20080868 Ver 2_Stream Buffer Impact and Mitigation Calculations_20100302

PCS
Phosphate AURORA
PCS PHOSPHATE COMPANY, INC.
P.O. BOX 48, AURORA, NC U.S.A. 27806
March 2, 2010
Mr. John Dorney
Division of Water Quality
North Carolina Dept. of ENR
Wetlands / 401 Unit
2321 Crabtree Blvd., Suite 250
Raleigh, NC 27604-2260
re: 404 Permit SAW-2001-10096 for PCS Mine Continuation
Dear Mr. Dorney:
1,1AR I.2010
DENR • WATER QUALITY
MMIDS AND STOR;WWATER OWWCH
PCS Phosphate Company, Inc. (the Company) hereby requests your determination
of the amount of stream buffer mitigation required by the 404 Permit issued to the
Company on June 10, 2009.
In support of this request we have attached hereto a notebook containing what the
Company believes are the buffer impacts and appropriate mitigation calculations.
Sincerely,
Ross M. Smith
Manager, Environmental Affairs
PCS Phosphate Company, Inc.
R PotashCorp
Aurora
PCs
Phosphate VAURORA

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0 PotashCorp-Aurora (PCS Phosphate Company, Inc.)
Stream Buffer Mitigation Credits
(Acres)
•
Buffer Mitigation Credits
Mitigation Project
without RHWS with RHWS

Hell Swamp 21.0 42.0
Upper Back Creek 4.4 16.6
Sage Gut 2.2 14.1
Rutman Creek Watershed 0.0 20.2
Bay City Farm 0.0 7.7

Total 27.6 100.6
RHWS: Riparian Headwater Systems buffer credit
Hell Swamp based on 5/7/09 application (Figure dated 3/27/09)
Back Creek based on September 2008 plan
Sage Gut based on January 2009 plan
Rutman Creek based on December 2008 plan
Bay City based on Fig. 13 of FEIS plan
0
i LEGEND FOR PCS PHOSPHATE BIOTIC COMMUNITIES
•
Biotic community number Biotic community description
1A Public Trust waters
1 B Perennial stream
1C Intermittent stream
2 Wetland brackish marsh complex
3 Wetland bottomland hardwood forest
4 Wetland herbaceous assemblage
5 Wetland shrub - scrub assemblage
6 Wetland pine plantation
7 Wetland hardwood forest
8 Wetland mixed - pine hardwood forest
9 Wetland pine forest
10 Wetland ocosin - bay forest
11 Wetland sand ridge forest
12 Pond
13 Wetland maintained area
14 Upland herbaceous assemblage
15 Upland shrub - scrub assemblage
16 Upland pine plantation
17 Upland hardwood forest
18 Upland mixed - pine hardwood forest
19 Upland pine forest
20 Upland sand ridge forest
21 Upland agricultural land
22 Upland non - vegetated/maintained area

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PERERMAL(19) LF. KMWTTEMIC) LF.
HUDDLES CUT 0
2558
0 74
TOOLEY CREEK 0 667
JACOBS CREEK 0 662
201 9rpoJ 51p TOTAL LF. 0 3961
IMPACTS OUTME NCPC MODFIED ALT L BOUNDARY
fACPC IIOOIF'IE? ALT L - EFiA01Mf! a__ __ _
Ns NiG1iWY •IWY•? 1118
to PUBl1C TRUST AREAS 36 LF. (0.02 ACRES)
7A REIIEMIWL 31RFA11(CNML)<t[l0GAUM 220 LF. (0.16 ACRES)
2 YEAR WALT
BUDCKS PERENNIAL
(18) W1FRIBTTLM
(1C)
TOTAL LF.
20(19 0 2556 2558
2010-2011 0 214 214
2012-2013 0 547 547
2014-2015 0 662 662
2D16-2017 0 0 0
TOTAL LF. 0 3981 3961
0 1160 3200
NJ' LA M MT
•
NCPC Modified Alternative L Buffers
2 Year Impact Blacks 2009.2017 7nna 1
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COMM
1A

