30a_NCS000250_NCDOT Falls GREEN Report 22Nov2013 with Cover

STORMWATER
MANAGEMENT
PROGRAM
Falls Lake Watershed
Version 1.0 1 January 2014
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PROGRAM
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for New and Existing Development
in the Falls Lake Watershed
Version 1.0 1 January 2014
Prepared for:
NC Department of Transportation
1590 Mail Service Center
Raleigh, NC 27699-1590
919.707.6700
Prepared by:
UM
1600 Perimeter Park Drive
Suite 400
Morrisville, NC 27560
919.461.1100

■
1.0 Background 1
2.0
Introducing GREEN
3
3.0
New Development Program
5
4.0
Existing Development Program
12
5.0
Nutrient Management Education Program
19
6.0
Annual Reporting
19
7.0
Contacts
20
8.0
References
21
9.0
Acronyms and Abbreviations
22
Appendix A.
NCDOT Roads in the Falls Lake Watershed
Appendix B.
NCDOT Inspection and Maintenance Program
Appendix C.
NPDES Certification Statement
Appendix D.
Baseline Nutrient Loads from North Carolina Department of
Transportation in the Falls Lake Watershed
Appendix E.
Interim Development Nutrient Loads from North Carolina
Department of Transportation in the Falls Lake Watershed
1.0 Background
In 2010, the North Carolina Environmental Management Commission (EMC) approved the Falls Lake Water
Supply Nutrient Rules (Falls Lake Rules or Rules) (NCDENR, 2010), which established a nutrient management
strategy for Falls Lake designed to reduce algal growth in the lake. As part of these rules, contributors of
nutrients to Falls Lake, including the North Carolina Department of Transportation (NCDOT), are required to
reduce their loading of total nitrogen and total phosphorous in order to meet percent reduction goals to
restore water quality standards in the lake. The Falls Lake nutrient management strategy requires NCDOT to
develop and implement a Stormwater
Management Program for all new
development and existing development
activities. This document describes NCDOT's
Stormwater Management Program for New
and Existing Development, which addresses
nutrient runoff from new and widened
roads, new non -road development, and
existing road and non -road development.
Table 1 presents NCDOT's implementation
schedule for these activities.
PAGE 1

JANUARY 2014
1.1 Nutrient Management in North Carolina
Management of excessive nutrient loading to receiving streams
has been, and continues to be, a widespread effort in North
Carolina. Prevalent eutrophication and algal blooms in the mid-
1970s to 1980s and publicized fish kills in the mid-1990s have
elevated the issue of nutrient management to the forefront of
environmental programs in North Carolina. The EMC first began
addressing nutrient issues in the Chowan River Basin in 1979
when the occurrence of nuisance algal blooms led to its
- designation as a Nutrient Sensitive Water (NSW). Since that
Selected North Carolina watersheds time, similar water quality concerns have emerged in the Neuse
with eutrophication concerns River and Tar -Pamlico River Basins and the Jordan Lake, Falls
Lake, and High Rock Lake watersheds. As the monitoring efforts
of the North Carolina Department of Environment and Natural
Resources (NCDENR) have expanded and the collective
understanding of nutrient issues has improved, the EMC has
increasingly directed resources to managing nutrient loads into
North Carolina rivers, lakes, and estuaries.
1.2 NCDOT's Approach to Nutrient Management
NCDOT's response to nutrient
management is focused on proactive
compliance that is fair, reasonable, and
proportionate to its contribution.
NCDOT has managed nutrients in the
highway environment through riparian
area compliance, National Pollutant
Discharge Elimination System (NPDES)
stormwater requirements, scientific
research, and taking active roles in state
technical advisory committees. The Falls
Lake Rules apply to all existing and new
development, as defined in 15A North
Carolina Administrative Code (NCAC)
02B .0276, that lies within or partially
within the Falls Lake watershed. The
affected area includes portions of
NCDOT Highway Divisions 5 and 7 as
shown in the adjacent figure.
Division 5
Pf RS!]ry
Division T
GRAN VI I l I
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WAKE
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Falls Lake Watershed
Lower Watershed
UUpper Watershed o to
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PAGE 2

kl.
2.0 Introducing GREEN
NCDOT directs, plans, constructs, maintains, and
operates one of the largest state -maintained
roadway system in the nation. The size, diversity,
and geographic extent of this transportation
network is reflected in NCDOT's numerous and
unique stormwater management initiatives. In
1998, NCDOT established the Highway Stormwater
Program to manage its NPDES stormwater permit
requirements as well as other state stormwater
programs. The Highway Stormwater Program is an
NCDOT-wide initiative to manage and minimize the
effects of stormwater runoff from NCDOT facilities.
Given NCDOT's responsibility for more than 1,800
miles of roadway in the Falls Lake watershed (see
figure in Appendix A), a cost effective nutrient
management strategy tailored to transportation is
necessary. In order to address existing and future
nutrient management needs, NCDOT initiated the
Guided Reduction of Excess Environmental
Nutrients (GREEN) Program to integrate and
enhance NCDOT's stormwater and nutrient
management practices and to support NCDOT's
compliance with the Falls Lake Rules. The GREEN
Program functions in collaboration with NCDOT's
existing NPDES and state stormwater management
activities and is designed to achieve the following
objectives (also depicted on page 4):
1. Maintain compliance and accountability.
2. Increase NCDOT staff awareness of
nutrient -related water quality issues.
3. Leverage and optimize existing
environmental programs for nutrient
management.
N.C. DEPARTMENT OF TRANSPORTATION
GREEN
Guided Reduction of Excess Environmental Nutrients
JANUARY 2014
4. Collect and document scientific research
related to nutrient loading from NCDOT
roadways and industrial areas.
5. Facilitate communication with resource
agencies and the public.
The GREEN Program encompasses requirements
for both new and existing development as
described in this document.
In order to address near term and future nutrient
management needs, NCDOT has initiated the Guided
Reduction of Excess Environmental Nutrients (GREEN)
Program to integrate and enhance NCDOT's stormwater
and nutrient management practices and to support
NCDOT's compliance with the Falls Lake Rules.
PAGE 3

Maintain compliance
and accountability
Keeping streams, Rivers & Lakes Clean
cr
8y
3 Leverage and optimize existing
environmental programs for
nutrient management
5 Facilitate communication with
resource agencies and the public
JANUARY 2014
2 Increase NCDOT staff
awareness of nutrient -
related water quality issues
41 Collect and document
scientific research related to
nutrient loading from NCDOT
roadways and industrial areas
R-
-4 .,
iO
PAGE 4

3.0 New Development Program
In keeping with the GREEN Program's mission and
objectives, NCDOT crafted a new development post -
construction stormwater runoff control program for
nutrient management (hereafter referred to as the
New Development Program). Under 15A NCAC
02B .0281 (9)(c), NCDOT is required to:
Establish a program for post -construction
stormwater runoff control for new development,
including new and widening NCDOT roads and
facilities. The program shall establish a process by
which the Division [of Water Quality] shall review
and approve stormwater designs for new NCDOT
development projects. The program shall
delineate the scope of vested projects that would
be considered as existing development, and shall
define lower thresholds of significance for
activities considered new development.
To facilitate implementation of the new develop-
ment program, project categories have been defined
as new road development (see Table 2 for
examples) and new non -road development (see
Table 3 for examples).
For the purposes of compliance with the Falls Lake
Rules, new road development is defined as any new
road construction, road widening, road upgrade, or
other activity resulting in net new built upon area
occurring within the NCDOT right-of-way (ROW) or
easement, with the exception of projects listed in
Table 3 on page 6. The new road development
category encompasses projects such as interchange
modifications, roadway widening, addition of
acceleration and deceleration lanes, median
crossovers, new and widened hydraulic structures
for stream crossings (e.g., bridges and culverts), and
installation of structures for safety and signage.
Projects involving permanent new built -upon area
added within the NCDOT ROW or easement that
supports pedestrian mobility associated with a new
or existing roadway corridor, such as bus shelters
and sidewalks, are also considered new road
development projects. Examples of new road
development projects are provided in Table 2.
JANUARY 2014
New location roadways
Roadway widening
New acceleration/deceleration lanes
Interchange modifications
New bridges or culverts
Bridge or culvert replacements
Median crossovers
Sidewalks within NCDOT ROW
Bus shelters within NCDOT ROW
Greenway Trails within the NCDOT ROW
Weigh stations
Borrow and waste sites associated with NCDOT
road construction'
1 This table provides examples of new road development
projects and is not intended to be an exhaustive list.
Z Borrow and waste sites may be operated by contractors
and may be outside the NCDOT ROW.
PAGE 5

New non -road development is defined as any new
NCDOT facility or any modification to an existing
facility that increases the net built -upon area and
that does not otherwise qualify as new road
development. Typically, new non -road development
projects are not within the NCDOT ROW. These
projects can include construction of new or upgrades
to existing maintenance yards, rest areas, office
buildings, training facilities, parking lots, or other
non -road development. Examples of new non -road
development projects are provided in Table 3.
Road and non -road projects that result in no net
increase in built -upon area are deemed as existing
development projects and are not subject to the
New Development Program. When it is uncertain as
to which category a new development project
belongs, NCDOT staff and the regional NCDENR
Division of Water Resources (NCDWR)
representative will coordinate to determine proper
project category based on the definitions and
examples provided in this section.
Sections 3.1 and 3.2 provide a discussion of the
proposed compliance process for new road and new
non -road development projects based on the unique
requirements associated with each project category.
Vested projects considered existing development are
defined for both new road and new non -road
development projects. In addition, projects that are
considered to be insignificant for nutrient loading
are defined through specific project examples. The
proposed process for review and approval of
stormwater designs, including compliance with the
riparian buffer protection requirements in 15A NCAC
02B .0233 and .0242, is also outlined in the following
two sections for each project category.
JANUARY 2014
Rest areas
Maintenance yards
Office buildings
Training facilities
Parking lots
Railroad facilities
Material testing laboratories
Material storage facilities
1 This table provides examples of new non -road development
projects and is not intended to be an exhaustive list. Project
examples assume a net increase of new built -upon area.
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3.1 New Development Program - New and Widening Road Projects
The new development program for new and widening road projects must meet the purposes defined in Rule
15A NCAC 02B .0281 (1) applicable to roads which includes achieving the highest practicable level of
treatment; ensuring that the integrity and nutrient processing functions of receiving waters and associated
riparian buffers are not compromised by erosive flows; and protecting the water supply uses within the
watershed. Achieving these goals will be implemented through use of the nutrient removal capabilities of
vegetated riparian buffers. Rules .0281 (9)(c)(i) and .0281 (9)(f) define the criteria for compliance with these
goals. Rules .0233 and .0242 define the buffers that are protected and activities inside and outside the
protected buffers which are regulated. Additionally requirements for the maintenance of diffuse flow through
riparian buffers are set forth in Rule .0233 (5) and .0242 (9). Rule .0242 provides requirements for mitigation
of unavoidable impacts to riparian buffers.
PAGE 6

JANUARY 2014
3.1.1 Review and Approval Process
Rules 15A NCAC 02B .0281 (9)(c), and (9)(f) — IMM�
require that NCDOT "establish a process by 15 NCAC 02B .0281
which the Division [of Water Quality] shall
review and approve storm -water designs (9)(c)(i) For new and widening roads, weigh stations, and
replacement of existing bridges, compliance with the
for new NCDOT development projects and riparian buffer protection requirements of Rules 15A NCAC
"address compliance with the riparian 028.0233 and .0242 shall be deemed as compliance with
buffer protection requirements of 15A the purposes of this Rule;
NCAC 02B .0233 and .0242 through a
(9)(f) Address compliance with the riparian buffer
Division [of Water Quality] approval protection requirements of 15A NCAC 028.0233 and .0242
process." For many years, riparian buffer through a Division approval process.
protection requirements have been in place
across North Carolina in selected water-
sheds, including the Neuse River Basin, the Tar -Pamlico River Basin, the Randleman Lake watershed, and
along the main stem of the Catawba River. To address these requirements, staff from NCDOT and NCDWR
regional offices have collaborated over the years to develop project review and approval processes to
facilitate accountability and compliance. New location roadway projects typically involve an extensive
planning process during which NCDWR reviews the project alignment to determine that NCDOT has made
every reasonable effort to avoid impacts to the buffer, wetlands, and other water resources. During the
design process NCDWR reviews the project yet again to verify the protection of water quality standards
and that NCDOT is in compliance with the requirements of Rules .0233 and .0242 if NCDOT proposes a use
within the buffer. Such uses are carefully reviewed by NCDWR to ensure the maintenance of the buffer's
nutrient removal functions as defined in Rule .0233. Uses not provided for in the Table of Uses are
considered Prohibited and not protective of the nutrient removal functions of the buffer and thereby are
not an option for NCDOT. Since the effective date of the .0233 and .0242 Rules in the late 1990's, NCDOT
and NCDWR have extended this riparian buffer protection review and approval process to the Falls Lake
watershed. Given that the current process has been demonstrated to be successful and sustainable,
NCDOT does not propose any modifications under the Falls Lake GREEN New Development Program.
3.1.2 Vested Projects
15A NCAC 02B .0281 (9) requires that the New
Development Program "delineate the scope of
vested projects that would be considered as
existing development." To facilitate consistency
with the existing riparian buffer protection review
and approval process, vested new and widening
road projects are defined in Rule 15A NCAC 02B
.0233 (3) for existing uses that are present and
ongoing. The provisions in Rule .0233 (3) were
developed, in part, with new roadway projects in
mind and have been successfully integrated into
the riparian buffer protection review and approval
process for many years. NCDOT does not propose
any modifications to the existing vesting provisions
under the Falls Lake GREEN New Development
Program.
PAGE 7

