mitigation plan will be prepared that includes
stream geometry measurements and wetland characterization from a reference (relatively undisturbed)
site in the region. Quantitative data collected during the design planning stage may affect mitigation
activities proposed in this preliminary study.
3.0 EXISTING CONDITIONS
3.1 Streams
The Site encompasses a reach of Back Creek, two unnamed tributaries to Back Creek, and one associated
floodplain wetland. The upstream Back Creek drainage basin is approximately 2.0 square miles at the
Site outfall. Both Back Creek and a small unnamed tributary enter the Site through culverts beneath
Interstate 40. The small unnamed tributary flows southwest across the Site for approximately 950 linear
feet prior to discharging into the main stem of Back Creek. Back Creek flows south across the Site for
approximately 3315 linear feet before converging with a secondary tributary in the west-central portion of
the Site. Back Creek flows southeast for approximately 2130 additional linear feet across the Site prior to
its outfall in the southernmost portion of the Site.
The on-site streams have been characterized based on fluvial geomorphic principles (Rosgen). Table 1
provides a summary of measured stream geometry attributes under existing conditions (considered to be
unstable) and a preliminary estimate of potentially stable stream attributes. Stream geometry and
substrate data have been evaluated to orient stream restoration based on a classification, utilizing fluvial
geomorphic principles (Rosgen). Stream classes associated with the Site include E, C, and F stream
types. Historically, on-site reaches may have been characterized as E 4/5-type streams.
Back Creek and the unnamed tributaries appear to have been impacted by land clearing, erosive flows,
1
livestock grazing, and agricultural activity. Grazing of livestock near stable E-type streams typically
leads to channel adjustments including increases in bank erosion, width/depth ratio, stream gradient, and
sediment supply. In addition, these impacts may lead to decreases in channel sinuosity, meander-width-
ratios, and sediment transport capacity. Back Creek and the unnamed tributaries are expected to continue
to erode and deposit sediment into receiving streams until a stable stream pattern has been carved from
the adjacent floodplain.
3.2 Wetlands
Jurisdictional wetlands are defined by the presence of three criteria: hydrophytic vegetation, hydric soils,
and evidence of wetland hydrology during the growing season. Currently, one wetland approximately 0.5
acres in size contains hydric soils and occurs south of the main power line adjacent to the western
mitigation boundary. The wetland is vegetated by sedges, rushes, tag alder, and tulip tree, and evidence
of wetland hydrology was observed during the field surveys. A ditch extends through the wetland area
and discharges into Back Creek. Down-cutting of stream channels and ditching of spring heads may have
effectively lowered the adjacent groundwater table and soil saturation.
4.0 MITIGATION CONCEPT
The primary goals of this mitigation concept include 1) construction of a stable, riffle-pool stream
channel; 2) enhancement of the water quality functions; 3) creation of a natural vegetation buffer along
the on-site stream reaches; 4) restoration of wildlife habitat associated with a riparian corridor/stable
stream; 5) restoration of jurisdictional wetland hydrology to the adjacent floodplain; and 6) establish a
conservation easement which will include all mitigation activities and address land owner concerns.
Primary activities designed to restore the stream and wetland complex include 1) stream restoration; 2)
wetland restoration/enhancement; and 3) vegetative planting (Figure 2). The mitigation concept outlined
in Figure 2 is expected to restore approximately 6395 linear feet of stream and restore/enhance
approximately 0.5 acre of jurisdictional wetland.
4.1 Stream Restoration
Opportunities for stream restoration are designed to provide a stable stream channel and in-stream aquatic
habitat while protecting adjacent stream banks from extensive erosion. The cross-sectional area of the on-
site channels appears to have become unstable due to excessive bank erosion from deforestation, livestock
trampling, and channel widening resulting from increased/erosive flow velocities.
Stream mitigation options should focus on the reduction of channel cross-sectional area (decreasing bank-
height-ratio). By reducing the existing channel cross-sectional area a suitable floodprone area may be
restored and bank-height-ratios may be reduced to 1.0. This may be achieved by excavating a new
floodplain bench and/or installing in-stream habitat/grade control structures; thus, eliminating the lateral
confinement of the stream reaches.
4.2 Wetland Restoration/Enhancement
Alternatives for wetland restoration/enhancement are designed to restore a fully functioning wetland
system that will provide surface water storage, nutrient cycling, removal of imported elements and
compounds, and will create a variety and abundance of wildlife habitat. Wetland
restoration/enhancement alternatives are based primarily on professional judgment, and a reference
2
wetland is expected to be investigated to determine vegetative features, micro- and macro- topographic
variations, and soil structure components to be targeted during Site development.
Portions of the Site composed of hydric soils may have been impacted by channel incision, vegetative
clearing, livestock grazing, and earth movement associated with agricultural practices. These areas are
characterized by herbaceous and shrub vegetation, under severe impact from soil compaction by livestock
trampling. Wetland mitigation options should focus on the restoration of vegetative communities,
elevating groundwater tables to jurisdictional conditions, and the re-establishment of soil structure and
micro-topographic variations within the existing floodplain.
Restoration of wetland hydrology and wetland soil attributes may involve 1) excavation and grading of
elevated spoil and sediment embankments; 2) placement of impervious channel plugs along ditches; 3)
backfilling of entrenched stream reaches; 4) scarification of pasture soils prior to planting; and 5)
construction of ponds/fresh water marsh within the adjacent floodplain. In addition, the construction of
(or provisions for) surface water storage depressions (ephemeral pools) also adds an important component
of groundwater restoration activities. These mitigation activities are expected to result in the restoration
of approximately 0.5 acre of jurisdictional wetland at the Site.
5.0 ADDITIONAL INFORMATION
Mr. Stamey may be interested in proceeding with the project in several phases. His vision for the phased
approach consists of three phases including Phase 1) just south of the upper road crossing to just south of
the convergence of the two streams; Phase 2) just south of the upstream convergence to just north of the
downstream convergence; and Phase 3) from the downstream convergence to the ford (Figure 2). Mr.
Stamey has expressed a need for a phased approach to determine the success of proposed mitigation
options prior to committing additional properties to the project.
3
Table 1
Stream Geometry and Classification
Stamey Farm Mitigation Site
DA
Abkf
Wbkf
...............
Dbkf
......... ...
Dmax,....
.......... .....
Wbkf/Dbkf
FPA
........... . . . . . . . . . . . . . . . . ..........
ENT
........... ....... L B H . . . . ...........
B H R
Existing conditions (E-type)
Median Range
0.
...............__9......................
.................... 0. ?.....-..._.. 0
..........
20.2
_ .................................. 17.3-34.2
................._....................................................
4 1._.0 ................... ..............3.1...0................ 7 5.0
...............
11.1
.................................................... 96- 17.7
....... .........._.. .........................................
..... ........................................ ................ .....?._.6.....-...?...?...........
................2_._6...................... ..................._2....`?.......-...3. 2..........

