Soils Evaluation & Site Registration

The Site Registration is typically the first step in the process of obtaining a septic permit, and developing or dividing a piece of land. A Site Registration is a recorded document filed with Clallam County Environmental Health (EH) describing various conditions found on the site. A typical Site Registration will provide a description of soil texture, soil depths, and the depth to a restrictive layer. Contact a Licensed Designer (PDF) to begin the process of submitting a Site Registration.

Perc TestToday, instead of a simple perc test, a soils profile evaluation and an official Site Registration confirmed by a County Sanitarian is required. The official Site Registration filed with Environmental Health Services registers the findings of the soils evaluation in a particular spot. It states soil conditions, when the evaluation was done, and if it appears the site is capable of supporting an on-site sewage disposal system meeting all current Clallam County Health department policies and regulations.

A major goal of on-site codes is to minimize the adverse effects to public health that on-site septic systems (OSS) may have on ground and surface waters. To this end, the consideration of vertical separation - which is the amount of suitable soil (measured vertically) below the proposed trench bottom and a restrictive layer - becomes critical and is the key to achieving proper treatment.

Soils Evaluation ProcessSoil Separation

A county Environmental Health Specialist will schedule a time to meet your septic system designer at your building site to confirm the soils evaluation. The texture, compaction and color of the soil are analyzed. Using State standards, this information is then used to determine not only the percolation rate but also the soils limitations.

A soils evaluation can be done at any time of year. Soil color will give indications of soils that may be seasonally wet. If there is a disagreement or uncertainty about a seasonal water table, a decision may be delayed until the site is observed through the winter months.

Digging the Test Holes

Digging a Test HoleA minimum of two pits are required, however sites where soils are marginal or where soil types vary over a short distance may require more than two pits. Test pits are usually dug 50 to 100 feet apart, most often using a backhoe. They must meet Department of Labor and Industries standards and Department of Health's Guidelines for Test Pit Construction (PDF). They must be large enough for a person to get in and out of safely. If you wish to dig your own test pits, contact your septic system designer for any specific preferences or more information.

Typically, your sewage system designer will need to dig two test holes in the proposed primary drainfield area and one hole in the proposed reserve drainfield area before the inspection. The holes should be at least 6 feet deep (unless the water table or a restrictive layer is shallower than 6 feet), at least 2 feet wide, and sloped to allow access into the hole.

The holes should be dug in the location of the proposed drainfield. Your designer should determine this, but here are a few hints:

  • Downhill from the house site if possible.
  • Stay away from swales and drainage ways, and areas that are seasonally wet.
  • Keep 100 feet away from all wells and surface water, including irrigation ditches.
  • Septic systems cannot be located on slopes in excess of 45% (24 degrees).
  • It is helpful if property boundaries and the proposed house site are marked ahead of time.

Refilling Test Holes

It is the property owner's responsibility to refill test pits. This should be done as soon as possible after the soils have been evaluated. Unfilled test pits may be a danger to people and wildlife. The owner may be liable for injuries or loss if the test pits are not refilled.

Soils That Drain Too Fast vs Not At All

Sites with soils that drain too fast require a special system to treat the sewage more effectively before it goes into the drainfield. Advanced on-site system technology has allowed more sites to be developed over the years, but they cannot solve all problems. For example, some sites do not have deep enough soils, or have a shallow water table. Some sites do not have room for the required setbacks to be met. These constraints may prevent approval of a septic permit. A seasonal water table may limit the development possibilities at a site and must be tested for.

Indications of a Seasonal Water TableTest Hole

In the course of evaluating soils for the purpose of on-site septic system design, certain soil characteristics such as, color, mottling, root penetration and compaction may be observed that indicate the presence of a seasonal water table. In such cases it may be useful to observe the soils during the wet season to determine actual water table.

  • Historic information in division files
  • Alterations of landscape which, in the opinion of Environmental Health, could alter the flow of surface/ground water on the site
  • Observations of wetland habitat or vegetation
  • Proximity to water bodies, such as irrigation ditches, marshes, shorelines, streams, lake, etc.
  • Areas or lots located in floodplains

Seasonal Water Table Observation

When it is determined that an area requires a seasonal observation, the applicant will be informed of that decision and instructed to apply for a Seasonal Water Table Observation Permit. Fees will be required as per the fee schedule in effect at that time. The responsibility for the application and providing observation ports will lie with the applicant.

How Long a Site Registration is Valid

Dirt and Measuring TapeA Preliminary Site Registration is good for ONE year. Your septic system designer should file the Official Site Registration paperwork once the soils have been confirmed by Environmental Health Staff or submit the septic system design for approval. Site registrations for which no decision has been issued within 12 months following the date of application (due to lack of action by the applicant) shall expire by limitation.

An Official Site Registration does not have an expiration date so long as the original findings remain valid. It simply states the soil conditions at the time the evaluation was done. It is sometimes necessary to re-evaluate the soil if conditions change. For example, a proposed building location may require the drainfield to be located in an area different from planned. Certain activities such as grading, filling or logging of the property can alter the original findings and render the Site Registration invalid. Excess stormwater may also damage or alter the soils. Please note that the need for possible reevaluation increases the longer it has been since the soils were originally evaluated.

Caution: Approval of Official Site Registrations by the county does not constitute approval of either a future building or septic permit and all permits will be in compliance with all applicable state and county regulations at the time of application. An Approved Official Site Registration does not allow your site to be `grandfathered' for a specific type of system at some future date. At the time of installation, any septic design must meet all other current codes and requirements.

Site Registration for Land Subdivision

State and local codes have long required a soils evaluation to be done for land subdivisions to ensure that suitable soils for on-site septic system (OSS) exist on each proposed lot to prevent the creation of lots that later would be found to effectively be "unbuildable". Thorough evaluation of proposed parcels is strongly encouraged to locate areas where vertical separation greater than or equal to 24 inches can be maintained in all seasons of the year. Site registrations performed for the purpose of land division must also include information demonstrating that the proposed water supply is adequate.