JANUARY 2014
3.1.3 Insignificant Projects and Activities
NCDOT will comply with the applicable riparian buffer protection requirements of Rules 15A NCAC
02B .0233 and .0242. Under these rules 'insignificant projects' are not expressly recognized, therefore
NCDOT is not proposing to create a definition for insignificant projects.
3.2 New Development Program - New Non -Road Projects
New NCDOT non -road development must achieve the Falls Lake nutrient load reduction goals in the
manner set forth in Rule 15A NCAC 02B .0281 (9)(c)(ii) (rule text provided on page 9).
For the purposes of compliance with the Falls Lake Rules, new non -road development is defined as any
new NCDOT-owned and operated facility installation or significant facility upgrade that results in a net
increase of built -upon area and that does not meet the criteria for new road development. Generally,
new non -road development is located outside of the NCDOT ROW. Examples of non -road development
projects include, but are not limited to, office facilities, parking lots, rest areas, and maintenance yards.
Refer to Table 3 for additional project examples of new non -road development.
Nutrient reduction goals have been
established for new non -road development
that is not vested and that exceeds a defined
lower threshold of significance (described in
Section 3.2.3). These requirements are
outlined in 15A NCAC 02B .0281 (9)(c)(ii)
(provided on page 9), where specific nitrogen
and phosphorus load reduction goals within
the Upper Falls Lake and Lower Falls Lake are
defined. The load reduction goals are
established relative to either an area -weighted
average loading rate of all developable lands -
as of a baseline period defined in 15A NCAC
02B .0275, or to a percentage reduction based Stormwater control measure implemented at the
on the project specific predevelopment NCIDOT Guilford (East) County Maintenance Yard
loading rate. In order to meet these loading
rate targets, NCDOT may consider the use of engineered stormwater control measures (SCMs). The
effectiveness of these controls to remove nutrients will be assessed using the NCDOT Jordan/Falls Lake
Stormwater Load Accounting Tool (NCDOT-JLSLAT) (see summary box on page 9 for additional information)
or through another calculation method that is acceptable to NCDWR. Per 15A NCAC 02B .0281 (9)(c)(iii),
NCDOT has the "option of offsetting part of their nitrogen and phosphorus loads by implementing or
funding offsite management measures." These off -site measures are allowable only after achieving 50
percent or more of the needed nitrogen and phosphorus load reduction on the developed site. NCDOT
may also make offset payments to the North Carolina Ecosystem Enhancement Program when necessary
to meet site -specific reduction requirements. In addition to maintaining compliance with the Falls Lake
Rules, new non -road development is also required to meet the conditions of NCDOT's statewide NPDES
permit and other stormwater rules where applicable. Hence, every new NCDOT non -road development
project will undergo a thorough stormwater management evaluation to assess compliance with multiple
sets of requirements in the Falls Lake watershed.
PAGE 8

JANUARY 2014
15 NCAC 02B .0281 (9)(c)(ii)
New non -road development shall achieve and maintain the nitrogen and phosphorus percentage load reduction
objectives established in 15A NCAC 02B .0275 relative to either area -weighted average loading rates of all
developable lands as of the baseline period defined in 15A NCAC 02B .0275, or to project -specific pre -development
loading rates. Values for area -weighted average loading rate targets for nitrogen and phosphorus, respectively, are
expressed in units of pounds per acre per year: 2.2 and 0.33. The NCDOT shall determine the need for engineered
stormwater controls to meet these loading rate targets by using the loading calculation method called for in Item
(13) of this Rule or other equivalent method acceptable to the Division. Where stormwater treatment systems are
needed to meet these targets, they shall be designed to control and treat the runoff generated from all surfaces by
one inch of rainfall. Such systems shall be assumed to achieve the nutrient removal efficiencies identified in the July
2007 version of the Stormwater Best Management Practices Manual published by the Division provided that they
meet associated drawdown and other design specifications included in the some document. The NCDOT may
propose to the Division nutrient removal rates for practices currently included in the BMP Toolbox required under its
NPDES stormwater permit or may propose revisions to those practices or additional practices with associated
nutrient removal rates. The NCDOT may use any such practices approved by the Division to meet loading rate
targets identified in this Sub -item. New non -road development shall also control runoff flows to meet the purpose
of this Rule regarding protection of the nutrient functions and integrity of receiving waters.
NCDOT Jordan/Falls Lake Stormwater Load Accounting Tool
North Carolina State University (NCSU), in conjunction with NCDENR, developed JLSLAT as a tool for addressing the
Jordan Lake nutrient requirements. JLSLAT is a Microsoft Excel (2007) workbook that allows a user to specify site
conditions, such as physiographic province, soil hydrologic group, and precipitation station, and estimate nutrient
loading from the pre- and post -development land use conditions, as well as model the impact of various SCMs on
post -development stormwater runoff quality.
The Falls Lake Rules acknowledge the unique nature of
NCDOT areas and associated nutrient controls and states,,,i
"NCDOT may propose to [NCDWR] nutrient removal rates
for practices currently included in the BMP Toolbox
required under its NPDES stormwater permit, or may
propose revisions to those practices or additional
practices with associated nutrient removal rates" (15A "
NCAC 02B .0281 (9)(c)(ii)). Based on an extensive review
and assessment of NCDOT's water quality research data,
NCDOT, in coordination with NCSU, built upon the existing
JLSLAT (Version 1.1) framework and methodology by
updating JLSLAT to include land use and land cover (LULC)
categories and SCMs specific to industrial facilities, rest
areas, and non -roadway projects under NCDOT INCIDOT Jordan/Falls Lake Stormwater Load
jurisdiction. The NCDOT accounting tool, NCDOT-JLSLAT, Accounting Tool
addresses the unique LULC conditions at NCDOT facilities
and incorporates the range of NCDOT's nutrient management practices to estimate nitrogen and phosphorus
loading from NCDOT project sites. On July 12, 2012, the EMC formally approved NCDOT-JLSLAT for new non -road
development projects for use in demonstrating compliance with new non -road development nutrient reduction
requirements identified in 15A NCAC 02B .0281.
In a separate report titled, "Transportation Land Use/Land Cover and Stormwater Control Measure Updates for the
Jordan/Falls Lake Nutrient Accounting Tool" (NCDOT, 2012a), NCDOT has prepared a description of the steps taken
to adapt JLSLAT for NCDOT applications for use in project planning in the Jordan Lake and Falls Lake watersheds.
NCDOT-JLSLAT users are referred the JLSLAT User's Manual (NCSU, 2011) for instructions on how to use the tool.
PAGE 9

JANUARY 2014
3.2.1 Review and Approval Process
Rule 15A NCAC 02B .0281 (9) requires that NCDOT "establish a process by which the Division [of Water
Quality] shall review and approve stormwater designs for new NCDOT development projects." To meet this
requirement and the load reduction goals, NCDOT will internally review and approve projects using the
procedures described in this section. NCDOT will
also update the Post -Construction Stormwater Program
(PCSP) to include provisions that promote compliance
with this document and will submit the update to
NCDWR for review and approval. NCDOT's PCSP
defines implementation of the NCDOT BMP Toolbox,
NCDOT staff and contractor training to
implement the Toolbox and incorporates
watershed strategies to control runoff from
new NCDOT development and redevelopment.
Yes ► Project not considered
<*>
Projects that rely on the use of NCDOT-JLSLAT
new development
will be certified by a NC licensed professional
and require that the professional affirm that
the tool was used in conformity with the EMC-
No
approved version or another method
acceptable to NCDWR (See Appendix C for a
Project
copy of the certification language). Site plan
disturbance area
and NCDOT-JLSLAT reviews will be supervised
is % acre or more and No
through NCDOT's Hydraulics Unit. Upon
net increase in built -
upon area?
approval, NCDOT will enter the results of these
reviews along with certification of completed
projects into a rule compliance database and
Yes
report on these activities annually as part of
NCDOT's NPDES stormwater permit. Annual
NCDOT prepares
NCDOT-JLSLAT with
reporting will include a list of certified projects,
preliminary site plan.
descriptions of the projects and associated
SCMs, project -specific copies of NCDOT-JLSLAT
and other supporting calculations, an
NCDOT Hydraulics Unit
accounting of nutrient offset payments and
reviews site plan and
NCDOT-JLSLAT.
offsite management measures, and a summary
of changes in nutrient loads associated with
these activities. Similar to other NPDES permit
requirements, NCDOT's new non -road
development activities under the GREEN
Nutrient load or
percentage target No
Revise site plan to include
additional nutrient reduction
Program will receive regular NCDWR review
achieved?
measures.
and assessment under existing NPDES auditing
procedures. Assigning NCDOT the responsibil-
ity of compliance and oversight promotes an
Yes
efficient and environmentally protective
approach that reduces the overall level of
NCDOT approves final
NCDWR resources needed to implement the
NCDOT-JLSLAT and site
plan. Project documented
Cnual reporting to
Rule. This internal review and approval process
and logged to support
NCDWQ.
also allows streamlined organization within
reporting to NCDWQ.
NCDOT that promotes the objectives of the
GREEN Program and results in improved
coordination, efficiency, and timeliness of
Review and approval
projects.
. - - .. u -
PAGE 10

JANUARY 2014
In implementing the new non -road development rule, NCDOT will do the following:
1. Maintain high standards and expectations for environmental stewardship.
2. Provide nutrient training to NCDOT staff and contractors.
3. Determine rule applicability on a project -specific basis.
4. Apply NCDOT-JLSLAT, or other NCDWR approved method, during site design to facilitate load
reduction compliance accountability.
5. Design, review, and approve new non -road development projects.
6. Confirm that project design criteria meets the new non -road development requirements.
7. Oversee construction activities and validate the implementation of design specifications.
8. Consult with and report annually to NCDWR.
The review and approval process is illustrated on page 10. To identify the appropriate internal review and
approval process, NCDOT first determines whether a new project is a road project or a non -road project
(not shown in the figure). Once the project is identified as new non -road development, the area of
disturbance is determined. Disturbance, for the purposes of compliance with this rule, means any land -
disturbing activity associated with construction or development of a project. If the project exceeds the
lower threshold of significance for project size (described in Section 3.2.3 below), results in a net increase in
built -upon area, and is not listed as an excluded project (described in Section 3.2.3 below), then the nutrient
reduction requirements for new non -road development apply. For these projects, NCDOT-JLSLAT will be
used during the preliminary design process to determine if the proposed development exceeds project -
specific predevelopment loading rates or if it exceeds the area -weighted average loading rate targets [15A
NCAC 02B .0281 (9)(c)(ii)]. If the project exceeds both requirements, NCDOT will implement SCMs such that
either the pre- to post -development loading rate target or the subwatershed-specific area -weighted annual
loading rate target is met. Alternatively, if prohibitive site constraints exist, NCDOT will consider
implementing or funding offsite management measures per 15A NCAC 02B .0281 (9)(c)(iii). Prior to
preliminary plan approval, NCDOT will perform an additional, independent review to confirm that the
preliminary site plan achieves compliance with the NCDOT new non -road development rules. Upon NCDOT
approval, the preliminary site plan will be approved and the final NCDOT-JLSLAT and site plan will be
formally documented and logged for future reporting to NCDWR. Annually NCDOT will report to NCDWR on
measures taken to comply with the new non -road development rules.
3.2.2 Vested Projects
For the purposes of rule compliance, new non -road development projects that are part of NCDOT's Capital
Improvements Plan, or otherwise approved for funding by NCDOT prior to January 15, 2014, will be
considered vested. Vested projects will be considered as existing development and managed accordingly.
3.2.3 Insignificant Projects and Activities
The new non -road development Rule also requires NCDOT to define "lower thresholds of significance for
activities considered new development" (15A NCAC 02B .0281 (9)(c)). The GREEN program established a
lower threshold of significance for all non -road facilities of one-half acre in the Jordan Lake Watershed
(NCDOT, 2012b). Given this precedent and the similarity in facility types and activities (as shown in Table 3)
anticipated in the Jordan and Falls Lake watershed, the lower threshold for significance for non -road
facilities in the Falls Lake watershed is one-half acre. This threshold was selected after evaluating the
nutrient load changes associated with a variety of typical projects that NCDOT undertakes at its non -road
facilities. Based on this evaluation, the one-half acre threshold was selected because it is expected to
capture most all development projects including those that result in changes to existing drainage.
PAGE 11

JANUARY 2014
Additionally, all projects at NCDOT industrial facilities, regardless of disturbance area, will be covered under
site -specific Stormwater Pollution Prevention Plans (SPPPs) which include best management practices
(BMPs) to address nutrient management and minimize the potential for stormwater impacts.
The Rules recognize that NCDOT is engaged in a wide variety of projects and allow for a list of insignificant
projects to be proposed as part of the stormwater program. For this reason, NCDOT developed a project
type exclusion list (Table 4) to identify projects that are not subject to the new non -road development Rules
(15A NCAC 02B .0281 (9)(c)(ii); rule text provided on
page 9). These project types were selected after Table 4. Projects considered
careful review of the Minimum Criteria List (19A road development
NCAC 02F .0102), which lists the "types and classes of
threshold of activities at and below which Noise barriers or alterations to existing public
environmental documentation under North Carolina buildings to provide for noise reduction
Environmental Policy Act is not required" (NCDENR,
2003). The project types listed in Table 4 include Landscaping projects
those from the Minimum Criteria List that are not Activities involving maintenance or repair
considered to be subject to the new non -road needed to maintain the original function of an
development Rules. These projects are subject to existing project or facility without expansion or
new road development Rules. change in use
In summary, the new non -road development Rules
apply to projects that meet each of the three criteria:
1. Disturb one-half acre or more
2. Result in a net increase in built -upon area
3. Are not included in the project type exclusion
list (Table 4).
Sampling, monitoring, and related data -gathering
activities
1 This table provides examples of projects not considered
new non -road development and is not considered to be
an exhaustive list. In addition to the projects listed in
Table 4, other projects may be deemed as insignificant
and not considered new non -road development upon
approval by NCDWR.
4.0 Existing Road and Non -Road Development Program
The Rules require NCDOT to establish a program to
identify and implement load -reducing
opportunities on existing road and non -road
NCDOT development within the Falls Lake
watershed (15A NCAC 02B .0281 (9)(d)) (rule text
provided on page 13). The existing development
program applies to all NCDOT development
constructed prior to January 15, 2014, including
development that existed during the baseline
period (2006) and interim period (January 1, 2007
— January 15, 2014). Compliance with the NCDOT
existing development Rule and load reduction
objectives in 15A NCAC 02B .0275 is achieved
through a load reduction program that implements
structural SCMs, non-structural SCMs and other
activities aimed at reducing nitrogen and
phosphorous loading from existing road and non -
road NCDOT development in the Falls Lake
watershed.
PAGE 12

