20160627 Ver 1_More Info Requested_20160718

Attachment A: 401 Stormwater Requirements
Excerpt from Water Quality Certification No. 3886 and 3890 and the Isolated and Other non -404
Jurisdictional Wetlands and Waters Permit
The requirements listed below shall be implemented in order to comply with Condition 12 of this
General Certification. For the North Carolina Department of Transportation, compliance with
NCDOT's Individual NPDES permit NCS000250 shall serve to satisfy the 401 and Isolated
Wetland Stormwater Requirements.'
A. Design and Implementation Requirements. All projects, regardless of project area,
amount of built -upon area or amount of jurisdictional impact, shall meet the following
stormwater design requirements:
i. Non -Erosive Discharge to Streams and Wetlands. Stormwater conveyances that
discharge to streams and wetlands must discharge at a non-erosive velocityprior to
entering the stream or wetland during the peak Flow from the ten-year storm.
ii. Vegetated Setbacks. A 30 -foot wide vegetated setback must be maintained adjacent to
streams, rivers and tidal waters in areas that are not subject to a state Riparian Area
Protection Rule or other more stringent vegetated setback requirements. The width of
the setback shall be measured horizontally from the normal pool elevation of impounded
structures, the top -of -bank of streams and rivers, and the mean high waterline of tidal
waters, perpendicular to shoreline. Vegetated setback and filters required by state rules
or local governments may be met concurrently with this requirement and may contain
coastal, isolated or 404 jurisdictional wetlands. Non jurisdictional portions of the
vegetated setback may be cleared and graded, but must be planted with and maintained
in grass or other vegetative or plant material .3
iii. Construction and Operation. The stormwater management plan must be constructed
and operational before any permanent building or other structure is occupied or utilized at
the site. The stormwater management plan, including drainage patterns, must be
maintained in perpetuity.°
iv. Coordination with Other Stormwater Programs. Projects that are subject to another
Division of Water Quality (DWQ) stormwater program, including (but not limited to) the 20
Coastal Counties, HQW, ORW or state -implemented Phase II NPDES, or a Certified
Community's stormwater management program, must be constructed and maintained in
compliance with the approved stormwater management plan.5
v. Stormwater Design Requirements for Projects Not Covered Under Item (iv).
Projects that are not subject to another DWQ stormwater program or a Certified
Community's stormwater program shall meet all of the following requirements:
a. Low Density. A site is low density if all the following requirements are met
The development has a built upon area of twenty-four percent (24%) or less,
considering both current and future development. When determining the amount
of built upon area, coastal wetlands shall be included; however, ponds, lakes and
rivers as specified in North Carolina's Schedule of Classifications shall be
excluded. If a portion of project has a density greater than 24%, the higher
density area must be located in an upland area and away from surface waters
and drainageways to the maximum extent practicable .6
2. All stormwater runoff from the built upon areas is transported primarily via
vegetated conveyances designed in accordance with the most recent version of
the NC DWQ Stormwater Best Management Practices Manual. Alternative
designs may be approved if the applicant can show that the design provides
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Attachment A: 401 Stormwater Requirements
equal or better water quality protection than the practices specified in the manual.
The project must not include a stormwater collection system (such as piped
conveyances) as defined in 15A NCAC 02B.0202(60).7
b. High Density. Projects that do not meet the Low Density requirements shall meet
the following requirements:
1. Stormwater runoff from the entire site must be treated by structural stormwater
controls (BMPs) that are designed to remove eighty-five percent (85%) of the
average annual amount of Total Suspended Solids (TSS). Stormwater runoff
that drains directly to Nutrient Sensitive Waters (NSW) must also be treated to
remove thirty percent (30%) of Total Nitrogen (TN) and Total Phosphorus (TP).8
2. All BMPs must be designed in accordance with the version of the NC DWQ
Stormwater Best Management Practices Manual that is in place on the date of
stormwater management plan submittal. Alternative designs may be approved if
the applicant can show that the design provides equal or better water quality
protection than the practices specified in the manual.9
3. DWQ may add specific stormwater management requirements on a case-by-
case basis in order to ensure that a proposed activity will not violate water quality
standards.70
4. DWQ may approve Low Impact Developments (LIDS) that meet the guidance set
forth in the Low Impact Development: A Guidebook for North Carolina."
