20140944 Ver 1_Updated_Impact_Tables_20141016

CAROLINA
ECOSYSTEMS, INC.
October 14, 2014
3040 NC 42 West, Clayton NC 27520
P:919- 606 -1065 — F:919 -585 -5570
Ms. Karen Higgins
1617 Mail Service Center
Raleigh, NC 27699 -1617 RECEIVED
RE: Response to Additional Info Request for Project # 14 -0944 OCT 16 2014
South Fork Basin Improvements DENR -LAND QUALITY
Forsyth County, North Carolina STORMWATER PERMITTING
Dear Ms. Higgins;
Carolina Ecosystems, Inc. (CEI) has been in discussion with Sue Homewood of the Winston -
Salem Regional Office related to the above referenced project. The purpose of this letter is to
provide responses to Ms. Homewood's questions as well as revised plans and permit information
for review and issuance of a 401 Certification for this project. A copy of this information is also
being provided to the US Army Corps of Engineers for their review and possible modification of
the 404 Permit for this project.
The sections below summarize our discussion points (in bold) regarding the South Fork Basin
Improvements PCN, along with our team's responses (in italics). Also, a stream impact table
with additional information, a map showing the permanent stream crossings in relation to access
points for maintenance, and revised figures and plans from the original PCN have been attached.
Within the stream impact table, new columns have been highlighted with a bold outline, and
revised information is shown in red.
On the major crossings (e.g. South Fork Muddy and Salem Creeks), was boring/drilling
evaluated? If so, please provide additional justification on why it is not practical.
Trenchless methods, while often non - invasive to the surface waters, often require large
construction areas, cost exceedingly more than conventional open -cut methods, and still pose
some risk of disturbing the bottom of the creek or stream. The presence of rock can complicate
the trenchless method as well. The designers always consider trenchless methods for utility
crossings with these and other factors in mind. For this project, traditional open -cut was the
most practical method of crossing the streams and tributaries. Also, given the size of the
pipelines being installed, a trenchless jack and bore method would require a welded steel casing
pipe, further reducing the cover between the top of the pipe and the bottom of the stream. In
some cases along the gravity sewer project, this method might daylight the pipe in the bottom of
the tributary streams and not meet minimum separation requirements.
How will the large (see above) stream crossings be built? Will coffer dams and dewatering
be implemented? Will coffer dams be constructed in stages?
Coffer dams will be phased as shown in Detail E on Sheet D03 of the Muddy Creek WWTP
Influent Transfer Force Main plan set. Construction will occur in two phases and the stream
will be dewatered while allowing stream flow to continue uninterrupted in a portion of the
channel.

Ms. Karen Higgins
October 14, 2014
Page 2 of 4
Permanent stream crossings on South Fork interceptor lines: Is the riprap outlet
protection needed? If so can it be limited to the banks rather than bed ,of the channel
similar to what NCI OT does with pipe crossings? If not, the riprap in the bed will be
counted as a permanent impact.
NCDENR Land Quality requires bottom and some bank stabilization downstream of culverts to
prevent erosion For this project, it is most likely that the main creek channel will be
approaching bank full conditions when the culverts in the tributary streams experience high
volume of flow from upstream, creating a backwater condition NCDENR LQ typically requires
the consultant.to design for a 10 year storm, flow through a culvert with free discharge,
regardless of backwater conditions Therefore, we provide a detail for stabilization of the
bottom and side slopes of the channel to prevent erosion. Under a free discharge condition, the
water coming through the pipe will create a pool at the culvert's outlet which will eventually
erode back under the outlet of the pipe, undermining the culvert Providing a permanent
measure to prevent erosion an the bottom of the channel is important to prevent this. Our
calculations have determined that reticulated concrete block matting (armorflex for example)
will absorb the higher discharge shear stress in these locations Reticulating block matting is
also easier and less invasive to install in streams with active or standing water Whale it is more
beneficial to water quality to allow the stream to return to its normal conditions downstream of
the culverts, our past experience with obtaining a LQ permit has required permanent measures
downstream of culverts in order to obtain the LQ permit The block matting will be installed at
the bed elevation of the stream in order to not block aquatic passage We are revisiting each
crossing to determine if there is any more room to minimize this impact — this will be updated in
the revised plans
Can the permanent stream crossings be limited to 15 feet? If not, please provide additional
justification for the wider,access requirement.
Crossings are designed for 20 feet as the tributary streams being crossed are relatively incased
(often 5 or more feet deep) Therefore, in order to place the pipe in the bed of the stream and
provide adequate cover with stable slopes, additional maintenance area width is required to
allow for a 1 S ft permanent access path over the pipe
Are the permanent stream crossings only in areas where maintenance access is impractical
due to lack of alternative access points?
As can be seen on the attached map showing the permanent stream crossing locations and
permanent access locations for maintenance, the stream crossings requiring permanent culverts
are in locations that do not have easy access for maintenance The one exception is the eastern
most crossing, which is located near Old Salisbury Road This location has a very short run to
be maintained, and without a crossing would require excessive mobilization and demobilization
to maintain the upper section of the corridor as a separate unit

