Monday, February 20, 2017

14 percent of septics are failing because we saw the dye

I wasn't going to write about this 14 percent thing because I didn't really think it needed explanation to begin with. But, there it is, still out there. Like a thing that exists, because it came out of the mouth of County Commissioner Gary Edwards:
The main thing we need to get to the bottom of is what science brought this about because it has been alleged that 14 percent of septic systems failing each year — that is pure malarkey. That means at the end of a seven-year period we would have had 98 percent of septic system fail, that is pure ludicrous.
Basically, there's a fairly good estimate out there that somewhere around 14 percent of septics system are polluting into streams and bays each year. This data, in the case of Thurston County came from an on-site study of septic systems around Henderson Inlet in the late 90s.

What county staff did was put a dye into the septic systems around Henderson Inlet and 14 percent of the tested systems leaked that dye into places where they shouldn't be leaking anything because septic systems shouldn't be polluting. But they did.

What that particular study didn't say is that 14 percent fail each year. Obviously, if you go around and test septic systems at one point in time and finding a failure rate, what you're doing is finding how many septics would be failing at any given point. 

Commission Edwards apparently picked up his bad math from Glen Morgan's blog.

What is a little more interesting is that the 1999 study took a look at two places, Henderson Inlet and the Thurston County stretch of the Nisqually reach. The Nisqually reach septics had an even worse failure rate, in the neighborhood of 20 percent.

Morgan took a shot at the 14 percent number by pointing out that repair permits issued by the county indicate that less that one percent of the septics in the Deschutes watershed had failed. That assumes a one to one ratio of permits for repair and actually polluting septics.

But, it would seem that a failing to the point of needing obvious repair and a polluting septic are not the same thing:
Sometimes a (septic) failure is obvious, other times it’s not so obvious and not an easy thing to confirm. When a failure is not obvious but water quality data or other information seems to implicate a system as a problem system, additional measures must be taken.  
Dye testing is an effective way to verify a failure, but must be done correctly based on established procedures. Little is more definitive than seeing bright green dye flowing in a backyard or in surface water after passing through a property’s plumbing. 
Waiting for a homeowner to ask for a permit to repair their septic system is a very low bar to estimate failing septic systems. And, not all backed up or broken septics are polluting. And, certainly, there are septic systems that would work from the point of view of the homeowner but would leach pollutants.

Dye testing, the type of study that the 14 percent number came from, is much more accurate to asses the one thing that we're talking about here, whether a septic system is polluting.


James Haynes said...

As always, thank you Emmett. We are living in an age when powerful people are doing their level best to kick empirical reality downstairs. You are doing your job as a journalist and countering them with genuine facts.

I hope (probably in vain) that somebody at the Daily Zero picks up on your analysis and publicizes it.

Who Watches Who Governs? said...

Emmett, my friend, you are better than this post would indicate. The study done in the Henderson Watershed was flawed less because they were able to find 14 (of the approximately 4,000+ septic systems in that watershed) to be problematic. The problem is that this "14%" number was replicated in various reports as a projection of the "failing" septic systems in the county. Specifically, this 14% projection was used in the Deschutes Watershed study as recently as last year as a factual projection of the "failing systems" in that watershed when the true number was less than 0.5% - even providing a very generous estimate of the study.

More significantly this collective and extrapolated ignorance was cut and paste widely by the Thurston County Health Department and repeated like a religious mantra despite all practical evidence to to the contrary. The objective of this obsession with tortured data was mainly political and financial - the goal was to institute the widely discredited "Crap Tax" to bolster the Thurston County Health Department's budget, not because of any health emergency.

Even more interesting, this "14%" number was repeated in King County's recently discredited and ultimately rejected effort to impose their own "Turd Tax" on septic systems up there. Rather than rely on imaginary numbers like silly 14% fiction invented by Thurston County, I helped organize a team of volunteers to pour through every King County Health Department Septic System investigation or complaint over the last 14 years. This required pulling all the available files in Bellevue and manually reviewing every complaint and categorizing the results based on the health department inspectors. There are roughly 84,000 septic systems in King County (compared to roughly 52,000 in Thurston). Roughly 4000 complaints had been filed over a 14 year period. Based on King County Health Departments own records, approximately 50% of these complaints had either nothing to do with septic systems (sewer leaks, illegal trailers, etc) or there were no problems found upon inspection (yes, this included dye tests in many cases). Most of the remainder were very minor problems that were easily repaired, quickly notices, and did not result in anything more than a de minimis event. There is no reason to falsify or fake "studies" to push a public policy outcome that helps achieve little more than grow a bureaucracy.

My argument is that public money would be better directed at real significant sources of contamination and pollution like the wastewater treatment facilities who dump hundreds of millions of gallons of raw sewage into puget sound every year.

Emmett said...

Hi Glen,

Here's what I'm having a problem with, whether a "failed" septic, something that would be reported (like up in King County) or needing repair (like in your Thurston County data) is the same thing as a polluting septic. It seems to me that a perfectly functioning septic from the point of view of a neighbor or a homeowner could still pollute.

Thad Curtz said...

In fact, if you look at the study by way of the link in the last sentence of the first paragraph in Emmett's post, you find that Emmett's number is correct, and Glen's wrong. 14% of the Henderson septics that were tested were "failing", where "failing" means that sewage effluent marked by dye showed up on the ground or in surface water runoff paths like beach seeps and bulkhead drains AND a water sample with more than 200 fecal coliform bacteria per 100 ml was collected from the same site. Another 25% of the systems tested were "suspect", where that means effluent marked by dye showed up, OR those fecal coliform levels were found, but not both. (The numbers are in Table 3 on page 12.) (They wanted to study this shoreline area because elevated fecal coliform levels in the inlet were shutting down the commercial shellfish industry's harvests there.)

There were only 210 septics in the stretches of Henderson Inlet's shoreline that they studied, and they were only able to test 27% of those, or 58 systems, because you have to have the owner's permission to do this legally. Nine systems (or 14%) were failing. Another 14 systems (or 25%) were suspect. Maybe that's where Glen ended up with the impression that only 14 systems were "failing".

In any case, Glen's wrong about the 14%, and as a result the complaints about its subsequent misuse seem pretty groundless. In particular, the "4,000+ septic systems in the watershed" are completely irrelevant, because the study only wanted to test 210 systems along the shoreline, and it only ended up with the owner's permission to test 58 of them.

Nonetheless, it certainly isn't clear that you can generalize from this study to say anything about tje condition of all the septics in the County. I'm not enough of a statistician to even say confidently that having results for 14% or 25% of 58 systems allows you to generalize about the condition of the 210 they were trying to find out about, and they don't do any statistical analysis. (I would think that's a reasonably strong result statistically.) In any case, the study begins by saying that other County surveys have shown that septics near on the shoreline are "more likely to directly impact water quality than those in upland areas." They are close to streams, subsurface drainage areas, and the shoreline. Furthermore, "soils along the marine shoreline in Thurston County typically have severe limitations for drainage and proper septic systems functioning including impermeable clay or cemented till layers, seasonal high water tables, and very slow permeability."