Published September 2007

A Failing Grade?

By Roger E. Machmeier, Ph.D. (page 98)

An onsite professional puts the Answer Man on the spot with a question regarding a recent mound inspection.

Question:

Living in Minnesota, the Land of 10,000 Lakes, I was called upon to do a compliance inspection for a 14-year-old mound. The house was for sale. The mound had 24 inches of washed sand on top of a 24-inch layer of filled soils.

Drilling into the washed sand, we found standing effluent directly below the rock area. The soil was so saturated that sand was washing into the test hole. The house is currently occupied by a single female, and there are no leaking plumbing fixtures. What should I do?

A. Give it a green light (pass it),

B. Give it a red light (fail it),

C. Give it an amber light (pass it with a “buyer beware” warning),

D. Attend another University of Minnesota workshop with a good attitude adjustment hour.

Answer:

You pose some interesting options. But first, I will ask readers to consider a question: If you were buying this house, which light would you like to have turned on?

Since I am also from the Land of 10,000 Lakes, and since I recognized the name in the questioner’s e-mail address, I contacted him for a little more information. The writer had attended several onsite sewage treatment workshops I conducted.

When mound systems were introduced in Minnesota, the mound had to be placed on two feet of original and suitable soil. The soil could not be seasonally saturated closer than two feet of the ground surface. The soil had to have suitable structure. With one foot of clean sand under the rock layer of the mound, a three-foot separation was made.

The two-foot requirement was modified to only one foot of original and suitable soil. But two feet of clean sand had to be placed on the soil to maintain the three-foot separation. The soil still had to be original soil and not a filled soil.

Filled soils were not allowed for any type of onsite sewage treatment system. When soil is moved from its original location, drastic changes take place. The soil structure is destroyed. The ability of the soil to absorb moisture is severely restricted. Soil with a percolation rate of 15 minutes per inch might end up with a percolation rate of 120 minutes per inch when moved to a different location.

Additional information showed that a fill soil had been placed where the mound was located. Not only was the soil compacted, but it was of a very poor texture for sewage treatment.

The sand layer under the mound was only five feet wider than the rock area. This meant there was only a 20-foot wide sand area in contact with the underlying soil. The sand area should have extended out at least 15 feet more on each side of the rock layer for a sand area 50 feet wide. This additional area would have allowed for more percolation into the underlying soil.

Seepage concerns

The house was occupied by a single female, and no leaking plumbing fixtures were identified. However, this information does not define how much liquid may have been pumped into this mound. In this case, there should have been a water meter in the house to measure the amount of sewage flowing to the septic tank. There should also have been a cycle counter on the pump delivering the effluent to the mound.

A water meter would tell how much water was being used in the house. However, it may not tell how much water was going into the mound. Why is this? The reason is that soil water may have been infiltrating into the tanks.

Since fill soil was used, this means that the soil is seasonally saturated to the ground surface. The septic tank is located below the surface of the ground. The pumping tank is located below the surface of the ground.

Groundwater could easily be infiltrating into either or both of these tanks. Concrete tanks have a joint where the cover is attached and joints where the manhole is located. If concrete mortar was used on these joints, water may be seeping into the tanks. The reason is that concrete shrinks a little upon drying and leaves a small crack. If these cracks are below the water level in this saturated soil, there may be a constant seepage into both the septic tank and the pump tank. A mastic compound must be used to positively seal joints in concrete tanks and connections.

It is obvious that the mound was improperly installed.

The person who asked the question gave the system the red light, which I believe is correct. However, the property owner protested that decision and the local government said that the system was OK. Does this sound familiar? Let’s hope that a lesson has been learned. I’m afraid that the next homeowner will have septic system problems.

Additional comments

Here is where the writer’s option D would come into play. At the workshops I presented, we had an “attitude adjustment hour” after the class work was complete on the second day, where installers and local government officials could get acquainted. Both sides encountered problems in their work, but had similar objectives in seeing proper onsite sewage treatment systems installed.

State agency personnel often attended the workshops. They received feedback from the installers and local government officials. A workable state sanitary code must have provisions providing for proper design and installation of onsite treatment systems. But the code must also be enforceable at the local level.

If a state sanitary code does not have input from installers and local government officials, I don’t believe it will be effective.

In Minnesota, we’ve had valuable input and a strong statewide organization for installers. There is also a strong and active organization of local government officials, such as zoning officers and health department personnel. Both groups are represented on an advisory council to the state agency in charge of the state sanitary code.

These “attitude adjustment hours’’ helped get them acquainted and ready to cooperate for the good of the statewide onsite sewage treatment program. I believe that each state needs to take a similar approach.