A good onsite system design starts with gathering all available information about the site. This usually means a visit to the local health department office. It can also mean a visit to the county assessor’s office. The local health or environmental department office is obvious because that is where the plan review and permit will be issued, and where compliance inspections will originate.

Some important information can be obtained at the assessor’s office relative to system design and installation. First look for a description of the lot or parcel in terms of size, shape, location and ownership. Identify whether the lot is developed or undeveloped. An undeveloped lot is one where improvements have not been made, which probably means more siting and design options are available. A developed lot, with streets and other amenities – including rural water supply – already in place, indicates the system location may have already been determined by being hemmed in by other lot improvements. If the driveway, house, etc., are already in place, it’s possible the area set aside for the system will have been cut or filled.

CHECK RESTRICTIONS

If there is an existing dwelling, the assessor’s office will have the most up-to-date information on the number of bedrooms and other pertinent information. This can be compared with the system information provided in the permit from the health department. These numbers should match so the estimated flow for the dwelling reflects what is actually there. The assessor’s office will have records on any property restrictions or covenants, including easements, that may not show up in the permit document but could impact the system design for the site.

You may find existing documents relating to onsite systems on the property, including design and permit information, at the health or environment department. You may also find a record of previous problems with the system. It can be helpful from a design standpoint to identify areas of special attention to avoid similar problems with the new design and installation. Also connected with the permit information will be records on property restrictions. Resolve discrepancies with the assessor information before continuing with design work.

Look for property restrictions, such as whether the property is included in any type of special management zone for onsite systems. This will either restrict the type of system allowed or provide certain credits for designing elements into the system. One example of this is areas where state and local governments identify special zones for the reduction of nitrogen delivered to coastal estuaries. Many western states have such zones along major river systems with coarse-textured alluvial soils or over areas of groundwater aquifers that are a source of drinking water.

This restriction fits with the important know your risk part of the design process. Here the risk of elevated nitrogen levels is either a health concern in drinking water or an environmental concern in elevated levels found in estuaries. In these cases, the risks could help define what type of nitrogen reduction strategies can be employed. There may be special financial considerations to encourage use of different technologies to reduce the nitrogen load. These considerations may be at the homeowner level or at the state and local level through state or federal grants and assistance. The other parts of know the risk factor into the actual soil and landscape condition on the site itself and the intended use. Is it a residence or another establishment such as a restaurant?

COMMUNICATION IS KEY

In previous discussions, we have highlighted how important it is for a service provider to establish a relationship and good communication with the homeowner. To ensure good design work, it is critical to establish anticipated water-use patterns. One example brought this fact home to us in a very undesirable manner.

We were designing a demonstration project for a relatively new product. We made the usual assumptions of water use based on the number of bedrooms, people in the house and the size of the house. As we monitored the sewage treatment trenches, it quickly became obvious that one of two things had happened: either we had totally misread the soils or significantly higher amounts of water were being used than we had estimated. We installed a water meter and found that water was being used at roughly twice our estimated daily flow. The important message here is that users have a major impact on the system and communication is essential.

Another common example from our area is the impact of seasonal or periodic use. Many residences in our lakeshore areas serve as a second home for the occupants. Homeowners come and go depending on their vacation time and recreational pursuits. This situation does not lend itself to certain technologies such as ATUs, which require consistent loading to function best. So if it is a seasonal residence and additional pretreatment is necessary, an alternative should be pursued.

FOR MORE INFORMATION

Resources are available to help designers make sure they are asking homeowners the right questions. The one we point to first is the University of Minnesota website (www.septic.umn.edu). There the designer will find a number of helpful assets, including a homeowner survey, which provides a way to ask for and track homeowners’ usage patterns. A similar set of forms is available as part of the Consortium of Institutes for Decentralized Wastewater Treatment (CIDWT) operation and maintenance manual. Any of the organizations involved in the CIDWT can provide information on the manual. The National Association of Wastewater Technicians provides that manual for a fee.