JANUARY 2014
As described in this section, the existing development program requirements will be implemented through
various NCDOT programs and units, including the Highway Stormwater Program, Hydraulics Unit, Roadside
Environment Unit, and others. In addition, the existing development program will encompass NCDOT
activities to identify NCDOT stormwater outfalls from Interstates, US, and NC primary routes (15A NCAC 02B
.0281 (9)(a)) and identify and eliminate illegal discharges into NCDOT's stormwater conveyance system (15A
NCAC 02B .0281 (9)(b)). Section 4.1 of this report provides a summary of NCDOT's baseline and interim
development nutrient loads. These loads provide a foundation on which future existing development
nutrient reductions will be reported. Section 4.2 of this report describes load -reducing activities, three
examples of NCDOT programs through which implementation of those activities will occur, annual reporting,
and anticipated collaboration with NCDWR and others to support further development of nutrient
accounting methods.
15 NCAC 02B .0281 (9)(d)
Establish a program to identify and implement load -reducing opportunities on existing development within the
watershed. The long-term objective of this effort shall be for the NCDOT to achieve the nutrient load objectives in
15A NCAC 02B .0275 as applied to existing development under its control, including roads and facilities:
(i) The NCDOT may achieve the nutrient load reduction objective in 15A NCAC 02B .0275 for existing roadway
and non -roadway development under its control by the development of a load reduction program that
addresses both roadway and non -roadway development in the Falls watershed. As part of the accounting
process described in Item (13) of this Rule, baseline nutrient loads shall be established for roadways and
industrial facilities using stormwater runoff nutrient load characterization data collected through the
National Pollutant Discharge Elimination System (NPDES) Research Program under NCS0000250 Permit Part
II Section G;
(ii) The program shall include estimates of, and plans for offsetting, nutrient load increases from lands
developed subsequent to the baseline period but prior to implementation of its new development program.
It shall include a technical analysis that includes a proposed implementation rate and schedule. This
schedule shall provide for proportionate annual progress toward reduction objectives as practicable
throughout the proposed compliance period. The program shall identify the types of activities NCDOT
intends to implement and types of existing roadway and non -roadway development affected, relative
proportions or a prioritization of practices, and the relative magnitude of reductions it expects to achieve
from each;
(iii) The program to address roadway and non -roadway development may include stormwater retrofits and other
load reducing activities in the watershed including: illicit discharge removal; street sweeping; source control
activities such as fertilizer management at NCDOT facilities; improvement of existing stormwater structures;
use of rain barrels and cisterns; stormwater capture and reuse; and purchase of nutrient reduction credits;
(iv) NCDOT may meet minimum implementation rate and schedule requirements by implementing a combination
of at least six storm water retrofits per year for existing development in the Falls watershed or some other
minimum amount based on more accurate reduction estimates developed during the accounting tool
development process;
(v) To the maximum extent practicable, retrofits shall be designed to treat the runoff generated from all
surfaces by one inch of rainfall, and shall conform to the standards and criteria established in the most
recent version of the Division -approved NCDOT BMP Toolbox required under NCDOT's NPDES stormwater
permit. To establish removal rates for nutrients for individual practices described in the Toolbox, NCDOT
shall submit technical documentation on the nutrient removal performance of BMPs in the Toolbox for
Division approval. Upon approval, NCDOT shall incorporate nutrient removal performance data into the
BMP Toolbox. If a retrofit is proposed that is not described in the NCDOT BMP Toolbox, then to the
maximum extent practicable, such retrofit shall conform to the standards and criteria set forth in the July
2007 version of the Stormwater Best Management Practices Manual published by the Division, or other
technically equivalent guidance acceptable to the Division;
PAGE 13

.. ~� JANUARY 2014
4.1 Nutrient Load Accounting for Baseline and Interim Development
As a first step in developing the load reduction program, the Rules require NCDOT to establish baseline
nutrient loads for NCDOT roadways and industrial facilities (15A NCAC 02B .0281 (9)(i)) and to include
estimates of, and plans for offsetting, nutrient load increases from lands developed subsequent to the
baseline period but prior to the implementation of the new development program (15A NCAC 02B .0281
(9)(ii)). For the purposes of compliance with the Falls Lake Rules, the baseline period is defined as calendar
year 2006 and interim period is defined as the period that is subsequent to the baseline period but prior to
the implementation of the new development program. Interim period development includes changes in
development that occurred between January 1, 2007 and January 15, 2014.
NCDOT's nutrient loads during the baseline
and interim development periods were WARMF LEFDC
watershed model lake model
developed using a variety of datasets,
accounting tools and watershed and lake
models available for the Falls Lake water- NCDOT's percentage of Baseline delivered load
total delivered nutrient for all sources
shed. NCDOT's baseline loads, shown In load (by tributary) (by tributary)
Table 5 below, were developed using Falls
Lake watershed and lake models (WARMF
and EFDC) that were used to develop the NCDOT baseline nutrient load
Rules. NCDOT's baseline loads were delivered to Falls Lake
approved by the North Carolina EMC on July
12, 2012. Supporting documentation
discussing the methods used to calculate • load in Falls Lake was
the baseline load is provided in a report calculated using existing watershed.models
titled Baseline Nutrient Loads from North that were prepared.
Carolina Department of Transportation in
the Falls Lake Watershed (NCDOT, 2012c) (see Appendix D). Nutrient load changes associated with NCDOT
interim development areas were based on a detailed assessment of NCDOT road and non -road development
during the 2007-2014 period, NCDOT-JLSLAT, and uniform pre -development annual loading rate estimates of
2.89 pounds/acre/year for TN and 0.63 pounds/acre/year for TP described in the Rule (15A NCAC 02B .0281
(5)(a)). Post -development TN and TP loads were calculated using GIS-based land cover area estimates and
NCDOT-JLSLAT. Results of this analysis demonstrated a net decline in annual loads from NCDOT interim
development and are in keeping with a number of NC research studies that have reported low nutrient
concentrations in road runoff; particularly from secondary roads (which account for 99% of the interim road
development area). A detailed summary of the interim development analysis is presented in Appendix E.
Table S. NCDOT Baseline
Lake Watershed"
and Interim
Development
Period TN
and TP Loads (pounds/year) in the
Falls
boom
I Total Nitrogen
Load (pounds/year)
Total Phosphorus
Load (pounds/year)
Non-NCDOT
=
Net
Non-NCDOT
Net
Baseline
NCDOT
NCDOT
Baseline
NCDOT
NCDOT
terim Period
Development
Development
Load
Development
Development
Load
Primary Roads
Secondary Roads
1 Methods used to calculate NCDOT baseline and interim development period loads are provided in Appendix D and E, respectively.
z Loads associated with secondary road development are considerably higher than loads for primary road development because
99% of the interim period road development was associated with secondary roads.
PAGE 14

kl.
JANUARY 2014
4.2 Implementation of Nutrient Load -Reducing Opportunities
15A NCAC .0281 (9)(d)(iii) summarizes the types of activities that NCDOT may use to meet the existing
development Rule. Compliance activities will include a wide variety of structural and non-structural controls
that NCDOT and NCDENR find to demonstrate a capacity to reduce nutrients from existing road and non -
road development. Structural SCMs are designed to reduce pollutant transport and loadings to surface
waters by holding and treating runoff during storm events. Non-structural SCMs are processes, policies, or
practices implemented to influence behaviors, decisions, or actions that reduce the amount of pollution
entering surface waters. Some examples of non-structural SCMs applicable to the highway environment
include street sweeping, public outreach and education, and management of fertilizer application within the
ROW. Non-structural SCMs can also be decision -making practices that guide NCDOT staff to engage in
alternative activities or use alternative designs
that result in reduced nutrient loading. NCDOT
will also implement other load reducing
activities in the watershed including: illicit
discharge removal; improvement of existing
stormwater structures; use of rain barrels and
cisterns; stormwater capture and reuse; and
purchase of nutrient reduction credits as _
described at 15 NCAC 02B .0281 (9)(d)(iii).
NCDOT will initiate implementation of the
EMC-approved stormwater management
program for its existing development no later
than January 15, 2014 so as to contribute
toward the achievement of the Stage I and
Stage 11 objectives described in 15A NCAC 02B
.0275. The implementation rate and schedule
for Stage I and Stage 11 are described below:
Stage I Rate and Schedule
NCDOT will implement load reducing opportunities throughout the Falls Lake watershed to contribute to
the achievement of the Stage I objective. NCDOT will implement six retrofits per year or a combination of
structural and nonstructural nutrient load measures equivalent to six retrofits per year as described in 15A
NCAC 02B .0281 (9)(d)(iv). NCDOT will continue this annual implementation rate until the Stage I objective is
achieved.
Stage II Rate and Schedule
NCDOT will initiate the EMC-approved stormwater management program for its existing development no
later than the Stage II beginning date specified in 15A NCAC 02B .0275. To the maximum extent technically
and economically feasible, NCDOT will implement six retrofits per year or a combination of structural and
nonstructural nutrient load measures equivalent to six retrofits per year as described in 15A NCAC 02B
.0281 (9)(d)(iv). NCDOT will give priority to implementing load reducing opportunities in the Upper Falls
Lake watershed. NCDOT will continue this annual implementation rate until the Stage II objective is
achieved.
In the event that the timeframes for achieving the Stage I and Stage II objectives overlap, NCDOT will
implement six retrofits per year or a combination of structural and nonstructural nutrient load measures
equivalent to six retrofits per year as described in 15A NCAC 02B .0281 (9)(d)(iv).
PAGE 15

JANUARY 2014
NCDOT will implement management measures described in NCDOT's Stormwater Best Management
Practices Toolbox (BMP Toolbox) and NCDENR's Stormwater Best Management Practices Manual, as well as
other structural and non-structural nutrient load reducing activities, for which NCDOT can supply nutrient
load reducing estimates. To the maximum extent practicable, BMP retrofits will be designed to treat the
runoff generated by the one -inch rainfall event and to conform to the standards and criteria established in
the most recent version of the NCDOT BMP Toolbox. It is anticipated that NCDOT will achieve the annual
goal through implementation of a variety of structural and non-structural SCMs; some of which are yet to
be evaluated for their nutrient -removal capability. To support this decision -making process, NCDOT
commits to work cooperatively with NCDWR to develop tools and accounting methods for a wide range of
load reducing activities that have not been evaluated. For SCMs that have been evaluated, NCDOT will rely
on the nutrient accounting tool which defines relative magnitudes of loads based on physiographic region,
drainage area, soil type, and climate variables. As practicable, NCDOT commits to implement practices on
existing road and non -road development using existing retrofit project identification and implementation
practices. Historically, NCDOT has implemented a wide range of BMP retrofits at maintenance yards,
welcome centers, rest areas, and material storage facilities as well as in the linear ROW. Typical BMP device
types installed under the NCDOT Retrofit Program are shown in the adjacent figure. The selection of BMPs
depend on a number of
Stormwater Wetlands, factors, such as whether the
Detention (Dry and 9%
wet), 16% � Proprietary Devices project is roadway or non -
(Inserts, Islands, roadway, and are designed to
Vaults), 6%
Buffer, 4% meet project -specific treat-
ment objectives. In the Falls
Infiltration (Rain
Level Spreader, 4% Lake watershed NCDOT will
Gardens, Basins and Stabilization, 4% continue to implement these
Chambers), 20%
�Swales, 4% practices at roadway and non -
Water Harvesting, 3% roadway facilities (e.g. NCDOT
Hazardous Spill Basin, offices, maintenance yards,
2% and storage facilities) as
�PSH & Environmental appropriate. The selection
Site Design, 1%
Media Filters process for identifying load
(Bioretention, Permeable Pavement,
Filtration, etc.), 25% Green Roof, 1% 1% reducing opportunities used to
meet the six retrofit -
equivalents will prioritize those
Summary of IBIVIP device types and historic implementation under which achieve the greatest
NICIDOT's Retrofit Program since inception. nutrient load reduction for the
lowest cost.
NCDOT implements a wide range of stormwater management programs and activities through several
business units. Under NCDOT's GREEN program for existing development, many of NCDOT's existing
activities that address stormwater requirements (for example, project planning, programming, project
development, design, construction, and maintenance) will be optimized to address the nutrient reduction
initiatives in Falls Lake. NCDOT has developed statewide programs to implement NPDES and other
environmental requirements that are similar in nature to the existing development Rules. NCDOT requests
that implementation of these stormwater activities and programs also satisfy one or more of the
requirements under the Falls Lake Rules. Four examples of existing NCDOT programs that will be
instrumental in implementing the existing development Rules include NCDOT's Stormwater System
Inventory and Prioritization Program, BMP Retrofit Program, Inspection and Maintenance Program
(Appendix B), and Illicit Discharge, Detection, and Elimination Program (IDDEP). These programs, among
PAGE 16

JANUARY 2014
many other programs, are required under NCDOT's NPDES stormwater permit and are described in the
following subsections. These standards and practices will be applied in the Falls Lake watershed, in
identifying and implementing retrofits and other load reducing activities to meet the retrofit directive of six
control -equivalents per year.
15 NCAC 02B .0281 (11)(d) requires NCDOT to "submit annual reports to the division summarizing its
activities in implementing each of the requirements in Item (9) of this Rule" Annual reporting to NCDENR
will include a description of structural SCMs, non-structural SCMs, offset payments, and other measures that
reduce nutrient loading from existing development. NCDOT will report on changes in nutrient loads
associated with these activities, including nutrient accounting workbooks or calculations and the types of
existing road and non -road development affected. Nutrient load reductions will be estimated using NCDOT-
JLSLAT, established removal rates for individual practices as recommended by the Nutrient Scientific
Advisory Board, or other NCDWR-approved procedures that are based on sound science. NCDOT anticipates
that annual reporting will occur in conjunction with NCDOT's NPDES stormwater permit annual reporting.
Similar to other NPDES permit requirements, NCDOT's existing development activities under NCDOT's
GREEN program will receive regular NCDWR review and assessment under existing NPDES auditing
procedures.
4.2.1 Stormwater System Inventory and Prioritization Program
NCDOT maintains a statewide inventory of implicit outfalls as part of the Department's Stormwater System
Inventory and Prioritization Program. This inventory has cataloged over 116,000 state maintained road
crossings over waterbodies and is updated annually to account for additional implicit outfalls from new road
construction. In addition, NCDOT identifies outfalls in the field from the NCDOT ROW within selected
priority areas using mapping -grade global positioning system (GPS) equipment and customized software as
part of the Department's Field Inventory Program. Through this program, NCDOT identifies stormwater
outfalls from interstate, US, and NC primary routes as required under 15A NCAC 02B .0281 (9)(a). Annual
reporting will include a summary of activities undertaken through this program to identify outfalls from
primary routes in the Falls Lake watershed.
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PAGE 17

