HomeMy WebLinkAbout20_NPDES Outfall Screening SOP
NPDES Outfall Screening Program:
Standard Operating Procedures
City of Greensboro, North Carolina
MS4 Stormwater Permit NCS000248
April 2022
TABLE OF CONTENTS
PURPOSE ............................................................................................................................... 5
OUTFALL DETERMINATIONS ............................................................................................... 5
NPDES OUTFALLS (MAJOR MS4 OUTFALL) ........................................................................... 5
STEPS FOR MAPPING NPDES OUTFALLS ............................................................................... 5
OUTFALL MAP AND INSPECTION DASHBOARD .......................................................................... 5
INSPECTION/SCREENING PROCEDURES .......................................................................... 6
FREQUENCY ......................................................................................................................... 6
PREPARATION ...................................................................................................................... 6
Ambient Conditions ........................................................................................................ 6
Equipment ...................................................................................................................... 7
Safety Procedures .......................................................................................................... 7
INSPECTING AND DOCUMENTING ...................................................................................... 7
ENTERING OUTFALL INFORMATION ......................................................................................... 7
ENTERING SCREENING INFORMATION...................................................................................... 9
Outfall Not Screened ...................................................................................................... 9
Outfall Screened ............................................................................................................. 9
FOLLOW-UP PROCEDURES ............................................................................................... 11
REFERRALS........................................................................................................................ 11
Water Quality................................................................................................................ 11
Field Operations Department ....................................................................................... 12
Erosion and Sediment Contol ....................................................................................... 12
TRAINING ............................................................................................................................. 12
REVISION LOG
Revision Number Date Revision(s) Staff
ACRONYMS/ABBREVIATIONS
Acronym Definition
BMP Best Management Practice
DMLR Division of Energy, Mineral, and Land Resources
EAM Enterprise Asset Management
ESC Erosion & Sediment Control
GIS Geographic Information Systems/Science
HDPE High-Density Polyethylene
IDDE Illicit Discharge Detection and Elimination
IO Inlet/Outlet
MS4 Municipal Separate Storm Sewer System
NCDEQ North Carolina Department of Environmental Quality
NPDES National Pollutant Discharge Elimination System
OM Operations Management
PVC Polyvinyl Chloride
SOP Standard Operating Procedures
USGS United States Geological Survey
WQ Water Quality
PURPOSE
Outfall Inspections is a Best Management Practice (BMP) that supports section D, Illicit Discharge
Detection and Elimination (IDDE), of the City of Greensboro’s Municipal Separate Storm Sewer
System (MS4) NPDES permit as issued by the North Carolina Department of Environmental Quality
(NCDEQ). The IDDE section sets forth the criteria for compliance, including ordinances, reporting
mechanisms, proactive and responsive approaches to pollution concerns, etc.
Inspecting outfalls to detect dry-weather flows is a proactive approach to eliminating pollution. This
BMP, in conjunction with other BMPs, supports the Stormwater Management Division’s overall
objectives for identifying and eliminating illicit discharges and improper disposals. (Refer the I DDE
Program Plan for additional information.)
OUTFALL DETERMINATIONS
NPDES OUTFALLS (MAJOR MS4 OUTFALL)
The City of Greensboro’s MS4 Permit, issued by DMLR, defines NPDES outfalls as follows:
“…discharges from a single pipe with an inside diameter of 36 inches or more or its equivalent
(discharge from a single conveyance other than circular pipe which is associated with a drainage area
of more than 50 acres); or for municipal separate storm sewers that receive storm water from lands
zoned for industrial activity (based on comprehensive zoning plans or the equivalent), an outfall that
discharges from a single pipe with an inside diameter of 12 inches or more from its equivalent
(discharge other than a circular pipe associated with a drainage area of 2 acres or more).”
