SEPTIC DESIGN FAQ'S
ARE YOU A LICENSED SEPTIC DESIGNER?
YES! Click here to verify my status.
WHAT IS A SEPTIC DESIGN?
In the State of Washington, all new homes or structures that are not serviced by public sewer districts are required to have a legal conforming functioning septic system. These septic systems are governed by the Washington State Department of Health at the state level and your county Health Department at the local level. The design is completed by an Engineer or Licensed Septic Designer, like myself and submitted to the County or State Health Department. In Whatcom County, this Septic Design is reviewed, approved (or denied) by Whatcom County Health Department and subsiquently becomes your Septic System Permit. In Whatcom County this permit is valid for installation for up to 3 years. If a permit expires, this process must be completed again.
HOW MUCH DOES A SEPTIC SYSTEM DESIGN COST?
The Cost of a Septic System design is dependent on the site and location, but most septic designs we complete are in the $1,500 - $2,000 range. Commercial septic system designs may be more involved and the cost is reflected for these systems.
WHAT IS THE PROCESS OF GETTING A SEPTIC DESIGN APPROVED?
There are 5 components to the septic system design from beginning to approval.
1. PRE-DESIGN CONSULTATION
Meeting with you, the owner, is a very important step in the design process. Although site constraints are going to affect the type and size of system that is required for each lot, learning your wants and desires for the septic system is very important in the choosing locations and system types. Are you concerned about the look of the system? Are maintenance requirements important to you? How many bedrooms are you looking to build? Power consumption? Answers to these questions may be the difference in getting the perfect system for your needs.
2. SOILS ANALYSIS
The soil analysis is the most important factor in determining your septic system type, size and location. During the soils analysis, we will dig test pits in selected areas of the proposed drainfield perimeter. These pits will give us information about water table depth and soil type, which are used to determine the design type. In Washington state, we need a minimum of 12" from native soil surface to the water table to install a legal conforming septic system. The soil type (1-7) will determine the size, based on how many bedrooms are proposed. From this information, we can site the system on a site plan for installation.
3. SITE STAKING/MEASUREMENTS
Once the information from #2 are taken into consideration, we will stake out the area of the drainfield and the soil test pits. Typically, there are 4 corner stakes for the primary drainfield area and a minimum of 2 stakes for the soil logs. From there, we will take measurements and gather information to create the perfect septic design for your site.
4. SEPTIC DESIGN CREATION/SUBMISSION
All the information gathered is used in the creation of the Septic System Design that is submitted to the local health jurisdiction. Once the submittal has taken place, the health department will visit the site to confirm the soil type, water table, measurements and setbacks. Typcally, the health department will visit the site within a week of submission, but is regularily on site within 1-2 days. After the site visit, the Health Inspector will make a determination. Sometimes, there are revisions required, which prolong the process, but the review and approval can range from 1 day to 2 weeks. If a wet season check is required to verify water table during the wet season, then all designs will be held until Dec. 1. The wet season is Dec. 1 - April 30.
After all revisions have been completed and the health authority is satisfied with the design, the design will be approved and a Septic System Permit will be issued. The permit is valid for 3 years (5 years for Skagit County) from the date of approval. The owner or owner's agent will be required to sign for and pick up the permit. Once picked up, it can be distributed to installers for pricing. We are a Licensed Installer as well, so everything can be done in one stop from beginning to completion!
WHY DOES MY PROPERTY NEED A MOUND?
Water table. 30" from the native soil surface to water table (or assumed water table) is needed to design and install an in-ground pressure system at minimum. This can be reduced to 18" if a pre-treatment unit is designed. This includes tanks with Aerobic Treatment Units (aka A.T.U's) that enhance the treatment before it is distributed to the water table. Other options are Glendon Bio-Filter, Loweridge OSCAR. These systems are typically installed in 12"-30" of water table. Choosing the system type is dependent on the site constraints first and your preference second.
WHY CAN'T I HAVE A GRAVITY SYSTEM?
The most common question I get asked is.....I had a gravity system at my old house, why can't I have one here? Gravity, while not common in Whatcom County, is still designed and installed as a septic system. The issue that comes into play here is the water table first, and gravity second.
A gravity system requires a minimum of 42" from the native soil surface to the Water table, this is assuming the infiltration bed is installed only 6" into the ground. The problem here is that there is not enough slope from the sewer line from the house to drainfield in 90% of these applications. It is more common to need 60" of water table and there are only a few area around the county with conditions to support a gravity system.
Most systems installed before 2007 were governed under a different set of rules and regulations. What may have met code then, doesn't neccessarily meet code now.