................................. 5 .-9
........_........
95.0
. . . . . . . .............. . . . . . ...... .................. .. 65.0- 190.0
.... .................................................... . . . . . . . . . . . . . . . .
8.6
................ ............._.......
................_.:?.....-20.0
3
4.0
..................................... _..... ....... 3.9-4.5
........................................... . _..........................
1.5 1.2- 1.8
Dimension
Existing Conditions (F-type)
Median Range
...............0... 6...................................... ..............._N /A.....................
............_1.4 ._.?? ......................................
.....................
...............NSA

...........__?...._0 ...................................
9
................N /A
.....................
.............?._5_.._?.....................................
.....................
................ NSA
..............._................... .....................................
A
.....................................................
................?...._.` ....................................... ................N/A
.....................
..........._.. ?. 6 .............................. .... _._ ......._...._N /A.............._._.
20.3
........... ...................................
......................................
N?A
._._3
...........__._._ ................ N/A
..... ........_.._................
_......... ._9.................................... _ ................ NA....................
3.3 N/A
Proposed Conditions
Median Range
1.1
.. ........ . .................. _ ........ 0.6-2.0
...... . ............. ...........................................
21.6
....................................... .... 14.5-34.2
......................................_.._.. _..............
59.5
. . . .. . . .. . .. . . . . . . . . . . . . . . . . . . . 31.0-91.0
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.5
............... . . .. . .. . . . . . . . . . . . . . . . . . . . 1 1.2 - 17.9
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..................
....

... _ ................................ ...........__.. ..... 4..._- .. .. 9
..
...._
?..._? .......................
......_ ................. ?..8....2.4
. . . . . . . . . . . . . . . . . . . . . . . . . .
8.4_ 8.0-9.4
?_38 ....................