4.2.2 BMP Retrofit Program
NCDOT's BMP Retrofit Program identifies and
implements SCM retrofits to preserve and protect
surface waters from pollutant loading due to NCDOT
activities. Statewide, this program addresses NCDOT
NPDES BMP retrofit compliance requirements by
identifying a minimum of 14 sites per year that are
appropriate for retrofit installation and implementing
a minimum of five retrofit projects per year and 70
retrofits over the five year NPDES permit term. In
meeting these requirements, the BMP Retrofit
program manager works closely with NCDOT Highway
Stormwater Program's Research, TMDL, BMP Toolbox,
and Post -Construction Stormwater Control program
managers and various NCDOT Units, to develop
standards (such as details, specifications, cost
estimating) and processes to facilitate the
implementation of creative practices that improve
water quality and reduce environmental impacts.
4.2.3 Illegal Discharge Detection and Elimination Program
TAM It CHEAP!
1110 ITOP MICK DUMPING.
If YOU !EE IT, REPORT IT!
ra � iooa<e n�� o a e
DO Y . JR PART to help prevent Stormwater Pollution.
Report illegal dumping and illicit connection findings to
your immediate supervisor.
JANUARY 2014
NCDOT Is required to Identify and eliminate Illegal discharges
into NCDOT's stormwater conveyance system" (15A NCAC 02B
.0281 (9)(b)) in the Falls Lake watershed. Compliance with this
requirement is achieved through continued implementation of
NCDOT Highway Stormwater Program IDDEP activities as
required under NCDOT's NPDES stormwater permit. Through
IDDEP, NCDOT detects and eliminates illicit discharges, spills,
and illegal dumping into the NCDOT transportation separate
storm sewer system, and reports such findings to NCDENR for
appropriate enforcement. The NCDOT IDDEP consists of various
staff, contractor, and volunteer training initiatives, investigating
and reporting findings, and maintaining a standard point of
contact and tracking database. NCDOT also collaborates with
municipalities and other appropriate agencies to identify and
report illegal discharges. When members of NCDOT staff identify
a potential illicit discharge or illegal dumping site along NCDOT
ROW, it is documented and reported to the NCDOT IDDEP point
of contact and others as appropriate. Once verified, the activity
is either resolved by NCDOT or reported to NCDENR within 30
days as required by NCDOT's NPDES stormwater permit.
Reporting of discrete illegal discharges or dumps identified
through NCDOT's IDDEP will occur on an as -needed basis
Example(typically within 30-days of verification). Annual reporting will
" ' ' include a summary of activities performed in the Falls Lake
NCIDOT's IDDEP to educate staff watershed under the NCDOT IDDEP.
PAGE 18

5.0 Nutrient Management Education Program
15 NCAC 02B .0281 (9)(e) requires NCDOT to educate
staff and contractors on proper application of nutrients
in highway rights of way. In keeping with this require-
ment, NCDOT will initiate a Nutrient Management Edu-
cation Program for staff and contractors who apply ferti-
lizers on highway rights of way in the Falls Lake water-
shed. The training will address issues specific to the
unique aspects of nutrient management for linear trans-
portation construction and maintenance activities and
will emphasize the most current state -recognized tech-
nical guidance on proper nutrient management.
NCDOT will utilize its web -based North Carolina Learning
Center System and other training venues to connect staff
and contractors with interactive training on nutrient
management. The training will include content analo-
gous to North Carolina State University Cooperative Ex-
tension Service Nutrient Management Training including
topics such as a general overview of water quality im-
pacts from nutrient applications along roadsides; how
nutrients move in a linear transportation environment;
roadside conservation practices for nutrient manage-
ment; and how to make nutrient application decisions.
As an ongoing effort to minimize pollutant potential of
stormwater runoff and in accordance with NCDOT's
NPDES permit, the department continues to conduct
annual training for staff who manage the application of
fertilizers. In addition to this training, NCDOT partners
with the North Carolina Department of Agriculture and
Consumer Services (NCDA&CS) to analyze soil samples
and provide recommendations on fertilizer composition
and application rates.
6.0 Reporting
JANUARY 2014
15 NCAC 02113.0281(9)(e)
Initiate a "Nutrient Management Education
Program "for NCDOT staff and contractors
engaged in the application of fertilizers on
highway rights of way. The purpose of this
program shall be to contribute to the load
reduction objectives established in 15A NCAC
028.0275 through proper application of
nutrients, both inorganic fertilizer and organic
nutrients, to highway rights of way in the Falls
watershed in keeping with the most current
state -recognized technical guidance on proper
nutrient management.
NCDOT will report annually to NCDENR on the measures taken to comply with the Rules. For new
development projects, NCDOT will submit a description of new non -road certified projects and associated
SCMs, project -specific copies of NCDOT-JLSLAT and other supporting calculations, nutrient offset payments
and offsite management measures, and changes in nutrient loads associated with these activities. For existing
development, annual reporting will include a description of structural SCMs, non-structural SCMs, offset
payments, and other measures used to reduce nutrient loading along with associated nutrient load
reductions. NCDOT will report on significant SCM maintenance or rehabilitation activities performed by
Division Roadside and Environmental Unit Engineers (responsible for SCM maintenance) and report on how
nutrient load reduction performance was affected. Lastly, annual reporting will include a summary of
activities undertaken to identify outfalls from primary routes and reports of illegal discharges and dumps
identified in the Falls Lake watershed. It is anticipated that GREEN program activities will be reported in
conjunction with NCDOT's Annual Stormwater Report for the NCDOT Highway Stormwater Program
submitted each November in compliance with its NPDES Permit.
PAGE 19

7.0 Contacts
Andy McDaniel, PE
NC Department of Transportation
Hydraulics Unit
1590 Mail Service Center
Raleigh, NC 27699-1590
919.707.6700
[e-mail]
Ken Pace, PE
NC Department of Transportation
Roadside Environmental Unit
1557 Mail Service Center
Raleigh, NC 27699-1557
919.707.2927
[e-mail]
JANUARY 2014
PAGE 20

�i
8.0 References
JANUARY 2014
NCDENR, 2003. Department of Transportation's Minimum Criteria. 19A NCAC 02F. Raleigh, NC: North
Carolina Office of Administrative Hearings.
NCDENR, 2009. Falls Lake Watershed Analysis Risk Management Framework (WARMF) Development. Final
Report. Prepared by N.C. Department of Environment and Natural Resources, Division of Water Quality,
Planning Section, Modeling/TMDL Unit. October 2009.
NCDENR, 2010. Falls Lake Rules. 15A NCAC 02B .0275 through .0282 and amended .0235 and .0315 Raleigh,
NC: North Carolina Office of Administrative Hearings. Approved by the North Carolina Rules Review
Commission on December 16, 2010. Effective January 15, 2011.
NCDENR, 2013. http://portal.ncdenr.org/web/faIIslake (accessed April 2013).
NCDOT, 2009. NCDOT Land Use Analysis in the High Rock Lake Watershed, North Carolina. Prepared by URS
Corporation - North Carolina for the NCDOT Highway Stormwater Program.
NCDOT, 2010. North Carolina Department of Transportation Metadata Content Standard for Geospatial
Data. Recommendations from Data Quality Group. Version 1.1.3. December 3, 2010.
NCDOT, 2012a. Transportation Land Use/Land Cover and Stormwater Control Measure Updates for the
Jordan/Falls Lake Nutrient Accounting Tool. Prepared by URS Corporation for the NC Department of
Transportation. Final version date June 2012 and approved by the NC EMC on July 12, 2012.
NCDOT, 2012b. Stormwater Management Program for New Development in the Jordan Lake Watershed.
Prepared by URS Corporation for the NC Department of Transportation. Final version date October 2012
and approved by the NC EMC on November 8, 2012.
NCDOT, 2012c. Baseline Nutrient Loads from North Carolina Department of Transportation in the Falls Lake
Watershed. Prepared by URS Corporation for the NC Department of Transportation. Final version date
June 2012 and approved by the NC EMC on July 12, 2012.
NCDOT, 2012d. NCDOT Right -of -Way and Impervious Area Land Use Analysis in the Jordan Lake Watershed.
Prepared by URS Corporation for the NCDOT Highway Stormwater Program. November 2012.
NCDOT, 2013a. Interim Development Nutrient Loads from North Carolina Department of Transportation in
the Falls Lake Watershed. Prepared by URS Corporation for the NC Department of Transportation.
Prepared July 2013.
NCDOT, 2013b. http://www.ncdot.gov/it/gis/ (accessed April 2013).
NCSU, 2011. Jordan/Falls Lake Stormwater Load Accounting Tool (Version 1.0) User's Manual. Revised
January 31, 2011.
NC OneMap, 2013. http://www.nconemap.com/ (accessed April 2013).
USDA, 2013. Natural Resources Conservation Service, United States Department of Agriculture. Web Soil
Survey. Available online at http://websoilsurvey.nres.usda.gov/ (accessed June 2013).
PAGE 21

JANUARY 2014
9.0 Acronyms and Abbreviations
BMP
Best Management Practice
CMY
County Maintenance Yard
DMV
Division of Motor Vehicles
EFDC
Environmental Fluid Dynamics Code
EMC
Environmental Management Commission
FGDC
Federal Geographic Data Committee
Ft
Square Feet
GIS
Geographic Information System
GPS
Global Positioning System
GREEN
Guided Reduction of Excess Environmental Nutrients
I&M
Inspection and Maintenance
IDDEP
Illicit Discharge, Detection, and Elimination Program
JLSLAT
Jordan/Falls Lake Stormwater Nutrient Load Accounting Tool
Lbs
Pounds
LOS
Level of Service
NC
North Carolina
NCAC
North Carolina Administrative Code
NCDA&CS
North Carolina Department of Agriculture and Consumer Services
NCDENR
North Carolina Department of Environment and Natural Resources
NCDOT
North Carolina Department of Transportation
NCDOT-JLSLAT
NCDOT Jordan/Falls Lake Stormwater Nutrient Load Accounting Tool
NCDWQ
North Carolina Division of Water Quality
NCDWR
North Carolina Division of Water Resources
NCSU
North Carolina State University
NLCD
National Land Cover Data
NPDES
National Pollutant Discharge Elimination System
NSW
Nutrient Sensitive Water
PCSP
Post Construction Stormwater Program
QA/QC
Quality Assurance / Quality Control
ROW
Right-of-way
SCM
Stormwater control measure
SCMS
Stormwater Control Management System
SPPP
Stormwater Pollution Prevention Plan
SR
Secondary Route
US
United States
USDA
United States Department of Agriculture
WARMF
Watershed Analysis Risk Management Framework
Yr
Year
PAGE 22

JANUARY 2014
Appendix A
NCDOT Roads in the Falls Lake Watershed

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JANUARY 2014
Appendix 6
NCDOT Inspection and Maintenance
Program

This page is intentionally left blank

JANUARY 2014
NCDOT Inspection and Maintenance Program
NCDOT has installed numerous stormwater control measures (SCM) within NCDOT rights -of -way across the
state to reduce the amount of pollutants found in stormwater. A SCM is an engineered structure or device
that is generally designed to slow down or hold water for a short time and remove pollutants before the
water is released to a surface water body or as the water infiltrates to the ground. SCMs are widely
referred to as best management practices (BMPs). They are also called "post -construction SCMs" because
they are designed to stay in place and treat runoff after an impervious surface is built, as opposed to
temporary erosion control practices (e.g., silt fences, sediment basins) used during a construction project.
As of the spring of 2013, NCDOT's active SCM inventory included over 1,450 SCMs statewide.
Stormwater control measures must be routinely inspected and maintained so that they continue to
function as designed. If proper maintenance is not provided, the pollutant removal performance of the SCM
may be compromised. NCDOT has developed an Inspection and Maintenance (I&M) Program to address
NPDES permit requirements for maintaining SCM assets. This program includes dedicated personnel
responsible for the functionality of NCDOT's Stormwater Control Management System (SCMS, pronounced
"skims") website, an SCM I&M Manual, training, program auditing, and cross -training between design
engineers, construction, and maintenance staff to increase stormwater control measure I&M awareness
within NCDOT.
I&M Program — National Pollutant Discharge Elimination System
Compliance Overview
The overall goals of the I&M Program are to maintain National Pollutant Discharge Elimination System
(NPDES) permit compliance and provide NCDOT field personnel the tools they need to effectively inspect
and maintain SCM inventories.
Initially, the I&M Program team worked with NCDOT Information Technology staff and developed a
database to track SCM inventories, inspections, and maintenance. NCDOT performed baseline inspections
on all known stormwater controls and piloted an I&M Program with Division 3. During this pilot program
the I&M team began developing a website to manage SCM inventories, document inspections and
maintenance, and track the initiation and design of retrofit SCMs. A naming convention was agreed upon
and the I&M Program team drafted the SCM I&M Manual.
Division Roadside Environmental Engineers refer to NCDOT's SCM I&M Manual for proper SCM function,
inspection details, and maintenance techniques. I&M activities are documented in SCMS, and Level of
Service (LOS) ratings are assigned to each SCM inspected. In addition, NCDOT Hydraulics Unit staff utilize
SCMS to track and document information related to the design and construction of retrofit SCMs.
In recent years, the I&M Program has focused on training Division Roadside Environmental and Division
Environmental personnel to manage their SCM inventories and document the inspection and maintenance
of their stormwater controls on the SCMS website. Additionally, upgrades were made to SCMS to increase
functionality and the I&M Program team provided training to division personnel on these upgrades.
Anticipated program updates include the addition of chapters to the Stormwater Control I&M Manual and
the promotion of communication between design, construction, and maintenance personnel.
The I&M Program is an integral element of NCDOT's NPDES Program. While the program receives NCDWQ
approval on an annual basis, NCDOT is in regular communication with NCDWQ regarding the components
and activities performed under the I&M Program throughout the year.
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NCDOT's SCMS
NCDOT developed the SCMS website to track SCM inventories and manage the I&M performed on their
stormwater control measures (see Figures B1 and 132). SCMS offers extensive functionality including
entering and storing I&M records for each SCM; mapping/location features; tracking SCM inventories by
division, county, or individually; tracking research on a specific control; storing SCM-specific regulatory
and roadway data; storing images and documents associated with an SCM; and generating reports. Each
time an inspection is performed for a SCM, a grade or LOS rating is assigned based on the status of the
SCM. Inspection details, maintenance needs determined at the time of the inspection, and the LOS rating
are tracked in SCMS. NCDOT division and Highway Stormwater Program management can view the status
of inspection records, the average LOS's per division, and the I&M history for each SCM, among many
other I&M program indicators. The divisions are, in turn, measured on the average LOS of their active
stormwater control measures.
Business DMV I Kewsroom I, Programs i I Projects II Travel & Maps
Control ID:
Paper ID:
TIP:
Latitude:
Longitude:
Distance: •Select-.�
Control Type: -Select-
Divsion:-Seled-.v
County: -Select-
Phase: -Select-
Ina[tive: ❑
Removed: ❑
Research: ❑
Retrofit: ❑
Notes Keywords:
Search
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Business 11 DNV 11 Newsroom 11 Programs jj Projects jI Travel & Maps
Caad ID: IN-3-32 SW-3033 Phm Maintenance Type: Scormwater Weiland (SW)
.r_rer,i Hy1ro"C RaaCs Reg"lat�ons Contacts Desyn Conutn,etKM Petals D ents Images 4:­-
Inspection and
Maintenance
Assign/View Research
. View Control Map
General Information
County: Durham d
Control Type: Stormwater Wetland [SW] �►
Control ID: IM- 5- 32-SW-3D55
Hydro ID:
Retrofit: ❑
TIP: !-030608
Road Tier: Interstate
Tier Type: iStatewid4 V_
Route Type: I Y
'Route: iI-85
Removed: Control has been removed from the
round.
Inactive:I
Inspection Frequency: _l1 ManthS
Nearest Town: Durham
A
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NCDOT's Stormwater Control Measure I&M Manual
NCDOT developed a Stormwater Control Measure I&M Manual to serve as guidance for inspecting and
maintaining stormwater controls on NCDOT's rights -of -way. The first four introductory chapters include a
general discussion of inspection requirements and maintenance considerations (including plant species
identification and reporting requirements for post -construction, structural SCMs).
The remaining chapters are dedicated to the different types of stormwater controls. Each chapter focuses
on a specific SCM and includes a general description of the SCM and its components, guidance on I&M
requirements for each component of the SCM, photos of the SCM, and detailed diagrams of the SCM (see
example in Figure 133) that show the major treatment mechanisms.
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Appendix C
NPDES Certification Statement

