It’s Fall, y’all! It is a great time to be inspecting outfalls. The irrigation water has stopped flowing and the snow has yet to come. Now is the perfect time to review! Below we discuss what an outfall is, why and when to inspection outfalls, what needs to be included in an outfall inspection and real examples of outfall inspection forms from MS4s.
What is an Outfall?
Most MS4’s include outfall inspections as part of their Illicit Discharge Detection and Elimination programs. But what is an outfall exactly? Under the IDDE section of the General Permit, Utah has defined an outfall as,
“a point source at the point where a municipal separate storm sewer discharges to Waters of the State and does not include open conveyances connecting two municipal separate storm sewers, or pipes, tunnels or other conveyances which connect segments of the same stream or other Waters of the State and are used to convey waters of the State.”
Other states also include discharges from a storm water system into another MS4 system. Water can be discharged from pipes, tunnels, ditches, swales, etc. Outfalls can be small or large, some up to 20 feet in diameter.
Some MS4s only have a handful of outfalls. Others contain many, many outfalls. For example, Bountiful, Utah is 13.47 square miles and contains 256 outfall locations. While across the US, East Hempfield, PA is 21.16 square miles and contains 353 outfall locations. Larger still is Philadelphia, PA at 141.7 square miles and contains 164 CSO (combined sewer overflow) outfalls and more than 450 stormwater outfalls.
Why and when do we inspect Outfalls?
“We normally do only dry weather inspections at outfalls where water from storm drains enters our streams; they are done to screen for illicit discharges/connections.”
– Todd Christensen Bountiful, Utah
According to the Utah permit 184.108.40.206.3, dry weather screening or outfall inspection activities are for the purpose of verifying outfall locations and detecting illicit discharges that discharge within the Permittee’s jurisdiction to a receiving water.
In Utah, outfalls need to be inspected at least once every 5 years for the main reason of identifying illicit discharges and possible contamination in the stormwater supply. Generally, MS4s divide the number of their outfalls over a five-year span allowing them to inspect 20% per year. However, some locations are identified as High Priority and therefore are inspected every year. As an example, in Bountiful, they have 256 outfalls. Of those, only seven are high priority and need to be inspected every year.
What needs to be included in an outfall inspection?
“To me, the most important thing is whether or not there is a discharge that is off colored or has an odor.”
– JD Shepherd Mapleton, Utah
While some states may require a standard form, the state of Utah does not. After speaking with some inspectors and Public Works Directors, a list was compiled of important aspects and information that needs to be on a dry weather screening/outfall inspection.
- Identification information about the outfall
- Current Weather Information
- Past Weather Information
- Nature of Discharge
- Quality (color, odor, clarity, solids, foam, benthic growth)
- Flow present
- Quality of the flow and water
Examples of Outfall and Dry Weather Screening Forms
That is all nice and good, but wouldn’t it be great to see the real forms other MS4s are using to inspect their outfalls? You can! Check out our Outfall Inspection Forms page where you can see the forms South Salt Lake, Draper and Mapleton are using.
So what’s holding you back? Grab your inspection form and get out there and start inspection those outfalls!
If you are looking for a way to complete your inspections on your mobile device and to save them as attachments to your GIS data, then you are looking for UtiliSync! Send me an email today and we can have you ready to go tomorrow.
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