NCS000402_16_Mebane 2020 IDDE Program Update_20210621

CITY OF MEBANE
Mebane, North Carolina
Illicit Discharge and
Elimination Program
Prepared by:
Eli
alley, williams, carmen & king, inc.
engineers and architects
740 chapel hill road - post office box 1179
burlington, north carolina 27216-1179
2012
Project No. 10076
Revised: December 2020

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Table of Contents
1. Introduction............................................................................................................................1
A. Legal Basis.........................................................................................................................1
B. Definitions..........................................................................................................................1
C. Categories of Illicit Discharges...........................................................................................2
D. Exempt Discharges............................................................................................................3
2. Determine Priority Areas/Identify Hotspots............................................................................3
A. Delineate Subwatersheds..................................................................................................3
B. Land Use or Zoning Data...................................................................................................3
C. Industrial NPDES Permit Holders......................................................................................3
D. Areas known to have problems or complaints...................................................................4
E. Septic Systems..................................................................................................................4
F. Results of Outfall screening...............................................................................................4
3. MS4 Map...............................................................................................................................4
4. Dry weather flow screening...................................................................................................4
5. Procedures for Illicit Discharge Removal...............................................................................5
A. Identifying the Type of Discharge.......................................................................................5
B. Finding the Source.............................................................................................................7
C. Remove/Correct Illicit Discharge........................................................................................7
6. Inspection Program................................................................................................................7
7. Public Education....................................................................................................................8
8. Establish Public Reporting Hotline.........................................................................................8
9. Training..................................................................................................................................8
10. Household Hazardous Waste Collection...............................................................................8
11. Recordkeeping and Tracking System....................................................................................8
12. Program Assessment and Evaluation....................................................................................9

1. INTRODUCTION
This document describes the City of Mebane's plan for identifying and eliminating illicit
discharges and connections within its jurisdictional area. This plan has been developed to
partially fulfill the requirements of the City's NPDES Stormwater Permit No. NCS000402 issued
by the State of North Carolina Department of Environmental Quality, Division of Energy,
Mineral, and Land Resources (NCDENR-DEMLR) and the Comprehensive Stormwater
Management Plan developed by the City. Much of this plan is based on guidance provided in
the Center for Watershed Protection's manual titled Illicit Discharge Detection and Elimination: A
Guidance Manual for Program Development and Technical Assessments. This current version
of the plan follows successful completion of the original MS4 mapping program.
The City of Mebane is located in both the Cape Fear and Neuse River Basins. The City's storm
sewer system discharges into portions of MoAdans Creek, Mill Creek and Haw Creek. The land
use in the City's jurisdiction is predominately residential or institutional, with very little industry at
this point. This plan includes identifying areas likely to have illicit discharges, locating and
screening storm sewer system outfalls, developing and maintaining a storm sewer system map,
procedures for detecting and removing illicit discharges, and program assessment and
evaluation procedures.
Much of the storm sewer system within the City of Mebane's jurisdictional area was mapped
during the City's first permit cycle (2005-2010). This mapping focused on locating and screening
storm system outfalls, locating storm sewer structures, determining drainage areas, and
creating a map of the storm sewer system.
A. Legal Basis
The City adopted an Illicit Discharge Ordinance in 2006. This ordinance is found in the
City's Code of Ordinances and provides the City with the basic legal tools necessary to
conduct investigations, determine sources of illicit discharges, and enforce the removal
of illicit discharges or connections.
B. Definitions
Illicit Discharge: Any direct or indirect non -storm water discharge to the storm drain
system, except as exempted below.
Illicit Connections: An illicit connection is defined as either of the following:
Any drain or conveyance, whether on the surface or subsurface, which allows an illegal
discharge to enter the storm drain system, including but not limited to any conveyances
which allow any non -storm water discharge including sewage, process wastewater, and
wash water to enter the storm drain system and any connections to the storm drain
system from indoor drains and sinks, regardless of whether said drain or connection had
been previously allowed, permitted, or approved by an authorized enforcement agency
or,
Any drain or conveyance connected from a commercial or industrial land use to the
storm drain system which has not been documented in plans, maps, or equivalent
records and approved by an authorized enforcement agency.
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MS4: Municipal Separate Storm Sewer System. A conveyance or system of
conveyances (including roads with drainage systems, municipal streets, catch basins
curbs, gutters, ditches, manmade channels, or storm drains) that transports stormwater
to receiving streams, lakes, and/or oceans.
C. Categories of Illicit Discharges
The following table was developed by MACTEC Engineering & Consulting for the
Scripps Institution of Oceanography in San Diego California. It is a summary of the
types, characteristics, and examples of illicit discharges.
Frequency
Continuous: Discharge occurs most or all of the time.
Intermittent: Discharge occurs over a short period. (i.e. a few hours a day or a few days a year.)