0.00

0.00

0.00

0.00

0.00

0.00
1 B 0.00 0.00 0.00 0.00 0.00 0.00
IC 0.00 0.00 0.00 0.00 0.00. 0.00
2 0.00 0.00 0.00 0.00 0.00 0.00
3 1.80 0.00 0.00 0.00 0.00 1.80
4 0.00 0.00 0.00 0.00 0.00 0.00
5 0.00 0.00 0.00 0.00 0.00 0.00
6 0.00 0.05 0.00 0.00 0.00 0.05
7 0.75 0.00 0.40 0.61 0.00 1.76
8 0.58 0.22 0.34 0.00 0.00 1.14
9 0.00 0.05 0.00 0.00 0.00 0.05
10 0.00 0.00 0.00 0.00 0.00 0.00
11 0.00 0.00 0.00 0.00 0.00 0.00
12 0.00 0.00 0.00 0.00 0.00 0.00
13 0.00 0.00 0.00 0.00 0.00 0.00
14 0.00 0.00 0.01 0.00 0.00 0.01
15 0.00 0.00 0.00 0.00 0.00 0.00
16 0.00 0.00 0.00 0.00 0.00 0.00
17 0.34 0.00 0.00 0.00 0.00 0.34
18 0.16 0.00 0.05 0.00 0.00 0.21
19 0.00 0.00 0.00 0.00 0.00 0.00
20 0.00 0.00 0.00 0.00 0.00 0.00
21 0.00 0.00 0.00 0.00 0.00 0.00
22 0.05 0.03 0.04 0.00 0.00 0.13
BUFFER TOTALS 3.69 0.36 0.84 0.61 0.00 5.50
.7UIJLUt. VVVL. a.IJ V.JL U.14 U.b1 0.00 4.80
Subtot. Up 0.56 0.03 0.10 0.00 0.00 0.69
3.69 0.36 0.64 0.61 0.00 5.50
r J4'?fi22=MOO N.l l 0513pBMORVJABLC$I10180P'M;MG MOp ALi ? BOfrC [OM Z YR .MrgOi ??MEO 6Uf 0.11 qL5
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NCPC Modified Alternative L Buffers
2 Year ImDact Blocks 2009.2017 Zone 2

1 A 7
0.00
0.00
0.00
0.00
0.00 is
0.00
1 B 0.00 0.00 0.00 0.00 0.00 0.00
1 C 0.00 0.00 0.00 0.00 0.00 0.00
2 0.00 0.00 0.00 0.00 0.00 0.00
3 0.98 0.00 0.00 0.00 0.00 0.98
4 0.00 0.00 0.06 0.00 0.00 0.06
5 0.02 0.00 0.00 0.00 0.00 0.02
6 0.00 0.07 0.00 0.00 0.00 0.07
7 0.56 0.00 0.16 0.45 0.00 1.17
8 0.43 0.19 0.23 0.00 0.00 0.85
9 0.00 0.03 0.00 0.00 0.00 0.03
10 0100 0.00 0.00 0.00 0.00 0.00
11 0.00 0.00 0.00 0.00 0.00 0.00
12 0.00 0.00 0.00 0.00 0.00 0.00
13 0.00 0.00 0.00 0.00 0.00 0.00
14 0.00 0.00 0.04 0.00 0.00 0.04
15 0.13 0.00 0.02 0.00 0.00 0.15
16 0.00 0.00 0.00 0.00 0.00 0.00
17 0.16 0.00 0.00 0.00 0.00 0.16
18 0.15 0.00 0.07 0.00 0.00 0.22
19 0.00 0.00 0.00 0.00 0.00 0.00
20 0.00 0.00 0.00 0.00 0.00 0.00
21 0.01 0.00 0.00 0.00 0.00 0.01
22 0.08 0.03 0.04 0.00 0.00 0.15
BUFFER TOTALS 2.52 0.32 0.62 0.45 0.00 3.91
Subtot. Wet. 1.99 0.29 0.45 0.45 0.00 3.18
Subtot. Up 0.53 0.03 0.17 0.00 0.00 0.73
2.52 0.32 0.62 0.45 0.00 3.91
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1] 1'1004
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LEGEND
= Ncpa modaltl 2009.shp
Ncpc bufr blo z1 2009.shp (3.685 Acres)
3-1.80
7 - 0.75
8 - 0.58
15 - 0.00
17 - 0.34
18 - 0.16
22 - 0.05
Ncpc bufr bio z2 2009.shp (2.52 Acres)
3-0.98
5 - 0.02
7 - 0.56
8 - 0.43
15 - 0.13
17 - 0.16
18 - 0.15
21 - 0.01
22 - 0.08
0 Ncpc Modified Alt L 5/26109
n
0
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1000 0 1000 Feet
Zone 1
•
Waters of the US Areas - 3.13 Acres
Welland Areas (Without Ponds and Creeks) - 3.13 Acres
Upland Areas - 0.56 Areas
Zone 2
Waters of the US Areas -1.89 Acres
Welland Areas (Without Ponds and Creeks) -1.99 Acres
Upland Areas - 0.53 Acres
•
•
L
Ncpc_bufr bia_z1 2010_11.shp (0.357 Acres)
3 - 0.00
6 - 0.05
B-0.22
9 - 0.05
22 - 0.03
Ncpc bufr bio z22010_11.shp (0.32 Acres)
6 - 0.07
8 - 0.19
L 9 - 0.03
22 - 0.03
Ncpc Modified Aft L 5126/09

