ON-SITE Wastewater Newsletter

Spring 1997


We begin again

Under construction

The plastic limit

Some preliminary results calculated from the first 50 surveys of septic problems in Indiana

Septic Systems Revealed

Who are we?

Homer & Maud

Contact us

We begin again...

We've blown the dust off, oiled the machinery, warmed up, and are off on another on-site wastewater disposal project. This one centers around you. Some of you may remember the first septic project (On-Site) from the early ‘80s. The project has two main parts.

Part one involves looking at septic system failure in Indiana. Properly sited, constructed, and maintained systems have the potential for an almost indefinite life... or so we thought.

How long are septic systems really lasting?

How old is an "old" septic system?

Why are they failing?

How many are failing?

What needs to be improved?

How big an impact have alternative systems and improved technology had on solving some of these problems?

These are just some questions that we are trying to address. The truth is that we all have ideas and educated guesses to the answers to these questions, but nobody knows. This is where you come in. We have begun by asking you what answers you have to these questions. We've asked you for copies of your on-site wastewater disposal permit applications and to fill out a questionnaire. So far 59 counties have sent in materials, and more are arriving each day. Thank you!

Part two of this project has a similar purpose as the old on-site program of 1980-1985. Technology has advanced by leaps and bounds in the last 12 years. We are looking at what improvements or alternative systems would work best in Indiana. So far we have dug into the literature and sent out questionnaires to neighboring states, asking them what systems they have looked at and how well they have worked. We are currently developing procedures for testing alternative technologies and hope to get at least one trial system built this summer.

We now officially welcome you (back) to our newsletter, On-Site. This newsletter was sent out periodically during the previous project and many of you commented that it was the best part of the project. We hope to include project updates as well as helpful information.
Thank you for joining us.

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Under construction...

As part of the project, we are developing a standardized county database computer program for on-site wastewater permit applications. The permit applications that you sent showed a wide range in the amount of data collected. This database includes information which counties most commonly request on permit applications. Some of you already have an electronic record keeping system which you are happy with. Our proposed standard database is in no way mandatory; it is simply available. Other counties are not yet computerized, but have indicated that they hope to purchase a computer shortly.

Building a database which can easily store, retrieve, and modify records takes time and effort. We would like those counties, as well as counties who are considering upgrading their record keeping systems, to take a look at our proposed standard database program. We will furnish a copy on request. This database runs on a PC computer. It will be in Microsoft Access 97, which runs on Windows 95 or Windows NT. Access can accept records from Paradox, Dbase, FoxPro, Lotus 1-2-3 and other Microsoft Office applications. As we gain experience importing other types of files, we will let you know our findings.

Why are we doing this? Since counties keep separate sets of records, it is difficult to measure the scope of on-site septic problems. Such a measure may help develop support for research, education, and monitoring programs. We would like to work closely with several counties who currently have computerized records. A standardized database program would save the cost of specialized programming in each county and save training costs since several counties could do joint training of personnel. In addition, our survey results to date show that at most three counties use the same computer program. This makes it extremely difficult to assimilate data from different counties for statewide analysis.

Why Microsoft Access? There are many relational database programs available that would work, but this seemed the most suitable for our needs in terms of versatility, power and usability. Many of you already use Microsoft products. Access is also used by Purdue University and the State Board of Health. It allows you to graph, query (or retrieve specific data), and network with relative ease.

Here are some results from the surveys. At the time this table was made, 50 counties had sent in their responses.


Computer Information  
Counties using computers: 33
Personal Computers: 28
Macintosh: 2
Computer Programs used  
Microsoft products: 7
Unspecified Windows programs: 3
Paradox: 3
Q and A Symantec: 3
Lotus Approach: 2


Looking into the future, Access has considerable potential. For instance, Microsoft Access 97 can be hooked up to the Internet. Since information about a property's septic history is public record, homeowners, Realtors, contractors, and bankers could locate this information on the internet. Not only would this be a valuable information service, but it may generate recognition and support for our field.

If you have any comments or suggestions on items to include in this database, please let us know. We want this database to work for you!

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The Plastic Limit

Questions that come up over and over again are, "Why can't I construct my system when the soil is wet?" and, "When is the soil too moist?" This is a very basic on-site question and is answered in nearly every publication dealing with construction practices. Excavating soils with more than 15-20 percent clay when they are wet will lead to severe compaction, greatly reduced soil permeability, and possibly cause premature failure. This includes most soils in Indiana! Of course no one likes this answer, but ignoring this basic truth almost always causes severe problems later on.

The plastic limit test is often used as a means of checking for conditions leading to compaction. If the soil can be rolled into a flexible wire 1/8th inch in diameter without it's breaking or crumbling, then the soil is too wet. Some argue that this test is an unnecessary obstacle to progress (and making money). But, in fact, it is "scientific" and has been used in construction for nearly a century. This test is one of the "Atterberg Limits." The plastic limit and the liquid limit define the moisture content of soil in the plastic state.

