Managing Onsite and Decentralized Wastewater Systems

Oct. 12, 2004
Proposed guidelines recommend communities provide an adequate level of management for onsite/decentralized wastewater system operations

About the author: A. R. Rubin is a professor and extension waste management specialist for biological and agricultural engineering at the North Carolina State University. He also is visiting scientist for the EPA, OWM Washington, D.C. Rubin can be reached via e-mail at [email protected].


Onsite/decentralized wastewater treatment systems include individual onsite or cluster wastewater systems used to treat at or near the source, relatively small volumes of wastewater, generally from individual dwellings, or groups of dwellings and businesses. With the exception of the Class V wells, onsite/decentralized systems are not regulated directly at the federal level and there are major inconsistencies in the management approaches utilized to sustain an onsite wastewater infrastructure at the state and local level.

EPA’s proposed guidelines recommend that communities provide an adequate level of management for onsite/decentralized wastewater systems operating in a community. A management program is defined as a series of elements and associated activities that address the planning, siting, design, installation, operation, maintenance, monitoring, personnel management, organizational management, and enforcement of onsite/decentralized wastewater treatment and dispersal systems.

Therefore, a management program involves, in varying degrees, local and state regulatory personnel, developers and builders, soil and site evaluators, engineers and designers, contractors and installers, manufacturers, service providers, management entities, property owners and individuals with the political will to facilitate a comprehensive management program.

As community systems develop, land- based wastewater management as well as the more common NPDES systems will proliferate to accommodate wastewater management needs in areas where the onsite system is inappropriate. The costs associated with community-wide programs generally allocate over 60% of cost to the collection component of the system. Maintenance of community-wide systems requires allocation of resources. In some instances, the cost to collect and treat wastewater in rural communities exceeds the ability of the residents to pay. Here, grants may be available to offset some of the cost.

Model management programs

Five separate Model Programs are presented as a progressive series in which the management requirements of wastewater systems become more rigorous as the system technologies become more complex or as the sensitivity of the environment increases. Each of the Model Programs share the common goal of ensuring that human health and the environment are protected. Each Model Program includes a set of management objectives, an accompanying set of associated elements, and activities targeted at the satisfactory achievement of the objectives.

The Model Programs are a benchmark for a state, tribal or local unit of government to:

  • Identify its management objective;
  • Evaluate whether its current program is adequate; and
  • Determine both an appropriate management program, and the necessary program enhancements to achieve its management objectives and public health and environmental goals.

EPA recognizes that states, tribes and local governments need a flexible framework and guidance to best tailor their programs to the specific needs of the community, and to the institutional capacity of the regulatory authority. These Model Programs are not intended to supercede existing federal, state, tribal and local laws and regulations, but rather be a complement to them.

The particular Model Program selected for an area should be based upon the potential for onsite systems to impact the public health, upon the sensitivity of the environment to wastewater discharges, and upon the complexity of the treatment technology to be used. The level of oversight incorporated into the management program should increase as the potential for negative impacts to public health or environmental degradation increases. Examples of parameters to consider in assessing public health and environmental sensitivity include soil permeability, depth to groundwater, aquifer type, receiving water use, proximity to surface waters, topography, geology and available space.

Other areas that may have a more direct impact on public health would include areas of shellfish harvesting and swimming.

An area with moderately permeable soils and a deep groundwater table may be designated as an area of low public health risk and environmental sensitivity, while an area with excessively permeable soils with a shallow water table used for a drinking water source may be designated as an area of higher concern. Especially for those watersheds where a determination has been made that the onsite system is degrading the water quality standards, Model Program 3, 4, or 5 should be selected to allow for restoration of the watershed.

For more detailed information, refer to the EPA Onsite Design Manual (revisions are being drafted).

Influencing the programs The complexity of the treatment system should also influence the Model Program selected. As a treatment system’s complexity increases to meet management objectives or system performance standards, the need for a high level of operation and maintenance increases to ensure that malfunctions do not occur.

