Grays Harbor County

Septic System FAQ's

Office Hours:
8:00 am - Noon,
1:00 pm - 4:30 pm

Environmental Health E-Mail

Environmental Health Jeff Nelson, R.S. Director
100 W Broadway, Suite 31
Montesano, WA 98563-3614
(360) 249-4222
(360) 249-3203 Fax

Ensuring the proper design, installation and maintenance of On-Site
Sewage System (OSS).
If you are seeking to construct a new residence or modify an existing residence, please contact a Permit Coordinator who can ensure you complete all applicable paperwork. Also, all on-site sewage disposal systems (septic systems) in Grays Harbor County must be designed by a Washington State licensed On-Site Designer or Professional Engineer, (see link below for a listing). You may want to speak with your designer or engineer prior to submitting your application.

PERMITS/AS-BUILT DRAWINGS: Call (360) 249-4222 or e-mail to request a copy of your permit/as-built. Please have your parcel number and address ready to serve you efficiently. Please let us know if you have called before and left a message with another Environmental Health Specialist so we don't duplicate the work in searching your permit information.

Mike Bernheine
Environmental Health Specialist III
On-Site Sewage / Land Use Review
Eric Khambatta, R.S.
Environmental Health Specialist III
On-Site Sewage / Water Recreation Facilities / Recreational Vehicles / Lab


On-Site Septic Application   Site Plan
Note: This form needs to be printed on 8 ½ X 14” Paper
  Loan Report Application
On-Site Septic Designers, Installers & Pumpers       Septage Disposal Report Form
A Homeowner's Guide to On-Site Septic Systems   Frequently Asked Questions (FAQ's)   Water Availability Verification
Required for
Building Permit
Landscaping Your Drainfield, Protect Your Investment        



WARNING! Failure to provide all the information requested may delay
review of your application. Please read Application packet carefully.

Tank Pumping Frequencies

  Tank Pumping Frequency Chart

The following information is provided to help you prepare the site for inspection by an environmental health specialist.

All new Septic Permit Applications must be submitted with design.

Site Preparation:

Two test holes are required per site. The test holes must be located in, or adjacent to, the areas designated as the primary and the reserve drainfield. 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 not 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 provided 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.
  Call before you dig. Requirements: when digging greater than 12 inches. Call 8-1-1 to avoid running into underground utilities.

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
Water supply line under pressure
Surface water
Building foundation
Property line or easement line
Curtain drain or culverted ditch:
    A.  Up gradient from system component
    B.  Down gradient from system component

Septic System Types

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.

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 has any questions about septic systems, please call (360) 249-4222. Office hours are Monday thru Friday 8:00am to 5:00pm. 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.


USDA Rural Development Septic Repair Program Fact Sheets/NEW 504 info sheet.pdf

Washington State Dept. of Health Wastewater Management Program

National Small Flows Clearinghouse

Grays Harbor Public Health and Social Services