NCS000450_Carrboro Illicit Discharge Program Plan_20220630

Town of Carrboro

Illicit Discharge, Detection
and Elimination (IDDE) Plan

May 2022

Town of Carrboro, NC
Public Works Department
Stormwater Division

NPDES Permit #NCS000450

Contents
1 Justification ........................................................................................................................................... 4
1.1 NPDES Permit No. NCS000450 ................................................................................................... 4
2 Background ........................................................................................................................................... 4
3 Goals and best management practices .................................................................................................. 4
3.1 Best Management Practices .......................................................................................................... 4
3.2 Program evaluation and assessment .............................................................................................. 9
4 Storm Sewer Map ............................................................................................................................... 10
4.1 Permit requirement ...................................................................................................................... 10
4.2 Mapping initiative ....................................................................................................................... 10
4.3 Cityworks and GIS ...................................................................................................................... 10
4.4 Additional resources ................................................................................................................... 10
5 Prohibit non-stormwater discharges, implement appropriate enforcement procedures and actions ... 10
5.1 Permit requirement ...................................................................................................................... 10
5.2 Illicit discharge ordinance (Town Code) .................................................................................... 11
5.3 Enforcement actions .................................................................................................................... 11
5.4 Enforcement tracking .................................................................................................................. 12
6 Detect, address and track illicit discharges ......................................................................................... 12
6.1 Permit requirement ...................................................................................................................... 12
Implement a program to detect dry weather flows .............................................................................. 12
6.2 Locating priority areas ................................................................................................................ 12
6.3 Conducting dry weather flow field observations ........................................................................ 14
6.4 Investigating sources of identified illicit discharges ................................................................... 16
6.4.1 Responding to reports of illicit discharge ........................................................................... 16
6.4.2 Remote investigation........................................................................................................... 16
6.4.3 Outfall Inspections .............................................................................................................. 17
6.4.4 Storm drain network investigations .................................................................................... 17
6.4.5 Septic system investigations ............................................................................................... 18
6.5 Remedying sources of illicit discharge ....................................................................................... 18
6.6 Preventing illicit discharges ........................................................................................................ 18
6.7 Documentation and Tracking ...................................................................................................... 18
6.7.1 Stormwater hotline and email ............................................................................................. 18
6.7.2 Cityworks ............................................................................................................................ 19
6.7.3 Event Tracking Spreadsheet ................................................................................................ 19
7 Education ............................................................................................................................................ 19
7.1 Permit requirement ...................................................................................................................... 19
Provide Employee Training ................................................................................................................ 20

7.2 Public employees ........................................................................................................................ 20
7.3 Businesses ................................................................................................................................... 20
7.4 General public ............................................................................................................................. 20
7.4.1 Homeowners’ Manual ......................................................................................................... 20
7.4.2 Stormwater website ............................................................................................................. 20
8 Goals ................................................................................................................................................... 21
8.1 Inlet labeling ............................................................................................................................... 21
8.2 Adopt-a-stream program ............................................................................................................. 21
9 Related documents .............................................................................................................................. 21

1 Justification
1.1 NPDES Permit No. NCS000450
The Town of Carrboro has a Stormwater Discharge permit under the National Pollutant Discharge
Elimination System effective 1/1/2022 until 12/31/2026. The permit authorizes the point source discharge
of stormwater runoff from the municipal separate storm sewer system (MS4), sets forth the minimum
management measures required to implement a successful stormwater management program, and
introduces objectives and Best Management Practices (BMPs) for each measure. Section D: Illicit
Discharge Detection and Elimination (IDDE) is attached to this document, and the objectives and BMPs
listed therein shall be referenced throughout this plan.

This plan fulfills the following permit objective:
(a) Implement and enforce a program to address the detection and elimination of illicit
discharges into the MS4.

This plan also fulfills the following permit BMP:
BMP Measurable Goals
Maintain an Illicit Discharge Detection
and Elimination Program
Maintain a written Illicit Discharge Detection and Elimination
Program, including provisions for program assessment and
evaluation and integrating program.

2 Background
Illicit discharges are defined as the release of a pollutant into the storm sewer system or surface waters,
directly (discharged within the physical limits of the storm sewer system, stream, pond or lake) or indirectly
(discharged outside the physical limits but in such a manner that the pollutant is carried to these systems).
The Town of Carrboro maintains an illicit discharge ordinance expressly prohibiting such discharges as
well as illicit connections, which are the connection of drains or lines that convey pollutants and/or
wastewater to the storm sewer system.

The Town is committed to upholding its illicit discharge ordinance in order to both comply with its NPDES
permit and protect the water quality of its receiving streams and uphold the effectiveness and integrity of
its municipal separate storm sewer system. The below plan details the best management practices,
procedures, steps and methods that the Town has integrated into its operations in order to identify, prevent
and remedy illicit discharges and connections throughout its jurisdiction.
3 Goals and best management practices
3.1 Best Management Practices
The Town has initiated Best Management Practices in order to comply with those set out in the NPDES
permit. These are described in detail in the Town’s Stormwater Management Program (SWMP) and are
listed below:

Table 15: Illicit Discharge Detection and Elimination BMPs
Permit
Ref.
3.4.1: MS4 Map
Measures to develop, update and maintain a municipal storm sewer system map including stormwater
conveyances, flow direction, major outfalls and waters of the United States receiving stormwater discharges.
A B C D

Table 15: Illicit Discharge Detection and Elimination BMPs
BMP
No. Description of BMP Measurable Goal(s) Schedule for
Implementation
Annual Reporting
Metric
16. Continuously update stormwater system map
The Town shall maintain a
stormwater system map and
GIS database based on field
work to locate infrastructure
and devices, and continuously
updated as infrastructure
changes. The map includes all
above and below ground Town
owned and maintained
stormwater infrastructure along
with key attribute information.
1. Add new infrastructure as it is
constructed.
1. Continuously
Permit Years 1-5
1. Total number of
outfalls mapped
Number of outfalls
added during permit
year
Total miles of above
ground infrastructure
Total miles of below
ground infrastructure
17. Maintain Stormwater Control Measure inventory and map
The Town shall identify and
maintain a database of
Stormwater Control Measures
(SCMs), integrated into
existing stormwater system
map. The map shall distinguish
between privately/non-Town-
owned and Town-owned
SCMs.
1. Add new SCMs as they are
constructed.
1. Continuously
Permit Years 1-5