Transitory: Discharge occurs rarely, usually a singular event.
Flow Type
• Sewage and Septage: Flows that are produced from sewer pipes and septic systems.
• Washwater. Flows generated from a wide variety of activities and operations (i.e. vehicle and
equipment washing).
• Liquid Wastes: Refers to a wide variety of flows such as oil, paint, and process water.
• Tap Water: Flows derived from leaks and losses during the distribution of drinking water in the water
supply system or water from hydrant and fire suppression system flushing. Specific to SIO seawater
losses will considered under this category.
• Landscape Irrigation: Flows derived from excess potable water used for irrigation enters a storm
water conveyance system.
• Groundwater and Spring Water. Flows occur when local water table rises above the bottom
elevation of the storm water conveyance system and water enters the storm water conveyance
system through open joints and cracks, or where open channels or pipes may intercept seeps and
springs.
• Air Conditioning and Refrigeration Condensate: Flows derived from the condensate produced by
air conditioners or refrigerators.
• Pools, Fountains, Water Tanks, and Aquariums: Flows derived from leaks and losses from pools,
fountains, water tanks, and aquariums and the associated appurtenances.
• Aboveground Storage Tanks: Flows derived from leaks and losses from emergency generators
and transformers.
Mode of Entry
• Direct. Discharge is connected directly to the storm water conveyance system through a sewage
pipe, shop drain, or other kind of pipe. Tend to produce continuous and intermittent discharges.
o Sewage Cross -Connection: A sewer pipe improperly connected to the storm water conveyance
system producing a continuous discharge of raw sewage from the pipe.
o Straight Pipe: Refers to relatively small diameter pipes or hoses that intentionally bypass the
sanitary connection or septic drain fields, producing direct discharges into open channels or
streams.
o Industrial or Commercial Cross -Connection: Occur when a drain pipe is improperly
connected to the storm water conveyance system producing a discharge wash water, process
water, or other inappropriate flows into the storm drain pipe (i.e. shop drains).
• Indirect: Flows generated outside the storm water conveyance system that enter through storm drain
inlets or by infiltrating the joints of the pipe. Tend to produce intermittent or transitory discharges.
o Groundwater and Spring Water Seepage: (see Flow Type)
o Spills: Transitory discharges that occur when a spill travels across an impervious surface and
enters a storm drain inlet (i.e. gasoline from an accident).
o Dumping: Transitory discharge created when liquid wastes such as oil, grease, paint, solvents,
and various other related fluids are dumped purposefully or ignorantly into the storm water
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o Outdoor Washing Activities: Intermittent or transitory washing activities including, but not
limited to, washing of fueling areas, outdoor storage areas, parking lots, and vehicles or
equipment.
o Non -Target Irrigation from Landscaping: Intermittent discharges from over -watering,
misdirected sprinklers, or broken sprinkler heads or pipes that send potable water over
impervious surfaces into a storm water conveyance system.
D. Exempt Discharges
The following Non-stormwater discharges are allowed into 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
■ Flows from riparian habitats
and wetlands
■ Dechlorinated swimming pool
discharges
■ Street wash water
■ Other non-stormwater
discharges for which a valid
NPDES discharge permit has
been approved and issued by
the State of North Carolina
2. DETERMINE PRIORITY AREAS / IDENTIFY HOTSPOTS
To identify the areas within the MS4 with a high potential of illicit discharges and connections,
available data was collected and analyzed, and an illicit discharge potential (IDP) was assigned
to geographic areas. Outfalls within areas with a higher IDP were screed initially and all other
outfalls were screened subsequently. This data is used to guide outfall inspections. Following
are the types on information that were initially used to prioritize the MS4.
A. Delineate Subwatersheds
The MS4 was divided into smaller, more manageable units known as subwatersheds.
These are shown on the MS4 Map and are available through GIS.
B. Land Use or Zoning Data
Land use or zoning maps were used to identify potential generating sites or "hotspots".
In general, industrial and commercial land use have a higher potential for illicit
discharges than residential.
C. Industrial NPDES Permit Holders
Industrial sites produce a wide range of flows that can cause illicit discharges. The most
common continuous discharges are operations involving the disposal of rinse water,
process water, wash water and contaminated, noncontact cooling water. Spills and
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leaks, ruptured pipes, and leaking underground storage tanks are also a source of
indirect discharges. A list of the industrial NPDES stormwater permit holders within the
City's jurisdiction will be obtained from NCDEQ and updated annually. These sites will
be added to the MS4 map and the areas in which they are located will be given a high
priority for outfall screening and MS4 mapping.
D. Areas known to have problems or complaints.
Informal interviews with City employees are conducted to determine the nature and
location of any past complaints that may be related to illicit discharges or connections.
