Can an inappropriate septic setback affect more than just your health?

Regardless of what your level of education is, you likely know that if your septic system isn't far enough away from your drinking water / house / swimming pool / driveway, you're going to have a bad time. There are other factors to take into consideration, of course, like soil composition, pre-discharge sewage treatment, and potential break-out areas, but in general you want to keep your septic system far away from the rest of your life.

There are certain geographic areas where a traditional on-site sewerage system just isn't going to be feasible because of high water tables, or poor soils, or just small lot sizes. In B.C., the Sewerage System Regulation is fairly outcome based: maintain a 30m setback from a well, hire an "authorized person" to do the work, and you'll be just fine. It's up to the professional expertise of the authorized person to determine appropriate setbacks and siting for the sewage systems. If you're in one of these tough geographic areas, your course of action is typically a) hire an engineer to design you a treatment plant that treats the effluent before it goes into the soil, or b) find an Onsite Wastewater Practitioner who's willing to fudge some data to get your system in the ground.

Apparently, there are considerations besides just public health when you're looking to place your septic system in a less-than-ideal location. In Ohio, only 6.4% of soils have the requisite 4' vertical separation to allow for traditional tank-and-field on-site sewerage systems. As mentioned above, there are alternatives to traditional systems, but those typically cost a fair bit more money and require some professional input (which also doesn't come cheap). A recent study has shown that costs associated with inadequate sewerage systems can include repair costs, human health costs, increased system maintenance costs, and a "loss of property valuation".

The study looked 800 on-site sewerage systems (out of a possible 22000 in Licking County, OH), of which 616 used traditional tank-and-field systems. They only looked at those for which appropriate soils data was available, leaving them with a sample size of 549 properties for the study. Using the hedonic pricing method, which "uses the different characteristics of a traded good, such as real estate, to estimate the value of a non-traded good, such as water or soil quality", the researchers were able to identify the effect that a well-functioning septic system had on property values in the county.

The researchers looked at a number of variables that could have an effect on property value (property size, number of bedrooms, etc.), but their specific hypothesis was looking at the quality of soils with regard to sewage disposal. They found that a property with soils suitable for a traditional leach field system were worth $14,062 more than a comparable property with soils unsuitable for an onsite sewerage system. Properties with soils suitable for a mound system were worth $12,897 more. This correlated to a difference of 6.8% and 6.2%, respectively. Interestingly, these price differences were actually higher than the cost in Ohio of installing a drip irrigation or mound system.

While the research outcome does a fantastic job of tying economic benefits in with good soil profiles, it's worth noting that the median value of a housing unit in the county of study was $110,700. As of January, 2014, the median value of a housing unit in the North Okanagan (where I live) is $238,750, or 2.2x higher. It would be valuable to look at similar statistics in places with higher housing costs (where onsite sewerage is prevalent, unlike Metro Vancouver) to see if similar correlations between quality soils and housing values could be found.

Source: Vedachalam, S., Hitzhusen, F.J., & Mancl, K.M. (2013) Economic analysis of poorly sited septic systems: a hedonic pricing approach. Journal of Environmental Planning and Management, 56(3), 329-344.
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