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JANUARY 2014
NPDES Certification Statement
Please see Section 3.2.1 for additional information regarding the applicability of this certification statement.
"I certify, under penalty of law, that this document and all attachments were prepared under
my direction or supervision in accordance with a system designed to assure that qualified
personnel properly gather and evaluate the information submitted. Based on my inquiry of the
person or persons who manage the system, or those persons directly responsible for gathering
the information, the information submitted is, to the best of my knowledge and belief, true,
accurate, and complete. I am aware that there are significant penalties for submitting false
information, including the possibility of fines and imprisonment for knowing violations."
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Appendix D
Baseline Nutrient Loads from North
Carolina Department of Transportation in
the Falls Lake Watershed

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Highway
Stormwater
Baseline Nutrient Loads from North Carolina
Department of Transportation in the Falls Lake
Watershed
In partial fulfillment of 15A NCAC 02B .0281
Prepared by:
URS Corporation — North Carolina
1600 Perimeter Park Drive
Suite 400
Morrisville, NC 27560
Prepared for:
NC Department of Transportation
Hydraulics Unit
1590 Mail Service Center
Raleigh, NC 27699-1590
919.707.6700
[e-mail]
This report was approved by the North
June 2012 Carolina Environmental Management
Commission on July 12, 2012.
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Introduction
The Falls Lake Rules (15A NCAC 02B .0275-.0282, .0235, and .0315) establish a nutrient management
strategy designed to reduce algal growth in Falls Lake through the reduction of nitrogen and phosphorus
sources in the watershed. Under the rules, all major contributors of nutrients in the watershed,
including the North Carolina Department of Transportation (NCDOT), are required to reduce their
loading of total nitrogen (TN) and total phosphorous (TP) and to meet specific percent reduction goals to
restore water quality standards in the lake. The rules were approved by the N.C. Rules Review
Commission on December 16, 2010 with an effective date of January 15, 2011.
As part of the stormwater requirements for state and federal entities (15A NCAC 02B .0281), by July 15,
2012, North Carolina Division of Water Quality (NCDWQ) is required to submit a nutrient accounting
framework to the North Carolina Environmental Management Commission (EMC) for approval. The
framework shall:
"... include tools for quantifying load reduction assignments on existing development for parties
subject to this Rule, load reduction credits from various activities on existing developed lands, and a
tool that will allow subject parties to account for loading from new and existing development and
loading changes due to BMP implementation. The Division shall work in cooperation with subject
parties and other watershed interests in developing this framework." (15A NCAC 02B .0281 (13))
Additionally, 15A NCAC 02B .0281 (9)(d)(i) states:
"As part of the accounting process described in Item (13) of this Rule, baseline nutrient loads shall be
established for roadways and industrial facilities using stormwater runoff nutrient load
characterization data collected through the National Pollutant Discharge Elimination System
(NPDES) Research Program under NCS0000250 Permit Part 11 Section G,"
In accordance with these requirements, the NCDWQ, NCDOT, and URS developed an approach for
calculating baseline nutrient loads for NCDOT in the Falls Lake watershed. The approach is based on
existing data and models used to develop the Falls Lake Rules. This report describes the technical
approach and steps used to calculate NCDOT's baseline TN and TP loads.
Overview of Existing Models
In 2009, NCDWQ completed a watershed model and lake nutrient response model in accordance with
Session Law 2005-190 (North Carolina Senate Bill 981) and to address impaired chlorophyll -a and
turbidity conditions in Falls Lake. These models were subsequently used to support the development of
the Falls Lake Nutrient Management Strategy and Rules.
Watershed Analysis Risk Management Framework (WARMF) — This model was used by
NCDWQ to simulate conditions in the Falls Lake watershed and, in particular, quantify nutrient
contributions from point and nonpoint sources (NCDWQ, 2009a). The model was calibrated in
five main tributaries draining to the upper watershed: Flat River, Knap of Reeds Creek, Ellerbe
Creek, Little River and Eno River. The remainder of the watershed model was not calibrated,
• Environmental Fluid Dynamics Code (EFDC) — This model simulates conditions within Falls Lake
and was applied by NCDWQ to predict chlorophyll -a concentrations in the lake in response to
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tributary nutrient loading and in -lake processes (NCDWQ, 2009b). This model was used as the
basis for the Stage I and II nutrient reduction goals stated in the rule (15A NCAC 02B .0275 (3)).
Technical Approach for Calculating NCDOT Baseline Loads
The Falls Lake WARMF and EFDC models provide the best available estimates of existing nutrient source
contributions in the watershed and nutrient loading to the lake. As presented in Figure 1, for this
project, output from the Falls Lake WARMF model was used to determine NCDOT's relative percentage
of nutrient load delivered to Falls Lake during the 2006 baseline period. Tributary flow and water quality
inputs, available in the EFDC model, were used to determine the TN and TP tributary loads delivered to
Falls Lake from all sources in the watershed during the baseline period. TN and TP loads from NCDOT
were calculated for each tributary by multiplying the NCDOT percentage of total delivered load by the
total delivered baseline load in each tributary. NCDOT TN and TP loads for the entire watershed were
then calculated as the sum of all NCDOT tributary loads.
WARMF
watershed model
NCDOT's percentage of
total delivered nutrient
load (by tributary)
EFDC
lake model
Baseline delivered load
for all sources
(by tributary)
NCDOT baseline nutrient load
delivered to Falls Lake
Figure 1. Method Used to Calculate NCDOT's Baseline Nutrient Load in Falls Lake.
For this evaluation, all model parameters, inputs and outputs were used "as is" with the exception of
soil layer hydrology input revisions requested by NCDWQ (see discussion on page 4); no additional flow
or water quality data was used, nor was any data removed from the original datasets. All decisions
related to the methods and technical approaches used in this project were discussed in detail with
NCDWQ staff during the project and are described in this report.
Because the Falls Lake EFDC and WARMF models were developed in parallel, and model boundary
conditions were not directly linked, NCDWQ, NCDOT and URS collaborated on a method to align WARMF
subwatershed and catchment boundaries with the EFDC tributary boundaries. This step was necessary
for this evaluation because tributary boundary conditions in EFDC (Figure 2) were used to define the
total delivered loads while WARMF catchments were used to calculate the associated percentage of
delivered load that was attributable to NCDOT in those tributary loads. WARMF subwatershed and
catchment assignments to tributaries (Figure 3), developed for this evaluation, were made based on
their proximity to tributary boundaries in EFDC.
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Figure 2. Falls Lake EFDC Model Tributary Inputs (Source: NCDWQ, 2009b).
Figure 3. Falls Lake WARMF Subwatersheds and Corresponding EFDC Tributary Assignments.
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NCDOT Percentage of Baseline Nutrient Loads Delivered to Falls Lake
The relative percentage of TN and TP loads attributable to NCDOT was calculated using WARMF
estimates of delivered NCDOT loads in the seventeen subwatersheds shown in Figure 3. In general, this
process involved an accounting of NCDOT's relative contribution from WARMF tributaries and
catchments that drain directly to Falls Lake. NCDOT's percent contribution in tributary loads, was based
on the percentage of delivered load ("Source Contribution" in WARMF) attributable to NCDOT at the
downstream reach, prior to its confluence with the lake. Similarly, for catchments that drain directly to
Falls Lake, the relative load attributable to NCDOT ("Source Contribution") was used to estimate the
percentage of NCDOT delivered load in these catchments. An area -weighted approach was then used to
incorporate NCDOT's relative contribution in the catchments that drain directly to the lake with
NCDOT's contribution in the tributaries. A similar area -weighted approach was used in subwatersheds
where two streams (in WARMF) were grouped as a single tributary input (in EFDC).
The remainder of this section provides a step-by-step summary of the approach used to calculate the
percentage of delivered load attributable to NCDOT in each of the 17 subwatersheds:
1. During preliminary model discussions with NCDWQ the project team identified revisions that
were needed for the New Light Creek subwatershed (subcatchment 2551) in WARMF. Based on
NCDWQ instruction, URS revised model inputs for "Initial Moisture," "Field Capacity" and "Sat.
Moisture" soil layer hydrology inputs in subcatchment 255 such that they match inputs used for
subcatchment 72 (Adugna Kebede, NCDWQ, personal communication, May 17, 2012).
Subcatchment 72 is located directly downstream of subcatchment 255. The revised soil layer
hydrology input parameters are presented in Table 1.
Table 1. Soil Layer Hydrology Input Revisions in New Light Creek (Subcatchment 255).
Layer
Initial Moisture
Field Capacity
Sat. Moisture
1
0.3
0.4
0.5
2
0.2
0.3
0.45
3
0.22
0.22
0.35
4
0.35
0.2
0.35
5
0.35
0.15
0.35
2. The Falls Lake WARMF model was run with a beginning date of January 1, 2004 and an ending
date of December 31, 2005. Upon completion of the model run, the model was resaved as
"FallsLakenewbound_04-05_nlc" and closed. This model scenario served the purpose of
providing an initial condition for the baseline, 2006 model simulation period.
3. The Falls Lake WARMF model was opened and saved under a new project file name
("FallsLakenewbound_06_nlc"). The model beginning date was defined as January 1, 2006 and
ending date was defined as December 31, 2006. The "Initial Conditions from WARMF Start File"
was checked and "FallsLakenewbound 04-05 nlc" file was selected as the initial condition file.
1 Subcatchment 255 is labeled as "Subcatchment ID 455" in WARMF.
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The model was run for all watersheds and, upon completion, saved as
"FallsLakenewbound 06 nlc".
4. WARMF subwatersheds and catchments were assigned to EFDC tributaries as presented in
Figures 2 and 3.
WARMF simulates NCDOT as a unique land cover category and assigns TN and TP loads to
NCDOT similar to other land categories and nutrient sources in the watershed. Using WARMF
output, the percentage of TN and TP loads delivered to Falls Lake attributable to NCDOT was
calculated in each subwatershed (1-17). In most cases, this calculation included an assessment
of NCDOT's contribution in the tributary as well as NCDOT's contribution in catchments that
drain directly to Falls Lake, as follows:
a. Subwatersheds that drain to tributaries —TN and TP loads for all tributaries were
obtained in WARMF using the "Source Characterization" output. The percentage of total
load attributable to NCDOT was calculated for each tributary by dividing the total
tributary load (kg/year) by NCDOT's contribution load (kg/year) in each tributary.
Catchments that drain directly to Falls Lake — TN and TP loads for all catchments
draining directly to Falls Lake were obtained in WARMF using the "Source
Characterization" output. The percentage of total load attributable to NCDOT was
calculated for each catchment by dividing the total load (kg/year) by NCDOT's
contribution load (kg/year) in that catchment.
c. Tributaries with impoundments — WARMF uses the "managed load" category to
account for loads draining to impoundments that are modeled within a subwatershed.
To account for the NCDOT percentage of managed load that is delivered to Falls Lake,
the percentage of load delivered to the lake that is attributable to NCDOT is multiplied
by the total load from "Managed Flow" at the downstream segment to the lake. This
load is then added to the reported delivered load for NCDOT at the tributary -lake
confluence to arrive at the total delivered load attributable to NCDOT from that
tributary.
6. Using the catchment size and percent load contributions from NCDOT, an area -weighted
approach was used to incorporate NCDOT's relative contribution in the subwatersheds that
drain directly to the lake with those catchment contributions that drain to tributaries. Similarly,
an area -weighted approach was used in cases where two streams (in WARMF) were grouped as
a single tributary input in EFDC.
Baseline Nutrient Loads Delivered to Falls Lake from All Sources
Flow and water quality inputs used to develop the Falls Lake EFDC model were used to determine the
baseline nutrient load from all sources in the watershed. The following steps outline the approach used
to calculate the total delivered TN and TP loads for all sources in each of the 17 EFDC tributaries:
USGS flow and water quality data for calendar year 2006 were obtained from two Falls Lake
EFDC model input files: "qser.inp" and "wgpsl.inp". Daily flow data (cubic meters per second)
were copied from the EFDC "qser.inp" file into Microsoft Excel and the "Text to Columns" Excel
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function was used to arrange data. Drainage area ratios for each tributary and the number of
receiving lake segments were obtained from the "qser.inp" and "efdc.inp" files and tabulated.
Daily flows were multiplied by the corresponding drainage area ratios and number of receiving
lake segments to calculate daily flow (cubic meters per second) for each tributary.
2. Daily water quality data (concentrations as mg/L) were obtained from the EFDC "wqpsl.inp" file
and transferred into Microsoft Excel. The "Text to Columns" Excel function was then used to
arrange data in separate cells by parameter and daily data for five nitrogen species and four
phosphorus species.
Daily TN and TP loads for each tributary were calculated for each nitrogen and phosphorus
species using daily nutrient concentrations, daily flow data (calculated under step 1) and unit
conversion factors. Annual TN and TP loads were calculated as the sum of daily loads for each
respective nutrient species. The TN annual load was based on the sum of refractory particulate
organic nitrogen, labile particulate organic nitrogen, dissolved organic nitrogen, ammonia
nitrogen, and nitrite + nitrate nitrogen annual loads. The TP annual load was based on the sum
of refractory particulate organic phosphorus, labile particulate organic phosphorus, dissolved
organic phosphorus, and total orthophosphate annual loads.
NCDOT Baseline Nutrient Loads
Baseline TN and TP loads were calculated for NCDOT in the Falls Lake Watershed by multiplying the
fraction of total load attributable to NCDOT by the corresponding total TN and TP delivered loads by
tributary. The final, baseline NCDOT TN and TP loads delivered to Falls Lake are presented in Tables 2
and 3.
Table 2. 2006 Baseline TN and TP Loads (pounds/year) for all Sources and NCDOT in the Upper, Lower,
and Entire Falls Lake Watershed.
Baseline Loads from all Sources
NCDOT Baseline Loads
(pounds/year)
(pounds/year)
TN
TP
TN
TP
Upper Watershed
1,081,425
136,852
12,542
1,714
Lower Watershed
137,738
18,686
2,114
216
Entire Falls Lake Watershed
1,219,163
155,538
14,657
1,931
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Table 3. NCDOT Percentage of Total Delivered Nutrient Loads and 2006 Baseline Loads (pounds/year) for all Sources and NCDOT by
Tributary.
Upper/
NCDOT Fraction of Total
Baseline Load From All
NCDOT Baseline Load
Tributary
Lower
Delivered Load (%)
Sources (pounds/year)
(pounds/year)
TN
TP
TN
TP
TN
TP
Label
Stream Name
Watershed
Q1
Flat River
Upper
1.5%
0.4%
123,748
10,466
1,798
38
Q2
Knap of Reeds Creek
Upper
0.4%
0.1%
160,110
43,366
647
26
Q3
Little River and Eno River
Upper
1.1%
0.9%
223,301
20,127
2,397
191
Q4
Ellerbe Creek
Upper
1.2%
2.4%
432,292
42,731
5,186
1,022
Q5
Unnamed Tributary
Upper
2.9%
4.0%
15,246
1,826
437
73
Q6
Panther Creek and Rocky Branch
Upper
1.5%
1.6%
18,422
2,550
269
41
Q7
Ledge Creek and Lake Rogers
Upper
1.3%
1.1%
42,687
5,114
542
57
Q8
Little Lick Creek
Upper
2.1%
3.4%
40,528
5,609
866
192
Q9
Robertson Creek
Lower
0.9%
0.5%
21,026
2,566
181
13
Q10
Beaverdam Creek
Lower
0.4%
0.3%
18,552
2,264
73
7
Q11
Smith Creek
Lower
1.1%
0.4%
18,552
2,264
201
10
Q12
Lick Creek
Upper
1.6%
1.5%
25,091
5,063
400
75
Q13
New Light Creek
Lower
1.2%
0.7%
27,210
3,321
320
24
Q14
Upper Barton Creek
Lower
1.8%
1.1%
13,591
2,742
250
30
Q15
Lower Barton Creek
Lower
5.1%
2.2%
14,637
2,953
740
65
Q16
Horse Creek and Lowery Creek
Lower
2.3%
4.1%
15,382
1,638
349
67
Q17
Honeycutt Creek and Cedar Creek
Lower
0.0%
0.0%
8,789
936
0
0
All Tributaries
1,219,163
155,538
14,657
1,931
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Project Deliverables
The following electronic files were used to support information presented in this report:
1. WARMF modeling files —WARM F model inputs and outputs are provided in a folder titled
"FallsLake—NewCalNewAg." Two models runs used to support this project include:
"FallsLakenewbound_04-05_nlc" —this model run includes revisions to "Initial
Moisture," "Field Capacity" and "Sat. Moisture" soil layer hydrology inputs in New Light
Creek (subcatchment 255) based on NCDWQ instruction and as described on page 4 of
this document. This model run was used to simulate the January 1, 2004 — December
31, 2005 initial condition for the baseline, 2006 model simulation period.
"FallsLakenewbound-06—nlc" —this model run includes revisions to "Initial Moisture,"
"Field Capacity" and "Sat. Moisture" soil layer hydrology inputs in New Light Creek
(subcatchment 255) based on NCDWQ instruction and as described on page 4 of this
document. This model run was used to simulate the January 1, 2006 — December 31,
2006 baseline period.
2. EFDC modeling files — EFDC modeling inputs used to support this project are included in a model
folder titled "Fina12006Moclel."
3. Calculations used to support the NCDOT baseline TN and TP load analysis are presented in the
following two Microsoft Excel files:
a. "EFDC Nutrient Loads .xlsx" —This Excel file includes flow and water quality data
obtained from EFDC and all calculations related to the baseline loads for TN and TP for
all sources in each tributary.
"WARMF and NCDOT Baseline Loads.xlsx" —This Excel file includes delivered nutrient
loads from WARMF, calculations used to determine NCDOT's relative percentage of TN
and TP loads delivered to Falls Lake in each tributary (Q1-Q17), and calculations used to
determine NCDOT's delivered TN and TP loads in each tributary and watershed -wide.
References
NCDWQ, 2009a. Falls Lake Watershed Analysis Risk Management Framework (WARMF) Development —
Final Report. Prepared by the NC Department of Environment and Natural Resources, Division of Water
Quality, Modeling and TMDL Unit. October 2009.
NCDWQ, 2009b. Falls Lake Nutrient Response Model — Final Report. Prepared by the NC Department of
Environment and Natural Resources, Division of Water Quality, Modeling and TMDL Unit. November 30,
2009.
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Appendix E
Interim Development Nutrient Loads from
North Carolina Department of
Transportation in the Falls Lake Watershed