1000 0 1000 Feet
•
Zone 1
Waters of the US Areas - 0.32 Acres
Wetland Areas (WKW Ponds and Creeks) - 0.32 Acres
Upland Areas - 0.03 Acres
Zone 2
Waters of the US Areas - 0.29 Acres
Welland Areas (Without Ponds and Creeks) - 0.29 Acres
Upland Arses - 0.03 Acres

•
LEGEND
13.shp
3.shp (.8432 Acres)
' 8 - 0.34
14 - 0.01
15 - 0.00
18 - 0.05
22 - 0.04
Ncpc buFr bio z2_2012_13.shp (0.62 Acres)
4 - 0.06
7 - 0.16
8 - 0.23
14 - 0.04
15 - 0.02
18 - 0.07
22 - 0.04
= Ncpc Mod(fled Aft L 5/26!09
•
Zone 1
Waters of the US Areas - 0.74 Acres
Wetland Arses (Without Ponds and Creeks) - 0.74 Acres
Upland Aces - 0.10 Acres
Zone 2
Waters of the US Areas - 0.45 Acres
W:Uand Areas (Without Ponds and Creeks) -OAS Acres
Upland Areas - 0.17 Acres
•

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1000 0 100c
mmmmwwlmmmm?
Lone 1
Waters of the US Areas - 0.61 Acres
Wetland Areas (Without Ponds and Creeks) - 0.61 Acres
Upland Areas - 0.00 Ades
Zone 2
Waters of the US Areas - 0.45 Acres
Wetland Areas (Without Ponds and Creeks) - 0.45 Acres
Upland Areas - 0.00 Acres
0 Ncpc modald2014_15.shp
Ncpc bufr bio z1 1014_15.shp
M 7 - 0.61
Ncpc bufr bio z2 2014 15_rev.shp
M 7 - 0.45
19 - 0.00
U Ncpc Modified AU L 5/26/09
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IVMRWJ7ENT - 126 -.r
201F2012
'0 768 %TAi 1 r
1C - 230 T07AL .f
162 L F
113] L F
a22 L F
37a L F ]58 L F

1056 L r
178: F. W LF
128 L F. PORIB CFM
579. F HAITI r11M
2018-2017
19 - 115b IQ tAL Lt
20IF2017
IC - 178 '0-AL LF
2=-202]
1C - 2100 IOIAL 0

0 1.600 3.200
IpBp t 26" M na
166 L F
25- LF.
1 F
161 L.F
202+-2026
' PERENNIAL(18) L.F. TOTAL L.F.
20+ TOrA_ L
PORTER CREEK 2,533
TOTAL L.F.
*MMITWW(1C) L.F. 4,786
PORTER CREEK (2,356)
DURHAM CREEK (2.430)

Stream Impael LF

Scale: As shown Drawn b : BFG W
Dafe: 11 /20/09
Approved by: m?"`s i2-os
2 YEAR IMPACT
BLOCKS PERENNNL
(18) INTERMITTENT
(1C)
TOTAL L.i.
2016-2017 1765 178 1943
2010-2019 768 2304 3072
2020-2027 0 0 0
2022-2023 0 2100 2100
2024-2025 0 204 204

TOTAL L.F.

2533

4786 Msdllled AllernefWe L - Bonnerton
PCS PHOSPHATE MINE CONTINUATION
7319
•
Bonnerton Modffied Altemative L Buffers
2 Year Imnact Blocks 2016-2025 Zone 1
•
1A 0.00 0.00 0.00 0.00 0.00 0.00
1B 0.00 0.00 0.00 0.00 0.00 0.00
1 c 0.00 0.00 0.00 0.00 0.00 0.00
2 0.00 0.00 0.00 0.00 0.00 0.00
3 0.00 0.03 0.00 2.25 0.92 3.20
4 0.00 0.00 0.00 0.00 0.00 0.00
5 0.00 0.00 0.00 0.60 0.12 0.72
6 0.00 1.00 0.00 0.00 0.00 1.00
7 0.00 1.37 0.00 0.00 0.00 1.37
8 0.00 1.01 0.00 0.41 0.00 1.42
9 0.00 0.09 0.00 0.06 0.00 0.15
10 0.00 0.00 0.00 0.00 0.00 0.00
11 0.00 0.00 0.00 0.00 0.00 0.00
12 0.00 0.00 0.00 0.00 0.00 0.00
13 0.00 0.00 0.00 0.00 0.00 0.00
14 0.00 0.00 0.00 0.00 0.00 0.00
15 0.00 0.00 0.00 0.05 0.00 0.05
16 0.00 0.00 0.00 0.00 0.00 0.00
17 0.00 0.34 0.00 0.00 0.00 0.34
18 0.00 0.00 0.00 0.00 0.00 0.00
19 0.00 0.00 0.00 0.00 0.00 0.00
20 0.00 0.00 0.00 0.00 0.00 0.00
21 0.00 0.00 0.00 0.00 0.00 0.00
22 0.00 0.00 0.00 0.05 0.00 0.05
BUFFER TOTALS 0.00 3.84 0.00 0.00 0.00 8.30
buutot. wet. O.UU 3.50 0.00 3.32 1.04 7.86
Subtot. Up 0.00 0.34 0.00 0.10 0.00 0.44
0.00 3.84 0.00 3.42 1.04 8.30
174562241MOd_All L 051309IBonnenonAables/Bon Mod AK L &o Com Imp B1ks_Table_Z1.x1s
12/1/2009

