Most people in rural areas of northern Michigan don't have access to municipal sanitary sewer service. For the majority of these people, this is not a big deal because they can dispose of their wastewater on site using a low-cost and reliable conventional septic system.
Conventional septic systems come in two basic flavors: gravity and pressure. For more about conventional septic systems and their care, see my previous post, “What goes down doesn’t always stay down!”
Unfortunately, the trusty and affordable conventional septic system is not an option available to everyone. Many properties in our area have limiting site conditions that render them unsuitable for installation of any kind of conventional septic system.
Typical examples of sites with limiting site conditions include:
- Sites with high groundwater table. For instance, lakefront and other low-lying areas.
- Sites with unsuitable soils, such as: clay, hardpan, muck, peat, etc.
- Sites with steep slopes.
- Environmentally sensitive sites.
- Insufficient area to install meet minimum setback requirements.
In the past, the only allowable option for many property owners dealing with limited sites was to install holding tank (or to just not to build at all).
A holding tank system is just what the name implies. It's nothing more than a group of large buried tanks that collect the wastewater flowing out of the household. Once the holding tanks fill up, an alarm lets the homeowner know that it's time to pump the tanks.
The pumping frequency depends on a lot of factors, including the number of users, the intensity of their use and the size of the holding tanks. Some people, especially those with larger families (lots of showers and laundry), end up having to pump every two weeks or less. Other people rigorously control their use and often manage to stretch out pumping intervals to a month or two.
Now don't get me wrong — there's nothing inherently wrong with a holding tank system. The waste is hauled off-site and disposed of safely and with relatively little impact on the environment. The problem for many people is that all this pumping gets pretty expensive. For example, the annual cost of pumping holding tanks can exceed the annual cost of property taxes for certain homeowners. Talk about a ‘drain' on your budget!
Now here's some good news. Under revised rules in many of the local health department districts in northern Michigan, many properties with existing holding tanks, and also some vacant sites which were formerly considered ‘unbuildable' are now candidates for on-site disposal. Typically, some form of an alternative system is required on these sites. Depending on the health department rules and the site conditions, alternative systems can take several forms:
Pressure Mound System (PMS)
A pressure mound system is very similar to a conventional pressurized septic system. The main difference between a PMS and a conventional pressurized system is the extra step of putting in a layer of clean sand fill to raise the disposal field (this fill material is what creates the raised mound). The raised mound converts a formerly unsuitable area on the property into a suitable disposal area.
Advanced Treatment System (ATS)
These systems come in two main categories: Media Filtration and Aerobic Treatment Systems. They work by circulating septic effluent through media filters (sand, peat, jute, plastic, etc.) or by mixing air into the septic effluent. Advanced treatment systems effectively reduce the concentration of pollutants in the treated effluent which allows for on-site disposal on sites unsuitable for conventional septic systems. These systems are becoming more widely accepted by local health departments.
So where to go from here?
The first step in determining if your property is a candidate for an alternative system is to contact your local health department and arrange a site inspection. After reviewing your site conditions, the health department will be able to tell you what your options are. If it an alternative system is allowable, the costs of installation are usually outweighed by the savings in pumping costs over the long term.
Thanks for reading my blog — I hope you found it helpful and informative. Also, a big thanks to all the on-line Record-Eagle readers who enjoyed my last blog “Creepy crawly tree eaters” and who wrote with their questions and gypsy moth horror stories.
If you have any questions about holding tanks, alternative treatment systems, or any other engineering related topic, please feel free to contact me at firstname.lastname@example.org. I'll try my best to answer any questions you might have.