STEPS FOR MAPPING NPDES OUTFALLS
Outfalls are mapped by staff in the Water Resources Engineering Division using ArcGIS (e.g., ArcMap
and ArcPro). Using the zoning layer as a base map and the MS4 permit requirements, major outfalls
are identified and marked as NPDES outfalls. As new areas are developed, staff uses as-builts to
map new infrastructure, including NPDES outfalls. These updates are ongoing and live, with edits
showing almost immediately on the outfall inspection map and applications.
OUTFALL MAP AND INSPECTION DASHBOARD
Inspection status and other information can be determined by viewing the NPDES Outfall Inspections
Dashboard.
The initial view of the dashboard gives the following information:
Total number of NPDES outfalls
Total number of outfalls inspected and attempted during the current permit cycle (or within the
past five years)
Number of outfalls inspected by month, quarter, and year
Color-coded legend describing outfall colors
o Green: Outfall inspected
o Purple: Outfall visited; unable to inspect
o Orange: Outfall nearing five-year mark
o Red: Needs inspected; last inspection greater than five years
In addition, the map is interactive such that the user can select outfalls in a specific subbasin, specify
dates for number of inspections, and search for specific outfalls. Clicking on an outfall will bring up
information specific to that outfall, including its inspection history and any photos.
INSPECTION/SCREENING PROCEDURES
FREQUENCY
Outfall screening is ongoing, with the goal of inspecting all major outfalls at least once during the
permit cycle. An outfall may be inspected more often if warranted through concerns, citizen reports,
etc.
PREPARATION
Ambient Conditions
Outfall inspections should take place during ambient conditions, or dry-weather flows. Ambient
conditions for outfall screening is defined as >72 hours with <0.1" of rainfall. General guidance
indicates that if the rainfall amount was <0.1", it may not be necessary to wait a full 72 hours
assuming surface waters have returned to baseflow. These facts can be verified in multiple ways,
including using USGS rainfall and stream flow data.
Equipment
The following list identifies potential equipment needed to efficiently perform outfall inspections.
Technical equipment (cell phone, tablet, hot spot, etc.)
Water quality guidebook
Charging cords
Flashlight
Manhole pick
Inspection camera
Bush axe
Safety boots
Reflective vest
Gloves
Hardhat
First-aid kit
Suncreen and insect repellent
Muck boots/waders
Safety Procedures
Observe the following safety protocols when performing field work, including outfall inspections.
Safety-toed boots and a reflective safety vest must be worn at all times.
Park vehicle in secure area and keep locked at all times.
Avoid being alone in situations where potential danger is present or you feel uncomfortable.
Avoid contact with any possible illicit substances.
Practice safe manhole and grate removal and never grab with your hands. Use two people if
necessary.
Be mindful of traffic and all surroundings. Avoid checking inventory in the street, but if
completely necessary, set up time with stormwater construction and maintenance to
adequately block off road.
Do not enter a manhole or any other confined space.
Stay hydrated and be mindful of risks involving sunburn and insect bites.
Utilize the first-aid kit located in vehicle if needed. Be sure to replace any items used or
removed from first-aid kit.
INSPECTING AND DOCUM ENTING
Two ArcGIS applications are used for outfall screening: Field Maps and Survey123. Staff can access
these from a city-issued phone, tablet, or other device. (Note that screenshots may differ across
device types.)
ENTERING OUTFALL INFORMATION
1. Access the Field Maps application from the home screen. Choose NPDES Screening Web Map.
2. Find the desired location
by clicking on the
location button, entering
the address, or
zooming in manually.
3. Select a red or an orange outfall. (Red has not been screened during the current permit cycle;
orange is nearing expiration.) Once selected, the outfall will appear in the menu on the left. Click it
to expand the information about the outfall and scroll down to the Survery123 link. Click the link
and Survey123 will automatically open.
4. Complete the following:
Select name from dropdown menu.
Select Yes or No regarding industrial NPDES outfall
status. (This helps GIS department verify the accuracy
of the GIS layers.)
Select the current weather conditions from the
dropdown menu.
Enter the approximate temperature (optional).
Survey123 will automatically fill in pertinent information, including
the date, time, location, subbasin, and pipeIO’s asset number.
