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SEPTIC SECTION

Brian Dickey, Senior Environmental Health Specialist On-Site Sewage/Well bdickey@co.pacific.wa.us Cell (360) 589-3599
John Muth, Environmental Health Specialist On-Site Sewage/Well South County jmuth@co.pacific.wa.us Cell (360) 589-2559
Randy Steeves, Environmental Health Specialist On-Site Sewage/Well North County rsteeves@co.pacific.wa.us Cell (360) 589-3709

 

Welcome! to the Septic section of Community Development.  The goals of the Pacific On-Site Sewage program is  to protect public health and the environment from the adverse effects and impacts from failing or inadequate on-site systems which, in turn will ensure our drinking water, streams, and rivers remain safe for today and future generations to enjoy.

 

ON-SITE SEWAGE SYSTEM APPLICATION REQUIREMENTS
The first step for installing an on-site sewage system are to complete a permit application, pay the appropriate fees, and prepare test holes for the site evaluation.  In order for the Pacific County Department of Community Development to provide the most efficient service to you, it is necessary that your application packet be complete and include detailed information about your property. 

The permit fee for a new septic system to serve a single-family residence is $400.  The fee for a septic alteration or repair is $125, while the fee for a septic evaluation to determine whether the site is suitable for a septic system under current state and county regulations is $250.

Additional fees are required for application processing ($30) and for design review ($150).  Additional fees may also be required for critical areas assessment ($100), zoning/setback check ($30), road review ($40), addressing ($20), and/or shoreline exemption ($100). Please call (360) 642-9382 or (360) 875-9356 to verify permit fees before submitting your application.

 

WARNING!  Failure to provide all the information requested may delay review of your application.
The following information is provided to help you prepare the site for inspection by an environmental health specialist.
Site Preparation
  • Three test are required per site.  The test holes must be located in, or adjacent to, the areas designated as the primary and the reserve drainfield.  In sandy soils, each test hole should be approximately 18" in diameter and at least 3' deep.  In other soils, holes must be 2' wide and 6' deep with a ramp cut into the ground for gaining access into the hole.  If holes dug in non-sandy soils do no have an adequate ramp, or if the spoils of the holes are too close and present a safety hazard, the site will not be evaluated.
  • Adequate directions to the site must be provide on the permit application.
  • Clear access and on-site markings must be present to lead the inspector to the test holes.  The property corners, accessible route to the test holes, and the test holes themselves must all be marked with flagging tape.  Holes may be covered with plywood or other materials, but it is not required.
Site Development Plan
In addition to the above site preparation, it is necessary to include the following information as part of a site plan along with your development application:
  1. Designated areas for the proposed primary and reserve drainfield.  For sizing requirements, see table below.
  2. Location of test holes
  3. Property lines and lot dimensions
  4. Distance from property lines to proposed drainfield
  5. Location of any proposed or existing structures and driveways
  6. On proposed site and adjacent properties:
  7. Location and distance to any surface water or well within 100' of the proposed drainfield
  8. Location and distance to any pressurized water line within 20' of the proposed drainfield
  9. Location of any proposed or existing drainage structures (e.g. ditches, swales)
  10. An arrow indicating which direction is north

Warning!   The installation of a septic system requires the commitment of a section of your property. 

Please consider carefully the location that you have chosen.
Horizontal Setback Requirements for System Components
Item Requiring Setback Primary and Replacement Drainfield (ft.) Septic Tank and Pump Chamber (ft.)
Well or suction line 100 50
Water supply line under pressure 10 10
Surface water 100 50
Building foundation 10 5
Property line or easement line 5 5
Curtain drain or culverted ditch:
   a.  Upgradient from system componenet 10 --
   b.  Downgradient from system component 30 5

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The type of septic system required depends on a number of factors. Most importantly, the soil texture, the soil structure, and the horizontal and vertical distances to the water table, wetlands, and open water will determine which kind of septic system you will be permitted to install. The following chart outlines the general type of systems depending upon the distance from the surface of the ground to the restrictive layer.                                                                                                                             

                                                                                                                          

Distance from Ground Surface to Restrictive Layer (winter water table, hardpan, solid clay)

Type of System
Less than 12 inches

12 to 18 inches

18 to 30 inches

30 to 42 inches (silt/clay soils)

30 to 72 inches (sandy soils)

Greater than 42 inches (silt/clay soils)

Greater then 72 inches (sandy soils)

 None

ATU or Sand Filter with a Mound

Sand Filter or a Mound

Pressure

Pressure

Gravity*

Gravity

 

Horizontal distances from wells, wetlands, and open water play an important part in determining what type of septic system will be required. These distances will vary slightly depending upon if you need a repair to an existing septic system or if you are building a new single-family residence.

