We provide Licensed Septic System Designs, Test Hole Evaluations, and Perc Testing for all of Spokane County, WA.


Septic System Designs

Ranging from conventional gravity systems, pressure distribution to enhanced treatment systems and mounds.



Gravity distribution septic systems are the oldest, least expensive and most common on-site sewage treatment technology and can be installed in areas where there are 48” or greater of suitable soils.


Pressure distribution systems are used when suitable soil depths are less than 48” but greater than 34” or in instances when the drainfield is located upgradient from the desired homesite. A submersible pump is used to transport effluent from the pump chamber to the drainfield. While more expensive than conventional gravity, a pressure distribution system allows the entire length of drainfield to be dosed and at intervals which allow the drainfield to recover (or dry out) between doses.


Enhanced treatment systems are required in addition to pressure distribution when suitable soil depths are at least 12” but less than 36”. Treatment can be provided through public domain technologies (sand lined trenches/beds, mounds, sand filters) or proprietary treatment technologies (Aerobic Treatment Units, Subsurface Drip, Adventex Systems). Which technology is best is a matter of opinion. The developers of proprietary systems have invested substantial time and money in bringing their product to market and as a result their products come at a higher cost than public domain technology. In addition, proprietary systems typically require the homeowner to sign a service contract with a certified professional.


Soil Evaluations

For real estate sales/purchase contracts/development feasibility studies.



Test hole evaluations, formerly known as perc test, are necessary when designing septic systems as they determine the size and level of treatment needed for required for each septic system. All our test hole evaluations include a detailed soils report and preliminary design layout for submission to Spokane Regional Health District when you apply for your septic permit.


Excavation & Installation Referrals

We work with a network of licensed professionals who can assist with your excavation and installation needs.

Spokane County’s

Checklist for Application to Install an On-Site Septic System

Click Here to Download

Spokane Regional Health District Liquid Waste Program’s

Application for On-Site Sewage System

Click Here to Download

More Helpful Resources & Links