1. Total number of
SCMs mapped
Number of SCMs
added during permit
year
Permit
Ref.
3.4.2: Regulatory Mechanism
Measures to provide an IDDE ordinance or other regulatory mechanism that provides legal authority to
prohibit, detect, and eliminate illicit connections and discharges, illegal dumping and spills into the MS4,
including enforcement procedures and actions.
BMP
No.
A B C D
Description of BMP Measurable Goal(s) Schedule for
Implementation
Annual Reporting
Metric
18. Update the Illicit Discharge Ordinance as necessary to maintain legal authority.
The Town shall ensure the
continued applicability,
accuracy and legal standing of
the IDDE provisions in the
Town Code.

1. Coordinate with Town Attorney to
conduct review of Illicit Discharge
Ordinance.

1. Permit Year 1

1. Yes/No/Status
2. Update Illicit Discharge Ordinance 2. Permit Year 1 2. Yes/No/Status
Permit
Ref.
3.4.3: IDDE Plan
Measures to maintain and implement a written IDDE Plan to detect and address illicit discharges, illegal
dumping and any non-stormwater discharges identified as significant contributors of pollutants to the MS4.
The plan shall provide standard procedures and documentation to:
a) Locate priority areas likely to have illicit discharges,
b) Conduct routine dry weather outfall inspections,
c) Identify illicit discharges and trace sources,
d) Eliminate the source(s) of an illicit discharge, and
e) Evaluate and assess the IDDE Program.

Table 15: Illicit Discharge Detection and Elimination BMPs
BMP
No.
A B C D
Description of BMP Measurable Goal(s) Schedule for
Implementation
Annual Reporting
Metric
19. Maintain a written IDDE Plan
The Town shall maintain a
written IDDE plan to detect and
address illicit discharges, illegal
dumping and non-stormwater
discharges identified as
significant contributors of
pollutants to the MS4,
including provisions for
program assessment and
evaluation and associated
documents.
1. Conduct comprehensive initial review
of current plan and revise accordingly.

1. Permit Year 1 1. Yes/No/Partial
2. Submit new plan to DEQ for review
and approval.

2. Permit Year 1 2. Date submitted
3. Implement written IDDE Plan.

3. Continuously
Permit Years 2 -
5
3. Yes/No/Partial
4. Conduct review of plan, standard
documentation, forms, procedures and
SOPs; make changes as necessary.

4. Annually
Permit Years 1-5
4. Yes/No/Partial
20. Locate priority areas most likely to have illicit discharges
The Town shall identify areas
with high Illicit Discharge
Potential (IDP) based on
physical factors, historical
problems, and surrounding land
use. The Town has developed
an Illicit Discharge Potential
matrix and scored
subwatersheds and identified
priority outfalls for illicit
discharge investigations.
1. Review/update MS4 inspection areas
using Illicit Discharge Potential matrix.
1. Annually
Permit Years 1-5

1. Review conducted:
Yes/No/Partial
Number of high priority
subwatersheds
21. Conduct routine dry weather outfall inspections
The Town shall implement a
program of conducting and
tracking dry weather outfall
inspections. The Town’s Illicit
Discharge Program Plan
includes a program for
conducting dry weather flow
field observations, prioritizing
outfalls by subwatershed and
their respective illicit discharge
potential. Inspections utilize the
written Outfall Inspection SOP,
Outfall Inspection Field Sheet,
and the IDDE Documentation
SOP.
1. Establish Outfall Reconnaissance
Inventory inspection schedule, with
minimum of 20% inspected annually
1. Permit Year 1

1. Yes/No/Partial
2. Develop ORI inspection procedure,
standard documentation and forms

2. Permit Year 1 2. Yes/No/Partial
3. Inspect minimum of 20% MS4 per
year (100% every 5 years)
3. Continuously
Permit Years 1-5

3. Number of outfalls
inspected
Number of illicit
discharges identified as
a result of outfall
inspections
22. Identify illicit discharges and connections, trace and eliminate sources
The Town’s Illicit Discharge
Program Plan includes a
program of identifying and
eliminating illicit discharges by
tracing their sources and
1. Investigate reports of illicit discharges
to determine sources.
1. Continuously
Permit Years 1-5

1. Number of potential
illicit discharges
reported
Number of verified
illicit discharges

Table 15: Illicit Discharge Detection and Elimination BMPs
pursuing enforcement as
necessary. The program
includes procedures for
responding to reports of illicit
discharges, conducting various
types of inspections to
determine sources, eliminating
illicit discharges and
connections, and issuing
enforcement as necessary.
2. Halt illicit discharges and remedy
illicit connections as necessary
2. Continuously
Permit Years 1-5
2. Number of illicit
connections and
discharges remedied
3. Issue verbal and written enforcement,
including Notices of Violation and
penalties as appropriate
3. Continuously
Permit Years 1-5
3. Number of
enforcement actions
issued for illicit
discharges or
connections
23. Evaluate and assess the IDDE program at least annually
The Town shall evaluate the
IDDE program at least annually
and incorporate changes as
necessary. Assessment will
utilize number of stormwater
hotline emails and voicemail
messages, illicit discharge
investigations conducted,
outcomes of investigations,
enforcement issued, chronic
violators, and areas of
improvement.
1. Review program implementation and
IDDE metrics at least annually.
1. Annually
Permit Years 1-5

1. Yes/No/Status
Permit
Ref.
3.4.4: IDDE Tracking
Measures for tracking and documenting the date(s) an illicit discharge, illicit connection or illegal dumping was
observed, the results of the investigation, any follow-up of the investigation, the date the investigation was
closed, the issuance of enforcement actions, and the ability to identify chronic violators.
BMP
No.
A B C D
Description of BMP Measurable Goal(s) Schedule for
Implementation
Annual Reporting
Metric
24. Monitor illicit discharges, investigations and enforcement actions
The Town shall maintain an
“Event Tracking” spreadsheet
of reported illicit discharges
including location, type,
enforcement actions, and
outcomes. The spreadsheet
1. Document illicit discharges in
accordance with the Illicit Discharge
Documentation SOP, including the
Event Tracking spreadsheet and
CityWorks.