A very important change in the physical load bearing capacity of soil occurs at the plastic limit. Load carrying capacity increases very rapidly as the moisture content decreases, and on the other hand, load carrying capacity decreases very rapidly as the moisture content increases beyond the plastic limit. Another way to look at this is to consider the compaction of soil for construction purposes. The relationship between soil bulk density and moisture content looks like this:


What does all this mean? The plastic limit test should be used, and excavation should not take place in soil that is too moist or wet. The problems resulting may not show up until months afterward when the system is covered and diagnosis of a failure is not possible. The homeowner is then left with a costly repair and often new trenches (if there is room). This could have been avoided with care and discipline in the initial construction.

Why do these problems occur? Often because the people selling lots do not recognize that the time of year and soil moisture content is important! After a push to build gets going a conscientious contractor can refuse to dig -- at the peril of their livelihood. We must recognize that, with septic systems, excavation cannot be done "anytime." In Indiana soils are going to be wet for long periods of time. Nonetheless, there is no excuse for poor practices that pass the problem on to the homeowner.

-J.E. Yahner, Professor of Agronomy

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Some preliminary results calculated from the first 50 surveys of septic problems in Indiana.


Primary Limiting Conditions Percentage of counties with problem
compact glacial till

52 %


30 %

coarse sand and gravel outwash

6 %


14 %

seasonal water table

82 %


Number of small communities without municipal sewage treatment


Average of the percent of residences served by on-site systems

53 %

Percent of new on-site systems requiring a perimeter drain (averaged by county)

60 %

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Septic Systems Revealed:

The Minnesota Extension Service has created an informative video on caring for your septic tank entitled Septic Systems Revealed. This video begins with how a septic system works, taking you to construction sites of both a traditional and a mound system. It explains the importance of proper siting and construction, with particular emphasis on the need for an unsaturated absorption area. It discusses proper maintenance procedures and clearly demonstrates what can happen if a tank is not properly maintained. It includes signs of potential failure and typical reasons for failure. It then goes over simple positive steps a homeowner can take to protect their septic tank investment.

This 24 minute video is a valuable educational tool, covering topics from bacterial biomats to water saving appliances. Homeowners, contractors, and newer health department personnel alike would benefit by understanding the importance of these systems and their maintenance to our health and environment. If you would like to purchase the tape for your county, the cost is $13.00 plus shipping and handling. To order, contact:

Minnesota Extension Service

University of Minnesota

Distribution Center, 20 Coffey Hall

1420 Eckles Avenue

St. Paul, Minnesota 55108-6069

Fax number: (612) 625-2207

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Project Staff:

Who are the people signing the letters, asking you for information, and answering your questions? The current project staff consists of Joe Yahner, Don Jones, and Catherine Taylor of Purdue University and Alan Dunn of the State Board of Health.

Joseph E. Yahner is a Professor and Extension Agronomist at Purdue University. He received his B.S. from Purdue University and his M.S. and Ph.D. from Oregon State University. His extension activities include on-site waste disposal, land use planning, farmland valuation, residential development, and water quality. He currently teaches a course entitled "Soils and Land Use." Visit our Land Use Planning Resource Center home page which includes information on on-site systems at http://www.agry.purdue.edu/agronomy/landuse/planning.

Don D. Jones is a Professor and Extension Agricultural Engineer in Agricultural and Biological Engineering at Purdue University. He received his B.S. and M.S. from the University of Illinois and his Ph.D. from Purdue University. His current extension and research interests include septic systems as well as livestock housing and manure management systems, computer applications (spreadsheets, multimedia) in agriculture, especially applied to environmental education and agricultural production systems. He has also helped develop a number of projects dealing with rural waste treatment and management.

Alan M. Dunn represents the State Board of Health, where he is currently the Supervisor of the Residential Sewage Disposal Program. He received his B.S. in Biology from Purdue University and is a Registered Environmental Health Specialist. In addition to overseeing the operation of the Indiana's residential sewage disposal program, Mr. Dunn also serves as the ISDH representative to the Great Lakes-Upper Mississippi River Board of State Public Health and Environmental Managers Ten States Standards Committee on Individual Sewage Systems; the Non-Point Source Task Force; and the Interagency Technical Task Force on E. coli contamination of Lake Michigan.

Catherine Taylor is the On-Site Wastewater Project Specialist. Her responsibilities so far have included constructing and analyzing the questionnaires and the development of the Access database. She received her B.S. from the University of Maryland in Biology and her M.S. from Purdue University in Agronomy. Her research was in Soil Microbiology looking at the environmental fate and sorption of pesticides.

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Homer and Maud Homeowner

"Gee, Maud, maybe this would be the perfect spot for the tomatoes"

Contact us

On-Site Editor: Catherine Taylor; Graphics and Design: Lou Jones.

e-mail: ctaylor@dept.agry.purdue.edu or ljones@dept.agry.purdue.edu

Address: Department of Agronomy, Purdue University, West Lafayette, IN 47907-1150.

Please contact us with your suggestions, comments or questions.

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