ENTERING SCREENING INFORMATION
Outfall Not Screened
1. If the outfall cannot be screened, select No.
2. Select the reason (vegetation, access
permission, other), adding comments if Other is
selected and/or if there are additional notes.
3. If needed, capture a photo by clicking on the
camera or folder icon.
4. Click the checkmark in the bottom right corner to
submit the survey. The screen will reset back
the main Survey123 application.
Outfall Screened
1. If the outfall can be screened, select Yes. This will expand the Outfall Description section.
2. Select the Pipe IO type (flared-end section, projected, headwall, or
outlet).
3. Select the pipe material (concrete, corrugated metal, HDPE, PVC,
iron, vitrified clay, stone, brick, other).
4. Select the pipe shape and enter the pipe dimensions. (Requested dimensions varies based on
pipe shape.)
5. If the pipe type is a headwall outlet, enter the Pipe IO depth. To
obtain depth, measure from the invert to the top of the headwall.
(This is recorded in surveyor’s feet: 1.0 = 12".)
6. Click the Outfall Physical Indicators and select observations for damage, deposits/stains, and
abnormal vegetation.
7. Select from the Submerged options.
(Selecting W ater or Sediment will
allow for additional fields of Partially
or Fully to be selected.)
8. Select the applicable responses for flow, odor, color, and floatables under Flow/Discharge
Physical Indicators.
Generally flow will be none or low, though higher flows may be present if the outfall is
downstream from a large drainage system and/or natural water sources (springs, ponds,
streams).
Provide a description of floatables for selections other than None.
9. Select the applicable option regarding the need for follow-up. (See the next section
for details on follow-up procedures and referrals.)
10. Capture photos of the outfall using the
camera icon.
11. When all survey responses have been
completed, click the checkmark in the
bottom right corner to submit the survey.
(The screen will reset back the main
Survey123 application screen. Go back to
the Field Maps application to locate the
next outfall screening.)
FOLLOW-UP PROCEDURES
REFERRALS
Water Quality
If it is an active water quality problem, the OM staff member should start tracking the potential
pollutant immediately in order to stop the discharge as soon as possible. To track the potential
pollutant, staff should track upstream through the stormwater infrastructure, open channels, etc., until
a possible source of the illicit discharge is found. The investigation should be photo-documented, and
Water Quality staff should be notified as soon as possible in order to help track the substance if
needed and/or be prepared to take over the investigation if the source in found. (See Erosion and
Sediment Control below if the pollutant is sediment from a construction site with a grading permit.)
If the source is not found, notes should be taken as to how far the substance was tracked, the
area where the potential pollution was found (residential, industrial, commercial), and any
other information that may be useful for Water Quality staff.
If the source is found, OM staff should make all efforts to stop the pollution from occurring. If a
perpetrator is found at the source, OM staff should obtain the following information as
applicable: individual’s name, company’s name (if applicable), phone number, and email
address. WQ staff will then take over the investigation, following enforcement procedures as
necessary.
If it is not an active discharge but OM staff suspects an intermittent problem or is unsure, he or she
can contact someone in the Water Quality section for guidance or potential follow-up.
Field Operations Department
Issues found with the overall structural condition of the outfall (riprap displacement, scour, headwall or
pipe separations, etc.) should be reported to Field Operations.
Erosion and Sediment Contol
Sediment (turbid water, sediment deposits, etc.) that is tracked to a construction site with a grading
permit should be immediately reported to ECS staff. ECS staff will investigate and implement the
appropriate procedures to eliminate construction runoff.
TRAINING
Training new employees on inspecting NPDES outfalls inspections typically includes (but is not limited
to) the following:
Review of applicable documents (outfall SOP, IDDE plan/SOP, pollution field guides,
ordinances, safety procedures, etc.)
Field training by experienced staff until new staff is deemed proficient
Documentation in Survey123 or other applications
Ongoing training takes place as processes or documentation procedures change or are updated.
When available, external training maybe be recommended to enhance the knowledge of new and
experienced staff.