08_NCS000250_NCDOT_Outfall ID Guidelines

Highway
Stormwater
Outfall Identification Guidelines
Prepared by:
Dewberry Engineers Inc.
2301 Rexwoods Dr
Suite 200
Raleigh, NC 27607
919.881.9939
NC License No.: F-0929
Prepared for:
NC Department of Transportation
Hydraulics Unit
1590 Mail Service Center
Raleigh, NC 27699-1590
919.707.6700
[e-mail]
March 2014
ti1111+• + r
•� 5E L `1
24

Highway
Stormwater
HeeGRAY
NOTICE OF PROPRIETARY INFORMATION
All rights reserved to
Dewberry Engineers Inc.
This document was designed, prepared, and submitted by Dewberry Engineers Inc. to
be used by the North Carolina Department of Transportation Highway Stormwater
Program and their authorized representatives.
None of this material is permitted to be reproduced in any way or distributed to anyone
other than authorized representatives of the recipient.

Highway
Stormwater
Contents
List of Common Acronyms, Terms, and Abbreviations.................................................................................. i
Definitions of Referenced Terms..................................................................................................................
ii
I. Outfall Identification Guidelines......................................................................................................
1
A. Field Crew Training......................................................................................................................
1
B. Preliminary Identification of Potential Outfall Locations
............................................................ 2
C. Extreme Weather Conditions......................................................................................................
5
D. Field Identification of Streams....................................................................................................
6
E. Field Identification of Outfalls......................................................................................................
8
F. Ten Foot Rule...............................................................................................................................
9
G. ROW Identification....................................................................................................................
11

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Highway
Stormwater
Outfall Identification Guidelines
List of Common Acronvms, Terms, and Abbreviations
DWQ— Department of Water Quality
ESRI — Environmental Systems Research Institute
FIP — Field Inventory Program
GIS —Geographic Information System
GPS —Global Positioning System
IP — Inventory Program
MS4— Municipal Separate Storm Sewer System
NCDENR — North Carolina Department of Environment and Natural Resources
NCDOT — North Carolina Department of Transportation
NCFMP — North Carolina Floodplain Mapping Program
NPDES— National Pollutant Discharge Elimination System
NRCS— Natural Resource Conservation Service
POTW — Publicly Owned Treatment Works
ROW — Right of Way
SR — State Route
TS4 — Transportation Separate Storm Sewer System
USGS — United States Geological Survey
WOS — Waters of the State
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Stori—aw Outfall Identification Guidelines
Definitions of Referenced Terms
Channel — a natural water -carrying trough cut vertically into low areas of the land surface by erosive action of
concentrated flowing water or a ditch or canal excavated for the flow of water [15A NCAC 02B .0233(2)(a)].
Ditch or canal — a man-made channel other than a modified natural stream constructed for drainage purposes that
is typically dug through inter -stream divide areas. A ditch or canal may have flows that are perennial, intermittent,
or ephemeral and may exhibit hydrological and biological characteristics similar to perennial or intermittent
streams [15A NCAC 02B .0233(2)(c)].
Ephemeral Streams — a feature that only carries stormwater in direct response to precipitation with water flowing
only during and shortly after large precipitation events. An ephemeral stream may or may not have a well-defined
channel, the aquatic bed is always above the water table, and stormwater runoff is the primary source of water.
An ephemeral stream typically lacks the biological, hydrological, and physical characteristics commonly associated
with the continuous or intermittent conveyance of water [15A NCAC 02B .0233(2)(d)]. Ephemeral streams are not
considered waters of the State (WOS).
Geodatabase — a geodatabase contains features where attribute data is stored and organized spatially.
Intermittent Streams — a well-defined channel that contains water for only part of the year, typically during winter
and spring when the aquatic bed is below the water table. The flow may be heavily supplemented by stormwater
runoff. An intermittent stream often lacks the biological and hydrological characteristics commonly associated with
the conveyance of water [15A NCAC 02B .0233(2)(g)].