Ms. Karen Higgins
October 14, 2014
Page 3 of 4
Provide a list of the stream crossings that are not perpendicular (75 to 105 degrees) and
justification for them.
Stream crossings were made perpendicular (between 75 and 105 degrees) to the maximum extent
practical As can be seen on the attached table, only 9 of the 24 crossings are outside the
recommended range Of these, only 3 are more than 10 degrees out (below 65 or above 115
degrees) Shifting the lanes to create perpendicular crossings was not practical as this project
parallels or replaces existing lines in primarily already disturbed corridors Shifting the
proposed line to accommodate this requirement would result in increased impacts and wider
construction corridors
Identify all locations where the construction corridor is within 10 feet of the bank of the
main stem streams.
The construction corridor is within 10 feet of the stream bank in two locations
SF Sheet C6 Station 59 +50 — the proposed line has been shifted away from the existing line in
this location to maximize distance from the stream Shifting further away is impractical as
there is a confluence point of a small side channeljust'upstream of the current construction
corridor. This would increase impacts and potentially cause bank instability in the area
between the two channels. The existing pipe will be abandoned in place in this area leaving
a concrete pipe buried between the stream and the new pipe. This will actually provide
added protection to the new installation as the stream meanders over, time.
SF Sheet C36 & 37 — a small tributary stream is within the existing sewer corridor in this
location. As stated in the permit application, construction will not impact the stream. Notes
will be added to the drawings directing the Contractor to not impact the stream or its banks
in this area. -See below for additional protection measures at this location.
At Site 21 (Sheets C36 and 37), consider dewatering the stream when construction is
directly adjacent to the channel in order to prevent water - quality violations during
construction. An example permit condition is provided.
The contractor will be required to avoid the stream channel when installing the pipe parallel to
it during construction We will incorporate the proposed dewatering language onto the
drawings as a note for additional' measures of protection in this area The example dewatering
language will be used as a basis for this note
If you have any questions or need additional information please contact me at your earliest
convenience at (919) 606 -1065 or phil.may @carolinaeco.com.
Sincerely,
Carolina Ecosystems, Inc.
Philip May
Senior Environmental Scientist

Ms. Karen Higgins
October 14, 2014
Cc. John Thomas — USACE Raleigh Regulatory Office
Ron Hargrove, Utilities Director, City of Winston -Salem
Terry Cornett, P.E., Black & Veatch
Mary Sadler, P.E., Hazen & Sawyer, Inc.
Attachments:
Table 1 - Stream Impact Summary (Revised)
Figure: Permanent Stream Crossings
Figure 3: Impact Locations (Revised)
Figure 4: Impact Sites (Revised)
Engineering Plans — South Fork Interceptor (Revised)
Page 4 of 4