A less complex treatment system, such as a conventional onsite septic system, tends to depend upon natural forces for the movement, treatment, and disposal of wastewater. The prescriptive elements of Model Program 1, properly applied, may be sufficient for the onsite systems to meet their potential as an effective wastewater treatment system. A more complex treatment system, such as a surface discharging aerobic system with filtration and disinfection, will require routine monitoring and attention from a professional technician to retain its potential as an effective wastewater treatment system, and requires, therefore, a higher level of management to accommodate this requirement. Refer to the EPA Onsite Design Manual (EPA, 2003) for guidance on performance and management requirements for onsite technologies.

EPA recommends Model Program 1, System Inventory & Awareness of Maintenance Needs, as a minimum level of management. Model Program 1 represents the recommended management needs for a program where conventional onsite systems, owned and operated by individual homeowners, are sited in areas of low environmental sensitivity, (i.e., no site or soil restrictions such as drinking water wells in close proximity or a high groundwater table). This type of wastewater treatment system is typically not adequately maintained, either because the homeowner tends to ignore even the most basic maintenance requirements or is uninformed as to what is required.

Also, the local regulatory agency is often not aware of the location of all systems within its service area. Model Program 1 is intended to raise the local regulatory agency’s awareness of the location of systems, raise homeowners’ awareness of basic system needs and ensure homeowners meet the system's basic needs. This Program is also necessary as a starting point for communities to have basic data that will allow them to make determinations if higher management levels are necessary. In the Albemarle (N.C.) Regional District this is being accomplished for a fee of $50 per visit.

Model Program 1 also addresses conventional onsite systems, most commonly incorporated into existing programs and representing the vast majority of systems currently in use. However, overall management of these systems is not adequate. Implementation of Model Program 1 will not only raise the quality of management of the typical onsite system but also will establish program elements to identify and deal with circumstances requiring even higher levels of management. A planning area may, for instance, have conditions where there are varying levels of environmental sensitivity. A higher level model, more appropriate for areas with higher sensitivities, can be incorporated into the overall management program to customize system management to the needs of the community or service area.

It is important that the management program be sufficient to adequately manage the full range of environmental conditions. For example, Model Program 3 might be selected for the more sensitive areas such as those along a lakefront or estuary, that have shown to have poor water quality, but a lower level model would still be appropriate for conventional systems in areas that are not as sensitive.

Model 2

EPA recommends Model Program 2, Management Through Maintenance Contracts, where sites with limiting conditions, such as small lot sizes, or restrictive soil conditions (i.e., slowly permeable soils, shallow soils with limited treatment capacity or high ground water table) are encountered in a small portion of a community. These limiting conditions require improved effluent dispersal to the soil or additional treatment units such as media filters or aerobic treatment units, and are typically operated through contract with equipment vendors. Model Program 2, therefore, sets higher expectations for a regulatory program and for educating homeowners.

Model 3

EPA recommends Model Program 3, Management Through Operating Permits, for situations where the receiving environment indicates a need for advanced levels of treatment, such as an unconfined aquifer used as a drinking water supply or a fish spawning area. Model Program 3, consistent with the increasing risk, recommends setting measurable performance standards and ensuring compliance by issuing renewable operating permits which indicate specific performance criteria to be achieved. The regulatory agency monitors these systems for compliance with the performance criteria. Performance-based management programs are operating for fees of $100.00 to $150.00 per visit.

Model 4

EPA recommends Model Program 4, Responsible Management Entity (RME) Operation & Maintenance, where engineered designs, such as aerobic treatment units, are required to overcome site, soil or environmental conditions that are not conducive to conventional or alternative onsite technology. Frequent monitoring and maintenance is needed in these situations. Model Program 4 recommends that operation and maintenance be provided by a public/private RME that is responsible for system performance to ensure the maintenance needs are met.

This program is operating in New Mexico at a cost of approximately $20.00/month.

Model 5

Model Program 5, RME Ownership & Management, represents the management needs of a more complex program where a very high level of control is required due to public health or environmental concerns or use of complex technologies. Model Program 5 includes the public/private RME as the designated management entity that both owns and operates the onsite systems in a manner analogous to a publicly or privately owned wastewater utility. In this level of management the utility maintains total control of all aspects of management, not just operation and maintenance. This program level operates in both the private utility model and the public utility model. The Tennessee Onsite Utility Co., charges at a rate of approximately $35.00/month while the Shannon City Utility provides water and sewer for approximately $38.00/month.

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