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E-Executive Summary
E-3
E-1.0
Background and Purpose
E-4
E-2.0
Interim Road and Non -Road Development Analysis
E-5
E-3.0
Interim Load Analysis
E-19
E-4.0
Data Limitations, Constraints, and Assumptions
E-22
Table ES-1. Nutrient loading associated with NCDOT road and non -road E-3
development that occurred during the interim period in the Falls Lake watershed
Table E-1. NCDOT non -road facilities in the Falls Lake watershed E-5
Table E-2. Datasets used in support of the road analysis
E-6
Table E-3. GIS attributes used to calculate ROW and impervious widths E-7
Table E-4. Attributes added by URS to calculate ROW and impervious area widths E-8
Table E-5. Description of GIS datasets associated with this report E-8
Table E-6. NCDOT impervious and ROW interim development areas in the Falls E-14
Lake watershed
Table E-7. Datasets used to support the non -road analysis
E-15
Table E-8. Pre -development and post -development land cover conditions at the E-16
Durham CMY (traffic services building)
Table E-9. NCDOT-JLSLAT inputs used to calculate nutrient loading changes E-19
associated with NCDOT interim primary road development for the post -
development condition
Table E-10. NCDOT-JLSLAT inputs used to calculate nutrient loading changes E-19
associated with NCDOT interim secondary road development for the post -
development condition
Table E-11. Pre -development and post -development nutrient loading conditions E-20
associated with NCDOT primary and secondary road development in the Falls Lake
watershed during the interim period. Pre -development loads are based on
uniform rates (15A NCAC 02B .0281 (5)(a)) and post -development loads are based
on NCDOT-JLSLAT
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Table E-12. NCDOT-JLSLAT inputs used to calculate nutrient loading changes E-20
associated with NCDOT interim non -road development for both pre -development
and post -development conditions at the Durham CMY (traffic services building)
Table E-13. Pre -development and post -development condition with BMP E-21
associated with non -road development at the Durham CMY (traffic services
building)
Table E-14. Nutrient loading associated with NCDOT road and non -road E-21
development that occurred during the interim period in the Falls Lake watershed
Figure E-1. An example of gaps greater than 1 foot (left). After editing, the ROW E-10
buffer is updated to represent the corrected ROW (right).
Figure E-2. An example of island polygons commonly found between the lanes of E-10
highways and interstates (left). URS inserted new polygons to fill the gaps (right).
Figure E-3. An example of editing in the impervious area polygon. Black -line E-12
polygons, shown in the left and middle image, were auto -generated using a buffer
on the road centerline. Red lines, shown in the middle image, identify manual
edits. The right image shows the corrected impervious area in red.
Figure E-4. An example of an inaccurate automated buffer due to an error in E-12
attribute data. Results from the automated buffer procedure (left image) and
corrected impervious area (right) are shown.
Figure E-5. An example illustrating a case where road centerlines and calculated E-13
impervious surface buffers do not match roads shown on aerial
orthophotographs.
Figure E-6. NCDOT ROW (white boundary) and impervious area (yellow boundary) E-14
associated with primary route interim period development. The Falls Lake
WARMF watershed model boundary is shown in red.
Figure E-7. Baseline, pre -development condition during 2006 (top image) and E-17
associated land cover categories (bottom image) at the Durham CMY.
Figure E-8. Proposed, interim period post -development condition (top image) and E-18
associated land cover categories (bottom image) at the Durham CMY. Site
changes include demolition of several small buildings and construction of a new
traffic services building, paint storage building, parking lot, and stormwater
wetland detention basin.
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E-Executive Summary
The Falls Lake Rules establish a nutrient management strategy to reduce algal growth in Falls Lake. As
part of the Rules, contributors of nutrients, including the NC Department of Transportation (NCDOT), are
required to reduce their loading of total nitrogen and total phosphorus in order to meet the nutrient
load objectives of the Rule and restore water
quality standards in the lake. The Rules
require NCDOT to develop and implement a
Stormwater Management Program for both
new and existing road and non -road
development activities, and account for
nutrient load changes on lands developed
subsequent to the baseline period but prior to
implementation of its new development
program (15A NCAC 02B .0281 (9)(d)(ii)). This
period, referred to as the "interim
development" period, began on January 1,
2007 and extends through January 15, 2014.
NCDOT's Stormwater Management Program
in Falls Lake must document NCDOT's interim
development load along with the intended
implementation rate and schedule for
15A NCAC 02B .0281 (9)(d)(111)
(ii) The program shall include estimates of, and plans
for offsetting, nutrient load increases from lands
developed subsequent to the baseline period but
prior to implementation of its new development
program. It shall include a technical analysis that
includes a proposed implementation rate and
schedule. This schedule shall provide for
proportionate annual progress toward reduction
objectives as practicable throughout the proposed
compliance period. The program shall identify the
types of activities NCDOT intends to implement and
types of existing roadway and non -roadway
development affected, relative proportions or a
prioritization of practices, and the relative
magnitude of reductions it expects to achieve from
each.
activities aimed at offsetting any increases in loads. As described in this report, NCDOT's interim
development area was defined using best available road and non -road datasets, project site plans and
aerial imagery. Nutrient loads associated with the interim development were calculated using uniform
pre -development loading rates and the nutrient accounting tool, NCDOT-JLSLAT. The net change in total
nitrogen and total phosphorus associated with NCDOT's interim development is presented in Table ES-1.
Table ES-i Nutrient loading associated with NCDOT
road and non -road development
that
occurred during the interim
period in the
Falls Lake watershed
Secondary R
W-e
All NCDOT
[Development
Interim Period Nutrient Loading
OPTOMW
DevelopME
I - 1 .1
Development Area (acres)
10
456
4
470
Total Nitrogen
Pre -development Load (Ibs/yr)
28
1,318
22
1,368
Post -development Load (Ibs/yr)
61
1,174
19
1,254
Net Interim Development Load (Ibs/yr)
33
(144)
(3)
(114)
Total Phosphorus
Pre -development Load (Ibs/yr)
6
287
6
299
Post -development Load (Ibs/yr)
4
214
2
220
Net Interim Development Load (Ibs/yr)
(2)
(73)
(4)
(79)
Ibs/yr = pounds per year
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E-1.0 Background and Purpose
As part of the stormwater requirements for state and federal entities, the North Carolina Department of
Transportation (NCDOT) is required to estimate nutrient load changes on lands developed subsequent
to the baseline period but prior to implementation of its new development program (15A NCAC 02B
.0281 (9)(d)(ii)). This period, referred to as the "interim development" period, begins on January 1, 2007
and extends through January 15, 2014. NCDOT's Stormwater Management Program in Falls Lake must
document the nutrient loading changes associated with NCDOT's interim development area along with
the intended implementation rate and schedule for activities aimed at offsetting any increases in loads.
In accordance with this requirement, NCDOT developed an approach for calculating the change in
nutrient loading associated with NCDOT's interim development area in the Falls Lake watershed. As
described in this report, the approach relied on best available Geographic Information System (GIS)-
based estimates of NCDOT road and non -road development during the baseline and interim period,
collaboration with NCDOT Division staff (Divisions 5 and 7), uniform predevelopment loading rates, and
NCDOT's Jordan/Falls Lake Stormwater Nutrient Load Accounting Tool (NCDOT-JLSLAT).
On July 12, 2012, baseline total nitrogen (TN) and total phosphorus (TP) loads were approved by the
North Carolina Environmental Management Commission (EMC) for NCDOT in the Falls Lake watershed.
These loads were calculated using models that were developed by NCDWQ to support the Falls Lake
Rules (NCDOT, 2012c). NCDOT's baseline development was based on NCDOT ROW estimates calculated
for the Watershed Analysis Risk Management Framework (WARMF) watershed model which were
developed using NCDOT's Road Condition 2004 GIS dataset. NCDOT's road centerline GIS dataset
includes routes (Interstate, US, NC, Secondary Routes, and Ramps) and attributes of the NCDOT state
road system, is updated four times annually by NCDOT's GIS Unit, and is distributed on NCDOT's
Enterprise GIS website. As described in Section E-2.0 of this report, the WARMF NCDOT ROW estimates
were, in part, used in this analysis to identify where NCDOT interim development had occurred in the
watershed.
In July 2012, the EMC also approved a NCDOT nutrient accounting framework for use in Falls Lake
watershed planning and rule compliance. The nutrient accounting framework, "NCDOT-JLSLAT",
maintains the fundamental structure of North Carolina Department of Environment and Natural
Resources' (NCDENRs') original Jordan/Falls Lake Stormwater Load Accounting Tool (JLSLAT) and the
methods used to evaluate loading rates and load reductions, while allowing NCDOT to estimate nutrient
loads specific to NCDOT facilities. A 2012 report titled Transportation Land Use/Land Cover and
Stormwater Control Measure Updates for the Jordan/Falls Lake Nutrient Accounting Tool (NCDOT,
2012a) summarizes the steps taken to adapt JLSLAT for NCDOT applications. As described in Section E-
3.0 of this report, NCDOT-JLSLAT was used to calculate changes in nutrient loads associated with
NCDOT's interim development for road and non -road areas.
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E-2.0 Interim Road and Non -Road Development Analysis
NCDOT development includes both road development and non -road development (see Tables 2 and 3 in
Section E-3.0 of the Falls Lake Guided Reduction of Excess Environmental Nutrients (GREEN) Report for
project type examples). NCDOT's road centerline GIS dataset' represents the best available resource for
identifying where changes to the NCDOT road system have occurred since the baseline period. The
dataset is updated frequently and it provides exhaustive details regarding NCDOT road and ROW
characteristics. The process for identifying NCDOT's interim development area included a detailed
comparison of NCDOT's baseline ROW dataset (used to support the WARMF watershed model) with
NCDOT's current road centerline GIS dataset (issued first quarter 2013). Using GIS, NCDOT roads
(polyline segments) that were added to the road centerline dataset during the interim period were
identified and exported as a separate GIS polyline layer. This layer was used as a basis for preparing
NCDOT interim development impervious area and ROW area polygon datasets. Characterization of the
interim development impervious and ROW areas involved a series of automated and manual editing
steps in ArcGIS (Sections E-2.1 of this document) that were similar to those performed by NCDOT staff
and contractors to support modeling studies in Falls Lake, High Rock Lake, and Jordan Lake watersheds
(NCDENR, 2009; NCDOT, 2009; NCDOT, 2012d).
NCDOT's interim development loads are affected by property transfers (sales or acquisitions) as well as
land cover changes on properties that existed during the baseline period. At the time of this analysis,
NCDOT operated and maintained eight non -road facilities in the Falls Lake watershed, including four
administrative buildings and four industrial facilities. A list of the eight non -road facilities is provided in
Table E-1.
Table E-i.. NCIDOT non -road facilities in the Falls
Administrative Facilities
Durham Division of Motor Vehicles (DMV) Office
Lake watershed
Industrial
Granville County Salt Storage Yard
Durham NCDOT Division Engineer Office
Durham County Maintenance Yard
Durham NCDOT Resident Engineer Office
Orange County Maintenance Yard
Durham NCDOT Resident Engineer Office Property
Person County Maintenance Yard
To identify non -road properties that may have been acquired by NCDOT during the interim period, URS
evaluated state-owned property GIS datasets, site plans and drawings maintained for NCDOT non -road
facilities. URS also conducted verbal inquiries with NCDOT Division 5 and Division 7 staff. These
evaluations and staff inquiries revealed that all eight non -road properties existed during the baseline
period and that no additional properties were acquired or sold by NCDOT in the Falls Lake watershed
during the interim period.
To identify changes in development within each of the eight non -road properties, URS technicians
evaluated a series of aerial imagery datasets to characterize land development changes. For this
1 NCDOT GIS available at https:Hconnect.ncdot.gov/resources/gis
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analysis, URS technicians evaluated orthophotographs for the years 2006 through 2010 to identify
changes in land cover on a site -by -site basis. This assessment revealed that changes in land cover had
occurred at the Durham County Maintenance Yard (CMY) but not at any of the remaining seven
facilities. Verbal inquiries with NCDOT Division 5 and Division 7 staff confirmed these findings. Section E-
2.2 of this document describes steps taken by URS to evaluate the land cover changes associated with
interim development at the Durham CMY.
E-2.1 Interim NCDOT Road Development
This section describes procedures used to develop the ROW and impervious areas associated with
changes in road development during the interim period. In general, NCDOT road development that
occurred since the baseline period was identified and exported to a separate polyline dataset. ROW and
impervious area polygons were then developed by buffering the polyline dataset (Section E-2.1.3).
Buffer distances were determined using attributes available in the road centerline data and, in select
cases, typical road widths as presented in NCDOT Roadway Design Manual or aerial imagery. Automated
procedures were followed by manual editing and quality assurance and control steps to promote
consistency and improve accuracy of final ROW and impervious area GIS datasets. All GIS-related steps
described in this report were performed using ArcGIS, Version 10.0.
E-2.1.1 Data Sources
Datasets that were used in support of the analysis are presented in Table E-2. Past (2004) and current
(2012 and 2013) NCDOT road centerline datasets were used to develop NCDOT ROW and impervious
area datasets. At the onset of the project, URS downloaded the most current NCDOT road centerline
dataset that was available at the time (fourth quarter 2012). During the project, NCDOT released an
updated version of the road centerline dataset (first quarter 2013). This updated version was evaluated
to identify revisions added since the fourth quarter 2012 release. These 2013 revisions were
incorporated in the development of ROW and impervious cover evaluations described in this section.
Aerial orthophotographs were used as a visual aid for the generation of ROW and impervious area
datasets. These images represent the best aerial orthophotographs available at the time of this project.
NCDOT Road Datasets NCDOT road dataset titled "Road Condition 2004" was used to support the
development of NCDOT's ROW for the WARM model. The fourth quarter
2012 and first quarter 2013 releases of NCDOT's road data
("RD_CHAR_MLPST") were used in defining changes in development since
the Road Condition 2004 dataset. All polyline datasets were obtained from
the NCDOT GIS Unit (NCDOT, 2013b).
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Table E-2. Datasets used in support of the road analysis (continued)
� Layer •- Description
NCDOT ROW used to This polygon dataset includes NCDOT ROW in the Falls Lake watershed
develop WARMF based on the Road Condition 2004 GIS layer. This dataset was prepared by
NCDOT during the development of the Falls Lake WARMF model (NCDENR,
2009). This dataset is titled "falls_nlcd2001".
Aerial imagery Statewide orthophotography (2010 and 2012) that is available through
nconemap.com. Data originate from the North Carolina Department of
Agriculture and Consumer Services.
Falls Lake watershed Watershed boundary obtained from NCDWQ's website (NCDENR, 2013).
boundary
In developing the ROW and impervious cover polygons, URS used existing attribute information
available in the NCDOT road datasets (presented in Table E-3) as well as new attributes that were
developed specifically for this project (presented in Table E-4).
Table E-3. GIS attributes used to calculate ROW and impervious widths
Attribute�- I I •
RW_WID ROW value estimating the width (measured in feet) of an NCDOT ROW.
SHLDR_LFT_TYP_CD
Type of left shoulder material. Shoulder type categories are as follows:
Grass or Sod = "1", Gravel or Stone = "2", Bituminous = "3", Curb
Bituminous = "4", Concrete = "5", Curb Concrete = "6", and Tie Bar = 171.
SHLDR_RGT_TYP_CD
Type of right shoulder material. Shoulder type categories are as follows:
Grass or Sod = "1", Gravel or Stone = "2", Bituminous = "3", Curb
Bituminous = "4", Concrete = "5", Curb Concrete = "6", and Tie Bar = "7".
SHLDR_WID_LFT_QTY
Left shoulder width. The total usable shoulder width (measured in feet) on
the left side of the road determined in the direction of the inventory. For
curbed sections, no value is presented.