....._ ..................9..`?.......'.... ?90

.......
._
10.2
_.. _ ............... _ _........... 7.0- 14.1
................ _..............................................
2..._.. .......................
......_ ................_. ......8.....- ...........
......
1.0 1.0- 1.2
Attribute
Wbelt
.
..................................
W belt/W b
Lm
......... . ...... . . . . . . . . ...........
Lm/Wbkf
.._..........LP-P........
................................
LP-P/Wbk
. . . . . .......... . ...................
SIN*
Existing Conditions (E-type)
Median Range
87
..... . ......... . . . . . . . . . . . . . . . . . . . . . . . 50- 117
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ................
7.8
.......................................... . ............. 4.5- 10.5
..................................... _ ........ ...............
60
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 - 65
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.4
.._...... ...... _..._ ................._.._..... 4.5-5.9
...........----._................ _..............
.................43.......................... ...................._2.5.....-....5 5.......
..............._ 3_.. 9......................... .................. 2......3
............-.............. .0....
1.3 N/A
Pattern
Existing Conditions (F-type)
Median Range
150
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117- 183
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.9
......... ............................................. 7.7- 12.1
............ ................. _......... _..................
60
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 - 65
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.8
....... _..... __ .................................... 3.3-4.0

__.......
.......... _...._................. ___........
.........._43 .............................. .................. ? 5....'...5 5.............
..........._?.._$ .. .. ......................... ........._._ ?._.. ?.....-...._3_._6...... _
1.3 N/A
Proposed Conditions
Median Range
101 50 183
7.5
.............................. . ........... 3.7- 13.6
................ _ .............................................
162
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135- 189
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.0 10.0-14.0
........_$_? ........................ ...................._6.8....-.._9 5...........
6
.............. _........ _................. 5-7
....... ........................ .................._...._......
1.4 1.3- 1.5
Profile
Existing Conditions (E-type) Existing Conditions (F-type) Proposed Conditions
Attribute Median Range Median Range Median Range
SSW 0.0035 N/A 0.0059 N/A 0.0044 0.0041-

.
.
.
.
..
.
.
.............................................
.. 0.0047
..................................................................................................................................
.............................................................
Salley ..........................................................................................................................................
0.0045 NA ...............................................
..
...............
.....
.....
....
.
...
.
0.0077 NA 0.0061 N/A
Stream
Type E 4/5 F 4/5 E 4/5
DA Drainage basin area (sq. mi.) BHR Bank height ratio flow bank height/Dmax
Abkf Bankfull cross-sectional area (riffle) (ftz) (riffle)]
Aexlsting Existing cross-sectional area (riffle) (ft') Wbelt Belt width (ft)
Wbkf Bankfull width (riffle) (ft) Lm Meander wavelength (ft)
Dbkf Average bankfull depth (riffle) (ft) Lp-p Length from pool to pool (ft)
Dmax Maximum bankfull depth (riffle) (ft) SIN Sinuosity (thalweg distance/straight-line
FPA Floodprone area (ft) distance)
ENT Entrenchment ratio (FPA/Wbkf) * Estimated visually in the field
LBH Low bank height (distance from SSW Slope of the water surface (rise/run)
thalweg to the top of low bank) (ft) Svalley Slope of the valley (rise/run)
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NC 28677
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EcoScience

Corporation

Stamey Farm Mitigation Site

Vicinity Map Dwn. by:
cLF
Ckd by:
GL
Date:
Januar
2003
FIGURE
Raleigh, North Carolina Iredell County, North Carolina y
Project:
02-113.03

41
f{ f r a ++e f ?y },1 I? ae! ? r
ST N - t yy,, _? i q - 1 y ..
^>•,. ; `.,Y Y !. w - - + .? •fK? a t,'YJ T
Step-Pool Structure
- .?
P
Energy
?.
Dissi uation
Structure l
(cross-vanes) Bench Excavation r a l
Phase Approach +
All,
Phase 1 - 5 acres ?. W.
Phase 2 6 acres
Phase 3 7 acres ti r ,, '"sF
} *`
y 6 Y : 3 R7 ? ;L t,'
Y'k. t o ity': . R` '"'' r +t n w ek t-, i3rl
YET Ya. ? YY.?'xT1? y i c•'?S ??yy .<'.
Fill Ditch
-1,114
6,. {t {y{d. F 11 Raj i 1 I6P? T lw
=IMr? r d;? y 'tea .2`.+ f .R+ 7F
0A. '?Jlf AN
41
f¢. s
Drawn by: CLF
Ecoscience Mitigation Concept checked by: GL Figure
Stamey Farm Mitigation Site Date:
Corporation Iredell County/ North Carolina January 2003 2
- Raleigh, North Carolina County, Project.
02-113.03