These discussions will be supplemented by IDDE recordkeeping to determine hotspots
not otherwise identified. This will happen annually within the stormwater program annual
reporting process.
E. Septic Systems
Subwatersheds located outside of the sewer service area are presumably served by
septic systems. Initially, these areas were prioritized for mapping due to the potential for
failing septic systems. After reviewing these areas, the City has limited jurisdiction over
these areas but continues to monitor the MS4 in these areas.
F. Results of Outfall screening
As the outfalls in the City's jurisdiction were mapped, any areas where the outfall density
per stream mile is greater than 20 are considered to have a high IDP. Follow-up outfall
screening will prioritize these areas.
3. MS4 MAP
Identifying and understanding the local storm drainage infrastructure and conveyance system is
an important first step in the development of an IDDE program. The City's GPS located GIS
map provides that basis and was completed during the first permit cycle. The map includes the
MS4, subwatersheds, storm drainage outfalls, streets, the water supply watershed area, new
development stormwater permits (including permitted and constructed SCM's), the wastewater
collection system and other GIS and City information. The map is to be updated with
improvements on at least an annual basis.
The intent of the MS4 map is to provide a basis for investigation of stormwater pollution while
also providing a guide for future outfall screening and stream walks.
4. DRY WEATHER FLOW SCREENING
The City will complete outfall screening and investigate dry weather flows. Initial field screening
of the MS4 outfalls was conducted during initial mapping activities. During the following permit
cycles, the City will conduct outfall screening in a manner so as to screen every outfall at least
once per permit cycle. The purpose of the screening is to locate those outfalls that have
continuous or intermittent dry weather discharges. Field inspectors will walk the receiving
streams identified in the City's stormwater permit, map the locations of stormwater outfalls,
record the physical characteristics of the outfall, photograph the outfall, and document physical
observations of any dry weather flow that may be present.
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The screening will be conducted from late fall to early spring when leaves are off the trees and
vegetative undergrowth is minimal. There must be a dry period of at least 48 hours before a
screening can be conducted. For each outfall where a dry weather flow is found, the field
inspector will check the flow for the physical characteristics shown in the following list.
■ Flow Rate ■ Temperature
■ Odor ■ Deposits/Stains
■ Color ■ Vegetation Conditions
■ Turbidity ■ Floatables
When an obvious illicit discharge is found, the field inspector will immediately notify the public
works department and track the discharge upstream to its source, if possible (see Section 4). A
severity rating, on a scale of 1 to 3, will be assigned for odor, color, turbidity, and floatables and
each outfall will be given a designation according to the following criteria:
Designation
Description
1: Obvious Discharge
Outfalls where there is an illicit
discharge that doesn't even
require sample collection for
confirmation.
2: Suspect Discharge
Flowing outfalls with high severity
on one or more physical
indicators.
3: Potential Discharge
Flowing or non -flowing outfalls
with presence of two or more
physical indicators.
4: Unlikely Discharge
Non -flowing outfalls with no
physical indicators of an illicit
discharge.
The outfall locations will be recorded on a map and the associated inventory will be maintained
in a GIS or database.
5. PROCEDURES FOR ILLICIT DISCHARGE REMOVAL
A. Identifying the Type of Discharge
Often identifying the type of discharge will help in determining a possible source. The
type of investigation will depend primarily on the land use within the outfall drainage area
with the goal to identify the most likely type of discharge. In residential areas, generally
the most common illicit discharges are sewage and wash water flows. Industrial -
commercial areas however, often have flows that are not composed of either sewage or
wash water. An exception to this process is for sanitary sewer overflows from the City's
wastewater collection system. These will be tracked through the City's collection system
program and annually reported within the City's MS4 program as well.
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Most illicit discharges are readily identifiable in the field, such as paint or oil. If the source
is not readily identifiable then the flow chart shown below will aid in identifying the type of
discharge. The methods shown require some field and laboratory analysis. Analysis for
Boron, Ammonia, and Fluoride are required to characterize the discharge as sewage,
wash water, tap water, or natural water in residential watersheds.
Intermittent flows are difficult to sample. Techniques to collect samples involve partially
damming up the pipe where the suspected discharge occurs and returning at a later time
to sample the discharge stored behind the dam. Another method involves the use of
Optical Brightener Monitoring (OBM) traps. When these absorbent pads are anchored in
the pipe or manhole to capture dry weather flows, they can be used to determine the
presence of flow and/or detergents. The pads are then retrieved after 48 hours and are
observed under a fluorescent light that will indicate if they have been exposed to
detergents. These methods, or variations on them, will be used to collect samples from
known or suspected intermittent flows.
Flow Chart to Identify Illicit Discharges.
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B. Finding the Source
The City will attempt to find the source of all dry weather flows. However, since many of
these flows may be intermittent or transitory, identifying 100% of dry weather flows is
unlikely.