Table 1: Stream Impact Summary Table
Impact
Site #
PCN
Impact
Original
Plan Sheet
(Station Number)
Plan Sheet
(Station Number)
Stream
Crossing
Angle
Type of
Impact
Stream
ID
Stream
Name
Perennial or
Intermittent
Type of
Jurisdiction
Stream
Width (ft)
Original
Total
Impact (ft)
Original
Permanent
Impact (ft)
Original
Temproary
Impact (ft)
Revised
Total
Impact (ft)
Revised
Permanent
Impact (ft)
Revised
Temproary
Impact (ft)
Riprap
Impact (ft)
2
S1
SF -05 (48 +95)
SF -05 (48 +95)
75
Culvert Installation
SAJ
UT 1 to South Fork Muddy Creek
Intermittent
Corps
3
53
20
33
53
20
25
8
3
S2
SF -C6 (58 +17)
SF -C6 (58 +17)
105
Excavation and Backfill
SAG
UT 2 to South Fork Muddy Creek
Perennial
Corps
4
44
0
44
44
0
44
6
S3
SF -C10 (90 +41)
SF -C10 (90 +41)
115
Culvert Installation
SAF
UT 3 to South Fork Muddy Creek
Intermittent
Corps
7
56
20
36
56
20
26
10
7
S4
SF -C12 (111 +35)
SF -C12 (111 +35)
110
Culvert Installation
SAE
UT 4 to South Fork Muddy Creek
Intermittent
Corps
4
55
20
35
55
0
55
8
S5
SF -C13 (120 +72)
SF -C13 (120 +72)
80
Culvert Installation
SAD
UT 5 to South Fork Muddy Creek
Perennial
Corps
6
61
20
41
61
0
61
10
S6
SF -C16 (155 +81)
SF -C16 (155 +81)
115
Culvert Installation
SAC
UT 6 to South Fork Muddy Creek
Perennial
Corps
7
56
20
36
56
20
26
10
11a
S7
SF -C18 (178 +18)
SF -C18 (178 +18)
145
Culvert Installation
SAB
UT 7 to South Fork Muddy Creek
Intermittent
Corps
3
60
20
40
48
0
48
12
S8
SF -C19 (186 +41)
SF -C19 (186 +41)
105
Culvert Installation
SAA
UT 8 to South Fork Muddy Creek
Intermittent
Corps
2
60
24
36
60
20
32
8
17
S9
SF -C30 (3 +28)
SF -C28 (3 +28)
125
Excavation and Backfill
Sv
UT 9 to South Fork Muddy Creek
Perennial
Corps
5
52
0
52
52
0
52
18
S10
SF -C31 (16 +6S)
SF -C29 (16 +65)
8S
Excavation and Backfill
SY
UT 10 to South Fork Muddy Creek
Intermittent
Corps
8
40
0
40
40
0
40
19
S11
SF -C33 (37 +90)
SF -C31 (37 +90)
80
Excavation and Backfill
SX
UT 11 to South Fork Muddy Creek
Intermittent
Corps
3
33
0
33
33
0
33
20
S12
SF -C36 (60 +75)
SF -C34 (60 +75)
105
Excavation and Backfill
SU
UT 12 to South Fork Muddy Creek
Perennial
Corps
5
69
0
69
69
20
41
8
21
S13
SF -C38 (19 +51)
SF -C36 (19 +51)
100
Excavation and Backfill
SW
UT 13 to South Fork Muddy Creek
Intermittent
Corps
3
36
0
36
36
0
36
22
S14
MC -0O2 (13 +75)
MC -0O2 (13 +75)
75
Excavation and Backfill
SA
Muddy Creek
Perennial
Corps
4S
48
0
48
48
0
48
23
S15
MC -0O2 (15 +88)
MC -0O2 (15 +88)
115
Excavation and Backfill
SAS
UT to Muddy Creek
Intermittent
Corps
3
1 49
0
49
49
0
49
24
S16
MC -005 (48 +75)
MC -005 (48 +75)
90
Excavation and Backfill
SA
Muddy Creek
Perennial
Corps
50
40
0
40
40
0
40
25
S17
MC -005 (49 +80)
MC -CO5 (49 +80)
80
Excavation and Backfill
SAO
UT 1 to Salem Creek
Intermittent
Corps
1
58
0
58
58
0
58
26
S18
MC -008 (79 +27)
MC -008 (79 +27)
110
Excavation and Backfill
SAO
UT 2 to Salem Creek
Intermittent
Corps
1
42
0
42
42
0
42
27
S19
MC -009 (82 +13)
MC -009 (82 +13)
130
Excavation and Backfill
SAP
UT 3 to Salem Creek
Intermittent
Corps
2
56
0
56
56
0
56
29
S20
MC -C12 (114 +50)
MC -C12 (114 +50)
7S
Excavation and Backfill
SAT
UT 4 to Salem Creek
Intermittent
Corps
3
31
0
31
31
0
31
30
S21
MC -C13 (121 +63)
MC -C13 (121 +63)
105
Excavation and Backfill
SAU
UT 5 to Salem Creek
Perennial
Corps
3
40
0
40
40
0
40
33
S22
MC -C17 (165)
MC -C17 (16S)
8S
Excavation and Backfill
SAR
UT 6 to Salem Creek
Intermittent
Corps
3
40
0
40
40
0
40
34
S23
MC -C18 (176 +50)
MC -C18 (176 +50)
90
Excavation and Backfill
SA
Salem Creek
Perennial
Corps
45
40
0
40
40
0
40
36
S24
MC -C22 (208 +75)
MC -C22 (208 +75)
8S
Excavation and Backfill
SA
Salem Creek
Perennial
Corps
45
40
0
40
401
0
40
Totals
I
1
1,159
144
1,015
1,147
1 100
1,003
44