1. Continuously
Permit Years 1-5

1. Number of entries in
Event Tracking
spreadsheet per permit
year

Table 15: Illicit Discharge Detection and Elimination BMPs
documents the following: date
reported, date closed,
investigation ID #, location,
hotline report (Y/N), confirmed
illicit discharge (Y/N), nature
of discharge, results of
investigation, actions taken to
remedy illicit discharge,
enforcement actions issued, file
folder name, reporting party
(staff/public), investigator,
subwatershed, receiving stream.
The Town utilizes the
CityWorks platform for storing
and sharing details, photos and
comments. Staff shall follow
the Illicit Discharge
Documentation SOP.

2. Review illicit discharge database for
potential chronic violators at least
annually
2. Annually
Permit Years 1-5
2. Number of
established chronic
violators
Permit
Ref.
3.4.5: Staff IDDE Training
Measures to provide training for municipal staff and contractors who, as part of their normal job
responsibilities, may observe an illicit discharge, illicit connection, illegal dumping or spills. Training shall
include how to identify and report illicit discharges, illicit connections, illegal dumping and spills. Each staff
training event shall be documented, including the agenda/materials, date, and number of staff participating.
BMP
No.
A B C D
Description of BMP Measurable Goal(s) Schedule for
Implementation
Annual Reporting
Metric
25. Train municipal staff to identify illicit discharges
The Town shall train relevant
personnel on methods of
identifying illicit discharges,
connections, dumping or spills.
Personnel will take exams
before and after training to
evaluate comprehension.
1. Develop written training plan and
presentations for Town employees, first
responders, and contractors likely to
encounter illicit discharges
1. Permit Year 1

1. Yes/No/Partial
2. Train municipal staff to identify and
report potential illicit discharges
2. Annually
Permit Years 1-5

2. Number of staff
members trained
Percent of exams with
passing score
3. Evaluate effectiveness of training by
analyzing illicit discharges identified by
Town personnel
3. Annually
Permit Years 2 –
5

3. Percent illicit
discharges identified by
staff
Permit
Ref.
3.4.6: IDDE Reporting
Measures for the public and staff to report illicit discharges, illegal dumping and spills. The mechanism shall be
publicized to facilitate reporting and shall be managed to provide rapid response by appropriately trained
personnel.
BMP
No.
A B C D
Description of BMP Measurable Goal(s) Schedule for
Implementation
Annual Reporting
Metric
26. Monitor hotline and other reporting mechanisms for public and staff to report illicit discharges

Table 15: Illicit Discharge Detection and Elimination BMPs
The Town shall monitor the
stormwater hotline (phone and
email) for reports of illicit
discharges. IDDE reporting
shall follow the IDDE
Documentation SOP.
1. Develop written procedure for
documenting and communicating hotline
reports to relevant personnel, reporting
tracking system and relevant forms

1. Permit Year 1

1. Yes/No/Partial
2. Distribute flyers and educational
materials with reporting information to
Town personnel and public

2. Continuously
Permit Years 1 –
5
2. Number of
educational materials
distributed
3. Track hotline and email
communications
3. Continuously
Permit Years 1 –
5

3. Number of hotline
emails and phone calls
Number of inquiries
leading to confirmed
illicit discharges
4. Review efficacy of stormwater email
and hotline in identifying illicit
discharges with Town personnel at least
annually

4. Annually
Permit Years 1 –
5

4. Yes/No/Partial

3.2 Program evaluation and assessment
The Town assesses IDDE program effectiveness through the reporting metrics detailed above, which
include the following:
 Total number of outfalls mapped
 Number of outfalls added during permit year
 Total miles of above ground infrastructure
 Total miles of below ground infrastructure
 Total number of SCMs mapped
 Number of SCMs added during permit year
 Number of outfalls inspected
 Number of illicit discharges identified as a result of outfall inspections
 Number of potential illicit discharges reported
 Number of verified illicit discharges
 Number of illicit connections and discharges remedied
 Number of enforcement actions issued for illicit discharges or connections
 Number of entries in Event Tracking spreadsheet per permit year
 Number of established chronic violators
 Number of staff members trained
 Percent of exams with passing score
 Percent illicit discharges identified by staff
 Number of educational materials distributed
 Number of hotline emails and phone calls
 Number of inquiries leading to confirmed illicit discharges

In permit year 1, the Town will conduct a comprehensive initial review of both the IDDE Plan and Illicit
Discharge Ordinance. Additionally, the Town will review this IDDE Plan and related illicit discharge
standard documentation, forms, procedures, and SOPs annually. The Town will also annually review its
MS4 inspection areas using the illicit discharge potential matrix, program implementation and IDDE

metrics, illicit discharge database for potential chronic violators, and the efficacy of the stormwater email
and hotline in identifying illicit discharges.

Program evaluation metrics are tracked in the spreadsheet “Program Evaluation KPIs”.

4 Storm Sewer Map
4.1 Permit requirement
The applicable permit objective for this section is:
(b) Maintain a storm sewer system map, showing the location of all major outfalls and the
names and location of all waters of the United States that receive discharges from those
outfalls;

The applicable permit BMP for this section is:
BMP Measurable Goals
Maintain a Storm Sewer System Map
of Major Outfalls.
The permittee shall maintain a current a map showing major
outfalls and receiving streams.