5. Proposed new development undertaken by a local government solely as a public
road project shall follow the requirements of the NC DOT BMP Toolbox rather
than Items (1)-(4) above. 12
B. Submittal Requirements. The submittal requirements listed below apply only to projects
that require written authorization as indicated in the applicable General Certification as well
as projects that require an Isolated Wetlands Permit. Any required documentation shall
be sent to the Wetlands, Buffers and Stormwater Compliance and Permitting Unit at
1650 Mail Service Center, Raleigh, NC 27699-1650.
i. Projects that are Subject to Another DWQ Stormwater Program: If the project is
subject to another DWQ stormwater program, such as the 20 Coastal Counties, HQW,
ORW or state -implemented Phase II NPDES, then the applicant shall submit a copy of
the stormwater approval letter before any impacts occur on site. 13
Projects that are Subject to a Certified Community's Stormwater Program. If the
project is subject to a certified local government's stormwater program, then the applicant
shall submit one set of approved stormwater management plan details and calculations
with documentation of the local government's approval before any impacts occur on site.5
iii. Projects Not Covered Under Items (i) or (it). If the project is not subject to another
DWQ Stormwater Program or a Certified Community's stormwater program, then it shall
be reviewed and approved by the DWQ through the Water Quality Certification
authorization process.
a. Low Density. For low density projects, the applicant shall submit two copies of the
DWQ Low Density Supplement Form with all required items. 13
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Attachment A: 401 Stormwater Requirements
b. High Density. For high density projects, the applicant shall submit two copies of a
DWQ BMP Supplement Form and all required items at the specified scales for each
BMP that is proposed.t3
iv. Phasing. Stormwater management plans may be phased on a case-by-case basis, with
the submittal of a final stormwater management plan per Items (i) -(iii) above required for
the current phase and a conceptual stormwater management plan for the future phase(s).
The stormwater management plan for each future phase must be approved by the
appropriate entity before construction of that phase is commenced. The approved
stormwater management plan for each future phase must be constructed and operational
before any permanent building or other structure associated with that phase is
occupied. 4
v. Stormwater Management Plan Modifications. The stormwater management plan may
not be modified without prior written authorization from the entity that approved the plan.
If the project is within a Certified Community, then the applicant shall submit one set of
approved stormwater management plan details and calculations with documentation of
the local government's approval for record-keeping purposes. If the project is subject to
DWQ review, then the applicant shall submit two copies of the appropriate Supplement
Forms per Item (iii) above for any BMPs that have been modified for DWQ's review and
approval.75
The stormwater requirement for 401 applications is codified in 15A NCAC 02H .0506(b)(5) and
(c)(5).
2 Non erosive discharge rates are required in SL 2008-211§2(b)(1). The 10 -year design storm
standard is codified in 15A NCAC 02H .1008(f)(2) and .1008(g)(1).
3 30 -foot vegetated setbacks are required in SL 2006-246§9(d), SL 2008-211§2(b), 15A NCAC
02H .1006(2)(c) and .1007(1)(a).
4 Construction and maintenance of the stormwater plan is necessary to satisfy 15A NCAC 02H
.0506(b)(5).
s Conveys application procedure to streamline the permitting process and reduce any unnecessary
duplication in the review of stormwater management plans.
6 Low density built upon area thresholds are set in SL 2006-246§9(c) and SL 2008-21 1 §2(b).
The requirement for low density development to use vegetated conveyances is codified in SL
2006-246§9(c), SL 2008-211§2(b), 15A NCAC 02H .1006(2)(b) and .1007(1)(a). The Stormwater
BMP Manual is also referenced in 15A NCAC 02B .0265(3)(a) and .0277(4)(e).
a
85% TSS removal is required in SL 2006-246§9(d), SL 2008-211§2(b), 15A NCAC 02H
.1006(2)(c), 15A NCAC 02H .1007(1)(a). The 30% TN and TP removal requirements for NSW
waters are set forth in 15A NCAC 02B .0232, 15A NCAC 02B .0257(a)(1), 15A NCAC 02B
.0265(3)(a) and 15A NCAC 02B.0277(4).
9 The Stormwater BMP Manual is also referenced in 15A NCAC 02B .0265(3)(a) and .0277(4)(e).
10 The requirement for DWQ to ensure that water quality standards are protected before issuing a
401 certification is codified in 15A NCAC 02H .0506.
" The LID Toolbox is also referenced in 15A NCAC 02B .0277(4)(g).
12 The term "public road project" is defined in15A NCAC 02B .0265(3)(a).
13 Conveys application procedure to streamline the permitting process.
14 Phased development is addressed as a "common plan of development" in 15A NCAC 02H
.1003(3).
5 Procedures for modifying stormwater plans are set forth in 15A NCAC 02H .1011.
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