Modified Natural Stream — an on -site channelization or relocation of a stream channel and subsequent relocation
of the intermittent or perennial flow as evidenced by topographic alterations in the immediate watershed. A
modified natural stream must have the typical biological, hydrological, and physical characteristics commonly
associated with the continuous conveyance of water [15A NCAC 02B .0233(2)(h)].
Municipal Separate Storm Sewer System (MS4) — MS4s have the main purpose of conveying stormwater associated
with road drainage systems, municipal streets, catch basins, curbs, gutters, ditches, man-made channels or storm
drains. MS4s may be owned or operated by any municipality, State or Federal agency and discharge directly to
waters of the State (WOS) (40 CFR 122.26(b)(8)).
National Pollution Discharge Elimination System (NPDES) — an EPA program authorized under Section 402 of the
Clean Water Act regulating pollutant discharges from point sources to waters of the United States.
Natural Resource Conservation Service (NRCS) — a division of the United States Department of Agriculture (USDA)
responsible for providing conservation planning and assistance in relation to soil, air, and water quality.
Outfall — a point source at the point where the TS4 discharges to waters of the State (WOS) and does not include
open conveyances connecting two MS4's pipes, tunnels, or other conveyances which connect segments of the
same stream or other WOS and are used to convey WOS (40 CFR 122.26 (b)(9)).
Perennial Stream — a well-defined channel that contains water year round during a year of normal rainfall with the
aquatic bed located below the water table for most of the year. Groundwater is the primary source of water for a
perennial stream, but it also carries stormwater runoff. A perennial stream exhibits the typical biological,
hydrological, and physical characteristics commonly associated with the continuous conveyance of water [15A
NCAC 02B .0233(2)(i)].
Pipe 10 — the feature description used to indicate pipe inlet or outlet locations.
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Publicly Owned Treatment Works (POTW) —These treatment works are owned by a state or municipality and
includes any devices that are used to store, treat, recycle, and reclaim municipal sewage or industrial wastes. This
definition also includes conveyance measures such as pipes and sewers.
Right of Way (ROW) — a strip of land granted for a transportation facility. In the context of this manual ROW refers
to land owned by NCDOT that is used for the construction and operation of vehicular transportation and is part of
the State NC Highway System.
Stream — a body of concentrated flowing water in a natural low area or natural channel on the land surface [15A
NCAC 02B .0233(2)(k)].
"Ten Foot Rule" — a method used to determine whether to include a natural stream, channel or swale segment in
the FIP. If a pipe ends within 10' of the top of bank of waters of the State (WOS), the outfall shall be located at the
end of the pipe. If the pipe is less than 10' from the top of bank the outfall is located at the end of the channel at
the confluence with the WOS.
Transportation Separate Storm Sewer System (TS4) — a TS4 is a type of MS4 that collects and conveys stormwater
in a linear manner from roads with drainage systems, municipal streets, catch basins, curbs, gutters, ditches, man-
made channels or storm drains. These systems are owned or operated by the State, city, town, borough, county,
parish, district, association, or other public body having jurisdiction over disposal of sewage, stormwater, or other
wastes. These are not combined sewers and are not part of a Publicly Owned Treatment Works (POTW) (40 CFR
122.2).
TruPulse Laser — a type of laser rangefinder used to measure the distance to another object.
Waters of the United States (WOS) - For purposes of the Clean Water Act, "Waters of the United States" means (a)
All waters which are currently used, were used in the past, or may be susceptible to use in interstate or foreign
commerce, including all waters which are subject to the ebb and flow of the tide; (b) All interstate waters,
including interstate "wetlands"; (c) All other waters such as interstate lakes, rivers, streams (including intermittent
streams), mudflats, sandflats, wetlands, sloughs, prairie potholes, wet meadows, playa lakes, or natural ponds the
use, degradation, or destruction of which would affect or could affect interstate or foreign commerce including any
such waters: (1) Which are or could be used by interstate or foreign travelers for recreational or other purposes;
(2) From which fish or shellfish are or could be taken and sold in interstate or foreign commerce; or (3) Which are
used or could be used for industrial purposes by industries in interstate commerce; (d) All impoundments of
waters otherwise defined as waters of the United States under this definition; (e) Tributaries of waters identified in
paragraphs (a) through (d) of this definition; (f) The territorial sea; and (g) Wetlands adjacent to waters (other than
waters that are themselves wetlands) identified in paragraphs (a) through (f) of this definition (40 CFR 122.2).