•
Bonnerton Modified Alternative L Buffers
2 Year Imnar_t Rind-ke 2MR.2n95 7nna 9
•
rtC
1A
0.00
0.00
0.00 .,
0.00
0.00
0.00
1 B 0.00 0.00 0.00 0.00 0.00 0.00
I c 0.00 0.00 0.00 0.00 0.00 0.00
2 0.00 0.00 0.00 0.00 0.00 0.00
3 0.00 0.05 0.00 0.83 0.44 1.32
4 0.00 0.00 0.00 0.00 0.00 0.00
5 0.00 0.00 0.00 0.62 0.17 0.79
6 0.00 0.63 0.00 0.00 0.00 0.63
7 0.00 0.68 0.00 0.00 0.00 0.68
8 0.00 0.37 0.00 0.31 0.03 0.72
9 0.00 0.41 0.00 0.07 0.00 0.48
10 0.00 0.00 0.00 0.00 0.00 0.00
11 0.00 0.00 0.00 0.00 0.00 0.00
12 0.00 0.00 0.00 0.00 0.00 0.00
13 0.00 0.00 0.00 0.00 0.00 0.00
14 0.00 0.00 0.00 0.00 0.00 0.00
15 0.00 0.02 0.00 0.09 0.00 0.11
16 0.00 0.00 0.00 0.00 0.00 0.00
17 0.00 0.52 0.00 0.00 0.00 0.52
18 0.00 0.00 0.00 0.00 0.00 0.00
19 0.00 0.00 0.00 0.00 0.00 0.00
20 0.00 0.00 0.00 0.01 0.00 0.01
21 0 0.00 0.00 0.00 0.00 0.00
22 ]]!E4 0.00 0.00 0.05 000 0.05
BUFFER TOTALS 2.68 0.00 0.00 0.00 5.31
JuDtot. Wet. U.UU 2.14
Subtot. Up 0.00 0.54
0.00 2.68
0.00 1.83 0.64 4.62
0.00 0.15 0.00 0.69
0.00 1.98 0.64 5.31
17456224/Mon_Ait L_05130918onnertonltablesMon Mon Alt L Bw Corr Imp 8Ik9_TRbIe_Z2jds
12/1/2009
is
•
•
0
6 -1.00
7 -1.37
9 - 0.09
17 - 0.34
Son_modalti 2018 19_z2.shp (2.68 Acres)
13 - 0.05
6 - 0.63
7 - 0.68
8 - 0.37
9 - 0.41
15 - 0.02
17 - 0.52
Bon_revepamodaltl_bndy_051309.shp
Zone 1
Waters of the US Areas - 3.50 Acres
Wetland Areas (Without Ponds and Creeks) - 3.50 Acres
Upland Areas - 0.34 Acres
Zone 2
Waters of the US Areas - 2.14 Acres
Wetland Areas (Without Ponds and Creeks) - 2.14 Acres
Upland Areas - 0.54 Acres
•
•
?J
LEGEND
Bon_modalt1051309 202223.shp
Bon_modaltt_202223 z1.shp (3.42 Acres)
3 - 2.25
5 - 0.60
' 8-0.41
9 - 0.06
15 - 0.05
M 22 - 0.05
3on_modaltl 2022 23 z2.shp (1.98 Acres)
3 - 0.83
5 - 0.62
8 - 0.31
9 - 0.07
15 - 0.09
® 20 - 0.01
® 22 - 0.05
Bon_revepamodaltl bndy_051309.shp
(1)
1000 0 1000 Feet
Zone 1
Waters of the US Areas - 3.32 Acres
Wetland Areas (Without Ponds and Creeks) - 3.32 Acres
Upland Areas - 0.10 Acres
Zone 2
Waters of the US Areas -1.83 Acres
Wetland Areas (Without Ponds and Creeks) -1.83 Acres
Upland Areas - 0.15 Acres