4.2 Mapping initiative
The Town initiated a detailed stormwater mapping program in 2000. As of 2020, all drainage structures,
public and private, within the Town’s jurisdiction have been mapped utilizing GIS technology. Mapping
has been enhanced as new digital and as-built information has become available. In FY2008-2009, the
Town completed a major update to stream data that improved the accuracy and classification of perennial,
intermittent, and ephemeral streams; it also updated drainage areas, outfalls, ditches, SCMs and new system
features subsequent to the original mapping. The Town plans to undergo a Town-wide condition assessment
of stormwater infrastructure in 2022.

4.3 Cityworks and GIS
The Town utilizes Cityworks software, which incorporates existing GIS layers with asset management,
allowing efficient tracking and work order dispatch to appropriate personnel. Cityworks is available as both
a desktop and mobile platform – this allows personnel in the field to identify discrepancies between the
listed asset characteristics (e.g. outlet size, SCM type) and what is observed in order to increase accuracy.

4.4 Additional resources
The Town utilizes additional resources to supplement its mapping initiatives, including the following:
- NCDEQ Community Mapping System
- Orange County GIS Website
5 Prohibit non-stormwater discharges, implement appropriate
enforcement procedures and actions

5.1 Permit requirement
The applicable permit objective for this section is:
(c) Prohibit, through ordinance, or other regulatory mechanism, non-storm water
discharges except as allowed in this permit and implement appropriate enforcement
procedures and actions;

The applicable permit BMP for this section is:
BMP Measurable Goals
Maintain adequate legal authorities The permittee shall maintain an IDDE ordinances or other
regulatory mechanisms that provides the legal authority to
prohibit illicit connections and discharges.

Enforcement of the IDDE ordinance The permittee shall implement a mechanism to track the
issuance of notices of violation and enforcement actions as
administered by the permittee. This mechanism shall include
the ability to identify chronic violators for initiation of actions
to reduce noncompliance.

5.2 Illicit discharge ordinance (Town Code)
The Town’s Illicit Discharge Ordinance is located in the Town Code, Chapter 5 Article IV – Illicit
Discharges Into and Connections to Storm Sewer System (attached). The Ordinance achieves the following:
- Establishes regulatory authority to prohibit discharges of any pollutants directly or indirectly into
the storm sewer system or surface waters;
- Prohibits illicit connections to the storm sewer system
- Establishes the rights of town officers, agents and employees to enter on any premises with the
intention of enforcing the Ordinance;
- References the applicable penalties and remedies available for enforcement of the Ordinance
(located in Section 5-21 of the Town Code).

5.3 Enforcement actions
In the event that an illicit discharge is detected and its source is identified (see Section 7), the Stormwater
Division shall implement the following enforcement procedures and actions:
- Contact the responsible party via phone, email or in person to discuss the violation.
- Provide information regarding the nature of the discharge and the manner in which does not comply
with the Town Code; supply written documentation such as the Illicit Discharge Ordinance.
- Issue a formal written notice of noncompliance with the ordinance to the responsible party, stating
that the letter is a written warning to cease and desist the illicit discharge and that further
enforcement may follow.
- Should the illicit discharge continue, refer the matter to the Public Works Director and/or Town
Attorney for further action.

Enforcement actions are determined based on several factors, including the degree and extent of harm to
natural resources, public health and private property; duration and gravity of the violation; cost to the
violator or others of rectifying the damage; amount of money saved by the violator by noncompliance;
whether the violation was committed willfully or intentionally, negligently, or as the result of an
unforeseeable or unavoidable accident; whether the violator ceased the violation upon notice and took steps
necessary to limit or correct any damage; prior record of illicit discharges by the violator; and cost to the
town of enforcement procedures.

Enforcement actions may include the assessment of a civil penalty of up to $5,000 for a single event;
however, each day that a violation continues after the offender has been notified may constitute a separate
offense. In this case, penalties assessed on a daily basis may cumulatively exceed the $5,000 cap. See Town
Code Section 5-21 Penalties (attached).

Additional enforcement actions may also include the physical removal of an illicit connection from the
Town stormwater system, when it has been determined that such connection is prohibited. In all cases, the
Stormwater Division seeks to remedy compliance issues by communicating with the violator or property

owner and providing them with an opportunity to discontinue the illicit discharge before further
enforcement is needed.

5.4 Enforcement tracking
All incidents of suspected or known illicit discharges shall be documented and tracked according to the
IDDE Documentation SOP (attached) and as described in section 7.7 of this plan. Specifically, enforcement
actions shall be tracked via the Event Tracking spreadsheet.
6 Detect, address and track illicit discharges

6.1 Permit requirement
The applicable permit objectives for this section are:
(d) Implement a plan to detect and address non-storm water discharges, including illegal
dumping, to the MS4;

(f) Address the following categories of non-storm water discharges or flows (i.e., illicit
discharges) only if you identify them as significant contributors of pollutants to the MS4:
water line flushing, landscape irrigation, diverted stream flows, rising ground waters,
uncontaminated ground water infiltration, uncontaminated pumped ground water,
discharges from potable water sources, foundation drains, air conditioning condensation,
irrigation water, springs, water from crawl space pumps, footing drains, lawn watering,
individual residential car washing, charity car washes, flows from riparian habitats and
wetlands, dechlorinated swimming pool discharges, and street wash water (discharges or
flows from firefighting activities are excluded from the effective prohibition against non-
storm water and need only be addressed where they are identified as significant sources of
pollutants to waters of the United States).

The applicable permit BMPs for this section are:
BMP Measurable Goals
Implement a program to detect dry
weather flows
The permittee shall maintain a program for conducting dry
weather flow field observations in accordance with written
procedures.
Investigate sources of identified illicit
discharges.
The permittee shall maintain written procedures for
conducting investigations of identified illicit discharges.
Track and document investigations
illicit discharges
For each case the permittee shall track and document 1) the
date(s) the illicit discharge was observed; 2) the results of the
investigation; 3) any follow-up of the investigation; and 4) the
date the investigation was closed.
Provide a public reporting mechanism The permittee shall promote, publicize, and facilitate a
reporting mechanism for the public and staff to report illicit
discharges and establish and implement citizen request
response procedures.