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stormwater, Outfall Identification Guidelines
Outfall Identification Guidelines
NCDOT is currently operating under permit number NCS000250 re -issued by the State of North Carolina,
Department of Environment and Natural Resources, Division of Water Quality on September 10, 2010. Under this
permit, NCDOT operates a Transportation Separate Storm Sewer System (TS4). The TS4, a type of municipal
separate storm sewer system (MS4), is a conveyance or system of conveyances (including roads with drainage
systems, municipal streets, catch basins, curbs, gutters, ditches, man-made channels, or storm drains): (i) Owned
or operated by a State, city, town, borough, county, parish, district, association, or other public body (created by or
pursuant to State law) having jurisdiction over disposal of sewage, industrial wastes, storm water, or other
wastes...; (ii) Designed or used for collecting or conveying storm water in a linear environment and applicable non -
roadway and industrial facilities. (iii) Which is not a combined sewer; and (iv) Which is not part of a Publicly Owned
Treatment Works (POTW) as defined by 40 CFR 122.2.
Under Part II Section B (Post -Construction Controls) the permit defines the measures required to inventory the
stormwater system and develop a prioritization program. Objectives listed in this section include:
Management Measure
Measurable Goals
(a)
Maintain a stormwater system inventory
NCDOT will maintain a GIS-based implicit
of existing stormwater outfalls to
stormwater outfall inventory to include outfalls
sensitive waters.
from primary and secondary roadways.
The inventory shall be used to assist in the
location of retrofits, among other purposes.
(b)
Include in the inventory outfalls from new
The stormwater outfall inventory shall be
construction projects to all surface waters
updated annually to include outfalls from new
and wetlands.
construction projects.
(c)
Include outfalls for NCDOT industrial
The stormwater outfall inventory shall be
facilities in the inventory.
updated annually to include changes or
additions to previously inventoried NCDOT
industrial facilities.
(d)
Field outfall inventory procedure for
NCDOT will maintain the field outfall inventory
priority areas.
procedure, work with DWQ to identify priority
areas and report annually on priority areas.
According to North Carolina's G.S. 143-212(6), waters of the United States (or waters of the State within North
Carolina) is any stream, river, brook, swamp, lake, sound, tidal estuary, bay, creek, reservoir, waterway, or other
body or accumulation of water, whether surface or underground, public or private, or natural or artificial, that is
contained in, flows through, or borders upon any portion of North Carolina, including any portion of the Atlantic
Ocean.
In an effort to comply with these NPDES requirements NCDOT has developed the Field Inventory Program (FIP).
The FIP is a program specifically developed to collect and store the location and attributes of the stormwater
systems noted above.
A. Field Crew Training
Prior to beginning FIP activities, a training session is held for all field crew members. This training includes an
office review of data collection procedures and expectations, as well as hands-on field experience applying the
procedures using the data collection software. Discussions at the training session should focus on the guiding
principles of the FIP which include the importance of field safety, review of accuracy standards and techniques for
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Outfall Identification Guidelines
data collection, and an emphasis on consistency and efficiency during the data collection effort. Training resources
can be found in the FIP Procedures Manual and the Field Guide.
B. Preliminary Identification of Potential Outfall Locations
The term "outfall" means a point source at the point where the TS4 discharges to waters of the State (WOS) and
does not include open conveyances connecting to the MS4's, or pipes, tunnels or other conveyances which
connect segments of the same stream or other WOS and are used to convey WOS (40 CFR 122.26 (b)(9)).
Outtalls
Within the FIP there are various levels of data collection that are described in detail in the FIP Procedures Manual.