E
0
LEGEND
M Bon_modalt1051309 24 2025.shp
Bon_-modaltl 2024_25_z1.shp (1.04 Acres)
3 - 0.92
5 - 0.12
8 - 0.00
Bon_modaltl_2024_25 z2.shp (0.64 Acres)
L? 3 - 0.44
5-0.17
8 - 0.03
Bon_revepamodaltl_bndy_051309.shp
Zone 1
Waters of the US Areas - 1.04 Acres
Wetland Areas (Without Ponds and Creeks) -1.04 Acres
Upland Areas - 0.00 Acres
Zone 2
Waters of the US Areas - 0.64 Acres
Wetland Areas (Without Ponds and Creeks) - 0.64 Acres
Upland Areas - 0.00 Acres
I
1000 0 1000 Feet
•
C7

6AUN CREDt
J06L L F
497 1 F 2030-20M
2026-2029
U06
'664 lr
2026-2027
516 L F
U07
219 L F
2024-2025 BROOMFIEID SWAMP CRIV
8 - 1249 11", 11
'C - 2510 101AL if
626 L F
2034-2035
2032-2033
2030-2031
2036-2037
LOS
S23 I F
236-2039 143 l F
1363 LF
2040-2041
1103 L.r
CIP"Im Am
555 L F
212-2013
2046-2047 2044-2045

0 2000 4000
9GYt M rm
PLRLNNIAL(1D) L.F. INTERMITTENT(1C) L.F.

CYPRESS RUN 3466 0

UD8 497 1664

TOTAL L.F. 7799 3336

Slroam Impact LF

PCS PHOSPHATE MINE CONTINUATION

-Scale, As shown
w T
Oofa: 11 /20/09 "m r
A roved b :
2 YEAR IMPACT
BLOCKS PERENNIAL
(18) INTERMITTENT
(1C) TOTAL Li.
2024-2025 1249 2510 3759
2026 2027
- 3084 0 3084
2028-
2029
0
0
0
2030-2031 0 0 0
2o32-2x33 0 0 0
2034-2035 0 828 826
2036-2037 445 0 445
2038-2039 2466 0 2466
2040-2041 O 0 0
2042-2043 555 0 555
2044-2045 0 0 0
2046-2047 0 0 0

OTAL L.F.

799

336 BAILEY CREEK 3084 0
6ROOMFIELD SWAMP 0 826
UD5 523 0
UD7 229 It"
Modified Allor"allae L - South of 33
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LEGEND
Q S33_modalt1051309_;
S33_modalt1051309_2024_
7 - 0.11
-, 8 - 0.26
18 - 0.01
22 - 0.37
S33_modalt1051309_2024_
0 7 - 0.06
0 8 - 0.19
18 - 0.21
21 - 0.01
22 - 0.03
Zone 1
Waters of the US Areas - 0.37
Wetland Areas (Without Ponds
Upland Areas - 0.38 Acres
Zone 2
Acres
and Creeks) - 0.37 Acres
Waters of the US Areas - 0.25 Acres
Wetland Areas (Without Ponds and Creeks) - 0.25 Acres
Upland Areas - 0.25 Acres
•
.7
0
LEGEND
= S33_modalt1051309_2026_27.shp
S33_modalt1051309_2026_27_Z1.shp (4.30 Acres)
17 - 1.38
i 18 - 2.72
19 - 0.06
21 - 0.01
r 22-0.13
S33_modalt1051309_2026_27_z2.shp (2.89 Acres)
17 - 0.82
18 -1.87
® 19 - 0.04
21 - 0.02
22-0.14
Zone 1
Waters of the US Areas - 0.00 Acres
Wetland Areas (Without Ponds and Creeks) - 0.00 Acres
Upland Areas - 4.30 Acres
400 0 400 800 Feet
Zone 2
Waters of the US Areas - 0.00 Acres
Wetland Areas (Without Ponds and Creeks) - 0.00 Acres
Upland Areas - 2.89 Acres
S33
I_ PCS PHOSPHATE MINE CONTINUATION '
SCALE: AS SHOWN APPROVED BY: DRAWN BY, BFG
CPf17450N
x026.2027
•