SHLDR_WID_RGT_QTY
Right shoulder width. The total usable shoulder width (measured in feet) on
the right side of the road determined in the direction of the inventory. For
curbed sections, no value is presented.
SRFC_WID
Surface width. This attribute contains the paved surface width (measured in
feet) or from ditch to ditch on unpaved roads. This width may be for one
direction of travel or the total for both directions depending on the road
type and method of inventory. For multi -lane undivided highways with turn
lanes or mountable medians, the edge -to -edge or face-to-face width is
presented.
MDN_WID
Median width. The total median width (measured in feet) for divided
roadways. Median width includes the area from inside the edge of the
surface pavement to inside the edge of adjacent surface pavement.
Includes paved or unpaved median (inside) shoulder widths.
MDN_TYP_CD
Median type. Median type categories are as follows: Rigid Positive Barrier =
"1", Continuous Turn Lane = "2", Paved Mountable = "3", Curb = "4", Grass
_ "5", Unspecified Positive Barrier = "6", Parkland, Business, etc. _ "7",
Couplet = "8", and Flexible Positive Barrier = "9".
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E74 �Attributes
added by URS to calculate ROW and impervious area widths
AttributeTable
Description
BUFFER —LEFT
NCDOT-owned area (measured in feet) left of the road centerline.
BUFFER —RIGHT
NCDOT-owned area (measured in feet) right of the road centerline.
ROW —EST
Estimate of total NCDOT ROW width (measured in feet) calculated for a
given road segment.
BUFF_DIST
Estimate of NCDOT impervious road width (measured in feet) calculated for
a given road segment.
Table E-5 provides a description of datasets associated with this project. Metadata for the ROW and
impervious cover datasets were prepared using Federal Geographic Data Committee (FGDC) standards
and NCDOT guidelines (NCDOT, 2010).
Table E-5. Description of GIS clatasets associated with this report
GIS Dataset Name�-
NCDOT—Interim—ROW
NCDOT interim development ROW area in the Falls Lake watershed.
This dataset includes the roadway and any area adjacent to the
roadway that is under the ownership of NCDOT (e.g., median,
shoulders, and adjacent vegetated and non -vegetated corridors)
that were added during the interim period.
NCDOT_Interim_lmpervious
NCDOT interim development impervious area in the Falls Lake
watershed. This dataset includes paved road and shoulder surfaces
associated with NCDOT roads that were added during the interim
period.
NCDOT_Durham_CMY_Pre
Land cover type estimates for the pre -development condition at the
Durham CMY facility, Durham traffic services building.
NCDOT_Durham_CMY_Post
Land cover type estimates for the post -development condition at
the Durham CMY facility, Durham traffic services building.
E-2.1.2 Quality Assurance and Quality Control
The procedures used to develop the ROW and impervious area datasets required GIS technicians to
perform data processing and manipulation. Quality assurance and quality control (QA/QC) procedures
were used to aid in achieving the level of accuracy needed for this analysis. Because the ROW and
impervious surface area datasets were created using different methodologies, the QA/QC process
(described in Sections E-2.1.3 and E-2.1.4) for each dataset is specific to that dataset. After completion
of the draft NCDOT ROW and impervious datasets, a final review of each dataset was conducted by a
technician independent of the project.
E-2.1.3 Method to Develop the Interim Development ROW Dataset
NCDOT's fourth quarter 2012 NCDOT road centerline dataset was initially used to identify and
characterize where changes to the NCDOT road network had occurred in the Falls Lake watershed
during the interim period. During the course of this project, NCDOT released an updated road dataset
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(first quarter 2013) and URS evaluated this dataset to identify and incorporate any additional interim
period development that had been added since the fourth quarter 2012 release. This assessment
resulted in the addition of three secondary roads to the interim road dataset.
To identify changes in NCDOT road development that occurred during the interim period, the current
road centerline dataset (fourth quarter 2012 release, augmented by first quarter 2013 release) was first
clipped using the Falls Lake watershed boundary to isolate the area of interest. A visual comparison of
this dataset to the WARMF landuse polygon dataset (titled "falls_nlcd2001") was used to identify road
centerline segments present in the current (2013) road centerline datasets that were not present in the
"falls_nlcd2001." These new road centerlines were selected and exported as a new feature dataset
(referred to as "NCDOT interim period polyline dataset" in this report). This new feature dataset
included NCDOT development that occurred during the interim period through first quarter 2013
release of NCDOT's road centerline dataset and was used as the basis for preparing NCDOT interim
impervious and ROW areas. Attributes listed in Table E-3. GIS attributes used to calculate ROW and
impervious widths were added to this dataset. The ROW width (ROW_EST) calculation was dependent
on available data and road type. In previous NCDOT ROW evaluations, a separate methodology was used
to estimate ROW area for interstates (NCDENR, 2009; NCDOT, 2009; NCDOT, 2012d). For this analysis,
no interstates were added during the interim period, thus a separate analysis of interstate ROW was
unnecessary. The following formulas were used to calculate ROW_EST for US highway, NC highway,
secondary route (SR), and ramp road types:
I. If a value for RW_WID was available, then ROW_EST = RW_WID.
II. If a value for RW_WID was not available and SRFC_WID > 0 and MDN_WID <= 100, then
ROW EST = SRFC WID + MDN WID + SHLDR WID LFT QTY + SHLDR WID RGT QTY.
III. If a value for RW WID was not available and SRFC WID > 0 and either MDN WID > 100 or
MDN_TYP_CD < 3, then ROW_EST = SRFC_WID + SHLDR_WID_LFT_QTY +
SHLDR WID RGT QTY.
IV. If a value for RW_WID was not available, SRFC_WID = 0, and the road type was a ramp, then
ROW EST = 24.
V. If a value for RW_WID was not available, SRFC_WID = 0, and the road type was not a ramp, then
ROW_EST was populated based on the ROW_EST of adjacent or connecting road segments.
Using the calculated ROW_EST for each US, NC, SR and ramp centerline, a new ROW polygon dataset
was developed using left and right buffers and the following formulas:
• BUFFER —LEFT = ROW_EST/2
• BUFFER_RIGHT= ROW_EST/2
Next, 2010 aerial imagery was used to manually correct the ROW polygon dataset to resolve areas
where the ROW did not properly align with aerial imagery. During this step, GIS technicians identified
missing or incomplete polygons, gaps, slivers, islands, or incorrect polygons. Once identified, improper
geometry was updated and edited to properly represent NCDOT ROW for interim NCDOT development
in the Falls Lake watershed. These techniques did not require that ROW polygons line up precisely with
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ROW as indicated by aerial orthophotographs. Rather, the purpose of this exercise was to identify and
fix significant errors that could lead to the mischaracterization of ROW areas.
An Esri Topology was created to locate and fix any missing or incomplete polygons. The "Must Have No
Gaps" topology rule was chosen to eliminate voids or gaps of a specific size between polygons. The
specific size of the gaps, known as the tolerance, can be set within ArcGIS. For this project, the tolerance
was set to a distance of 1 foot. When the Topology Tool was utilized, gaps or slivers less than 1 foot
were automatically closed. Gaps or slivers greater than 1 foot were flagged for manual editing. Figure E-
1 displays a typical example of a gap or missing polygon. In the case of gaps that were greater than 1
foot, GIS technicians manually edited and merged the polygons to represent a continuous ROW surface.
Topology validation was rerun to confirm that the updated geometry did not contain gaps.
GAP
Figure E-2 illustrates an example of "islands," or areas of empty space surrounded by other ROW
polygons. Islands were typically encountered along major interstates, highways, and other divided roads
that featured two centerlines; one for each direction of traffic. These areas are part of the NCDOT ROW
even if they are farther from the centerline than indicated by the initial buffer attributes. GIS technicians
drew new polygons encompassing the "islands," then reran the topology validation to confirm that the
updated geometry did not contain gaps.
Islands
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E-2.1.4 Method to Develop the Interim Development Impervious Area Dataset
The impervious cover dataset was developed by first calculating the "BUFF_DIST" attribute for each road
segment in the NCDOT interim period polyline dataset. This polyline dataset was based on the first
quarter 2013 release of NCDOT's road centerline dataset and includes all roads that were added since
NCDOT's baseline ROW dataset that was used to support the WARMF watershed model). For US
highway, NC highway, SR, and ramp road types, "BUFF—DIST" was calculated as "SRFC—WID" divided by
2. For ramps with a "SRFC—WID" value of 0, the "BUFF—DIST" was set to a standard width of 24 feet. For
all road types except ramps, if SRFC_WID = 0, then "SRFC_WID" was populated based on adjacent or
connecting roads with a "SRFC—WID" value greater than "0." As previously described, no interstates
were added to the NCDOT road system during the interim period.
A polygon dataset representing NCDOT impervious area was generated by buffering the NCDOT interim
period polyline dataset using the BUFF —DIST attribute field. Next, the polygon dataset was manually
edited using 2010 aerial imagery to resolve cases where (1) the impervious area did not align with aerial
imagery, (2) there were missing pieces of the impervious area at intersections, or (3) there were slivers
of impervious area that were not included in the buffer. The techniques used did not require that
impervious area polygons line up perfectly with impervious surfaces shown by aerial orthophotographs.
Rather, these steps were taken to validate that estimates were a reasonable representation of
impervious surface for that feature area. This exercise allowed URS to identify and manually correct
errors that may have occurred using the automated procedures.
During the editing process, GIS technicians visually compared the calculated impervious surface
polygons to aerial orthophotographs to verify that the calculated area provided a relatively good
representation of the image provided in the aerial orthophotographs. A scale of 1:1,000-1:1,500 (scale
reciprocal) was used for this process. This process allowed for observance and correction of data
anomalies or errors. Anomalies were most often due to incorrect and/or inaccurate road centerline data
that were likely due to the relative age of the aerial photographs used to develop the original NCDOT
road centerline data. In instances where the buffer did not accurately represent the impervious surface
shown on the aerial photographs, the buffer was modified. In some instances where the buffer varied 4
feet or more from the actual impervious surface, the buffer was deleted, and the centerline was
rebuffered using a distance measured on the aerial orthophotograph by the GIS technician. Examples of
the editing process are shown in Figure E-3, Figure E-4 and Figure E-5.
When intersections were encountered, GIS technicians drew new polygons to represent the sections of
impervious surface that existed in the turn lane areas of the roads (Figure E-3).
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In some cases, attribute data used to develop the impervious dataset was inaccurate and thus led to
errors in the resulting impervious surface area (Figure E-4). In this instance, the width of the impervious
area buffer was overestimated when compared to the aerial orthophotograph (left). The image on the
right shows the corrected impervious area.
Occasionally, the road centerline was slightly misaligned when compared to the aerial
orthophotographs. In these cases, if the impervious surface polygon properly represented the total area
covered by the road, no edits were made (Figure E-5).
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E-2.1.5 Post -Processing of ROW and Impervious Area Datasets
A series of post -processing steps were performed to correct areas of overlap (double counting of road
areas) within the ROW and impervious datasets. Processing steps included the following:
1. In cases where roads of different classification intersect, the ROW or impervious area associated
with the intersected road was assigned to the roadway of higher priority. For this process, the
following priority ranking was used: Interstate (highest class) > US highway > NC highway > SR >
ramps (lowest class). To perform this step, both the ROW and impervious datasets were first
converted to separate datasets based on road type. This process involved using the "Select by
Location" ArcGIS feature, yielding one new dataset for each road type for both the ROW and
impervious datasets. Using the road hierarchy for each road dataset, the "erase" procedure was
applied on both the ROW and impervious datasets. This was accomplished by using an "erase"
command to extract the intersected pieces of NCDOT ROW or impervious area for lower class
road types and to prevent double counting of NCDOT ROW and impervious areas.
2. The "dissolve" procedure was performed for each individual road type (US highway, NC
highway, SR, and ramp) for each dataset.
3. The impervious dataset was merged with the ROW dataset to create the final ROW dataset. This
step was performed so that the ROW included all impervious area.
4. Using the baseline NCDOT ROW dataset, the "erase" procedure was applied to both ROW and
impervious cover datasets to remove any interim development ROW or impervious area that
overlapped with the baseline NCDOT area dataset.
S. Each dataset was clipped to the Falls Lake watershed boundary to remove any buffer area
outside the watershed boundary.
6. Impervious and ROW areas associated with each road type were calculated.
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E-2.1.6 Interim Road Development Results
Results of the interim road GIS analysis are presented in Table E-6. Of the 466 acres of interim
development ROW area, approximately 98% of the development area (456 acres) was associated with
secondary routes while 2% (10 acres) was associated with primary routes. The primary route interim
development area included one NC Highway 10-acre project (shown in Figure E-6).
Table E-6. NCDOT impervious and ROW
interim development
areas in the Falls
Lake
watershed
NCDOT NCDOT
Impervious Area
Pervious ROW
Entire ROW Area
Road Category Road Type
(Acres)
Area (Acres)
(Acres)
Interstate
I
Primary Routes
NC Highway
Secondary Roads
Secondary Routes
Ra
Note: All values presented in this table are based on a conversion of ArcGIS results (in square feet) to acreage and
the use of Gaussian rounding (also known as "banker's rounding') to arrive at values rounded to the nearest acre.
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E-2.2 Interim NCDOT Non -Road Development
As described in Section E-2.0, development changes during the interim period occurred at one NCDOT
non -road facility, the Durham CMY (3910 Guess Road, Durham, NC 27705). At the time of this analysis,
construction on a new traffic services building was underway, but not complete.
E-2.2.1 Data Sources
Datasets that were used to support the non -road development analysis are presented in Table E-7.
Aerial orthophotography was used as a visual aid to generate the pre -development land cover dataset.
At the time of this project, the construction of the Durham traffic services building on the Durham CMY
was in progress. Site plan drawings were used to estimate land cover areas associated with the
anticipated post -development condition.
E-2.2.2 Method to Develop the Interim Development Land Cover Dataset
To identify changes in development at the Durham CMY, URS technicians evaluated a series of aerial
imagery datasets for the traffic services building area of disturbance. Imagery collected in March 2006
was used as the primary source for characterizing the pre -development condition. Using ArcGIS,
technicians created polygons for each land cover in the project disturbance area and assigned each
polygon to a land cover category in NCDOT-JLSLAT. The pre -development condition included several
small buildings, parking lots, sidewalks, pervious, uncovered material storage, and open space areas. The
pre -development condition did not include any known structural stormwater controls. URS contacted
NCDOT Division staff to obtain a plan drawing for the anticipated traffic services building and used this
information to estimate the post -development condition. Similar to the pre -development condition
analysis, technicians evaluated the site drawings, prepared a land cover polygon dataset and area
estimates for the post -development condition using ArcGIS. Based on the post -development site plan,
the project area will include two buildings, parking lots, open space, and an extended wetland detention
basin. The extended wetland detention basin receives all of the runoff from the project area as shown in
the project design plans.
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JANUARY 2014
E-2.2.3 Interim Road Development Results
Tabulated results of the land cover types and associated areas (square feet) are presented in Table E-8.
Aerial imagery and land cover representation are shown in Figure E-7 and Figure E-8 for the pre -
development condition and post -development condition, respectively.
PAGE E-16

