Clackamas County Septic Program Site Evaluation Guide

A soil and site evaluation determines if a septic system can be approved on a lot. The evaluation considers all options including standard, pressure distribution, ATT, and sand filter systems. The minimum system allowed by the OAR 340-071 regulations for the site and soil conditions will be prescribed. If the minimum DEQ rules cannot be met, a denial notice will be sent to you providing details of the denial and possible options for moving forward. If approval is granted, a separate septic installation permit may be applied for by the property owner or their authorized representative.  

Site Criteria  

The suitability of a site for a septic system is largely determined by the type and depth of soil and the depth to the water table. Other factors include the size of the property, the slope, location of the system relative to streams, wells, cuts and fills, and whether sewer service is legally and physically available.

Application Process

Applications are submitted online through Development Direct.  Multiple lots will require a separate application for each lot. The county Site Evaluation fee plus the DEQ surcharge must be paid for each lot/application. 

The following must be submitted through Development Direct at the time of application

• Notice of Authorizing Representative form is required if the property owner is not the applicant.  
• A site plan filled out completely as per the minimum requirements.

To ensure the quickest and most accurate possible analysis of your site please pay special attention to the following guidelines.  Sites that do not adhere to the following risk denial or an extended review time.  

Test Pits  

• Test pits must be dug at the time of application. If test pits are not dug at the time of inspection, a re-inspection fee may apply, and your site evaluation will be rescheduled for a later date.
• Clackamas County recommends four test pits for an evaluation of a new lot (two in the proposed primary area and two in the proposed replacement area). A minimum of two test pits are required by the OAR 340-071 regulations for all site evaluations. A maximum of six test pits will be evaluated per application.
• Test pits must be dug per Test Pit Preparation guidance below. For fine textured soils (Silt, Clay) the stepped entrance is required during the wet months (usually October through June).  
• The “spoils” pile MUST be kept at least two feet away from the edge of the test pit.
• Test pits should be spaced 75’ to 100’ apart in the area where you intend to locate the original and replacement drainfields.
• Test pits should be located on the driest part of the property and should not be located within any of the setbacks.

Site Preparation

• If the test pits are not easy to find, mark a trail to them in the field
• Test pits should be labeled with a stake and bright colored tape.
• Identify the property corners on site using clearly marked stakes or similar means.
• Provide any lock combinations or key locations for locked gates with your application
• Inform the septic program of any animals or pets that need to be put away when submitting your application. Even generally well-behaved animals can prevent Soil Scientists from completing your evaluation and even cause a safety issue.  

Notification

Site evaluations are scheduled based on when a complete application, including fee payment, is received. Unfortunately, it is not possible to schedule the site visits, but we can call prior to our visit if requested. Please email SepticInfo@Clackamas.us for additional questions.  

Test Pit Preparation

To provide for pit stabilization and safe access, standard test pits for site evaluations must be prepared in the following manner:  

• The bottom of the pit shall be at least 2 feet wide and 4 feet long.  
• The depth shall be at least 4.5 feet and not exceed 5 feet.  
• Test pits shall be approximately 75 feet apart.  
• Test pits that are not dug according to these instructions or are otherwise unsafe to enter will be considered an incomplete application and delay the evaluation

Providing Access to the Test Pits:

For easy and safe access, all spoils need to be a minimum of 2 feet from the pit edge and one end of the test pit shall be either: 

• Sloped less than 45 degrees if the soil is dry or loose, or;
• Stepped (2 steps minimum) when soil is wet (See illustrations below)