•
Zone 1
0 S33_modalt1051309_2036_37.shp
S33_modalt1051309_2036_37_z1.shp (0.64 Acres)
17 - 0.31
18 - 0.32
_ 22 - 0.01
S33_modalt1051309_2036_37 z2.shp (0.47Acres)
17 - 0.21
18 - 0.22
21 - 0.00
[- 22 - 0.04
Waters of the US Areas - 0.00 Acres
Wetland Areas (Without Ponds and Creeks) - 0.00 Acres
Upland Areas - 0.64 Acres
Zone 2
Waters of the US Areas - 0.00 Acres
Wetland Areas (Without Ponds and Creeks) - 0.00 Acres
Upland Areas - 0.47 Acres
400 0 400 800 Feet
•
LEGEND
= S33_modalt1051309_2038 39.shp
S33 modalt1051309_2038_39_Z1.shp (3.42 Acres)
16 - 0.93
•
17 - 1.35
18-1.10
21 - 0.00
22 - 0.04
modalt1051309_2038_39 z2.shp (2.32 Acres)
16 - 0.62
17 - 0.87
18 - 0.76
21 - 0.03
22 - 0.04

0
Zone 1
Waters of the US Areas - 0.00 Acres
Wetland Areas (Without Ponds and Creeks) - 0.00 Acres
Upland Areas - 3.42 Acres
Zone 2
Waters of the US Areas - 0.00 Acres
Wetland Areas (Without Ponds and Creeks) - 0.00 Acres
Upland Areas - 2.32 Acres
600 0 600 Feet
•
LEGEND
S33_modalt1051309_2040_41.shp
nodalt1051309_2040 41_z1.shp (0.01 Acres)
8 - 0.00
22 - 0.01
nodalt1051309_2040_41_z2.shp (0.04 Acres)
8 - 0.01
21 - 0.01
22 - 0.02
•

100 0 100 Feet
rmmmm%mmmmi __.
0
Zone 1
Waters of the US Areas - 0.00 Acres
Wetland Areas (Without Ponds and Creeks) - 0.00 Acres
Upland Areas - 0.01 Acres
Zone 2
Waters of the US Areas - 0.01 Acres
Wetland Areas (Without Ponds and Creeks) - 0.01 Acres
Upland Areas - 0.03 Acres
C-I
•
0
LEGEND
= S33_modalt1051309_2042 43.shp
S33_modalt1051309_2042 43_z1.shp (0.80 Acres)
8 - 0.00
18 - 0.77
22 - 0.03
S33 modalt1051309_2042 43_z2.shp (0.57 Acres)
8 - 0.05
18 - 0.45
0 21 - 0.02
22 - 0.05
Zone 1
Waters of the US Areas - 0.00 Acres
Wetland Areas (Without Ponds and Creeks) - 0.00 Acres
Upland Areas - 0.80 Acres
Zone 2
Waters of the US Areas - 0.05 Acres
Wetland Areas (Without Ponds and Creeks) - 0.05 Acres
Upland Areas - 0.52 Acres