6.2 Locating priority areas
The Town has located priority areas for investigating illicit discharges through the development of an illicit
discharge potential (IDP) matrix, which ranks subwatersheds by a number of factors which may increase
their risk of illicit discharges. The IDP matrix was developed from the CWP IDDE Manual, Chapter 5:
Desktop Assessment of Illicit Discharge Potential.

The subwatersheds in the Town’s jurisdiction are divided as follows:

- Upper Bolin Creek
- Middle Bolin Creek
- Lower Bolin Creek
- Morgan Creek (Below University Lake)
- Upper University Lake (Morgan Glen)
- Lower University Lake
Maps of the subwatersheds are attached.

The TOC screening factors include the following:

Discharge Screening Factor Definition
Past discharge complaints and reports Frequency of past discharge complaints, hotline
reports, and spill responses.
Storm water outfall density Density of mapped stormwater outfalls in the
subwatershed.
Age of subwatershed development Average age of the majority of development in a
subwatershed.
Sewer conversion Subwatersheds that had septic systems but have
been connected to the sanitary sewer system.
Aging or failing sewer infrastructure Age and condition of the subwatershed sewer
network.
Density of aging septic systems Subwatersheds with a high density of septic drain
fields.

There are several factors typically included in illicit discharge potential screening that were not utilized for
the Town, either due to inapplicability or because they do not contribute significantly to relative IDP.
- Density of generating sites or industrial NPDES stormwater permits: There is one industrial
stormwater permit in Carrboro, located in the Morgan Creek subwatershed: Ready Mix Concrete,
located on Gutherie Avenue.
- Presence of older industrial operations: There is only one current industrial operation in
Carrboro: Ready Mix Concrete, located on Gutherie Avenue.
- Historic combined sewer systems: The Town of Carrboro was developed with separated sewer
systems and does not have a history of combined sewers in any area.

Once factors were chosen and defined, ranking of the factors was completed using personnel historical and
institutional knowledge as well as the MS4 map and septic system information from the Orange County
Environmental Health Department. Below is the completed and scored IDP matrix for the Town of
Carrboro.

Screening Factor
Upper
Bolin
Creek
Middle
Bolin
Creek
Lower
Bolin
Creek
Morgan
Creek
Upper
University
Lake
Lower
University
Lake
Past discharge complaints and
reports 1 2 2 3 0 0
Storm water outfall density 2 1 1 3 2 1
Age of subwatershed
development 2 2 3 3 1 1
Sewer conversion 0 3 0 1 0 0
Aging or failing sewer
infrastructure 1 2 3 3 0 0

Density of aging septic
systems 3 3 1 1 2 1
Raw IDP Score 9 13 10 14 5 3
Normalized IDP Score
(on scale from 0-3) 1.5 2.2 1.7 2.3 0.8 0.5
*updated September 9th, 2021

Therefore, subwatersheds are ranked in order of highest to lowest illicit discharge potential as follows:
- Morgan Creek
- Middle Bolin Creek
- Lower Bolin Creek
- Upper Bolin Creek
- Upper University Lake
- Lower University Lake

The Town’s Outfall Inspections (Section 6.3) are prioritized based on this ranking.

6.3 Conducting dry weather flow field observations
The Town conducts Outfall Inspections both in response to reported illicit discharge incidents and as a
means of inventorying outfalls to detect previously unnoticed illicit discharges or connections. Outfall
Inspections are conducted using the Outfall Inspection SOP (attached) and the Outfall Inspection Field
Sheet (attached). See section 6.4.3. for more information.

The Outfall Reconnaissance Inventory (ORI) is a tool recommended for Phase II communities to develop
a robust inventory of outfalls throughout their MS4, and includes walking stream miles throughout the
system to inspect and catalog all outfalls. Because the Town of Carrboro has developed a comprehensive
inventory of outfalls in its GIS database, a full inventory and stream walk program is not of immediate
importance and is therefore planned for the second and third years of the permit cycle.

However, the Town inspects priority outfalls throughout the system on a rotating basis. TOC currently has
51 priority outfalls in the system, which were identified based on illicit discharge potential and location,
and 20 major outfalls that are 36” or greater in diameter, and 4 “major combined” outfalls that are 36” or
greater in diameter and include both stormwater runoff AND a piped stream. The Town has developed a
rotating schedule whereby each outfall is inspected at least once every 5 years. The schedule is grouped by
subwatershed and subbasin and prioritized by illicit discharge potential as described above.

Priority, Major and Major Combined Outfalls (May 2022)
Outfall ID Outlet Type Subwatershed Subbasin Cycle Year
OUT-1102 Priority Outfall Morgan Creek 1574 A
OUT-1105 Priority Outfall Morgan Creek 1574 A
OUT-1247 Priority Outfall Morgan Creek 1574 A
OUT-1351 Priority Outfall Morgan Creek 1574 A
OUT-1355 Priority Outfall Morgan Creek 1574 A
OUT-1356 Priority Outfall Morgan Creek 1574 A
OUT-1432 Priority Outfall Morgan Creek 1574 A
OUT-1814 Priority Outfall Morgan Creek 1574 A
OUT-1317 Priority Outfall Morgan Creek 1643 A
OUT-1639 Priority Outfall Morgan Creek 1643 A

