Long Creek Sewer Spill

Few things are as appalling as a sanitary sewer overflow (SSO). Ripe with bacteria, industrial chemicals, pharmaceuticals, nutrients and more, it is one source of water quality degradation and contamination that becomes a skin contact issue because of the potential for bacterial infections. We want to flush our toilets and know that sewage will get to a wastewater treatment plant (WWTP) so that the sewage can be cleaned and bacteria killed. Sometimes, spills occur. It happens. 😉

The recent 15.4 million-gallon sewage spill into Long Creek — which empties into upper Lake Wylie by the U.S. National Whitewater Center (a popular recreation area) — is a great case example for a deeper look at the SSO issue and just how/why 15.4 million gallons could spill from one pipe.

Typical Sewer Overflows

A lot of SSOs occur during heavy rain, when stormwater infiltrates the sewer system (via manholes, gaps), mixes with sewage, and causes an overflow. This is often cited as “inflow and infiltration” or “I & I” by utilities. However, a lot of SSOs also occur when there isn’t rain. Sewer pipes and their lift stations get inundated with materials that shouldn’t be there — grease, rags, “flushable” or “disposable” wipes. On the “flushable” wipes issue, you CAN flush ’em, but they don’t necessarily keep moving and breaking down in the sewer lines, and they can cause SSOs.

Most SSOs are on the order of hundreds to around one thousand gallons. Every utility has them. Does Charlotte Water have more than others? Sure. They also have more than 4,000 miles of lines to keep an eye on for the approximately 1.2 million people it serves.

Unfortunately, SSOs often impact creeks because they occur near them. Why do we run sewer lines by creeks? Sewer lines are gravity fed to the WWTPs. Creeks are where water gathers also because of gravity.

How Do You Spill 15.4 Million Gallons?

As sewage builds up in a system, larger and larger pipes are needed to convey sewage to a WWTP. Now, creeks of course flood. But utilities know this and, aside from a few crossings, lines that parallel the creeks are set back. In the case of the Long Creek 15.4-million-gallon spill, the pipe was set back 50 feet.

Here’s where this incident becomes unique.

Long Creek 15.4 million gallon sewer spill
Depiction of how creek flow washed away the soil around a sewer pipe, causing it to collapse and spill.

It appears the spill did not start with the heavy rain of Monday, April 23rd, but rather with heavy rain on April 15. That runoff caused a tree on the bank toppled across Long Creek. It didn’t hit the pipe, but it caused Long Creek to flow around and over to the pipe, where it scoured the supporting soil around the pipe and caused it to fail. This was a 30″ line now submerged in a heavily flowing creek with muddy, saturated banks.

Repairs and diversion of the Long Creek and the adjacent sewer system
Repairs and diversion of the Long Creek and the adjacent sewer system. Note the pipe/sewage in the bottom right corner.

Not until after Monday’s (4/23) rain did someone contacted Charlotte-Mecklenburg Stormwater Services about the smell of sewage and some dead fish. Once their water quality folks confirmed the broken pipe, Charlotte Water started repairs. Charlotte Water looked back at its records for lost flow and provided an honest calculation — one three times larger than the next largest spills on record. But the spill was spread out over more than one week.

The Bigger Issue

This sewer line was buried 50 feet away from Long Creek. The diversion from the fallen tree was anomalous, as the spill total ended up being. Conventional wisdom would say that a 50-ft setback would be sufficient. However, our creeks respond differently to rainfall than they did when Mecklenburg County was almost exclusively forest and pasture. Impervious surface area — roads, sidewalks, parking lots, roofs — has created flashier runoff. No one wants standing water after a rain. They want a stormwater system to convey stormwater away quickly. Ideally, that stormwater would at least go through some sort of retention (to slow it down) and treatment (to filter out automotive fluids, brake dust, sediment, other contaminants) before entering a creek. Look behind large shopping centers, and you’ll often see these retention systems. But for a lot of residential developments, these stormwater measures have not been put in place as they should. Furthermore, citizens frequently complain about their stormwater fees included with their utility bill, often not understanding the services stormwater fees provide.