The FIP includes 3 ways for stormwater to leave the NCDOT Right -of -Way (ROW):
Tier la Outfall
• The end point of a pipe or channel discharging to WOS inside the NCDOT ROW
Tier lb ROW Discharge Point (not an outfall)
• The end point of a pipe or channel discharging out of the ROW before entering WOS
Tier Ic Outfall
• The end point of a pipe or channel discharging to WOS outside the ROW and conveying runoff from an
NCDOT ROW
Examples of each of these types of discharge points are on the following pages.
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Stormwater
Outfall Identification Guidelines
0 Existing Ditch
— — Culve FUBndge
1 — Waters of the state
Existing ROW
Outfall
Junctionflnlet
Pipe
Road Suface
1 i
i
i
i
11'IJti7
Type 1 a Outfall
IN Existing Ditch
CulverUBridge
i
Waters of the State
--- Existing RDA!
i
ROW Discharge Point
- Junctionllnlet
i
Pipe
Road Surface
i
i
i
i
..............
i
1 i
i
Type 1 b ROW Discharge
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Outfall Identification Guidelines
Type 1 c Outfall
IN Existing Ditch
CulverBndge
Waters of the State
i
- Existing ROW
Outfall
i
i
- Junction/Inlet
i
Pipe
i
i
i
i
r
i
.r
i
i
i
i
i
i
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11- Outfall Identification Guidelines
Initially, an area map of the potential outfall locations is prepared. An ESRI geodatabase is developed and
populated with the boundary of the proposed work area and known blue line streams. Sources may include 24K
NCDENR GIS layer, USGS and NCFMP stream data. These stream layers are then combined with the NCDOT primary
and secondary roadway layers (US, NC & SR designated routes) labeled with SR# and local road names. If
available, a recent aerial and municipal stormwater inventory data can also be added to the work map.
From this initial data a reference map book is created for use by field crews (See figure 1). This can be a series of
physical hard copy maps or digital maps made available as a base map layer on the data collector. The overall
intent of the above effort is to do as much preparatory work in the office as possible to reduce field time spent
searching for streams and outfalls. For this training example designation letters have been added for the types of
discharge points are likely to be found at each location. The field crew should review the map book to become
familiar with local land marks and be able to easily identify the limits of the work area before proceeding to the
field. An excerpt from the Little Alamance Creek Map Book is provided below. The yellow line indicates the basin
boundary and purple lines are the Burlington stormwater inventory.
Stormwater Paints
other values
Feature Type
•
• Other
■ Curb Inlet MH
Z, Curb Inlet Slab Top
• MH
Endwall
Headwall
Flared End
R Frame R Grate
R Grate Inlet
0 Junction Box
Pipe End
+ Yard Inlet
Stormwater Pipe
LittleAlamance Watershed
1. Example Map Book
When working with a new field crew it is important to review the first day's collection with IP Manager or Survey
Manager. If possible, one or both of these personnel should schedule a few hours to meet the field crew on site
and review the data collected, affirm procedures and practices and address any questions that have arisen. This
process can avoid revisits and help ensure meeting the project schedule.
C. Extreme Weather Conditions
During the collection of FIP data some judgment may be needed when dealing with various weather conditions.
Typically a minimum wait time of 48 hours after any rainfall event that creates runoff is recommended. During or
immediately following extreme weather conditions such as drought or flood, inventory field work should be
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completely avoided until the effects of extreme weather conditions have subsided. If that is not feasible, then the
IP Manager should provide guidance to the field crew on use of appropriate judgment for the unique climactic
conditions present when identifying streams and outfalls. Examples of guidance may include:
1. In drought conditions identification of WOS may be based primarily on indication of WOS in the map book
and application of other indicators noted below as a secondary verification.
2. In flood conditions the limits of WOS may not be readily identifiable in the field. In this case a similar
reliance on the map book as the primary indicator of WOS may be appropriate while ignoring ephemeral
streams and shallow depressions that have flowing or standing water present.
