News you did not get – until now. It’s about failing systems, only this time it wasn’t septic systems that failed. Add “exfiltration” and “infiltration to your vocabulary – here’s an editorial that may change your perspective.
In Miami, a major sewer line burst spilling more than 20 million gallons of raw sewage into the bay. http://www.miamiherald.com/2010/06/20/1690248/raw-sewage-spills-into-biscayne.html . The question must be asked. Are septic systems a huge problem? Are septic systems a justifiable target, or a target that can be easily blamed. We think the “easily blamed” is true.
Mid March, a lift station failure in Pace FL was reported in the Santa Rosa Press. Lift stations move municipal sewer contents to the wastewater treatment plants. This one was huge. A lightning strike was blamed for the rupture, although residents in the area say there was no lightning the day it was reported.
In the article a spokesperson for the Pace Water System said there is “no way of estimating how much sewage escaped after the rupture, so I did an estimate and told the Dept. of Environmental Protection 50,000 gallons.” There was mention in the article that there were prior complaints for more than a year that the lift station was leaking. Residents are extremely concerned about the impact on surrounding wetlands and bayous.
Here are some figures to absorb. Septic contractors were brought in to suck the sewage out of ditches and other areas surrounding the lift station. They worked eleven days, 24 hours a day. One truckload holds 4,200 gallons, and fills in approximately 1 ½ hours. Do the math, they always say. According to this information 739,200 gallons of creek water mixed with raw sewage recovered.
2,500 septic systems would have to be gathered all in one spot and completely explode their contents to equal the damage done by this one spill. However, septic systems do not explode. Raw sewage sinks to the bottom of the tank and happy little microbes eat bacteria. Not so with the lift station failure in Pace.
Now let’s talk about “exfiltration.” This is the term used in the wastewater industry to describe water and raw sewage that leaks out of a municipal sewer line BEFORE it reaches the municipal treatment plant. Estimates range from 10% to 40% depending on the age of the sewer line. Sewer lines older than 20-30 years experience a higher exfiltration rate than newer ones. There is no pre-treatment of exfiltrated sewage, because there is no tank with happy little microbes. It just leaks into the ground and the groundwater.
Again, we do the math. Our numbers are for one day. According to the Dept. of Health, there are 2.5 million septic systems in Florida serving approximately 6 million people who send 69.3 gallons of water and sewage per person/per day into their septic systems. Of the total flow, 10% is sewage, the other 90% is water from showers, washing machines, etc. Using DOH figures, 10% are failing in some fashion or another. Total untreated by septic systems is a little over 4 million gallons per day. It is important to remember, that a septic system in failure is hard to ignore and most are repaired to normal functioning within a few days. Only a small fraction of the 2.5 million systems would be bottomless tanks.
Exfiltration numbers for municipal sewers are based on 12,000,000 residents and approximately 1,000,000 tourists a day that are sending 69.3 gallons per person/per day into sewer lines. Using a generous 10% as our exfiltration factor, approximately 90 million gallons is seeping untreated from municipal sewers every day. That’s a 22:1 ratio!
It’s important to note that sewer leaks or breaks can go for years undetected. And, then there are lift station failures like the one in Pace, and line breaks like the one in Miami!
Now, consider that when the Wekiva Study Area Nitrogen Assessment was released in February 2008, it stated plainly that the “sewer input calculation (for nitrogen) did not consider losses due to exfiltration.” Septic systems were blamed for the remainder of the nitrogen input.
Infiltration, we are told is a larger problem than exfiltration! Infiltration happens when heavy rains fill sewer lines beyond the capacity of the municipal treatment plant to handle it. The result is “outfalls.” Outfalls are nothing more than a fancy word for dumping. They are permitted by Florida Dept. of Environmental Protection. There are ocean outfalls and inland river outfalls. We don’t have a number of gallons that are dumped from municipal plants each year, but it’s not a stretch of the imagination to think that the increase in fish kills and red tides during the summer rainy months might somehow be tied to this problem. However, septic drainfields too close to the high water table are taking the blame.
Two reasons for putting you through this little exercise.
(1) We sincerely hope people on sewers and legislators re-set their thinking and put into proper perspective the size of the septic system issue. A 22:1 ratio is significant proof that the amount of attention being paid to fixing the septic system problem is totally out of proportion to the size of the problem.
(2) We sincerely hope that the residents of Pace who are on septic systems, and septic owners in other parts of this state where lift station failures and outfalls might occur, do not get blamed for the pollution they more than likely did not cause.