Long Creek’s drainage basin has changed dramatically in recent years with northern Mecklenburg County’s development boom. Thus, the runoff in the creeks have changed. Water piles up more quickly and ultimately in a larger peak discharge. The same rainfalls now cause more flooding and more bank incision that can lead to pipe failures like this, especially when something like a downed tree diverts flow to a part of the creek channel that had not experienced such concentrated flow.

Still, even with more miles of line with the explosive growth in Mecklenburg County in recent years, attentiveness to SSOs has led to a decrease in the number of incidents.

Charlotte Water annual SSOs
Charlotte Water annual SSOs

What Can YOU Do?

Keep an eye and a nose out, and if you see/smell something, say something! All utilities need your help monitoring their infrastructure to identify when and where spills occur. If failures are not identified, they are not fixed, but that does not change the fact that sewage still runs into our waterways. You can also call the utility (311 in Charlotte) or email us (use the Catawba Water Watcher phone app and/or email us at sam@catawbariverkeeper.org). Take good pictures and note the location as precisely as possible.

Creek downstream of a sewer overflow
Creek downstream of a sewer overflow. Note the milky white/gray color. If you were there, you’d definitely note the smell, too.

Additionally, make sure you do not put anything down the drain that shouldn’t go. Charlotte Water notes that nearly half of all spills occur because of grease and [supposedly] “disposable” wipes.

When it rains, check up on a lift station or a manhole in a low-lying area. A case example of personal (Riverkeeper Sam Perkins) experience: In December 2015, I learned that there had been a SSO in my neighborhood off Park Road in Charlotte. It’s a low-lying area near a tributary to Little Sugar Creek. Charlotte Water stopped the SSO and made repairs. One week later, we had heavy rain, and I took a different route home through the neighborhood to make sure I went by that manhole. Sure enough, it was overflowing again with a mix of rain and sewage. I called Charlotte Water, they made repairs, and since then, I haven’t seen it overflow. I’ve had a similar experience near my gym.

Want to know where SSOs have occurred near you? We requested data on SSOs, geocoded their locations, summarized the data, and compiled it all in a map here for you (updates coming soon): http://catawba.maps.arcgis.com/apps/webappviewer/index.html?id=eb9f71512620458893b840543254e6e5

SSOs often occur over and over again in the same place. Charlotte Water needs your help to know when they need repairs. They [the utility] benefits, you [the utility customer] benefits and all of us enjoy better water quality in the process.

After the Spill

The heavy rain helped with both dilution and flushing of the sewage, though turbidity (sediment) in the water helps harbor bacteria. We generally tell people to avoid water for 24-48 hours after a larger (1″+) rain event, especially if water is still turbid or has an odor. Keep an ear out for “no-swim” advisories (though not just swimming; this means “no contact”) and for an “all clear” to be issued afterward. Again, bacteria are a skin contact issue unlike a lot of water quality contaminants.

Sampling Long Creek
Sampling Long Creek
Long Creek 4/24
Long Creek 4/24, still very turbid and full of bacteria, even without the ‘physical’ evidence of a sewer overflow.

We and Charlotte-Mecklenburg Stormwater Services have both been testing the water for bacteria. Our tests (specifically for E. coli), indicate it is improving, but safe tests have not come back such that the “no-swim” advisory can be lifted. Water quality concerns for bacteria start when levels reach 200 colony forming units (CFU)/100 mL. Below are some of the plate tests we run to test for E. coli. LC-2 4/24 was in the “too numerous to count” (TNTC) range of approximately 10,000 CFU/100 mL. By 4/26, LC-2 dropped to 900 CFU/100 mL. On 4/26, upstream of the spill, LC-4 was at 333 CFU/100 mL.

Long Creek Bacteria Progression
Some of our E. coli bacteria sample plates from Long Creek. LC-2 is downstream of the spill. 4/24 was just after the spill was stopped and water levels were still high. LC-2 4/26 shows improvement. On 4/26, we were also able to get a sample upstream of the spill, indicating some bacteria are present, though much less.

With enough time, bacteria will die off. Sunlight in particular helps to kill bacteria, which is why turbid water harbors bacteria (blocking sunlight). Stay tuned for updates, and keep an eye and a nose out!