Engineering and Design for Difficult Sites

When properly designed, installed and maintained, septic systems can be the most cost-effective and efficient method of wastewater treatment a homeowner can choose. There are many innovative designs for septic systems that allow them to be placed in areas with shallow soils or other site related conditions previously considered to be unsuitable.

What options do you have if an evaluation reveals no suitable site on your lot for a conventional septic system? What can you do if your system is failing and there is no place to build a new one?

If this is the case, alternative or innovative onsite system designs can often help property owners with site restrictions. Many problem sites can be served by such alternative system designs such as mound systems, low pressure distribution, wetland systems, or drip irrigation to name just a few.

Some alternative onsite systems have been used successfully for decades and much is known about their performances, reliability, cost, and maintenance needs. However, in some communities homeowners and developers may initially have a hard time getting approval for some systems because of inflexible regulation or health officials who are unaware of certain alternative system designs or have questions concerning performance, operation and maintenance. In some states, individual county health agencies must adopt an “Operation & Maintenance” (O&M) program before they are authorized to permit any alternative wastewater system. Without this O&M program, only conventional and state approved systems can be installed in their particular county.

Not all types of technology are approved for usage in every state. It is important that the individual or company employed to produce an alternative system solution be well versed in what is allowed and approved by the local and state agencies. Additionally, knowledge of the proper permitting, installation and inspection procedures is crucial.

In addition to the standard alternative systems utilized, it is possible for a skilled, trained, and licensed septic contractor to work with the homeowner or developer to have a sewage disposal system engineered and designed for a particular site. A system that may possibly encompass components and features from several types of systems, but will function to properly service the needs of the site in question. If the existing situation is a failing system, the current system should be utilized as much as possible and the new addition connected to assist it.

Failing Systems
The U.S. Environmental Protection Agency ( EPA ) has identified failing septic systems as a major source of groundwater pollution in some areas. However, most of these failures can be attributed to systems with poor design, lack of proper maintenance, incorrect installation, and inadequate site evaluations before installation. In the past, a lack of adequate regulation for septic system design and construction also contributed to septic system failures.

Site Evaluations
Today, thorough site evaluations are performed by health department inspectors along with a licensed trained sewage technician, if the property owner so chooses. A backhoe is normally utilized to dig pot holes in order to properly inspect the soil. Other aspects are taken into account before a system is recommended and the installation location established on the site. If this site evaluation is performed correctly and the entire site was evaluated for installation options, system failure should not occur due to the recommended system and installation location.

Regulations & Design
Even though it may not seem to be beneficial to the property owner during their time of stress, state and local health agency regulations are a valuable asset. These regulations assure that the system designed and permitted follows proven guidelines and meet quality health and product standards. By meeting or exceeding these standards, the property owner should feel confident in the function of the wastewater system.

Many characteristics of the site should be taken into consideration during the design process. These characteristic will dictate the various options available. For example:

Group lV ( 4 ) classification soil, clay texture, requires additional pretreatment as clay has smaller pores spaces and is tighter than other soils. Effluent moves downward at a much slower pace in this type of soil, therefore, by cleaning the effluent to a greater degree, less clogging of the pore spaces will occur allowing movement downward to increase in speed. Additional pretreatment can be achieved in a variety of ways including multiple tanks tied into series, installing a tank filter, or utilizing an aerobic unit prior to discharge.

Installation of two tanks in series will achieve a greater degree of pretreatment by allowing more settling to occur within the second tank before discharging to the lateral field or secondary treatment of the designed system. When designing a system with multiple tanks the first tank is required to be of the minimum size for the initial need at the site. In Kentucky, the second tank is required to be of the same size, however, many states only require a minimum of 50% capacity of the first tank. Nevertheless, it may prove to be most cost effective to install the second tank at the same size as the first allowing for additional volume.

Installation
Once a system has been engineered or designed and properly permitted for the site, it is imperative that the installation be in the precise location designated, per the site evaluation and permit approval. With alternative or specially designed systems it is equally important that the system be assemble precisely as designed. Any deviation from the approved plan could result in the permit being revoked and possible system failure. A trained septic system technician who is experienced in the installation of alternate and uniquely designed systems should be employed. It is unwise to allow untrained and inexperienced persons to install.

Inspection
Upon the completion of any new installation, system alteration or repair, an inspection should be performed. This inspection will be done per the permit issued for the work to be performed and will be conducted by the appropriate health agency inspector. A signed inspection form should be issued to the property owner to show that the system was installed correctly and in the exact location designated. With alternate or special designed system, the health agency inspector may opt to inspect during various stages as the work is being performed. This is to insure that the specification of the project approved are met.

Operation & Maintenance
Depending upon the type of system designed and installed, operation and maintenance can vary. It is vital to the life of any wastewater system that maintenance be performed consistently and appropriately. The more sophisticated the system the more knowledge the individuality in charge of the ongoing maintenance needs to possess. Important warning signs could go undetected by untrained persons and could produce costly repairs or part replacements. With systems that utilize chlorine contact, as in aeration units, the effluent from the unit could be disbursed untreated or in a substandard condition. This situation can endanger the health of the homeowner, their family and neighbors.

It is the homeowners responsibility to properly maintain their wastewater system, however, it is not always feasible for the homeowner to attend classes, read instructional material, or become skilled at servicing their new designed system personally. In these cases, the homeowner may elect to employ an experienced technician to be fully responsible for the proper operation and maintenance of the system installed.

Most sites can be developed with the correct wastewater system design. Keep in mind that alternate system designs may not prove to be cost effective to the property owner. Specialty systems typically increase the overall cost but can prove to be a viable solution for those who are intent on developing a particular site.

If a property owner has a particular location in mind, by no means be discourage by the first attempt to permit. Seek out experienced technicians or companies who specialize in engineering and design of wastewater systems and get a second opinion. They should be able to give options and alternative solutions to consider.

Other Topics:
Sewage Protection Program | Mound System | Low Pressure System | Drip System | Health Departments - Friends not Foes | Site Evaluations | Curtain Drains, Washer Lines & Filters |'New' Gribbins Whirlair for Spray & Direct Discharge | Lateral Field | Wetland System

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