500 0 500 Feet
DETERMINING IMPACTS AND CALCULATING MITIGATION CREDIT ON
• MULTI-RESOURCE SITES (Version 1.4 -10/19/09)
1.0 PURPOSE
The purpose of this document is twofold:
1) To provide guidance and clarification on correctly determining the amount of
impacts to regulated resources (streams, wetlands and riparian buffers) at permit
sites.
2) To provide guidance and clarification on determining the amount and types of
compensatory mitigation credit that can be generated on mitigation sites at which
multiple resources (e.g. streams, wetlands, regulated riparian buffers and/or
nutrient offset credits) have been restored.
This document involves the actual quantification of impacts and mitigation credits on the
ground at both impact sites and mitigation sites. Mitigation ratios are not addressed
unless indicated in a specific example. Mitigation ratios for stream and wetland impacts
are determined on a case-by-case basis by the U.S. Army Corps of Engineers and/or the
Division of Water Quality.
This policy clarification has been coordinated with the U.S. Army Corps of Engineers
and the U.S. Environmental Protection Agency. These procedures address 404/401
• pennitting and buffer and Isolated Wetland rules.
For simplicity, this document assumes all mitigation activities described in the various
examples are restoration activities. Multipliers for enhancement or preservation are not
considered.
It is also important to note that in determining compensatory mitigation generated at
mitigation sites, the examples given in this document assume the mitigation sites are
mitigation banks or In-Lieu-Fee sites, credits generated at these mitigation sites may be
used to provide compensatory mitigation for multiple impact sites.
For project-specific mitigation. the resource agencies will evaluate a proposed mitigation
site on a case-by-case basis, and will make a determination as to whether the proposed
mitigation site will provide satisfactory replacement of the functions and values lost at
the impact site.
2.0 DETERMINING IMPACTS AT PROJECT SITES
In submitting an application for impacts, either through submittal of a Pre-Construction
Notification (PCN) for a Nationwide Permit/General Water Quality Certification, or an
Individual Permit application/Individual 401 Water Quality Certification, the applicant
must calculate impacts to regulated resources and present the impact totals in the
application. Stream impacts are measured in linear feet (LF) of stream channel, as
measured along the thalweg of the stream. Wetland impacts are measured in square feet
(SF) or acres (area] measurement). Where State riparian buffer rules apply, buffer
impacts are also measured in square feet or acres.
Figure 1. Determination of stream and wetland impacts.
•
160'
Stream impacts = 160 LF
Wetland impacts = 0.27 acres
In the example shown in Figure 1, the impact consists of a corridor 160 feet wide,
impacting both a stream and adjacent wetlands. Stream impacts must include
pipes/culverts, fill slopes and dissipater pads. Wetland impacts include all fill in wetland
areas.
The applicant would need to provide satisfactory compensatory mitigation for 160 LF of
stream and 0.27 acres of wetlands.
In areas where state riparian buffer rules are present (e.g. Neuse or Tar-Pamlico basins),
buffer impacts must also be included in the application. If buffer impact thresholds are
exceeded, if the activity resulting in the impact is considered "allowable with mitigation",
or if a Variance requires mitigation under the buffer rules, buffer mitigation is also
required (Figure 2).
•
2
•
•
Figure 2. Determination of stream, wetland and riparian buffer impacts.
However, with respect to buffer mitigation, the buffer rules state that ".....wetlands
adjacent to surface waters or within 50 feet of surface waters shall be considered as part
of the riparian buffer but are regulated pursuant to 15A NCAC 2H .0506."'
Therefore, to calculate the mitigation requirement, the impacted wetland area is
subtracted from the total buffer impact. Therefore, the mitigation requirement for Figure
2 would be:
• 15A NCAC 02B .0233(3); 15A NCAC 02B .0243(3); 15A NCAC 02B .0259(3)
J
In the example shown in Figure 2, the impact consists of a corridor 160 feet wide,
impacting a stream, adjacent wetlands and riparian buffers. As shown above, the
wetlands are located within the riparian buffer. The impacts listed above would be
included in the application.
Stream mitigation = 160 LF
Wetland mitigation = 0.27 acres
ZI buffer impacts = 9,600 SF - 4,800 SF WL = 4,800 SF buffer requiring mitigation
Z2 buffer impacts = 6,400 SF - 3,200 SF WL = 3.200 SF buffer requiring mitigation
Applying Zone 1 and Zone 2 multipliers then determines how much buffer mitigation is
required.
Buffer mitigation required = (4,800 SF x 3) + (3,200 SF x 1.5) = 19,200 SF/0.44 acres
2.0 DETERMINING MITIGATION CREDIT AT MITIGATION SITES
As discussed previously, the following examples represent mitigation sites intended to
provide compensatory mitigation credit to multiple project sites. Therefore. these
examples represent either a mitigation bank or an ILF site.
•
•
4
Figure 3. Determination of stream and wetland credits on a mitigation site.
In the example shown in Figure 3, 1,000 LF of stream was restored through a wetland
area. Current interagency guidance requires that a stream restoration project include a
50-foot riparian buffer on each side of the stream (30 feet in the mountain counties).2
This riparian zone is a part of the stream restoration. The new Federal Mitigation Rule3
does not allow for the use of the same area of mitigation to offset multiple.) urisdictional
impacts. Therefore the wetland area within this riparian zone is subtracted from the total
available wetland credit at this site.
*Please note that the credit calculations described above are per the USEPA
interpretation of the Federal Mitigation Rule. The USACE interpretation is that the
ivetlands within the riparian buffer are available for use and sale as mitigation credit.
Figure 4. Determination of stream and wetland credit on Coastal Plain
Headwater Stream Restoration Sites.
r 1,000, '1
E
Stream Mitigation Guidelines. U.S. Army Corps of Engineers, U.S. Environmental Protection agency,
• N.C. Division of Water Quality. and N.C. Wildlife Resources Commission, 2003.
'33 CFR Part 332.30)(ii) and 40 CFR Part 230.930)(ii)
Stream credit = 900 LF
Wetland credit = 400,000 SF (9.18 acres) - 90,000 SF (area within the 100'
headwater valley) = 310,000 SF (7.12 acres)
The example in Figure 4 shows a site in the outer Coastal Plain on which a headwater or
zero-order stream restoration4 has been constructed, along with wetland restoration. The
guidance states that provided that success criteria are met, stream credit can be generated
from this site. Stream credit is measured by the valley length. Therefore, this site
generates 900 LF of stream credit. Wetland located within the 100-foot wide "valley"
count as the stream credit, so total wetland credit at this site includes all wetland areas
outside the headwater stream valley.
*Please note that the credit calculations described above are per the USEPA
interpretation of the Federal Mitigation Rule. The USA CE interpretation is that the
ivetlands within the 100' headii,aler valley are available.for use and sale as mitigation
credit.
Figure 5. Determination of stream, wetland and buffer credits on a mitigation
site.

