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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.