OUT-1341 Major Outfall Morgan Creek 1677 A
OUT-1015 Priority Outfall Morgan Creek 1677 A
OUT-1338 Priority Outfall Morgan Creek 1677 A
OUT-1928 Priority Outfall Morgan Creek 1677 A
OUT-1246 Major Combined Outfall Morgan Creek 1312 B
OUT-1086 Priority Outfall Morgan Creek 1312 B
OUT-1501 Priority Outfall Morgan Creek 1312 B
OUT-1789 Priority Outfall Morgan Creek 1312 B
OUT-1294 Major Outfall Morgan Creek 1473 B
OUT-1298 Major Outfall Morgan Creek 1473 B
OUT-1299 Major Outfall Morgan Creek 1473 B
OUT-1300 Major Outfall Morgan Creek 1473 B
OUT-1758 Major Outfall Morgan Creek 1473 B
OUT-1010 Priority Outfall Morgan Creek 1473 B
OUT-1297 Priority Outfall Morgan Creek 1473 B
OUT-1760 Priority Outfall Morgan Creek 1473 B
OUT-1929 Priority Outfall Morgan Creek 1473 B
OUT-2000 Priority Outfall Morgan Creek 1473 B
OUT-1660 Priority Outfall Morgan Creek 1631 B
OUT-1932 Priority Outfall Morgan Creek 1631 B
OUT-1032 Priority Outfall Morgan Creek 1135 C
OUT-1211 Priority Outfall Morgan Creek 1135 C
OUT-1278 Priority Outfall Morgan Creek 1135 C
OUT-1311 Priority Outfall Morgan Creek 1135 C
OUT-1312 Priority Outfall Morgan Creek 1135 C
OUT-1313 Priority Outfall Morgan Creek 1135 C
OUT-1361 Priority Outfall Morgan Creek 1135 C
OUT-1213 Major Combined Outfall Morgan Creek 1288 C
OUT-1088 Major Outfall Morgan Creek 1288 C
OUT-1367 Priority Outfall Morgan Creek 1288 C
OUT-1930 Priority Outfall Morgan Creek 1288 C
OUT-1282 Major Combined Outfall Morgan Creek 1536 C
OUT-1040 Priority Outfall Morgan Creek 1536 C
OUT-1084 Priority Outfall Morgan Creek 1536 C
OUT-1138 Priority Outfall Morgan Creek 1536 C
OUT-1139 Priority Outfall Morgan Creek 1536 C
OUT-1724 Priority Outfall Morgan Creek 1536 C
OUT-1136 Priority Outfall Morgan Creek 1582 C
OUT-1188 Priority Outfall Morgan Creek 1582 C
OUT-1755 Major Combined Outfall Morgan Creek 1142 D
OUT-1229 Major Outfall Morgan Creek 1142 D
OUT-1493 Major Outfall Morgan Creek 1142 D
OUT-1073 Priority Outfall Morgan Creek 1142 D

OUT-1752 Priority Outfall Morgan Creek 1142 D
OUT-1907 Major Outfall Middle Bolin Creek 736 D
OUT-1379 Major Outfall Middle Bolin Creek 830 D
OUT-1909 Priority Outfall Middle Bolin Creek 830 D
OUT-1999 Priority Outfall Middle Bolin Creek 933 D
OUT-1372 Major Outfall Middle Bolin Creek 1021 D
OUT-1421 Major Outfall Middle Bolin Creek 1153 D
OUT-1428 Major Outfall Lower Bolin Creek 1101 D
OUT-1424 Priority Outfall Lower Bolin Creek 1165 D
OUT-1118 Major Outfall Lower Bolin Creek 1252 D
OUT-1070 Priority Outfall Lower Bolin Creek 1252 D
OUT-1271 Priority Outfall Lower Bolin Creek 1252 D
OUT-1272 Priority Outfall Lower Bolin Creek 1252 D
OUT-1931 Priority Outfall Lower Bolin Creek 1252 D
OUT-1733 Priority Outfall Upper Bolin Creek 54 E
OUT-1940 Major Outfall Upper Bolin Creek 278 E
OUT-1842 Major Outfall Upper Bolin Creek 521 E
OUT-1175 Major Outfall Upper Bolin Creek 548 E
OUT-1865 Major Outfall Upper Bolin Creek 548 E
OUT-1875 Major Outfall Upper Bolin Creek 548 E

6.4 Investigating sources of identified illicit discharges
Stormwater Investigations may be prompted by reports via the stormwater hotline or email address, issues
observed by staff or personnel in other departments, observations from an outfall inspection, or for a variety
of other reasons. If it is determined that an issue requires investigation as an illicit discharge, it is
investigated using a variety of tools. In some cases, the source of the illicit discharge is strongly suspected
and reported directly; in this case, the Town confirms the information and moves directly to enforcement
if necessary. However, if the source is unknown, the Town proceeds using drainage area investigations,
storm drain investigations and/or characterization of the discharge.

6.4.1 Responding to reports of illicit discharge
The Stormwater Division has established a stormwater hotline [phone]) and shared email address
([e-mail]) which are used to report issues of flooding, potential illicit discharges, and
general inquiries. The number and email address are published on the Stormwater Division website
(www.townofcarrboro.org/287/Stormwater) and advertised during events and on promotional materials.
All voicemails recorded on the hotline and emails sent to the shared address are automatically and
immediately forwarded to all Stormwater Division Staff.

Upon receipt of an email or voicemail to the hotline, staff determine whether or not an illicit discharge
investigation is warranted, investigation and/or enforcement will follow. Staff respond to reports of illicit
discharge within one business day and begin investigation immediately. Staff coordinate with other
agencies including Orange Water and Sewer Authority and the Orange County Health Department,
Environmental Health Division.

6.4.2 Remote investigation
Before initiating field investigations, TOC staff gather and confirm reported information. Methods of
remote investigation include:

- Calling or emailing the party that reported the discharge
- Calling or emailing the suspected responsible party
- Reviewing previous issues in the same location or attributed to the same party
- Reviewing photographs and video of the illicit discharge
- Using the MS4 map to identify the upstream network of pipes and drainage ditches to target for
inspection

Town staff acknowledge that reports are sometimes reported erroneously due to a misunderstanding or
tension between parties. In order to best conserve labor and prevent unreasonable enforcement, all efforts
are made to confirm reported information before additional investigation or enforcement is pursued.