D. Field Identification of Streams
Identification of streams, and correspondingly WOS, is an involved process based on a detailed evaluation of a
multitude of factors along multiple segments of a given water course. NCDENR DWQ has a detailed course for
stream identification which is available at various times throughout the year. This process requires much more
time than is typically allowed in an FIP assignment. However, some level of stream identification is a critical skill set
for field crews to know. Therefore, we have summarized and simplified the NCDENR DWQ stream identification
process to allow preliminary identification by field crews that can be followed by experienced personnel as
needed. The field crew's first source for stream identification should be the indication of a stream in the Map
Book described above. If a water course is indicated in the Map Book and not found in the field after 5 minutes of
investigation then the crew should move on to the next potential outfall location. If a water course is encountered
in the field that is not included in the Map Book then additional judgment will be required to determine if this
water course should be considered in the inventory.
Types of Water Courses - The "Methodology for Identification of Intermittent and Perennial Streams and Their
Origins" 1 provides the following definitions for water courses that are of interest in the NCDOT FIP.
1. 'Stream' means a body of concentrated flowing water in a natural low area or natural channel on the
land surface. [15A NCAC 02B .0233(2)(k)]
2. 'Channel' means a natural water -carrying trough cut vertically into low areas of the land surface by
erosive action of concentrated flowing water or a ditch or canal excavated for the flow of water. [15A
NCAC 02B .0233(2)(a)]
3. 'Ditch or canal' means a man-made channel other than a modified natural stream constructed for
drainage purposes that is typically dug through inter -stream divide areas. A ditch or canal may have flows
that are perennial, intermittent, or ephemeral and may exhibit hydrological and biological characteristics
similar to perennial or intermittent streams. [15A NCAC 02B .0233(2)(c)]
4. 'Ephemeral (stormwater) stream' means a feature that carries only stormwater in direct response to
precipitation with water flowing only during and shortly after large precipitation events. An ephemeral
stream may or may not have a well-defined channel, the aquatic bed is always above the water table, and
stormwater runoff is the primary source of water. An ephemeral stream typically lacks the biological,
hydrological, and physical characteristics commonly associated with the continuous or intermittent
conveyance of water. [15A NCAC 02B .0233(2)(d)] — Note ephemeral streams are not considered WOS in
the NCDOT FIP.
'Intermittent stream' means a well-defined channel that contains water for only part of the year, typically
during winter and spring when the aquatic bed is below the water table. The flow may be heavily
supplemented by stormwater runoff. An intermittent stream often lacks the biological and hydrological
characteristics commonly associated with the conveyance of water. [15A NCAC 02B .0233(2)(g)]
'Modified natural stream' means an on -site channelization or relocation of a stream and subsequent
relocation of the intermittent or perennial flow as evidenced by topographic alterations in the immediate
watershed. A modified natural stream must have the typical biological, hydrological, and physical
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Store Outfall Identification Guidelines
characteristics commonly associated with the continuous conveyance of water. [15A NCAC 02B
.0233(2)(h)]
7. 'Perennial stream' means a well-defined channel that contains water year round during a year of normal
rainfall with the aquatic bed located below the water table for most of the year. Groundwater is the
primary source of water for a perennial stream, but it also carries stormwater runoff. A perennial stream
exhibits the typical biological, hydrological, and physical characteristics commonly associated with the
continuous conveyance of water. [15A NCAC 02B .0233(2)(i)]
The following are some practical indicators of perennial or intermittent streams for field crews to use that are
derived from the "Methodology for Identification of Intermittent and Perennial Streams and Their Origins". If after
evaluating these factors a stream designation still cannot be clearly made then treat the water course as a stream
to be conservative.
If one or more of the following are evident ... it's likely a stream
1. Water is flowing in the stream.
2. There is evidence of groundwater discharge into the channel or a groundwater table above the stream
flow is readily observable.
3. The stream has a well developed channel with continuous bed and bank geometry.
4. The stream has numerous bends and very few straight sections.
5. The stream has a frequent number of riffles (shallow fast running water) followed by pools (deep slow
moving water) along the entire reach.