Stream credit = 1,000 LF
Wetland credit = 400,000 SF (9.18 acres) - (50,000 x 2) = 300,000 SF (6.89 acres)
Buffer credit = 100,000 SF (2.295 acres)
a Information Regarding Stream Restoration with Emphasis on the Coastal Plain. Version 2 DRAFT.
• USACE and NCDWQ. April 4, 2007.
6
• The example shown in Figure 5 is located within a river basin with riparian buffer rules.
In this example, 1,000 LF of stream was restored, along with 400.000 SF (9.18 acres) of
wetlands. As per the example shown in Figure 3. wetlands within the riparian zone could
not be used to generate wetland credit. This site would generate 1,000 linear feet of
stream credit and 300.000 SF (6.89 acres) of wetland credit. In addition, riparian buffer
credit can also be generated, since applicants are required to provide both stream
mitigation and buffer mitigation (when thresholds are met) on impact sites. In addition,
previous DWQ guidance' established that stream mitigation is required under Sections
401 and 404 of the Clean Water Act, while buffer mitigation is required under state
buffer rules.
*Please note that the credit calculations described above are per the USEPA
interpretation of the Federal Mitigation Rule. The USACE interpretation is that the
wetlands ivithin the riparian buffer are available .for use and sale as nniligation credit.
Under this interpretation, no buffer credit could be generated if the area tt,ilhin the
riparian zone is used to generate ivetland credit.
•
• ` Buffer Clarification/Interpretation #004, January 2, 2007.
7
•
Figure 6. Determination of wetland and buffer credits at a mitigation site.
r i,ooo

Credit Scenario 1
Wetland credit = 400,000 SF (9.18 acres)
Buffer credit = 0
Credit Scenario 2
Wetland credit = 300,000 SF (6.89 acres)
Buffer credit = 100,000 SF (2.295 acres)
The example in Figure 6 shows a site at which no mitigation work was done on the
stream. Wetlands were restored on both sides of the stream. In the first scenario shown
above, the entire site is being used for wetland credit. In the second scenario, riparian
buffer credit is generated within the restored riparian zone (50 feet wide on each side of
the stream), with the remainder of the site being used for wetlands credit. Wetland and
buffer credit cannot be generated from the same area.
E
•
•
Figure 7. Determination of stream, wetland, buffer and nutrient offset credits on
a mitigation site.
Credit Scenario 1
Stream credit = 1,000 LF
Wetland credit = 300,000 SF (6.89 acres)
Buffer credit = 100,000 SF (2.295 acres)
Nutrient offset credit = 0
or
Credit Scenario 2
Stream credit = 1,000 LF
Wetland credit = 0
Buffer credit = 100,000 SF (2.295 acres)
Nutrient offset credit = 300,000 SF (6.89 acres)
or
1?
Credit Scenario 3
Stream credit = 1,000 LF
Wetland credit = 0
Buffer credit = 0
Nutrient offset credit = 400,000 SF (9.18 acres)
9
• The example in Figure 7 shows a site at which a stream was restored. along with
wetlands on both sides of the stream. This site is located within a buffered basin which
also has nutrient offset requirements. In all scenarios shown above, the site generates
1.000 LF of stream credit. Areas within the riparian zone could be used to generate ONE
of the following: riparian buffer credit or nutrient offset credit. As per previous
examples, wetland credit cannot be generated within the 50-foot riparian buffer. Areas
located outside the 50-foot riparian buffer but within a maximum of 200 feet from the
stream could be used to generate ONE of the following: wetland credit or nutrient offset
credit. Wetland and buffer credit or nutrient offset credit cannot be generated from the
same area.
*Please note that the credit calculations described above ar°e per the USEPA
interpr'elation of the Federal Mitigation Rule. The USACE interpretation is that the
ii,ellands within the riparian buffer are available for use and sale as mitigation credit.
Under this interprelation. no buffer or• nuth°ieni offset credit could be generated if the
area within the riparian gone is used to generaale ii?elland credit.
•
•
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CHILES, P.E.
2006220 ERS AND CQI JOB NO. ENGINE ,S AND CONSULTANTS
- NEB! BERN, NQRTH C SCALE: _ 60__- RN, NORTH CAROLINA