JANUARY 2014
P rvious Storag Roof
Open Space Parking Lot
Pervious Storage `
r ti
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JANUARY 2014
.. .... ......... .... .. . . ..... .
- - - - - - - ---
sToRAr.E,
limp
TM Bgc -mum-. gg D-
ILL,
- - - - - - - - - - - - - - - -
Open Space
PAGE E-18

JANUARY 2014
E-3.0 Interim Load Analysis
Changes in nutrient loading associated with NCDOT road development during the interim period were
calculated by first estimating changes to NCDOT's road system in the Falls Lake watershed (Section E-2.1
of this report) and then calculating the pre- and post -development load associated with those areas.
Pre -development TN and TP loading conditions were calculated using uniform loading rates of 2.89
pounds/acre/year for TN and 0.63 pounds/acre/year for TP as described in 15A NCAC 02B .0281 (5)(a).
Post -development nutrient loads from roads were calculated using NCDOT-JLSLAT and primary road
edge -of -pavement, secondary road edge -of -pavement, and open space (unfertilized) areas defined
through the ArcGIS analysis (Section E-2.1 of this report). Inputs used to calculate changes in nutrient
loads associated with interim primary and secondary road development are shown in Table E-9 and
Table E-10, respectively. NCDOT-JLSLAT results for primary and secondary interim road analyses are
shown in Table E-11.
Physiographic/Geologic Region Piedmont
Soil Hydrologic Group D1
Precipitation location Butner
Total Development Area (ft2) 420,641
Transportation - Primary road EOP 169,083
Pervious - Open space (unfertilized) 251,558
rl Ujt LA [II Cd NVII lye tJ _l lilt, UUC vvND , VVNI. [IIIU ul CII IU CIIC yl ll l lCllI y 1.1 ldl CI.Un ILCU uy L M U Null IlyUI ul uslt,
group (USDA, 2013).
Physiographic/Geologic Region
Soil Hydrologic Group
Precipitation location
Total Development Area (ftz)
Transportation - Secondary road EOP
Pervious - Open space (unfertilized)
Piedmont
D1
Butner
19,866,227
7,615,998
12,250,229
rruJeu cried Nuii LyNeN niuuue vvND , vvN1. diiu ur dnu die Nnrndniy uididuenceu uy uie v Null nyuiviugiL
group (USDA, 2013).
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JANUARY 2014
Non -road NCDOT interim development nutrient loading changes were calculated using results of the
ArcGIS exercise described in Section E-2.2 and NCDOT-JLSLAT. For this analysis, pre -development and
post -development loads were calculated using inputs presented in Table E-12. NCDOT-JLSLAT results for
the interim non -road analysis are presented in Table E-13.
Table E-12. NCDOT-JLSLAT inputs used to calculate
nutrient loading changes
associated with
NCDOT interim non -road development
for both pre -development
and
post -
development conditions at the Durham
rMCIDOT-JLSLAT
CMY (traffic services
building)
Land Use/Cover Category
NCDOT-JLSLAT
Input
Physiographic/Geologic Region
Piedmont
Soil Hydrologic• •
Di
Precipitation • •
Total Development Area (ft)
164,861
NCDOT-JLSLAT Land Use/Cover Category
Pre -development
(ft')
Post
-development (ft)
�. •
1162,431
18,642
Pervious,• -• storage
Transportation
• -
a- o
Open space (unfertilized)
Areas • by BMPsNor—
Post- evelopment areas treated by a stormwater
wetland at t e Durham
CMY
Post -development
area (ft)
treated by a
NCDOT-JLSLAT Land Use/Cover Category
Stormwater
Wetland
TransportationOpen
-
space (unfertilized)
Project area soil types include "WsB", "WsC" and "Ur" and are primarily characterized by the "D" soil hydrologic
group (USDA, 2013).
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JANUARY 2014
Resulting interim development TN and TP loads (pounds/year) for pre- and post -development
conditions are presented in Table E-14. Net TN and TP interim development loads, represent the change
in NCDOT loads during the interim period and are calculated by subtracting the pre -development loads
from the post -development loads. As shown in Table E-14, NCDOT interim development resulted in a
net decline in both TN and TP. TN loads declined by 114 pounds/year while TP load declined by 79
pounds/year.
WE
0 a -
Secondary Roa
Non -Road
All NCDOT
Interim Period Nutrient Loading
Development
Development
Development Area (acres)
10
456
4
470
Total Nitrogen
Pre -development Load (Ibs/yr)
28
1,318
22
1,368
Post -development Load (Ibs/yr)
61
1,174
19
1,254
Net Interim Development Load (Ibs/yr)
33
(144)
(3)
(114)
Total Phosphorus
Pre -development Load (Ibs/yr)
6
287
6
299
Post -development Load (Ibs/yr)
4
214
2
220
Net Interim Development Load (Ibs/yr)
(2)
(73)
(4)
(79)
Ibs/yr = pounds per year
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JANUARY 2014
E-4.0 Data Limitations, Constraints, and Assumptions
NCDOT does not maintain a single statewide spatial database of its impervious cover or ROW property
boundaries. As a result, the datasets described in this report were prepared using a methodology
expressly developed to support the Falls Lake interim development analysis. The procedures and
assumptions employed in the methodology represent a balance between managing the cost of
preparing the datasets and the relative accuracy needed to support the intended modeling purpose and
use of the information. The methodology employs simplifying assumptions, such as 'the ROW boundary
generally runs parallel to the road centerline'. This assumption is generally an accurate one, but in
reality, at any given location, the true ROW boundary may be skewed relative to the road centerline.
Additionally, the methodology did not provide for the realignment of road centerlines when it was
observed that these centerlines did not perfectly correspond with roads depicted in the aerial
orthophotography. However, if a considerable discrepancy was encountered, GIS technical professionals
used guidance from NCDOT and aerial orthophotography to modify the ROW and impervious area
polygons using best professional judgment. With these considerations in mind, NCDOT and URS
recommend that the use of these datasets be limited to the intended purposes described in this
document. These datasets should not be used for delineating actual property boundaries. NCDOT and
URS make no warranty, expressed or implied, regarding the accuracy or completeness of these datasets.
PAGE E-22