6.4.3 Outfall Inspections
The Town conducts outfall inspections utilizing the Outfall Inspection SOP (attached) and Outfall
Inspection Field Sheet (attached). In short, the procedure includes:
- Collecting background information
- Scheduling the inspection in Cityworks
- Gathering required materials and PPE
- Conducting the inspection
- Reporting results of the inspection
- Sending samples for analysis

The Outfall Inspection Field Sheet details information that is to be collected during the inspection,
including:
- Background Data: Location of the outfall, time and date of the inspection, surrounding land use,
and other relevant contextual information. This section may be partially completed before the
inspection.
- Outfall Description: Information about the outfall itself, including the material, shape, and
dimensions of the pipe or open drainage channel.
- Field Data for Flowing Outfalls: If collecting a sample, measurement of flow speed, depth and
width of flow, temperature, pH, and ammonia level of the flow using field kits.
- Physical Indicators for Flowing Outfalls Only: Physical characteristics of the flow, including odor,
color, turbidity and floatables, with a severity ranking from 1 to 3, as well as additional physical
indicators observed.
- Physical Indicators for All Outfalls: Physical characteristics of the outfall itself, including damage,
stains, abnormal vegetation, poor pool quality or benthic growth within the pipe.
- Overall Outfall Characterization: An overall characterization of the outfall based on the information
collected including a judgement of whether or not an illicit discharge may be occurring.
- Sample Collection: If a sample is being collected for analysis, notes of if it was taken from the flow
or pool, and whether or not an intermittent flow trap was set.
- Non-Illicit Discharge Concerns: Additional concerns you may have about the outfall.
- Additional Comments

6.4.4 Storm drain network investigations
In storm drain investigations, the goal is to narrow the potential source of the discharge by strategically
sampling or observing different locations throughout the MS4. Crews may use any of the following
methods: visual inspection at manholes; indicator sampling; sandbagging or damming at the trunk; smoke
testing; dye testing; or video observations.

Once a likely source of the illicit discharge is identified, the Town may proceed to eliminating the source
and/or enforcement as applicable.

6.4.5 Septic system investigations
The Town of Carrboro has partnered with the Orange County Health Department, Environmental Health
Division to maintain an inventory of on-site domestic wastewater systems within the Town’s jurisdiction
and reduce the amount of fecal coliform present in the stormwater system. Because OCEH maintains
authority for the septic systems throughout the County, the Town does not perform inspections of domestic
wastewater systems, issue permits, or manage maintenance reports. The attached Fecal Coliform Reduction
Program describes the partnership in detail.

As discussed in the Program, TOC staff will accompany OCEH staff on environmental surveys and
inspections performed within the Town and maintain a database of all incidents related to septic systems.
Conversely, if an illicit discharge is suspected to be due to a failing septic system, Town staff will
immediately notify OCEH for their response and enforcement.

6.5 Remedying sources of illicit discharge
The Town of Carrboro maintains the authority to remedy sources of illicit discharge or illicit connections
as noted in the Town Code Sections 5-21 Penalties and Remedies, 5-35 Enforcement and Chapter 11,
Article V, Part 2 regarding summary abatement of conditions dangerous and prejudicial to the public health.
Many corrective actions involve infrastructure modification or repair, such as in instances of direct
discharges like sewage cross-connections, straight pipes, industrial cross-connections, and commercial
cross-connections. Indirect discharges, like sewage from sewer breaks or failing septic systems, may also
require structural repairs, while transitory discharges may be eliminated with spill containment and clean-
up.

In cases where Town infrastructure is responsible for a discharge, the Stormwater Division refers the matter
to the Public Works Director and/or Superintendent to dispatch personnel as appropriate. Additionally,
Town personnel may be dispatched if it is not Town infrastructure, but if the matter is urgent and immediate
elimination is required. If investigation determines a party responsible for the discharge, the cost of clean-
up and/or repair may be invoiced to them directly. Due to the variety of circumstances under which illicit
discharges may occur, actions taken to repair the problem also vary.

6.6 Preventing illicit discharges
The Town of Carrboro prevents illicit discharges, in part, through three of its other required management
measures: public education and outreach, public participation and involvement, and municipal pollution
prevention and good housekeeping. Educational initiatives are described in section 7 of this document, with
the other initiatives described in the Town’s Stormwater Management Plan.

Additionally, TOC’s partnership with the Orange County Health Department, Environmental Health
Division helps to prevent discharges from domestic wastewater systems through inventory, maintenance
and inspection efforts. See section 6.4.5.

6.7 Documentation and Tracking
Illicit discharge investigations are documented and tracked in several ways.

6.7.1 Stormwater hotline and email
Any reports of illicit discharges that are reported through the stormwater hotline and email are recorded
following the IDDE Documentation SOP (attached). Emails from these hotlines are stored both in Microsoft
Outlook and on the Division’s shared server. All hotline calls and emails are logged in Cityworks and
tagged with “Stormwater Hotline” whether or not they result in an illicit discharge investigation. They are
also recorded in the Hotline and Illicit Discharge Summary Spreadsheet.

6.7.2 Cityworks
The Cityworks platform allows a stormwater investigation to be tracked from initiation to completion, with
all parties able to access the information. All illicit discharge investigations, no matter how they are
generated, are tracked through Cityworks. Once an investigation is opened, users can attach pictures,
emails, correspondence etc., write comments describing the situation, record the hotline caller, property
owner or other party and link the investigation to assets such as an inlet or outfall. The investigation can be
assigned to a user, while others can be tagged for their attention. If a field visit is warranted, users generate
work orders for the inspection, which is connected to the investigation and also allows labor hours or other
resources to be tracked. Enforcement documents are also attached as they are generated, and ultimately the
status of the investigation is changed to “closed” as it is completed. In this way, Cityworks allows
continuous tracking of ongoing investigations, summarizes relevant information, relates investigations to
outfalls and other assets, and allows easy evaluation of the IDDE program.