6. The channel is well -developed with relatively coarse streambed sediments compared to riparian soils
(floodplain). Piedmont streambed sediments should include coarse sand, gravel, or cobbles; Mountain
streambed sediments should include gravel, cobbles, or boulders and Coastal plain streambed sediments
should include medium or coarse sand.
7. The floodplains are relatively flat with depositional areas adjacent to the streams composed of alluvial
material such as sand. An active floodplain abuts and parallels the stream and is a continuum of the
stream bank.
8. Depositional bars or benches are obvious along the stream bed.
9. Abundant iron oxidizing bacteria is observed.
10. Large drift lines are prevalent along the upstream side of obstructions within the channel and the
floodplain.
11. Fish, crayfish, amphibians or wetland plants are present.
If one or more of the following are evident ... it's likely not a stream
1. Abundant amount of leaf litter is present throughout the length of the stream. Greater than 80% of the
active channel is covered with leaves and the thalweg (flow line) substrate is not visible.
2. A strong network of fibrous roots is persistent in the stream thalweg (flow line) and surrounding area.
3. Rooted plants are observed and cover over 75% of the streambed.
Modified Natural Streams - In many parts of North Carolina it may be difficult to differentiate between a ditch or
canal and a natural stream that has been modified. In the office topographic maps and Natural Resource
Conservation Service (NRCS) county soils maps may help to identify these instances. Topographic lines may
indicate a natural valley in which a natural stream could be present. Parallel topographic contour crenulations (V-
shaped contour lines) with angles of 90 degrees or less can be indicative of the presence of a stream. Features
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located outside of a natural crenulation (i.e. moving across a slope rather than perpendicular to it) may not be
natural or, alternatively, may be a relocated stream. NRCS county soil survey maps often show the presence of
linear soil mapping units, which are indicative of alluvial deposits and the presence of a stream.
During field identification the crew will need to rely more on the identification of the stream characteristics noted
above that may co -exist in a typical ditch or canal environment. An example of this is shown below where a
natural stream enters a ditch within the ROW (figure 2).
t Existing Ditch
-- Existing ROW
Cu1verU9ndge
i
i
Outfall
...-.. Waters ofthe State
---- Stream
Road Surrace
i
i
i
i
i
i
Figure 2. Modified Natural Stream Outfalls
E. Field Identification of Outfalls
A field trip scenario should involve the following steps:
1. The field crew receives direction from the IP Manager about the Tier (la, lb or Ic) of inventory requested
by the customer.
2. The field crew reviews the reference map book for the Work Area.
3. The field crew drives to a location identified in the reference map book.
4. The field crew performs reconnaissance of the TS4 while tracing it to the discharge location to WOS.
5. The field crew locates the actual outfall and collecting the required attributes.
The FIP allows the field crew to collect attribute and network connectivity information while linked to a submeter
GPS unit. The attribute information is obtained and assessed through visual observations at each structure or
feature in accordance with the selected Tier of the inventory. In certain cases field conditions may be present that
inhibit the crews from actually occupying the outfall to document its location. The following are some example
procedures to guide crews in completing the inventory should they encounter these conditions:
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1. Connectivity that cannot be field verified is assumed based on field experience and engineering judgment.
If an outfall is suspected, but not readily visible, the crew will spend approximately 5 minutes looking for it
before attributing the location as "unverified" in the Geodatabase and moving on to the next location.
2. If tree cover is present at an outfall location that will degrade the GPS signal and corresponding location
accuracy to an unacceptable level (based on the observer's experience as well as the accuracy information
of the GPS signal shown in the data collector), that location will be measured using the offset commands
while the GPS unit is in a location that has a clear unobstructed view of the sky.
3. If an outfall cannot be physically occupied due to standing water, dangerous traffic conditions, etc., its
location will be captured using the offset command. The typical procedure for an offset location is to get
as close as safely possible with the GPS and utilize the TruPulse Laser or other acceptable measuring
method (conventional cloth tape and level) to obtain the offset distance and angle.
