Traverse City Record-Eagle


Growing pressure for mounds?

By Erin ParkerOver the years, hundreds of property owners throughout northern Michigan have been forced onto holding tanks when their local health department determined that their property didn’t “perc.”  This happens with both new homes and, increasingly, with existing homes on older failing septic systems.

Holding tanks are required on sites with poor soils and/or high groundwater conditions. These tanks cost property owners thousands of dollars to install, and thousands more every year in pumping and disposal fees – fees which are sure to only increase over time.

Nowhere are holding tanks a bigger issue than in Benzie and Leelanau Counties. In the combined Benzie-Leelanau District Health Department (BLDHD for short), there are currently about 750 property owners on holding tanks.

In addition, many more properties have substandard septic systems, which are either failing or have already failed and which are polluting the groundwater, lakes, streams and occasionally, nearby wells.  It’s been estimated that about 12 percent of all existing septic systems in the two counties are substandard or failing. If true, that’s more than 3,000 systems!

Conventional Systems – The Chevy
Under the current BLDHD rules, conventional septic systems require 48″ of suitable soil above the seasonal high groundwater table.  This is a good basic rule and it has served well to protect the groundwater from contamination by pathogens and inorganic nutrients which are commonly present in septic system effluent.  However, meeting this rule can be a challenge on many sites, including many older existing home sites.  Prior to 2001 there was no option other than to install holding tanks.

Advanced Treatment Systems – The Cadillac
In 2001, the BLDHD adopted regulations allowing modern Advanced Treatment Systems (ATS for short) for on-site wastewater disposal.  The ATS systems were a positive, though partial, step forward in providing a holding tank alternative. ATS systems are compact modular treatment plants that use aerobic biological process to treat wastewater prior to disposal.  Currently, sites with as little as 12” of suitable soil above the seasonal high groundwater table can qualify for an ATS system.

While ATS systems have their place, there’s one big problem – they’re expensive to permit, install and maintain, and they’re cost prohibitive for the majority of property owners on holding tanks.  As a result, only fifteen ATS systems have ever been built in Benzie and Leelanau Counties.

Pressure Mounds – The Intermediate Solution
It’s become clear that a less complex and costly intermediate system is needed for those properties falling in the “twilight zone” between conventional system and ATS system requirements.  Probably the best available solution is the pressure mound.  A pressure mound is simply a conventional pressure system with the disposal field built on top of a layer of sand fill.  Because they are so simple, pressure mounds are affordable to install and easy to maintain.

The Band-Aid
In 2007, the BLDHD came up with the current set of rules which allow some owners of existing homes with failed systems to install partial pressure mounds on sites with more than 24” of suitable soil above seasonal high groundwater table.  The current rules leave many out in the cold. For example, those who own vacant lots with less than 48” of suitable soil are still out of luck.  So are owners of existing homes with old or failing septic systems on sites with less than 24” of suitable soil.  These property owners still face the very real and unsettling prospect of being forced onto holding tanks.

The Comparison
In contrast to the BLDHD, other health agencies in the region give property owners more flexibility for on-site disposal on marginal properties.  For example, Grand Traverse County has conventional system and ATS rules that are similar to the BLDHD’s.   However, five years ago, Grand Traverse County went a step further and allowed pressure mounds for sites falling between conventional and ATS system parameters.  These rules apply equally to existing homeowners with holding tanks or failed systems and those who own marginal vacant property and want to build.

Another good example is District #10, the health department serving Manistee, Kalkaska, Wexford, Oceana and Missaukee Counties, among others.  District #10 Health Department allows pressure mounds to be placed on any site with more than 12” of suitable soil.

PMS Myth Busters
There are those who oppose any changes to the current BLDHD rules. To support their position, they tend to point out commonly held misbeliefs about pressure mound systems. Let’s shed some light on a few of the most common myths floating around out there:

Myth#1Pressure mounds take up large areas & most properties are just too small to fit one in…
While it’s true that pressure mounds are a bit larger than conventional drainfields, they can usually be fit into even smaller properties.

Myth#2Pressure mounds are really ugly and lower property value…
Actually, pressure mounds can be attractively incorporated into the surrounding grades and landscaped.  Done right, they blend right in.  If anything, pressure mounds will increase property value as compared to holding tanks. Ask any realtor – they’ll tell you that holding tanks can lower property value by 20 percent or more – now that’s ugly.

Myth#3Only lakefront properties benefit from pressure mounds…
Not so, there are plenty of marginal sites that are nowhere near the water. These sites can have unsuitable soils (e.g., heavy clay), or they may be in an area with a perched groundwater table.

Myth#4Most property owners want cluster systems, not pressure mounds…
Usually the opposite is true.  Most property owners like having their own low-cost, no-hassle pressure mound as opposed to being burdened with the large upfront costs and red tape associated with a cluster system.

Myth#5Pressure mounds aren’t safe for the environment…
Not true.  Pressure mound systems are well documented to be safe and effective.  In fact, the MDNRE (formerly MDEQ) encourages pressure mounds for use in small community wastewater systems.  What’s bad for the environment is when property owners have to limp along with failing septic systems because the only other option is holding tanks.  Failing systems poison the environment, pollute the groundwater, ruin lakes and streams and can make people seriously sick.

The Next Step
Lately, BLDHD staff have been reviewing existing holding tank properties around Lake Leelanau to determine what can be done. A final report on the Lake Leelanau study is due out in September. Hopefully, this study will help illuminate the problem and pave the way for positive changes in the BLDHD rules.

Whatever form the proposed rule changes take, I suggest they start by providing relief to the hundreds of property owners with existing holding tanks and existing substandard, failing or failed on-site systems. Also, I’d say the changes shouldn’t discriminate between existing homeowners and those who want to build a home, as the current rules do.

To sum it up, pressure mound systems are good for overall public health and good for the environment. They are the most simple, safe, low-cost intermediate on-site disposal alternative for rural northern Michigan. When properly designed, they provide cost-effective on-site treatment and disposal on sites that otherwise would need expensive holding tanks or ATS systems.

If you’ve got questions about pressure mounds, holding tanks, ATS systems or any other topic, please leave a comment below or drop me a line at I’ll try my best to point you in the right direction.

  • Erin Parker

    Dear readers,

    I need to point out that there are significant some differences between the Grand Traverse County Health Department (GTCHD) and BLDHD ATS rules.

    fact, when the GTCHD wrote their ATS policy and procedure manual back in 2006, they actually learned from some of the mistakes made by the BLDHD.  

    The biggest differences:

    1.  The GTCHD gives credit for soil treatment (samples are taken from soil under the drainfield).  BLDHD requires effluent samples to be taken directly from the ATS discharge.

    2.  The GTCHD only requires one suitable
    sample after the system is up and running and then doesn’t require another
    sample for 5 years. The BLDHD requires exhaustive testing – 2 years of quarterly, 1 year of biannual,
    and then annual tests thereafter.  That’s 2 samples in 5 years (GTCHD) versus 12 (BLDHD).

    3.  The distance cut off for meeting the phosphorus standard
    is 100 feet from surface water in Grand Traverse County.  This standard, which is difficult to meet, is applied up to 500 feet away from surface water in Benzie-Leelanau.  Please note: phosporus is not a public health issue.  

    4.  One last difference is that Grand Traverse County requires any ATS to be NSF certified (this eliminates the fly by system manufacturers).  

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