6.7.3 Event Tracking Spreadsheet
The Event Tracking spreadsheet records and summarizes hotline calls/emails and IDDE investigations that
have taken place along with relevant details, outcomes, and their stormwater investigation ID number in
Cityworks. The information tracked in the spreadsheet includes:
- Date reported
- Date closed
- Cityworks Stormwater Investigation ID
- Location
- Hotline report? (yes/no)
- Illicit discharge? (yes/no)
- Non-Illicit Discharge Issue
- Nature of the discharge
- Results of the investigation (source of the discharge, etc)
- Action taken to eliminate the discharge
- Enforcement actions
- File folder name (located in G:\PW\Stormwater\NPDES Permit-Townwide\Required Managment
Measures\IDDE\Tracking\Events)
- Reporting party (public, staff, etc)
- Primary investigator
- Subwatershed
- Receiving stream

While Cityworks contains detailed information and attachments, the spreadsheet allows for easy reference
and summary. It also allows the Town to evaluate how many hotline calls/emails result in illicit discharge
investigations, as a form of evaluation of the program.
7 Education
7.1 Permit requirement
The applicable permit objective for this section is:
(e) Inform public employees, businesses, and the general public of hazards associated with
illegal discharges and improper disposal of waste;

The applicable permit BMPs for this section are:

BMP Measurable Goals
Provide Employee Training The permittee shall implement and document a training
program for appropriate municipal staff, who as part of their
normal job responsibilities, may come into contact with or
otherwise observe an illicit discharge or illicit connection.
Provide Public Education The permittee shall inform public employees, businesses, and
the general public of hazards associated with illegal discharges
and improper disposal of waste.

7.2 Public employees
The Town has developed written training plan and presentation for Town employees, first responders, and
contractors likely to encounter illicit discharges. The training includes methods of identifying illicit
discharges, connections, dumping or spills. Training occurs annually, with the Stormwater Division
tracking the number of staff members trained and percentage of exams with a passing score. Effectiveness
of the training is also evaluated by the percentage of illicit discharges identified by staff.

7.3 Businesses
The Stormwater website contains a plethora of information regarding illicit discharge identification,
prevention, remediation and best practices. One major area of educational outreach is outdoor washing,
such as mobile pressure washing and surface cleaning. The Town provides information regarding the
regulation of this wastewater and measures contractors should take to prevent releasing chemicals and
wastewater into the stormwater system. Additionally, the website contains information for apartment
complexes and other entities that maintain swimming pools and spas for their residents and guests. This
information also includes best practices, contact information for Orange Water and Sewer Authority, and
information about the harm caused by allowing pool wastewater to enter the stormwater system. The Town
has developed numerous brochures and other printable outreach materials for other businesses as well, such
as landscapers, directional boring companies, and car washes.

7.4 General public
7.4.1 Homeowners’ Manual
Stormwater staff have created the “Homeowner’s Watershed and Stormwater Handbook: A Homeowner’s
Guide to Carrboro’s Watersheds, Creeks, and Stormwater Management.” The document provides
information about local watersheds, how and why stormwater is managed in Carrboro, and the
responsibilities of residential property owners and the Town. The Manual provides education to the public
by explaining regulatory requirements that the Town must uphold to remain in compliance, as well as the
environmental importance of maintaining stream buffers and preventing pollution to the stormwater system
and creeks. It also provides recommendations for managing stormwater volume and quality by collecting
roof runoff, planting native vegetation and collecting yard debris before it enters the stormwater system,
among others. The Manual is available through the Stormwater website and is promoted regularly through
advertising on the Town’s website, newsletters, and social media. The Division also has created a form on
the website which allows neighborhood associations to request an education stormwater presentation
promoting the Manual at their neighborhood meeting.

7.4.2 Stormwater website
The Stormwater website contains abundant information that enables citizens to identify and report illicit
discharges, as well as remedy problems on their own property. The Stormwater Hotline and Illicit Discharge
Reporting tool are both featured on the main Stormwater page, and various subpages include information
regarding pet waste, home oil tanks, swimming pools, outdoor washing, and other activities. Most
importantly, the website highlights the importance of protecting stormwater and local surface water quality,

enables citizens to take action to prevent pollution, and provides the means to report potential problems to
Town authorities.

8 Goals
The Town of Carrboro plans to pursue additional program components related to the IDDE program, but
beyond those required by the MS4 permit. These goals include:

8.1 Inlet labeling
At this time, all storm drains within the MS4 are labeled with unique identifiers. However, since the
Cityworks program has been incorporated into the Town’s work flow, the storm drains have been given
different identifiers that do not necessarily match with those physically labeled. Ideally, the Town would
like to re-label storm drains with their Inlet ID that matches the GIS/Cityworks system. This would allow
employees and the public to accurately report inlets where an illicit discharge or other suspicious flow is
occurring, allowing Stormwater staff to more efficiently respond to reports. However, with over 2400 inlets
from the road, it would be a challenging long-term project to individually label each one, so this project is
planned for a later date.

8.2 Adopt-a-stream program
Carrboro is fortunate to have an engaged citizenry who frequently express a desire to participate in
environmental clean-up events or otherwise assist in protecting their environment. The Town would like to
pursue an adopt-a-stream program, allowing individuals, families, or neighborhoods to “adopt” a local
creek or stretch thereof. Adopters would be encouraged to clean up trash, report bank erosion or large
woody debris, and of course report any illicit discharges or potential illicit connections. This would reduce
the workload of the Town for conducting outfall reconnaissance investigations and stream walks and help
to ensure continuous monitoring of sensitive surface waters.
9 Related documents

See the following related documents, which support the planning, implementation and tracking of the
Town’s IDDE Program:
 NPDES Permit No. NCS000450 Section 3.4 Illicit Discharge Detection and Elimination Program
 Town Code Article IV Illicit Discharge Ordinance
 Town Code Section 5-21 Penalties
 Outfall Inspection SOP
 Outfall Inspection Field Sheet
 IDDE Documentation SOP
 IDDE Investigation Procedure
 Fecal Coliform Reduction Plan
 IDP Scoring Matrix
 MS4 Map
 Program Evaluation KPIs spreadsheet
 Event Tracking spreadsheet