Repairs: If you are within 300 feet of Willapa Bay or less than 100 feet from a well, open water, or a wetland, you will have to "upgrade" your drainfield to a more advanced type of system. If your drainfield is less than 75 feet from a well, wetland, or open water, you may need an Aerobic Treatment Unit (ATU).

New Construction: If you are 75 feet or less from a well, open water, or a wetland, you will be unable to install a septic system. If your drainfield is within 300 feet of Willapa Bay or located between 75 to100 feet from any well, open water, or a wetland, you will have to "upgrade" your drainfield to a more advanced type of system.

 

Septic System Types

Gravity

    In a conventional gravity fed drainfield, the septic tank effluent uses the force of gravity to flow to the drainfield through large diameter (4") pipes. A standard drainfield is a series of trenches (3 feet wide) or a bed (10 feet wide) dug 10-24" below the natural grade. A traditional trench consists of 6" of rock under a 4" perforated pipe, running the length of the trench. The pipe is covered with 2 inches of rock, a non-biodegradable fabric, and a minimum of 6" of soil cover. Allowing the effluent to slowly trickle from the pipes out into the gravel and down through the native soil provides acceptable treatment of harmful bacteria, viruses, and nitrates.

Pressure

    In a pressurized drainfield, the addition of a pump and a pump tank distributes septic tank effluent evenly throughout the drainfield. The pressure system also regulates the flow of effluent to the drainfield. The pump can be set to deliver a controlled amount of effluent over a controlled time. This controlled dosing helps prevent the drainfield from becoming overly saturated and prematurely failing. This system also uses alarms to alert the homeowner of high levels of effluent.

Mound or Sand Filter

    A mound or sand filter system is a type of design that is used where the water table is high or the soil is too restrictive to provide adequate treatment. A mound or sand filter is constructed of "ASTM C-33" sand that will treat the effluent before it reaches the restrictive layer. The effluent is distributed evenly throughout the bed by pressure, and then trickles through the ASTM C-33 sand before coming in contact with the plowed native soil (mound), or being collected and pumped to a shallow drainfield (sand filter).

Aerobic Treatment Unit

    Aerobic Treatment Units (ATUs) provide aerobic biological decomposition of wastewater constituents by mechanically bringing the wastewater in contact with air. ATUs come in different configurations and sizes, and incorporate a variety of approaches, including air pumps, air injectors, lift pumps and biological-contact surfaces (such as pipes, fabric, grids, gravels, and rotating disks). ATUs may also require UV light or chlorine tablets to destroy harmful pathogens prior to discharging effluent into the soil, usually through a pressure drainfield. ATUs will also be required to have an operation and maintenance agreement with a third party for the life of the septic system to ensure long term system performance.

If you need additional information, application forms, or have any questions about septic systems, please call (360) 642-9382 (Long Beach Peninsula) or call (360) 875-9356 (Grayland/Tokeland, Naselle, and Raymond/South Bend/Willapa Valley).  Office hours are Monday thru Friday 7:30 to 4:00. Additional information about septic systems, including technical publications on the different types of septic systems, can be found at the Washington State Department of Health website at following link.

Links

Washington State Dept. of Health Wastewater Management Program: www.doh.wa.gov/ehp/ts/WW/default.htm

EPA, United States Environmental Protection Agency: A Homeowners Guide to Septic Systems.pdf

National Small Flows Clearinghouse: http://www.nesc.wvu.edu/nsfc/nsfc_index.htm 

Thurston County Public Health, On-site Sewage Systems: http://www.co.thurston.wa.us/health/ehoss/index.html

                                       
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