For each dry weather discharge, the inspector, after conducting the outfall mapping,
documenting the physical characteristics, and performing visual flow observations, will
follow the pipe or drainage system upstream in an attempt to identify the general location
from which the discharge originates. The goal is to isolate the discharge between two
inlets. If the inspector cannot identify the specific source through visual observation, or if
the trail of the discharge dissipates, further investigations will be necessary and is likely
to require the outfall screening/testing noted in portion A.
Depending on the circumstances, the City may video those storm sewers that look
suspicious to identify pollutant sources that cannot be located through simple visual
observation and/or sampling. For example, the City may be able to determine, based on
visual observation and/or sampling, that an illicit connection exists between two specific
inlets. Video inspection of the stretch of storm sewer between these two manholes
could be used to isolate the exact source of the illicit connection/discharge.
In addition, letters may be sent to residents and businesses alerting them to the problem
that is under investigation to solicit their assistance in finding the source. A building by
building evaluation may also be used in areas where a problem has been isolated to a
small area.
The City may also conduct physical inspection of commercial and/or residential facilities
as needed to verify illicit connections detected through visual outfall inspection,
sampling, and/or manhole flow observation. As necessary, facility inspections will
include dye testing of suspect facility plumbing fixtures. All facility inspections will be
documented.
C. Remove/Correct Illicit Discharge
Once an illicit connection/discharge has been identified and verified, the City will notify
the owner in writing and direct them to eliminate the illicit connection/discharge within a
specified time frame. The notification will require the owner to inform the City when the
connection has been eliminated. The time frame for eliminating the illicit connection or
discharge will depend on the type of illicit connection/discharge and how difficult
elimination will be.
The City will follow up with the owner to ensure that the connection/discharge has been
eliminated. If the connection has not been eliminated, the City will enforce its Illicit
Discharge ordinance to obtain compliance.
6. INSPECTION PROGRAM
All outfalls were screened during mapping and are now screened at least once during each
permit cycle. Problem outfalls, and outfalls where illicit discharges were previously detected and
eliminated will be inspected more regularly. If two consecutive inspections show no evidence of
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dry weather flow or illicit discharge, the outfall will be inspected once every permit cycle. If a
complaint is received concerning a outfall, it will be inspected as soon as possible.
7. PUBLIC EDUCATION
The City will be assisted in educating the public by Stormwater Smart to educate the public
about hazards associated with illicit discharges and improper disposal of waste. Public
employees, businesses, and the general public will be targeted.
8. ESTABLISH PUBLIC REPORTING HOTLINE
The City will make use of the toll -free NCDENR Customer service hotline and the City's primary
phone number for reporting. These will be publicized in education materials targeting IDDE and
on the City's website. The City has not found the need to have a dedicated hotline that would
be answered by the same staff as the normal phone number. After notification, City staff is to
notify the City Public Services Director who will coordinate with investigation with the City's
contracted stormwater engineer.
9. TRAINING
City Public Works staff will receive specific training on screening and inspecting outfalls,
identifying, tracking, and removing illicit discharges and connections. Training is to be
completed annually when possible.
10. HOUSEHOLD HAZARDOUS WASTE COLLECTION
The City will work with Alamance and Orange County to provide household hazardous waste
collections. This encourages the general public to properly dispose of hazardous wastes
instead of illegally dumping them in the watershed. Currently this occurs approximately once a
year.
11. RECORDKEEPING AND TRACKING SYSTEM
The City will create and maintain a database that documents all activities associated with this
IDDE program including the following:
■ All outfall screening information.
■ All MS4 mapping information.
■ Number of dry weather flows found.
■ Number of illicit discharges/connections found.
■ Number of illicit discharges/connections removed.
■ Number of illicit discharges/connections found through citizen complaints.
■ Information on video, dye, and/or smoke testing performed.
■ Number of facility inspections.
■ Information on industrial facilities within the City's jurisdiction that have NPDES
stormwater permits.
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12. PROGRAM ASSESSMENT AND EVALUATION
The IDDE program is to be assessed and evaluated on an annual and permit cycle basis. The
program is to be evaluated based upon the following metrics. A productive program is expected
to comply with most metrics on an annual basis and all metrics on a permit cycle basis.
Program Assessment
Item
Annual
Annual
Expectation
Permit
Cycle
Permit Cycle
Expectation
% Public Works Staff Trained
75%
100%
Number of Illicit Discharges Reported
• of Illicit Discharges Investigated
100%
100%
• of Illicit Discharges Successfully Addressed
100%
100%
• of MS4 Outfalls Screened
20%
100%
New Construction Added to Map
100%
100%
Number of Sanitary Sewer Overflows
100%
100%
Household Hazardous Waste Collection
1
5
Summary to be provided in annual report
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