4. If stream bank erosion is present use additional caution in identifying this as an outfall. If an upstream
conveyance such as a ditch or modified stream leads to an erosion 'cut' in a stream bank then collect the
'cut' as an outfall. If unstable soil conditions near the 'cut' prevent occupying the physical location then
locate a nearby stable area and approximate the offset measurement to the outfall. If an upstream
conveyance is not evident then do not collect the erosion 'cut' as an outfall.
F. Ten Foot Rule
The "Ten Foot Rule" is a commonly used method for determining whether or not to include a natural stream,
channel or swale segment in the FIP. This can be applied in the following ways:
1. A pipe ending more than ten feet short of the top of bank of a WOS followed by a channel or ditch is
captured as a 'pipe 10' and channel with the outfall located at the end of the channel. Channel segments
shorter than 10' can be ignored. In this case the outfall would be located at the end of the pipe.
- Juncticn Bovinlei
Pipe
Outfall
-- Waters atthe State
---- Stream
Existing ROW
Road Surface
Outfall at Pipe End Channel
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Stormwaten
Outfall Identification Guidelines
Juncticn 6oxllnlet
Pipe
Outfm
..._ .= Waters atthe State
ii ---- Stream
- Existing ROW
Road Surtace
w ft
Outfall at Channel End
2. Deck drains (or scuppers that discharge directly from the deck) over land that do not discharge to a
defined conveyance are considered outfalls if they are within ten feet of WOS. Discharges of this type
occurring more than ten feet from WOS are not outfalls because they flow overland becoming sheet or
diffuse flow before reaching WOS.
Outfall — Open deck drains discharge
directly to stream
Not an Outfall — Closed drainage
discharges more than 10 feet from stream
Many unique field outfall conditions have been seen during previous pilot studies in the FIP. Some of these
include:
1. Outfall at bottom of catch basin or inlet (typical of catch basin on top of box culvert).
2. Continuous pipe crossing ROW would be ROW discharge point.
3. Pipe flowing to cross drain with no access should be hard placed as "assumed".
4. Bridge deck drains without collection pipe should be identified as outfall locating the most downstream
deck drain and noting the total number present.
5. Bridge deck drain with collector pipe should be located based on pipe outfall location when discharging to
WOS.
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6. A pipe ending short of WOS is a pipe 10 with a channel segment where the outfall is located at the end of
the channel. Channel segments shorter than 10' can be ignored making the end of the pipe the outfall.
7. Infiltration basins designed to retain stormwater do not have an outfall. Emergency overflow weirs are
not considered outfalls because they remain inactive during all but extreme events.
8. Underdrain outfalls are located at the end of pipe if entering WOS.
G. ROW Identification
NCDOT will provide right-of-way (ROW) data, where available, for use by field crews in determining the limits of
Tier la collection. However, NCDOT does not have complete ROW mapping coverage in many areas of the state. In
this case the field crew will be required to use other commonly identifiable features to determine the likely ROW
limits. These include:
1. Control access parallel to the roadway — the fence is typically the ROW limit.
2. Limit of mowing or other maintenance — the edge of mowing is typically the ROW limit.
3. Power poles — power poles are typically set just inside the ROW limit.
4. Back of ditch slope — the line where the ditch slope transitions back to natural grade may be the ROW
limit. Look for other indicators to confirm.
5. ROW monuments— If present monuments can be used to determine the ROW limits.
References
1. EPA Glossary— Office of Wastewater Management
http://cfpub.epa.gov/npdes/glossary.cfm#P
2. NC Division of Water Quality. 2010. Methodology for Identification of Intermittent and Perennial Streams
and their Origins, Version 4.11. North Carolina Department of Environment and Natural Resources,
Division of Water Quality. Raleigh, NC.
3. "Neuse River Basin: Nutrient Sensitive Waters Management Strategy: Protection and Maintenance of
Existing Riparian Buffers." 15A NCAC 02B .0233(2) (2000).
4. "Protection of the Environment." 40 CFR 122.2 (2013).
Final Report 11 March 2014